[PATCH 1/6] KEYS: Authorise keyctl_set_timeout() on a key if we have its authorisation key

[PATCH 1/6] KEYS: Authorise keyctl_set_timeout() on a key if we have its authorisation key

[David Howells]

Authorise a process to perform keyctl_set_timeout() on an uninstantiated key if
that process has the authorisation key for it.

This allows the instantiator to set the timeout on a key it is instantiating -
provided it does it before instantiating the key.

For instance, the test upcall script provided with the keyutils package could
be modified to set the expiry to an hour hence before instantiating the key:

	[/usr/share/keyutils/request-key-debug.sh]
	 if [ "$3" != "neg" ]
	 then
	+    keyctl timeout $1 3600
	     keyctl instantiate $1 "Debug $3" $4 || exit 1
	 else

Signed-off-by: David Howells <dhowells-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
---

 security/keys/keyctl.c |   17 ++++++++++++++++-
 1 files changed, 16 insertions(+), 1 deletions(-)

diff --git a/security/keys/keyctl.c b/security/keys/keyctl.c
index 6261745..639226a 100644
--- a/security/keys/keyctl.c
+++ b/security/keys/keyctl.c
@@ -1091,7 +1091,7 @@ error:
 long keyctl_set_timeout(key_serial_t id, unsigned timeout)
 {
 	struct timespec now;
-	struct key *key;
+	struct key *key, *instkey;
 	key_ref_t key_ref;
 	time_t expiry;
 	long ret;
@@ -1099,10 +1099,25 @@ long keyctl_set_timeout(key_serial_t id, unsigned timeout)
 	key_ref = lookup_user_key(id, KEY_LOOKUP_CREATE | KEY_LOOKUP_PARTIAL,
 				  KEY_SETATTR);
 	if (IS_ERR(key_ref)) {
+		/* setting the timeout on a key under construction is permitted
+		 * if we have the authorisation token handy */
+		if (PTR_ERR(key_ref) == -EACCES) {
+			instkey = key_get_instantiation_authkey(id);
+			if (!IS_ERR(instkey)) {
+				key_put(instkey);
+				key_ref = lookup_user_key(id,
+							  KEY_LOOKUP_PARTIAL,
+							  0);
+				if (!IS_ERR(key_ref))
+					goto okay;
+			}
+		}
+
 		ret = PTR_ERR(key_ref);
 		goto error;
 	}
 
+okay:
 	key = key_ref_to_ptr(key_ref);
 
 	/* make the changes with the locks held to prevent races */

[PATCH 2/6] CIFS: Fix a malicious redirect problem in the DNS lookup code

[David Howells]

Fix the security problem in the CIFS filesystem DNS lookup code in which a
malicious redirect could be installed by a random user by simply adding a
result record into one of their keyrings with add_key() and then invoking a
CIFS CFS lookup [CVE-2010-2524].

This is done by creating an internal keyring specifically for the caching of
DNS lookups.  To enforce the use of this keyring, the module init routine
creates a set of override credentials with the keyring installed as the thread
keyring and instructs request_key() to only install lookup result keys in that
keyring.

The override is then applied around the call to request_key().

This has some additional benefits when a kernel service uses this module to
request a key:

 (1) The result keys are owned by root, not the user that caused the lookup.

 (2) The result keys don't pop up in the user's keyrings.

 (3) The result keys don't come out of the quota of the user that caused the
     lookup.

The keyring can be viewed as root by doing cat /proc/keys:

2a0ca6c3 I-----     1 perm 1f030000     0     0 keyring   .dns_resolver: 1/4

It can then be listed with 'keyctl list' by root.

	# keyctl list 0x2a0ca6c3
	1 key in keyring:
	726766307: --alswrv     0     0 dns_resolver: foo.bar.com

Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-and-Tested-by: Jeff Layton <jlayton@redhat.com>
Acked-by: Steve French <smfrench@gmail.com>
---

 fs/cifs/cifsfs.c      |    6 ++--
 fs/cifs/dns_resolve.c |   69 +++++++++++++++++++++++++++++++++++++++++++++++++
 fs/cifs/dns_resolve.h |    4 +--
 3 files changed, 74 insertions(+), 5 deletions(-)

diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c
index c78d219..8a2cf12 100644
--- a/fs/cifs/cifsfs.c
+++ b/fs/cifs/cifsfs.c
@@ -935,7 +935,7 @@ init_cifs(void)
 		goto out_unregister_filesystem;
 #endif
 #ifdef CONFIG_CIFS_DFS_UPCALL
-	rc = register_key_type(&key_type_dns_resolver);
+	rc = cifs_init_dns_resolver();
 	if (rc)
 		goto out_unregister_key_type;
 #endif
@@ -947,7 +947,7 @@ init_cifs(void)
 
  out_unregister_resolver_key:
 #ifdef CONFIG_CIFS_DFS_UPCALL
-	unregister_key_type(&key_type_dns_resolver);
+	cifs_exit_dns_resolver();
  out_unregister_key_type:
 #endif
 #ifdef CONFIG_CIFS_UPCALL
@@ -976,7 +976,7 @@ exit_cifs(void)
 	cifs_fscache_unregister();
 #ifdef CONFIG_CIFS_DFS_UPCALL
 	cifs_dfs_release_automount_timer();
-	unregister_key_type(&key_type_dns_resolver);
+	cifs_exit_dns_resolver();
 #endif
 #ifdef CONFIG_CIFS_UPCALL
 	unregister_key_type(&cifs_spnego_key_type);
diff --git a/fs/cifs/dns_resolve.c b/fs/cifs/dns_resolve.c
index 22afe38..ff6fa2f 100644
--- a/fs/cifs/dns_resolve.c
+++ b/fs/cifs/dns_resolve.c
@@ -24,12 +24,16 @@
  */
 
 #include <linux/slab.h>
+#include <linux/keyctl.h>
+#include <linux/key-type.h>
 #include <keys/user-type.h>
 #include "dns_resolve.h"
 #include "cifsglob.h"
 #include "cifsproto.h"
 #include "cifs_debug.h"
 
+static const struct cred *dns_resolver_cache;
+
 /* Checks if supplied name is IP address
  * returns:
  * 		1 - name is IP
@@ -94,6 +98,7 @@ struct key_type key_type_dns_resolver = {
 int
 dns_resolve_server_name_to_ip(const char *unc, char **ip_addr)
 {
+	const struct cred *saved_cred;
 	int rc = -EAGAIN;
 	struct key *rkey = ERR_PTR(-EAGAIN);
 	char *name;
@@ -133,8 +138,15 @@ dns_resolve_server_name_to_ip(const char *unc, char **ip_addr)
 		goto skip_upcall;
 	}
 
+	saved_cred = override_creds(dns_resolver_cache);
 	rkey = request_key(&key_type_dns_resolver, name, "");
+	revert_creds(saved_cred);
 	if (!IS_ERR(rkey)) {
+		if (!(rkey->perm & KEY_USR_VIEW)) {
+			down_read(&rkey->sem);
+			rkey->perm |= KEY_USR_VIEW;
+			up_read(&rkey->sem);
+		}
 		len = rkey->type_data.x[0];
 		data = rkey->payload.data;
 	} else {
@@ -165,4 +177,61 @@ out:
 	return rc;
 }
 
+int __init cifs_init_dns_resolver(void)
+{
+	struct cred *cred;
+	struct key *keyring;
+	int ret;
+
+	printk(KERN_NOTICE "Registering the %s key type\n",
+	       key_type_dns_resolver.name);
+
+	/* create an override credential set with a special thread keyring in
+	 * which DNS requests are cached
+	 *
+	 * this is used to prevent malicious redirections from being installed
+	 * with add_key().
+	 */
+	cred = prepare_kernel_cred(NULL);
+	if (!cred)
+		return -ENOMEM;
+
+	keyring = key_alloc(&key_type_keyring, ".dns_resolver", 0, 0, cred,
+			    (KEY_POS_ALL & ~KEY_POS_SETATTR) |
+			    KEY_USR_VIEW | KEY_USR_READ,
+			    KEY_ALLOC_NOT_IN_QUOTA);
+	if (IS_ERR(keyring)) {
+		ret = PTR_ERR(keyring);
+		goto failed_put_cred;
+	}
+
+	ret = key_instantiate_and_link(keyring, NULL, 0, NULL, NULL);
+	if (ret < 0)
+		goto failed_put_key;
+
+	ret = register_key_type(&key_type_dns_resolver);
+	if (ret < 0)
+		goto failed_put_key;
+
+	/* instruct request_key() to use this special keyring as a cache for
+	 * the results it looks up */
+	cred->thread_keyring = keyring;
+	cred->jit_keyring = KEY_REQKEY_DEFL_THREAD_KEYRING;
+	dns_resolver_cache = cred;
+	return 0;
+
+failed_put_key:
+	key_put(keyring);
+failed_put_cred:
+	put_cred(cred);
+	return ret;
+}
 
+void __exit cifs_exit_dns_resolver(void)
+{
+	key_revoke(dns_resolver_cache->thread_keyring);
+	unregister_key_type(&key_type_dns_resolver);
+	put_cred(dns_resolver_cache);
+	printk(KERN_NOTICE "Unregistered %s key type\n",
+	       key_type_dns_resolver.name);
+}
diff --git a/fs/cifs/dns_resolve.h b/fs/cifs/dns_resolve.h
index 966e928..26b9eaa 100644
--- a/fs/cifs/dns_resolve.h
+++ b/fs/cifs/dns_resolve.h
@@ -24,8 +24,8 @@
 #define _DNS_RESOLVE_H
 
 #ifdef __KERNEL__
-#include <linux/key-type.h>
-extern struct key_type key_type_dns_resolver;
+extern int __init cifs_init_dns_resolver(void);
+extern void __exit cifs_exit_dns_resolver(void);
 extern int dns_resolve_server_name_to_ip(const char *unc, char **ip_addr);
 #endif /* KERNEL */
 

[PATCH 3/6] CIFS: Make cifs_convert_address() take a const src pointer and a length

[David Howells]

Make cifs_convert_address() take a const src pointer and a length so that all
the strlen() calls in their can be cut out and to make it unnecessary to modify
the src string.

Also return the data length from dns_resolve_server_name_to_ip() so that a
strlen() can be cut out of cifs_compose_mount_options() too.

Signed-off-by: David Howells <dhowells@redhat.com>
---

 fs/cifs/cifs_dfs_ref.c |    5 ++---
 fs/cifs/cifsproto.h    |    4 ++--
 fs/cifs/connect.c      |    1 +
 fs/cifs/dns_resolve.c  |   20 +++++++++-----------
 fs/cifs/netmisc.c      |   45 ++++++++++++++++++++++++---------------------
 5 files changed, 38 insertions(+), 37 deletions(-)

diff --git a/fs/cifs/cifs_dfs_ref.c b/fs/cifs/cifs_dfs_ref.c
index ac19a6f..37543e8 100644
--- a/fs/cifs/cifs_dfs_ref.c
+++ b/fs/cifs/cifs_dfs_ref.c
@@ -141,7 +141,7 @@ char *cifs_compose_mount_options(const char *sb_mountdata,
 	}
 
 	rc = dns_resolve_server_name_to_ip(*devname, &srvIP);
-	if (rc != 0) {
+	if (rc < 0) {
 		cERROR(1, "%s: Failed to resolve server part of %s to IP: %d",
 			  __func__, *devname, rc);
 		goto compose_mount_options_err;
@@ -150,8 +150,7 @@ char *cifs_compose_mount_options(const char *sb_mountdata,
 	 * assuming that we have 'unc=' and 'ip=' in
 	 * the original sb_mountdata
 	 */
-	md_len = strlen(sb_mountdata) + strlen(srvIP) +
-		strlen(ref->node_name) + 12;
+	md_len = strlen(sb_mountdata) + rc + strlen(ref->node_name) + 12;
 	mountdata = kzalloc(md_len+1, GFP_KERNEL);
 	if (mountdata == NULL) {
 		rc = -ENOMEM;
diff --git a/fs/cifs/cifsproto.h b/fs/cifs/cifsproto.h
index 2eaebbd..1f54508 100644
--- a/fs/cifs/cifsproto.h
+++ b/fs/cifs/cifsproto.h
@@ -86,8 +86,8 @@ extern unsigned int smbCalcSize(struct smb_hdr *ptr);
 extern unsigned int smbCalcSize_LE(struct smb_hdr *ptr);
 extern int decode_negTokenInit(unsigned char *security_blob, int length,
 			struct TCP_Server_Info *server);
-extern int cifs_convert_address(struct sockaddr *dst, char *src);
-extern int cifs_fill_sockaddr(struct sockaddr *dst, char *src,
+extern int cifs_convert_address(struct sockaddr *dst, const char *src, int len);
+extern int cifs_fill_sockaddr(struct sockaddr *dst, const char *src, int len,
 				unsigned short int port);
 extern int map_smb_to_linux_error(struct smb_hdr *smb, int logErr);
 extern void header_assemble(struct smb_hdr *, char /* command */ ,
diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index 399b601..7a78b49 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -1538,6 +1538,7 @@ cifs_get_tcp_session(struct smb_vol *volume_info)
 	if (volume_info->UNCip && volume_info->UNC) {
 		rc = cifs_fill_sockaddr((struct sockaddr *)&addr,
 					volume_info->UNCip,
+					strlen(volume_info->UNCip),
 					volume_info->port);
 		if (!rc) {
 			/* we failed translating address */
diff --git a/fs/cifs/dns_resolve.c b/fs/cifs/dns_resolve.c
index ff6fa2f..8de3b98 100644
--- a/fs/cifs/dns_resolve.c
+++ b/fs/cifs/dns_resolve.c
@@ -40,11 +40,11 @@ static const struct cred *dns_resolver_cache;
  * 		0 - name is not IP
  */
 static int
-is_ip(char *name)
+is_ip(const char *name, int len)
 {
 	struct sockaddr_storage ss;
 
-	return cifs_convert_address((struct sockaddr *)&ss, name);
+	return cifs_convert_address((struct sockaddr *)&ss, name, len);
 }
 
 static int
@@ -54,6 +54,10 @@ dns_resolver_instantiate(struct key *key, const void *data,
 	int rc = 0;
 	char *ip;
 
+	/* make sure this looks like an address */
+	if (!is_ip(data, datalen))
+		return -EINVAL;
+
 	ip = kmalloc(datalen + 1, GFP_KERNEL);
 	if (!ip)
 		return -ENOMEM;
@@ -61,12 +65,6 @@ dns_resolver_instantiate(struct key *key, const void *data,
 	memcpy(ip, data, datalen);
 	ip[datalen] = '\0';
 
-	/* make sure this looks like an address */
-	if (!is_ip(ip)) {
-		kfree(ip);
-		return -EINVAL;
-	}
-
 	key->type_data.x[0] = datalen;
 	key->payload.data = ip;
 
@@ -93,7 +91,7 @@ struct key_type key_type_dns_resolver = {
  * 	unc - server UNC
  * output:
  * 	*ip_addr - pointer to server ip, caller responcible for freeing it.
- * return 0 on success
+ * return the length of the returned string on success
  */
 int
 dns_resolve_server_name_to_ip(const char *unc, char **ip_addr)
@@ -131,7 +129,7 @@ dns_resolve_server_name_to_ip(const char *unc, char **ip_addr)
 	memcpy(name, unc+2, len);
 	name[len] = 0;
 
-	if (is_ip(name)) {
+	if (is_ip(name, len)) {
 		cFYI(1, "%s: it is IP, skipping dns upcall: %s",
 					__func__, name);
 		data = name;
@@ -164,7 +162,7 @@ skip_upcall:
 							name,
 							*ip_addr
 					);
-			rc = 0;
+			rc = len;
 		} else {
 			rc = -ENOMEM;
 		}
diff --git a/fs/cifs/netmisc.c b/fs/cifs/netmisc.c
index 3489468..b7f5975 100644
--- a/fs/cifs/netmisc.c
+++ b/fs/cifs/netmisc.c
@@ -139,17 +139,18 @@ static const struct smb_to_posix_error mapping_table_ERRHRD[] = {
  * Returns 0 on failure.
  */
 static int
-cifs_inet_pton(const int address_family, const char *cp, void *dst)
+cifs_inet_pton(const int address_family, const char *cp, int len, void *dst)
 {
 	int ret = 0;
 
 	/* calculate length by finding first slash or NULL */
 	if (address_family == AF_INET)
-		ret = in4_pton(cp, -1 /* len */, dst, '\\', NULL);
+		ret = in4_pton(cp, len, dst, '\\', NULL);
 	else if (address_family == AF_INET6)
-		ret = in6_pton(cp, -1 /* len */, dst , '\\', NULL);
+		ret = in6_pton(cp, len, dst , '\\', NULL);
 
-	cFYI(DBG2, "address conversion returned %d for %s", ret, cp);
+	cFYI(DBG2, "address conversion returned %d for %*.*s",
+	     ret, len, len, cp);
 	if (ret > 0)
 		ret = 1;
 	return ret;
@@ -164,37 +165,39 @@ cifs_inet_pton(const int address_family, const char *cp, void *dst)
  * Returns 0 on failure.
  */
 int
-cifs_convert_address(struct sockaddr *dst, char *src)
+cifs_convert_address(struct sockaddr *dst, const char *src, int len)
 {
-	int rc;
-	char *pct, *endp;
+	int rc, alen, slen;
+	const char *pct;
+	char *endp, scope_id[13];
 	struct sockaddr_in *s4 = (struct sockaddr_in *) dst;
 	struct sockaddr_in6 *s6 = (struct sockaddr_in6 *) dst;
 
 	/* IPv4 address */
-	if (cifs_inet_pton(AF_INET, src, &s4->sin_addr.s_addr)) {
+	if (cifs_inet_pton(AF_INET, src, len, &s4->sin_addr.s_addr)) {
 		s4->sin_family = AF_INET;
 		return 1;
 	}
 
-	/* temporarily terminate string */
-	pct = strchr(src, '%');
-	if (pct)
-		*pct = '\0';
-
-	rc = cifs_inet_pton(AF_INET6, src, &s6->sin6_addr.s6_addr);
-
-	/* repair temp termination (if any) and make pct point to scopeid */
-	if (pct)
-		*pct++ = '%';
+	/* attempt to exclude the scope ID from the address part */
+	pct = memchr(src, '%', len);
+	alen = pct ? pct - src : len;
 
+	rc = cifs_inet_pton(AF_INET6, src, alen, &s6->sin6_addr.s6_addr);
 	if (!rc)
 		return rc;
 
 	s6->sin6_family = AF_INET6;
 	if (pct) {
+		/* grab the scope ID */
+		slen = len - (alen + 1);
+		if (slen <= 0 || slen > 12)
+			return 0;
+		memcpy(scope_id, pct + 1, slen);
+		scope_id[slen] = '\0';
+
 		s6->sin6_scope_id = (u32) simple_strtoul(pct, &endp, 0);
-		if (!*pct || *endp)
+		if (endp != scope_id + slen)
 			return 0;
 	}
 
@@ -202,10 +205,10 @@ cifs_convert_address(struct sockaddr *dst, char *src)
 }
 
 int
-cifs_fill_sockaddr(struct sockaddr *dst, char *src,
+cifs_fill_sockaddr(struct sockaddr *dst, const char *src, int len,
 		   const unsigned short int port)
 {
-	if (!cifs_convert_address(dst, src))
+	if (!cifs_convert_address(dst, src, len))
 		return 0;
 
 	switch (dst->sa_family) {

Re: [PATCH 3/6] CIFS: Make cifs_convert_address() take a const src pointer and a length

[Jeff Layton]

On Thu, 22 Jul 2010 18:33:01 +0100
David Howells <dhowells@redhat.com> wrote:

> Make cifs_convert_address() take a const src pointer and a length so that all
> the strlen() calls in their can be cut out and to make it unnecessary to modify
> the src string.
> 
> Also return the data length from dns_resolve_server_name_to_ip() so that a
> strlen() can be cut out of cifs_compose_mount_options() too.
> 
> Signed-off-by: David Howells <dhowells@redhat.com>
> ---
> 
>  fs/cifs/cifs_dfs_ref.c |    5 ++---
>  fs/cifs/cifsproto.h    |    4 ++--
>  fs/cifs/connect.c      |    1 +
>  fs/cifs/dns_resolve.c  |   20 +++++++++-----------
>  fs/cifs/netmisc.c      |   45 ++++++++++++++++++++++++---------------------
>  5 files changed, 38 insertions(+), 37 deletions(-)
> 
> diff --git a/fs/cifs/cifs_dfs_ref.c b/fs/cifs/cifs_dfs_ref.c
> index ac19a6f..37543e8 100644
> --- a/fs/cifs/cifs_dfs_ref.c
> +++ b/fs/cifs/cifs_dfs_ref.c
> @@ -141,7 +141,7 @@ char *cifs_compose_mount_options(const char *sb_mountdata,
>  	}
>  
>  	rc = dns_resolve_server_name_to_ip(*devname, &srvIP);
> -	if (rc != 0) {
> +	if (rc < 0) {
>  		cERROR(1, "%s: Failed to resolve server part of %s to IP: %d",
>  			  __func__, *devname, rc);
>  		goto compose_mount_options_err;
> @@ -150,8 +150,7 @@ char *cifs_compose_mount_options(const char *sb_mountdata,
>  	 * assuming that we have 'unc=' and 'ip=' in
>  	 * the original sb_mountdata
>  	 */
> -	md_len = strlen(sb_mountdata) + strlen(srvIP) +
> -		strlen(ref->node_name) + 12;
> +	md_len = strlen(sb_mountdata) + rc + strlen(ref->node_name) + 12;
>  	mountdata = kzalloc(md_len+1, GFP_KERNEL);
>  	if (mountdata == NULL) {
>  		rc = -ENOMEM;
> diff --git a/fs/cifs/cifsproto.h b/fs/cifs/cifsproto.h
> index 2eaebbd..1f54508 100644
> --- a/fs/cifs/cifsproto.h
> +++ b/fs/cifs/cifsproto.h
> @@ -86,8 +86,8 @@ extern unsigned int smbCalcSize(struct smb_hdr *ptr);
>  extern unsigned int smbCalcSize_LE(struct smb_hdr *ptr);
>  extern int decode_negTokenInit(unsigned char *security_blob, int length,
>  			struct TCP_Server_Info *server);
> -extern int cifs_convert_address(struct sockaddr *dst, char *src);
> -extern int cifs_fill_sockaddr(struct sockaddr *dst, char *src,
> +extern int cifs_convert_address(struct sockaddr *dst, const char *src, int len);
> +extern int cifs_fill_sockaddr(struct sockaddr *dst, const char *src, int len,
>  				unsigned short int port);
>  extern int map_smb_to_linux_error(struct smb_hdr *smb, int logErr);
>  extern void header_assemble(struct smb_hdr *, char /* command */ ,
> diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
> index 399b601..7a78b49 100644
> --- a/fs/cifs/connect.c
> +++ b/fs/cifs/connect.c
> @@ -1538,6 +1538,7 @@ cifs_get_tcp_session(struct smb_vol *volume_info)
>  	if (volume_info->UNCip && volume_info->UNC) {
>  		rc = cifs_fill_sockaddr((struct sockaddr *)&addr,
>  					volume_info->UNCip,
> +					strlen(volume_info->UNCip),
>  					volume_info->port);
>  		if (!rc) {
>  			/* we failed translating address */
> diff --git a/fs/cifs/dns_resolve.c b/fs/cifs/dns_resolve.c
> index ff6fa2f..8de3b98 100644
> --- a/fs/cifs/dns_resolve.c
> +++ b/fs/cifs/dns_resolve.c
> @@ -40,11 +40,11 @@ static const struct cred *dns_resolver_cache;
>   * 		0 - name is not IP
>   */
>  static int
> -is_ip(char *name)
> +is_ip(const char *name, int len)
>  {
>  	struct sockaddr_storage ss;
>  
> -	return cifs_convert_address((struct sockaddr *)&ss, name);
> +	return cifs_convert_address((struct sockaddr *)&ss, name, len);
>  }
>  
>  static int
> @@ -54,6 +54,10 @@ dns_resolver_instantiate(struct key *key, const void *data,
>  	int rc = 0;
>  	char *ip;
>  
> +	/* make sure this looks like an address */
> +	if (!is_ip(data, datalen))
> +		return -EINVAL;
> +
>  	ip = kmalloc(datalen + 1, GFP_KERNEL);
>  	if (!ip)
>  		return -ENOMEM;
> @@ -61,12 +65,6 @@ dns_resolver_instantiate(struct key *key, const void *data,
>  	memcpy(ip, data, datalen);
>  	ip[datalen] = '\0';
>  
> -	/* make sure this looks like an address */
> -	if (!is_ip(ip)) {
> -		kfree(ip);
> -		return -EINVAL;
> -	}
> -
>  	key->type_data.x[0] = datalen;
>  	key->payload.data = ip;
>  
> @@ -93,7 +91,7 @@ struct key_type key_type_dns_resolver = {
>   * 	unc - server UNC
>   * output:
>   * 	*ip_addr - pointer to server ip, caller responcible for freeing it.
> - * return 0 on success
> + * return the length of the returned string on success
>   */
>  int
>  dns_resolve_server_name_to_ip(const char *unc, char **ip_addr)
> @@ -131,7 +129,7 @@ dns_resolve_server_name_to_ip(const char *unc, char **ip_addr)
>  	memcpy(name, unc+2, len);
>  	name[len] = 0;
>  
> -	if (is_ip(name)) {
> +	if (is_ip(name, len)) {
>  		cFYI(1, "%s: it is IP, skipping dns upcall: %s",
>  					__func__, name);
>  		data = name;
> @@ -164,7 +162,7 @@ skip_upcall:
>  							name,
>  							*ip_addr
>  					);
> -			rc = 0;
> +			rc = len;
>  		} else {
>  			rc = -ENOMEM;
>  		}
> diff --git a/fs/cifs/netmisc.c b/fs/cifs/netmisc.c
> index 3489468..b7f5975 100644
> --- a/fs/cifs/netmisc.c
> +++ b/fs/cifs/netmisc.c
> @@ -139,17 +139,18 @@ static const struct smb_to_posix_error mapping_table_ERRHRD[] = {
>   * Returns 0 on failure.
>   */
>  static int
> -cifs_inet_pton(const int address_family, const char *cp, void *dst)
> +cifs_inet_pton(const int address_family, const char *cp, int len, void *dst)
>  {
>  	int ret = 0;
>  
>  	/* calculate length by finding first slash or NULL */
>  	if (address_family == AF_INET)
> -		ret = in4_pton(cp, -1 /* len */, dst, '\\', NULL);
> +		ret = in4_pton(cp, len, dst, '\\', NULL);
>  	else if (address_family == AF_INET6)
> -		ret = in6_pton(cp, -1 /* len */, dst , '\\', NULL);
> +		ret = in6_pton(cp, len, dst , '\\', NULL);
>  
> -	cFYI(DBG2, "address conversion returned %d for %s", ret, cp);
> +	cFYI(DBG2, "address conversion returned %d for %*.*s",
> +	     ret, len, len, cp);
>  	if (ret > 0)
>  		ret = 1;
>  	return ret;
> @@ -164,37 +165,39 @@ cifs_inet_pton(const int address_family, const char *cp, void *dst)
>   * Returns 0 on failure.
>   */
>  int
> -cifs_convert_address(struct sockaddr *dst, char *src)
> +cifs_convert_address(struct sockaddr *dst, const char *src, int len)
>  {
> -	int rc;
> -	char *pct, *endp;
> +	int rc, alen, slen;
> +	const char *pct;
> +	char *endp, scope_id[13];
>  	struct sockaddr_in *s4 = (struct sockaddr_in *) dst;
>  	struct sockaddr_in6 *s6 = (struct sockaddr_in6 *) dst;
>  
>  	/* IPv4 address */
> -	if (cifs_inet_pton(AF_INET, src, &s4->sin_addr.s_addr)) {
> +	if (cifs_inet_pton(AF_INET, src, len, &s4->sin_addr.s_addr)) {
>  		s4->sin_family = AF_INET;
>  		return 1;
>  	}
>  
> -	/* temporarily terminate string */
> -	pct = strchr(src, '%');
> -	if (pct)
> -		*pct = '\0';
> -
> -	rc = cifs_inet_pton(AF_INET6, src, &s6->sin6_addr.s6_addr);
> -
> -	/* repair temp termination (if any) and make pct point to scopeid */
> -	if (pct)
> -		*pct++ = '%';
> +	/* attempt to exclude the scope ID from the address part */
> +	pct = memchr(src, '%', len);
> +	alen = pct ? pct - src : len;
>  
> +	rc = cifs_inet_pton(AF_INET6, src, alen, &s6->sin6_addr.s6_addr);
>  	if (!rc)
>  		return rc;
>  
>  	s6->sin6_family = AF_INET6;
>  	if (pct) {
> +		/* grab the scope ID */
> +		slen = len - (alen + 1);
> +		if (slen <= 0 || slen > 12)
> +			return 0;
> +		memcpy(scope_id, pct + 1, slen);
> +		scope_id[slen] = '\0';
> +
>  		s6->sin6_scope_id = (u32) simple_strtoul(pct, &endp, 0);
> -		if (!*pct || *endp)
> +		if (endp != scope_id + slen)
>  			return 0;
>  	}
>  
> @@ -202,10 +205,10 @@ cifs_convert_address(struct sockaddr *dst, char *src)
>  }
>  
>  int
> -cifs_fill_sockaddr(struct sockaddr *dst, char *src,
> +cifs_fill_sockaddr(struct sockaddr *dst, const char *src, int len,
>  		   const unsigned short int port)
>  {
> -	if (!cifs_convert_address(dst, src))
> +	if (!cifs_convert_address(dst, src, len))
>  		return 0;
>  
>  	switch (dst->sa_family) {
> 

Looks good. I like the fact that we'll no longer be munging the source
string in cifs_convert_address.

Acked-by: Jeff Layton <jlayton@redhat.com>

Re: [PATCH 3/6] CIFS: Make cifs_convert_address() take a const src pointer and a length

[Steve French]

I merged this (patch 3) - but patch 4 (and thus patch 5) did not merge.

Also patches 4 and 5 had trivial checkpatch warnings.

Patch 6 looks afs related so should probably merge out of your tree,
but it doesn't matter to me.
What about patches 1 and 2 - which is easier?

On Thu, Jul 22, 2010 at 12:33 PM, David Howells <dhowells-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> wrote:
> Make cifs_convert_address() take a const src pointer and a length so that all
> the strlen() calls in their can be cut out and to make it unnecessary to modify
> the src string.
>
> Also return the data length from dns_resolve_server_name_to_ip() so that a
> strlen() can be cut out of cifs_compose_mount_options() too.
>
> Signed-off-by: David Howells <dhowells-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
> ---
>
>  fs/cifs/cifs_dfs_ref.c |    5 ++---
>  fs/cifs/cifsproto.h    |    4 ++--
>  fs/cifs/connect.c      |    1 +
>  fs/cifs/dns_resolve.c  |   20 +++++++++-----------
>  fs/cifs/netmisc.c      |   45 ++++++++++++++++++++++++---------------------
>  5 files changed, 38 insertions(+), 37 deletions(-)
>
> diff --git a/fs/cifs/cifs_dfs_ref.c b/fs/cifs/cifs_dfs_ref.c
> index ac19a6f..37543e8 100644
> --- a/fs/cifs/cifs_dfs_ref.c
> +++ b/fs/cifs/cifs_dfs_ref.c
> @@ -141,7 +141,7 @@ char *cifs_compose_mount_options(const char *sb_mountdata,
>        }
>
>        rc = dns_resolve_server_name_to_ip(*devname, &srvIP);
> -       if (rc != 0) {
> +       if (rc < 0) {
>                cERROR(1, "%s: Failed to resolve server part of %s to IP: %d",
>                          __func__, *devname, rc);
>                goto compose_mount_options_err;
> @@ -150,8 +150,7 @@ char *cifs_compose_mount_options(const char *sb_mountdata,
>         * assuming that we have 'unc=' and 'ip=' in
>         * the original sb_mountdata
>         */
> -       md_len = strlen(sb_mountdata) + strlen(srvIP) +
> -               strlen(ref->node_name) + 12;
> +       md_len = strlen(sb_mountdata) + rc + strlen(ref->node_name) + 12;
>        mountdata = kzalloc(md_len+1, GFP_KERNEL);
>        if (mountdata == NULL) {
>                rc = -ENOMEM;
> diff --git a/fs/cifs/cifsproto.h b/fs/cifs/cifsproto.h
> index 2eaebbd..1f54508 100644
> --- a/fs/cifs/cifsproto.h
> +++ b/fs/cifs/cifsproto.h
> @@ -86,8 +86,8 @@ extern unsigned int smbCalcSize(struct smb_hdr *ptr);
>  extern unsigned int smbCalcSize_LE(struct smb_hdr *ptr);
>  extern int decode_negTokenInit(unsigned char *security_blob, int length,
>                        struct TCP_Server_Info *server);
> -extern int cifs_convert_address(struct sockaddr *dst, char *src);
> -extern int cifs_fill_sockaddr(struct sockaddr *dst, char *src,
> +extern int cifs_convert_address(struct sockaddr *dst, const char *src, int len);
> +extern int cifs_fill_sockaddr(struct sockaddr *dst, const char *src, int len,
>                                unsigned short int port);
>  extern int map_smb_to_linux_error(struct smb_hdr *smb, int logErr);
>  extern void header_assemble(struct smb_hdr *, char /* command */ ,
> diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
> index 399b601..7a78b49 100644
> --- a/fs/cifs/connect.c
> +++ b/fs/cifs/connect.c
> @@ -1538,6 +1538,7 @@ cifs_get_tcp_session(struct smb_vol *volume_info)
>        if (volume_info->UNCip && volume_info->UNC) {
>                rc = cifs_fill_sockaddr((struct sockaddr *)&addr,
>                                        volume_info->UNCip,
> +                                       strlen(volume_info->UNCip),
>                                        volume_info->port);
>                if (!rc) {
>                        /* we failed translating address */
> diff --git a/fs/cifs/dns_resolve.c b/fs/cifs/dns_resolve.c
> index ff6fa2f..8de3b98 100644
> --- a/fs/cifs/dns_resolve.c
> +++ b/fs/cifs/dns_resolve.c
> @@ -40,11 +40,11 @@ static const struct cred *dns_resolver_cache;
>  *             0 - name is not IP
>  */
>  static int
> -is_ip(char *name)
> +is_ip(const char *name, int len)
>  {
>        struct sockaddr_storage ss;
>
> -       return cifs_convert_address((struct sockaddr *)&ss, name);
> +       return cifs_convert_address((struct sockaddr *)&ss, name, len);
>  }
>
>  static int
> @@ -54,6 +54,10 @@ dns_resolver_instantiate(struct key *key, const void *data,
>        int rc = 0;
>        char *ip;
>
> +       /* make sure this looks like an address */
> +       if (!is_ip(data, datalen))
> +               return -EINVAL;
> +
>        ip = kmalloc(datalen + 1, GFP_KERNEL);
>        if (!ip)
>                return -ENOMEM;
> @@ -61,12 +65,6 @@ dns_resolver_instantiate(struct key *key, const void *data,
>        memcpy(ip, data, datalen);
>        ip[datalen] = '\0';
>
> -       /* make sure this looks like an address */
> -       if (!is_ip(ip)) {
> -               kfree(ip);
> -               return -EINVAL;
> -       }
> -
>        key->type_data.x[0] = datalen;
>        key->payload.data = ip;
>
> @@ -93,7 +91,7 @@ struct key_type key_type_dns_resolver = {
>  *     unc - server UNC
>  * output:
>  *     *ip_addr - pointer to server ip, caller responcible for freeing it.
> - * return 0 on success
> + * return the length of the returned string on success
>  */
>  int
>  dns_resolve_server_name_to_ip(const char *unc, char **ip_addr)
> @@ -131,7 +129,7 @@ dns_resolve_server_name_to_ip(const char *unc, char **ip_addr)
>        memcpy(name, unc+2, len);
>        name[len] = 0;
>
> -       if (is_ip(name)) {
> +       if (is_ip(name, len)) {
>                cFYI(1, "%s: it is IP, skipping dns upcall: %s",
>                                        __func__, name);
>                data = name;
> @@ -164,7 +162,7 @@ skip_upcall:
>                                                        name,
>                                                        *ip_addr
>                                        );
> -                       rc = 0;
> +                       rc = len;
>                } else {
>                        rc = -ENOMEM;
>                }
> diff --git a/fs/cifs/netmisc.c b/fs/cifs/netmisc.c
> index 3489468..b7f5975 100644
> --- a/fs/cifs/netmisc.c
> +++ b/fs/cifs/netmisc.c
> @@ -139,17 +139,18 @@ static const struct smb_to_posix_error mapping_table_ERRHRD[] = {
>  * Returns 0 on failure.
>  */
>  static int
> -cifs_inet_pton(const int address_family, const char *cp, void *dst)
> +cifs_inet_pton(const int address_family, const char *cp, int len, void *dst)
>  {
>        int ret = 0;
>
>        /* calculate length by finding first slash or NULL */
>        if (address_family == AF_INET)
> -               ret = in4_pton(cp, -1 /* len */, dst, '\\', NULL);
> +               ret = in4_pton(cp, len, dst, '\\', NULL);
>        else if (address_family == AF_INET6)
> -               ret = in6_pton(cp, -1 /* len */, dst , '\\', NULL);
> +               ret = in6_pton(cp, len, dst , '\\', NULL);
>
> -       cFYI(DBG2, "address conversion returned %d for %s", ret, cp);
> +       cFYI(DBG2, "address conversion returned %d for %*.*s",
> +            ret, len, len, cp);
>        if (ret > 0)
>                ret = 1;
>        return ret;
> @@ -164,37 +165,39 @@ cifs_inet_pton(const int address_family, const char *cp, void *dst)
>  * Returns 0 on failure.
>  */
>  int
> -cifs_convert_address(struct sockaddr *dst, char *src)
> +cifs_convert_address(struct sockaddr *dst, const char *src, int len)
>  {
> -       int rc;
> -       char *pct, *endp;
> +       int rc, alen, slen;
> +       const char *pct;
> +       char *endp, scope_id[13];
>        struct sockaddr_in *s4 = (struct sockaddr_in *) dst;
>        struct sockaddr_in6 *s6 = (struct sockaddr_in6 *) dst;
>
>        /* IPv4 address */
> -       if (cifs_inet_pton(AF_INET, src, &s4->sin_addr.s_addr)) {
> +       if (cifs_inet_pton(AF_INET, src, len, &s4->sin_addr.s_addr)) {
>                s4->sin_family = AF_INET;
>                return 1;
>        }
>
> -       /* temporarily terminate string */
> -       pct = strchr(src, '%');
> -       if (pct)
> -               *pct = '\0';
> -
> -       rc = cifs_inet_pton(AF_INET6, src, &s6->sin6_addr.s6_addr);
> -
> -       /* repair temp termination (if any) and make pct point to scopeid */
> -       if (pct)
> -               *pct++ = '%';
> +       /* attempt to exclude the scope ID from the address part */
> +       pct = memchr(src, '%', len);
> +       alen = pct ? pct - src : len;
>
> +       rc = cifs_inet_pton(AF_INET6, src, alen, &s6->sin6_addr.s6_addr);
>        if (!rc)
>                return rc;
>
>        s6->sin6_family = AF_INET6;
>        if (pct) {
> +               /* grab the scope ID */
> +               slen = len - (alen + 1);
> +               if (slen <= 0 || slen > 12)
> +                       return 0;
> +               memcpy(scope_id, pct + 1, slen);
> +               scope_id[slen] = '\0';
> +
>                s6->sin6_scope_id = (u32) simple_strtoul(pct, &endp, 0);
> -               if (!*pct || *endp)
> +               if (endp != scope_id + slen)
>                        return 0;
>        }
>
> @@ -202,10 +205,10 @@ cifs_convert_address(struct sockaddr *dst, char *src)
>  }
>
>  int
> -cifs_fill_sockaddr(struct sockaddr *dst, char *src,
> +cifs_fill_sockaddr(struct sockaddr *dst, const char *src, int len,
>                   const unsigned short int port)
>  {
> -       if (!cifs_convert_address(dst, src))
> +       if (!cifs_convert_address(dst, src, len))
>                return 0;
>
>        switch (dst->sa_family) {
>
>



-- 
Thanks,

Steve

[PATCH 4/6] DNS: Separate out CIFS DNS Resolver code

[David Howells]

From: Wang Lei <wang840925@gmail.com>

Separate out the DNS resolver key type from the CIFS filesystem into its own
module so that it can be made available for general use, including the AFS
filesystem module.

This facility makes it possible for the kernel to upcall to userspace to have
it issue DNS requests, package up the replies and present them to the kernel
in a useful form.  The kernel is then able to cache the DNS replies as keys
can be retained in keyrings.

Resolver keys are of type "dns_resolver" and have a case-insensitive
description that is of the form "[<type>:]<domain_name>".  The optional <type>
indicates the particular DNS lookup and packaging that's required.  The
<domain_name> is the query to be made.

If <type> isn't given, a basic hostname to IP address lookup is made, and the
result is stored in the key in the form of a printable string consisting of a
comma-separated list of IPv4 and IPv6 addresses.

This key type is supported by userspace helpers driven from /sbin/request-key
and configured through /etc/request-key.conf.  The cifs.upcall utility is
invoked for UNC path server name to IP address resolution.

The CIFS functionality is encapsulated by the dns_resolve_unc_to_ip() function,
which is used to resolve a UNC path to an IP address for CIFS filesystem.  This
part remains in the CIFS module for now.

See the added Documentation/networking/dns_resolver.txt for more information.

Signed-off-by: Wang Lei <wang840925@gmail.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Jeff Layton <jlayton@redhat.com>
---

 Documentation/networking/dns_resolver.txt |  146 ++++++++++++++++++
 fs/cifs/Kconfig                           |   17 +-
 fs/cifs/cifsfs.c                          |   13 --
 fs/cifs/dns_resolve.c                     |  229 ++++++-----------------------
 fs/cifs/dns_resolve.h                     |    2 
 include/keys/dns_resolver-type.h          |   23 +++
 include/linux/dns_resolver.h              |   34 ++++
 net/Kconfig                               |    1 
 net/Makefile                              |    1 
 net/dns_resolver/Kconfig                  |   27 +++
 net/dns_resolver/Makefile                 |    7 +
 net/dns_resolver/dns_key.c                |  210 +++++++++++++++++++++++++++
 net/dns_resolver/dns_query.c              |  159 ++++++++++++++++++++
 net/dns_resolver/internal.h               |   44 ++++++
 14 files changed, 708 insertions(+), 205 deletions(-)
 create mode 100644 Documentation/networking/dns_resolver.txt
 create mode 100644 include/keys/dns_resolver-type.h
 create mode 100644 include/linux/dns_resolver.h
 create mode 100644 net/dns_resolver/Kconfig
 create mode 100644 net/dns_resolver/Makefile
 create mode 100644 net/dns_resolver/dns_key.c
 create mode 100644 net/dns_resolver/dns_query.c
 create mode 100644 net/dns_resolver/internal.h

diff --git a/Documentation/networking/dns_resolver.txt b/Documentation/networking/dns_resolver.txt
new file mode 100644
index 0000000..d8e0ce1
--- /dev/null
+++ b/Documentation/networking/dns_resolver.txt
@@ -0,0 +1,146 @@
+			     ===================
+			     DNS Resolver Module
+			     ===================
+
+Contents:
+
+ - Overview.
+ - Compilation.
+ - Setting up.
+ - Usage.
+ - Mechanism.
+ - Debugging.
+
+
+========
+OVERVIEW
+========
+
+The DNS resolver module provides a way for kernel services to make DNS queries
+by way of requesting a key of key type dns_resolver.  These queries are
+upcalled to userspace through /sbin/request-key.
+
+These routines must be supported by userspace tools dns.upcall, cifs.upcall and
+request-key.  It is under development and does not yet provide the full feature
+set.  The features it does support include:
+
+ (*) Implements the dns_resolver key_type to contact userspace.
+
+It does not yet support the following AFS features:
+
+ (*) Dns query support for AFSDB resource record.
+
+This code is extracted from the CIFS filesystem.
+
+
+===========
+COMPILATION
+===========
+
+The module should be enabled by turning on the kernel configuration options:
+
+	CONFIG_DNS_RESOLVER	- tristate "DNS Resolver support"
+
+
+==========
+SETTING UP
+==========
+
+To set up this facility, the /etc/request-key.conf file must be altered so that
+/sbin/request-key can appropriately direct the upcalls.  For example, to handle
+basic dname to IPv4/IPv6 address resolution, the following line should be
+added:
+
+	#OP	TYPE		DESC	CO-INFO	PROGRAM ARG1 ARG2 ARG3 ...
+	#======	============	=======	=======	==========================
+	create	dns_resolver  	*	*	/usr/sbin/cifs.upcall %k
+
+To direct a query for query type 'foo', a line of the following should be added
+before the more general line given above as the first match is the one taken.
+
+	create	dns_resolver  	foo:*	*	/usr/sbin/dns.foo %k
+
+
+
+=====
+USAGE
+=====
+
+To make use of this facility, one of the following functions that are
+implemented in the module can be called after doing:
+
+	#include <linux/dns_resolver.h>
+
+ (1) int dns_query(const char *type, const char *name, size_t namelen,
+		   const char *options, char **_result, time_t *_expiry);
+
+     This is the basic access function.  It looks for a cached DNS query and if
+     it doesn't find it, it upcalls to userspace to make a new DNS query, which
+     may then be cached.  The key description is constructed as a string of the
+     form:
+
+		[<type>:]<name>
+
+     where <type> optionally specifies the particular upcall program to invoke,
+     and thus the type of query to do, and <name> specifies the string to be
+     looked up.  The default query type is a straight hostname to IP address
+     set lookup.
+
+     The name parameter is not required to be a NUL-terminated string, and its
+     length should be given by the namelen argument.
+
+     The options parameter may be NULL or it may be a set of options
+     appropriate to the query type.
+
+     The return value is a string appropriate to the query type.  For instance,
+     for the default query type it is just a list of comma-separated IPv4 and
+     IPv6 addresses.  The caller must free the result.
+
+     The length of the result string is returned on success, and a -ve error
+     code is returned otherwise.  -EKEYREJECTED will be returned if the DNS
+     lookup failed.
+
+     If _expiry is non-NULL, the expiry time (TTL) of the result will be
+     returned also.
+
+
+=========
+MECHANISM
+=========
+
+The dnsresolver module registers a key type called "dns_resolver".  Keys of
+this type are used to transport and cache DNS lookup results from userspace.
+
+When dns_query() is invoked, it calls request_key() to search the local
+keyrings for a cached DNS result.  If that fails to find one, it upcalls to
+userspace to get a new result.
+
+Upcalls to userspace are made through the request_key() upcall vector, and are
+directed by means of configuration lines in /etc/request-key.conf that tell
+/sbin/request-key what program to run to instantiate the key.
+
+The upcall handler program is responsible for querying the DNS, processing the
+result into a form suitable for passing to the keyctl_instantiate_key()
+routine.  This then passes the data to dns_resolver_instantiate() which strips
+off and processes any options included in the data, and then attaches the
+remainder of the string to the key as its payload.
+
+The upcall handler program should set the expiry time on the key to that of the
+lowest TTL of all the records it has extracted a result from.  This means that
+the key will be discarded and recreated when the data it holds has expired.
+
+dns_query() returns a copy of the value attached to the key, or an error if
+that is indicated instead.
+
+See <file:Documentation/keys-request-key.txt> for further information about
+request-key function.
+
+
+=========
+DEBUGGING
+=========
+
+Debugging messages can be turned on dynamically by writing a 1 into the
+following file:
+
+        /sys/module/dnsresolver/parameters/debug
diff --git a/fs/cifs/Kconfig b/fs/cifs/Kconfig
index 5739fd7..57f0aa9 100644
--- a/fs/cifs/Kconfig
+++ b/fs/cifs/Kconfig
@@ -71,14 +71,14 @@ config CIFS_WEAK_PW_HASH
 	  If unsure, say N.
 
 config CIFS_UPCALL
-	  bool "Kerberos/SPNEGO advanced session setup"
-	  depends on CIFS && KEYS
-	  help
-	    Enables an upcall mechanism for CIFS which accesses
-	    userspace helper utilities to provide SPNEGO packaged (RFC 4178)
-	    Kerberos tickets which are needed to mount to certain secure servers
-	    (for which more secure Kerberos authentication is required). If
-	    unsure, say N.
+	bool "Kerberos/SPNEGO advanced session setup"
+	depends on CIFS && KEYS
+	select DNS_RESOLVER
+	help
+	  Enables an upcall mechanism for CIFS which accesses userspace helper
+	  utilities to provide SPNEGO packaged (RFC 4178) Kerberos tickets
+	  which are needed to mount to certain secure servers (for which more
+	  secure Kerberos authentication is required). If unsure, say N.
 
 config CIFS_XATTR
         bool "CIFS extended attributes"
@@ -122,6 +122,7 @@ config CIFS_DEBUG2
 config CIFS_DFS_UPCALL
 	  bool "DFS feature support"
 	  depends on CIFS && KEYS
+	  select DNS_RESOLVER
 	  help
 	    Distributed File System (DFS) support is used to access shares
 	    transparently in an enterprise name space, even if the share
diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c
index 8a2cf12..2a0c892 100644
--- a/fs/cifs/cifsfs.c
+++ b/fs/cifs/cifsfs.c
@@ -45,7 +45,6 @@
 #include "cifs_fs_sb.h"
 #include <linux/mm.h>
 #include <linux/key-type.h>
-#include "dns_resolve.h"
 #include "cifs_spnego.h"
 #include "fscache.h"
 #define CIFS_MAGIC_NUMBER 0xFF534D42	/* the first four bytes of SMB PDUs */
@@ -934,22 +933,13 @@ init_cifs(void)
 	if (rc)
 		goto out_unregister_filesystem;
 #endif
-#ifdef CONFIG_CIFS_DFS_UPCALL
-	rc = cifs_init_dns_resolver();
-	if (rc)
-		goto out_unregister_key_type;
-#endif
 	rc = slow_work_register_user(THIS_MODULE);
 	if (rc)
-		goto out_unregister_resolver_key;
+		goto out_unregister_key_type;
 
 	return 0;
 
- out_unregister_resolver_key:
-#ifdef CONFIG_CIFS_DFS_UPCALL
-	cifs_exit_dns_resolver();
  out_unregister_key_type:
-#endif
 #ifdef CONFIG_CIFS_UPCALL
 	unregister_key_type(&cifs_spnego_key_type);
  out_unregister_filesystem:
@@ -976,7 +966,6 @@ exit_cifs(void)
 	cifs_fscache_unregister();
 #ifdef CONFIG_CIFS_DFS_UPCALL
 	cifs_dfs_release_automount_timer();
-	cifs_exit_dns_resolver();
 #endif
 #ifdef CONFIG_CIFS_UPCALL
 	unregister_key_type(&cifs_spnego_key_type);
diff --git a/fs/cifs/dns_resolve.c b/fs/cifs/dns_resolve.c
index 8de3b98..39a323d 100644
--- a/fs/cifs/dns_resolve.c
+++ b/fs/cifs/dns_resolve.c
@@ -4,6 +4,8 @@
  *   Copyright (c) 2007 Igor Mammedov
  *   Author(s): Igor Mammedov (niallain@gmail.com)
  *              Steve French (sfrench@us.ibm.com)
+ *              Wang Lei (wang840925@gmail.com)
+ *		David Howells (dhowells@redhat.com)
  *
  *   Contains the CIFS DFS upcall routines used for hostname to
  *   IP address translation.
@@ -24,212 +26,73 @@
  */
 
 #include <linux/slab.h>
-#include <linux/keyctl.h>
-#include <linux/key-type.h>
-#include <keys/user-type.h>
+#include <linux/dns_resolver.h>
 #include "dns_resolve.h"
 #include "cifsglob.h"
 #include "cifsproto.h"
 #include "cifs_debug.h"
 
-static const struct cred *dns_resolver_cache;
-
-/* Checks if supplied name is IP address
- * returns:
- * 		1 - name is IP
- * 		0 - name is not IP
- */
-static int
-is_ip(const char *name, int len)
-{
-	struct sockaddr_storage ss;
-
-	return cifs_convert_address((struct sockaddr *)&ss, name, len);
-}
-
-static int
-dns_resolver_instantiate(struct key *key, const void *data,
-		size_t datalen)
-{
-	int rc = 0;
-	char *ip;
-
-	/* make sure this looks like an address */
-	if (!is_ip(data, datalen))
-		return -EINVAL;
-
-	ip = kmalloc(datalen + 1, GFP_KERNEL);
-	if (!ip)
-		return -ENOMEM;
-
-	memcpy(ip, data, datalen);
-	ip[datalen] = '\0';
-
-	key->type_data.x[0] = datalen;
-	key->payload.data = ip;
-
-	return rc;
-}
-
-static void
-dns_resolver_destroy(struct key *key)
-{
-	kfree(key->payload.data);
-}
-
-struct key_type key_type_dns_resolver = {
-	.name        = "dns_resolver",
-	.def_datalen = sizeof(struct in_addr),
-	.describe    = user_describe,
-	.instantiate = dns_resolver_instantiate,
-	.destroy     = dns_resolver_destroy,
-	.match       = user_match,
-};
-
-/* Resolves server name to ip address.
- * input:
- * 	unc - server UNC
- * output:
- * 	*ip_addr - pointer to server ip, caller responcible for freeing it.
- * return the length of the returned string on success
+/**
+ * dns_resolve_server_name_to_ip - Resolve UNC server name to ip address.
+ * @unc: UNC path specifying the server
+ * @ip_addr: Where to return the IP address.
+ *
+ * The IP address will be returned in string form, and the caller is
+ * responsible for freeing it.
+ *
+ * Returns length of result on success, -ve on error.
  */
 int
 dns_resolve_server_name_to_ip(const char *unc, char **ip_addr)
 {
-	const struct cred *saved_cred;
-	int rc = -EAGAIN;
-	struct key *rkey = ERR_PTR(-EAGAIN);
+	struct sockaddr_storage ss;
+	const char *hostname, *sep;
 	char *name;
-	char *data = NULL;
-	int len;
+	int len, rc;
 
 	if (!ip_addr || !unc)
 		return -EINVAL;
 
-	/* search for server name delimiter */
 	len = strlen(unc);
 	if (len < 3) {
 		cFYI(1, "%s: unc is too short: %s", __func__, unc);
 		return -EINVAL;
 	}
-	len -= 2;
-	name = memchr(unc+2, '\\', len);
-	if (!name) {
-		cFYI(1, "%s: probably server name is whole unc: %s",
-					__func__, unc);
-	} else {
-		len = (name - unc) - 2/* leading // */;
-	}
-
-	name = kmalloc(len+1, GFP_KERNEL);
-	if (!name) {
-		rc = -ENOMEM;
-		return rc;
-	}
-	memcpy(name, unc+2, len);
-	name[len] = 0;
-
-	if (is_ip(name, len)) {
-		cFYI(1, "%s: it is IP, skipping dns upcall: %s",
-					__func__, name);
-		data = name;
-		goto skip_upcall;
-	}
 
-	saved_cred = override_creds(dns_resolver_cache);
-	rkey = request_key(&key_type_dns_resolver, name, "");
-	revert_creds(saved_cred);
-	if (!IS_ERR(rkey)) {
-		if (!(rkey->perm & KEY_USR_VIEW)) {
-			down_read(&rkey->sem);
-			rkey->perm |= KEY_USR_VIEW;
-			up_read(&rkey->sem);
-		}
-		len = rkey->type_data.x[0];
-		data = rkey->payload.data;
-	} else {
-		cERROR(1, "%s: unable to resolve: %s", __func__, name);
-		goto out;
-	}
-
-skip_upcall:
-	if (data) {
-		*ip_addr = kmalloc(len + 1, GFP_KERNEL);
-		if (*ip_addr) {
-			memcpy(*ip_addr, data, len + 1);
-			if (!IS_ERR(rkey))
-				cFYI(1, "%s: resolved: %s to %s", __func__,
-							name,
-							*ip_addr
-					);
-			rc = len;
-		} else {
-			rc = -ENOMEM;
-		}
-		if (!IS_ERR(rkey))
-			key_put(rkey);
-	}
+	/* Discount leading slashes for cifs */
+	len -= 2;
+	hostname = unc + 2;
 
-out:
-	kfree(name);
+	/* Search for server name delimiter */
+	sep = memchr(hostname, '\\', len);
+	if (sep)
+		len = sep - unc;
+	else
+		cFYI(1, "%s: probably server name is whole unc: %s",
+		     __func__, unc);
+
+	/* Try to interpret hostname as an IPv4 or IPv6 address */
+	rc = cifs_convert_address((struct sockaddr*)&ss, hostname, len);
+	if (rc > 0)
+		goto name_is_IP_address;
+
+	/* Perform the upcall */
+	rc = dns_query(NULL, hostname, len, NULL, ip_addr, NULL);
+	if (rc < 0)
+		cERROR(1, "%s: unable to resolve: %*.*s",
+		       __func__, len, len, hostname);
+	else
+		cFYI(1, "%s: resolved: %*.*s to %s",
+		     __func__, len, len, hostname, *ip_addr);
 	return rc;
-}
 
-int __init cifs_init_dns_resolver(void)
-{
-	struct cred *cred;
-	struct key *keyring;
-	int ret;
-
-	printk(KERN_NOTICE "Registering the %s key type\n",
-	       key_type_dns_resolver.name);
-
-	/* create an override credential set with a special thread keyring in
-	 * which DNS requests are cached
-	 *
-	 * this is used to prevent malicious redirections from being installed
-	 * with add_key().
-	 */
-	cred = prepare_kernel_cred(NULL);
-	if (!cred)
+name_is_IP_address:
+	name = kmalloc(len + 1, GFP_KERNEL);
+	if (!name)
 		return -ENOMEM;
-
-	keyring = key_alloc(&key_type_keyring, ".dns_resolver", 0, 0, cred,
-			    (KEY_POS_ALL & ~KEY_POS_SETATTR) |
-			    KEY_USR_VIEW | KEY_USR_READ,
-			    KEY_ALLOC_NOT_IN_QUOTA);
-	if (IS_ERR(keyring)) {
-		ret = PTR_ERR(keyring);
-		goto failed_put_cred;
-	}
-
-	ret = key_instantiate_and_link(keyring, NULL, 0, NULL, NULL);
-	if (ret < 0)
-		goto failed_put_key;
-
-	ret = register_key_type(&key_type_dns_resolver);
-	if (ret < 0)
-		goto failed_put_key;
-
-	/* instruct request_key() to use this special keyring as a cache for
-	 * the results it looks up */
-	cred->thread_keyring = keyring;
-	cred->jit_keyring = KEY_REQKEY_DEFL_THREAD_KEYRING;
-	dns_resolver_cache = cred;
+	memcpy(name, hostname, len);
+	name[len] = 0;
+	cFYI(1, "%s: unc is IP, skipping dns upcall: %s", __func__, name);
+	*ip_addr = name;
 	return 0;
-
-failed_put_key:
-	key_put(keyring);
-failed_put_cred:
-	put_cred(cred);
-	return ret;
-}
-
-void __exit cifs_exit_dns_resolver(void)
-{
-	key_revoke(dns_resolver_cache->thread_keyring);
-	unregister_key_type(&key_type_dns_resolver);
-	put_cred(dns_resolver_cache);
-	printk(KERN_NOTICE "Unregistered %s key type\n",
-	       key_type_dns_resolver.name);
 }
diff --git a/fs/cifs/dns_resolve.h b/fs/cifs/dns_resolve.h
index 26b9eaa..d3f5d27 100644
--- a/fs/cifs/dns_resolve.h
+++ b/fs/cifs/dns_resolve.h
@@ -24,8 +24,6 @@
 #define _DNS_RESOLVE_H
 
 #ifdef __KERNEL__
-extern int __init cifs_init_dns_resolver(void);
-extern void __exit cifs_exit_dns_resolver(void);
 extern int dns_resolve_server_name_to_ip(const char *unc, char **ip_addr);
 #endif /* KERNEL */
 
diff --git a/include/keys/dns_resolver-type.h b/include/keys/dns_resolver-type.h
new file mode 100644
index 0000000..9284a19
--- /dev/null
+++ b/include/keys/dns_resolver-type.h
@@ -0,0 +1,23 @@
+/* DNS resolver key type
+ *
+ * Copyright (C) 2010 Wang Lei. All Rights Reserved.
+ * Written by Wang Lei (wang840925@gmail.com)
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ */
+
+#ifndef _KEYS_DNS_RESOLVER_TYPE_H
+#define _KEYS_DNS_RESOLVER_TYPE_H
+
+#include <linux/key-type.h>
+
+extern struct key_type key_type_dns_resolver;
+
+extern int request_dns_resolver_key(const char *description,
+				    const char *callout_info,
+				    char **data);
+
+#endif /* _KEYS_DNS_RESOLVER_TYPE_H */
diff --git a/include/linux/dns_resolver.h b/include/linux/dns_resolver.h
new file mode 100644
index 0000000..cc92268
--- /dev/null
+++ b/include/linux/dns_resolver.h
@@ -0,0 +1,34 @@
+/*
+ *   DNS Resolver upcall management for CIFS DFS and AFS
+ *   Handles host name to IP address resolution and DNS query for AFSDB RR.
+ *
+ *   Copyright (c) International Business Machines  Corp., 2008
+ *   Author(s): Steve French (sfrench@us.ibm.com)
+ *              Wang Lei (wang840925@gmail.com)
+ *
+ *   This library is free software; you can redistribute it and/or modify
+ *   it under the terms of the GNU Lesser General Public License as published
+ *   by the Free Software Foundation; either version 2.1 of the License, or
+ *   (at your option) any later version.
+ *
+ *   This library is distributed in the hope that it will be useful,
+ *   but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See
+ *   the GNU Lesser General Public License for more details.
+ *
+ *   You should have received a copy of the GNU Lesser General Public License
+ *   along with this library; if not, write to the Free Software
+ *   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ */
+
+#ifndef _LINUX_DNS_RESOLVER_H
+#define _LINUX_DNS_RESOLVER_H
+
+#ifdef __KERNEL__
+
+extern int dns_query(const char *type, const char *name, size_t namelen,
+		     const char *options, char **_result, time_t *_expiry);
+
+#endif /* KERNEL */
+
+#endif /* _LINUX_DNS_RESOLVER_H */
diff --git a/net/Kconfig b/net/Kconfig
index 0d68b40..ad358e7 100644
--- a/net/Kconfig
+++ b/net/Kconfig
@@ -203,6 +203,7 @@ source "net/phonet/Kconfig"
 source "net/ieee802154/Kconfig"
 source "net/sched/Kconfig"
 source "net/dcb/Kconfig"
+source "net/dns_resolver/Kconfig"
 
 config RPS
 	boolean
diff --git a/net/Makefile b/net/Makefile
index cb7bdc1..d6030b4 100644
--- a/net/Makefile
+++ b/net/Makefile
@@ -67,3 +67,4 @@ ifeq ($(CONFIG_NET),y)
 obj-$(CONFIG_SYSCTL)		+= sysctl_net.o
 endif
 obj-$(CONFIG_WIMAX)		+= wimax/
+obj-$(CONFIG_DNS_RESOLVER)	+= dns_resolver/
diff --git a/net/dns_resolver/Kconfig b/net/dns_resolver/Kconfig
new file mode 100644
index 0000000..2ec47cb
--- /dev/null
+++ b/net/dns_resolver/Kconfig
@@ -0,0 +1,27 @@
+#
+# Configuration for DNS Resolver
+#
+config DNS_RESOLVER
+	tristate "DNS Resolver support"
+	depends on NET && KEYS
+	help
+	  Saying Y here will include support for the DNS Resolver key type
+	  which can be used to make upcalls to perform DNS lookups in
+	  userspace.
+
+	  DNS Resolver is used to query DNS server for information.  Examples
+	  being resolving a UNC hostname element to an IP address for CIFS or
+	  performing a DNS query for AFSDB records so that AFS can locate a
+	  cell's volume location database servers.
+
+	  DNS Resolver is used by the CIFS and AFS modules, and would support
+	  samba4 later.  DNS Resolver is supported by the userspace upcall
+	  helper "/sbin/dns.resolver" via /etc/request-key.conf.
+
+	  See <file:Documentation/networking/dns_resolver.txt> for further
+	  information.
+
+	  To compile this as a module, choose M here: the module will be called
+	  dnsresolver.
+
+	  If unsure, say N.
diff --git a/net/dns_resolver/Makefile b/net/dns_resolver/Makefile
new file mode 100644
index 0000000..c0ef4e7
--- /dev/null
+++ b/net/dns_resolver/Makefile
@@ -0,0 +1,7 @@
+#
+# Makefile for the Linux DNS Resolver.
+#
+
+obj-$(CONFIG_DNS_RESOLVER) += dns_resolver.o
+
+dns_resolver-objs :=  dns_key.o dns_query.o
diff --git a/net/dns_resolver/dns_key.c b/net/dns_resolver/dns_key.c
new file mode 100644
index 0000000..1b1b411
--- /dev/null
+++ b/net/dns_resolver/dns_key.c
@@ -0,0 +1,210 @@
+/* Key type used to cache DNS lookups made by the kernel
+ *
+ * See Documentation/networking/dns_resolver.txt
+ *
+ *   Copyright (c) 2007 Igor Mammedov
+ *   Author(s): Igor Mammedov (niallain@gmail.com)
+ *              Steve French (sfrench@us.ibm.com)
+ *              Wang Lei (wang840925@gmail.com)
+ *		David Howells (dhowells@redhat.com)
+ *
+ *   This library is free software; you can redistribute it and/or modify
+ *   it under the terms of the GNU Lesser General Public License as published
+ *   by the Free Software Foundation; either version 2.1 of the License, or
+ *   (at your option) any later version.
+ *
+ *   This library is distributed in the hope that it will be useful,
+ *   but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See
+ *   the GNU Lesser General Public License for more details.
+ *
+ *   You should have received a copy of the GNU Lesser General Public License
+ *   along with this library; if not, write to the Free Software
+ *   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ */
+#include <linux/module.h>
+#include <linux/moduleparam.h>
+#include <linux/slab.h>
+#include <linux/string.h>
+#include <linux/kernel.h>
+#include <linux/keyctl.h>
+#include <keys/dns_resolver-type.h>
+#include <keys/user-type.h>
+#include "internal.h"
+
+MODULE_DESCRIPTION("DNS Resolver");
+MODULE_AUTHOR("Wang Lei");
+MODULE_LICENSE("GPL");
+
+unsigned dns_resolver_debug;
+module_param_named(debug, dns_resolver_debug, uint, S_IWUSR | S_IRUGO);
+MODULE_PARM_DESC(debug, "DNS Resolver debugging mask");
+
+const struct cred *dns_resolver_cache;
+
+/*
+ * Instantiate a user defined key for dns_resolver.
+ *
+ * The data must be a NUL-terminated string, with the NUL char accounted in
+ * datalen.
+ *
+ * If the data contains a '#' characters, then we take the clause after each
+ * one to be an option of the form 'key=value'.  The actual data of interest is
+ * the string leading up to the first '#'.  For instance:
+ *
+ *        "ip1,ip2,...#foo=bar"
+ */
+static int
+dns_resolver_instantiate(struct key *key, const void *_data, size_t datalen)
+{
+	struct user_key_payload *upayload;
+	int ret;
+	size_t result_len = 0;
+	const char *data = _data, *opt;
+
+	kenter("%%%d,%s,'%s',%zu",
+	       key->serial, key->description, data, datalen);
+
+	if (datalen <= 1 || !data || data[datalen - 1] != '\0')
+		return -EINVAL;
+	datalen--;
+
+	/* deal with any options embedded in the data */
+	opt = memchr(data, '#', datalen);
+	if (!opt) {
+		kdebug("no options currently supported");
+		return -EINVAL;
+	}
+
+	result_len = datalen;
+	ret = key_payload_reserve(key, result_len);
+	if (ret < 0)
+		return -EINVAL;
+
+	upayload = kmalloc(sizeof(*upayload) + result_len + 1, GFP_KERNEL);
+	if (!upayload) {
+		kleave(" = -ENOMEM");
+		return -ENOMEM;
+	}
+
+	upayload->datalen = result_len;
+	memcpy(upayload->data, data, result_len);
+	upayload->data[result_len] = '\0';
+	rcu_assign_pointer(key->payload.data, upayload);
+
+	kleave(" = 0");
+	return 0;
+}
+
+/*
+ * The description is of the form "[<type>:]<domain_name>"
+ *
+ * The domain name may be a simple name or an absolute domain name (which
+ * should end with a period).  The domain name is case-independent.
+ */
+static int
+dns_resolver_match(const struct key *key, const void *description)
+{
+	int slen, dlen, ret = 0;
+	const char *src = key->description, *dsp = description;
+
+	kenter("%s,%s", src, dsp);
+
+	if (!src || !dsp)
+		goto no_match;
+
+	if (strcasecmp(src, dsp) == 0)
+		goto matched;
+
+	slen = strlen(src);
+	dlen = strlen(dsp);
+	if (slen <= 0 || dlen <= 0)
+		goto no_match;
+	if (src[slen - 1] == '.')
+		slen--;
+	if (dsp[dlen - 1] == '.')
+		dlen--;
+	if (slen != dlen || strncasecmp(src, dsp, slen) != 0)
+		goto no_match;
+
+matched:
+	ret = 1;
+no_match:
+	kleave(" = %d", ret);
+	return ret;
+}
+
+struct key_type key_type_dns_resolver = {
+	.name		= "dns_resolver",
+	.instantiate	= dns_resolver_instantiate,
+	.match		= dns_resolver_match,
+	.revoke		= user_revoke,
+	.destroy	= user_destroy,
+	.describe	= user_describe,
+	.read		= user_read,
+};
+
+static int __init init_dns_resolver(void)
+{
+	struct cred *cred;
+	struct key *keyring;
+	int ret;
+
+	printk(KERN_NOTICE "Registering the %s key type\n",
+	       key_type_dns_resolver.name);
+
+	/* create an override credential set with a special thread keyring in
+	 * which DNS requests are cached
+	 *
+	 * this is used to prevent malicious redirections from being installed
+	 * with add_key().
+	 */
+	cred = prepare_kernel_cred(NULL);
+	if (!cred)
+		return -ENOMEM;
+
+	keyring = key_alloc(&key_type_keyring, ".dns_resolver", 0, 0, cred,
+			    (KEY_POS_ALL & ~KEY_POS_SETATTR) |
+			    KEY_USR_VIEW | KEY_USR_READ,
+			    KEY_ALLOC_NOT_IN_QUOTA);
+	if (IS_ERR(keyring)) {
+		ret = PTR_ERR(keyring);
+		goto failed_put_cred;
+	}
+
+	ret = key_instantiate_and_link(keyring, NULL, 0, NULL, NULL);
+	if (ret < 0)
+		goto failed_put_key;
+
+	ret = register_key_type(&key_type_dns_resolver);
+	if (ret < 0)
+		goto failed_put_key;
+
+	/* instruct request_key() to use this special keyring as a cache for
+	 * the results it looks up */
+	cred->thread_keyring = keyring;
+	cred->jit_keyring = KEY_REQKEY_DEFL_THREAD_KEYRING;
+	dns_resolver_cache = cred;
+
+	kdebug("DNS resolver keyring: %d\n", key_serial(keyring));
+	return 0;
+
+failed_put_key:
+	key_put(keyring);
+failed_put_cred:
+	put_cred(cred);
+	return ret;
+}
+
+static void __exit exit_dns_resolver(void)
+{
+	key_revoke(dns_resolver_cache->thread_keyring);
+	unregister_key_type(&key_type_dns_resolver);
+	put_cred(dns_resolver_cache);
+	printk(KERN_NOTICE "Unregistered %s key type\n",
+	       key_type_dns_resolver.name);
+}
+
+module_init(init_dns_resolver)
+module_exit(exit_dns_resolver)
+MODULE_LICENSE("GPL");
diff --git a/net/dns_resolver/dns_query.c b/net/dns_resolver/dns_query.c
new file mode 100644
index 0000000..6c0cf31
--- /dev/null
+++ b/net/dns_resolver/dns_query.c
@@ -0,0 +1,159 @@
+/* Upcall routine, designed to work as a key type and working through
+ * /sbin/request-key to contact userspace when handling DNS queries.
+ *
+ * See Documentation/networking/dns_resolver.txt
+ *
+ *   Copyright (c) 2007 Igor Mammedov
+ *   Author(s): Igor Mammedov (niallain@gmail.com)
+ *              Steve French (sfrench@us.ibm.com)
+ *              Wang Lei (wang840925@gmail.com)
+ *		David Howells (dhowells@redhat.com)
+ *
+ *   The upcall wrapper used to make an arbitrary DNS query.
+ *
+ *   This function requires the appropriate userspace tool dns.upcall to be
+ *   installed and something like the following lines should be added to the
+ *   /etc/request-key.conf file:
+ *
+ *	create dns_resolver * * /sbin/dns.upcall %k
+ *
+ *   For example to use this module to query AFSDB RR:
+ *
+ *	create dns_resolver afsdb:* * /sbin/dns.afsdb %k
+ *
+ *   This library is free software; you can redistribute it and/or modify
+ *   it under the terms of the GNU Lesser General Public License as published
+ *   by the Free Software Foundation; either version 2.1 of the License, or
+ *   (at your option) any later version.
+ *
+ *   This library is distributed in the hope that it will be useful,
+ *   but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See
+ *   the GNU Lesser General Public License for more details.
+ *
+ *   You should have received a copy of the GNU Lesser General Public License
+ *   along with this library; if not, write to the Free Software
+ *   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ */
+
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/dns_resolver.h>
+#include <keys/dns_resolver-type.h>
+#include <keys/user-type.h>
+
+#include "internal.h"
+
+/*
+ * dns_query - Query the DNS
+ * @type: Query type (or NULL for straight host->IP lookup)
+ * @name: Name to look up
+ * @namelen: Length of name
+ * @options: Request options (or NULL if no options)
+ * @_result: Where to place the returned data.
+ * @_expiry: Where to store the result expiry time (or NULL)
+ *
+ * The data will be returned in the pointer at *result, and the caller is
+ * responsible for freeing it.
+ *
+ * The description should be of the form "[<query_type>:]<domain_name>", and
+ * the options need to be appropriate for the query type requested.  If no
+ * query_type is given, then the query is a straight hostname to IP address
+ * lookup.
+ *
+ * The DNS resolution lookup is performed by upcalling to userspace by way of
+ * requesting a key of type dns_resolver.
+ *
+ * Returns the size of the result on success, -ve error code otherwise.
+ */
+int dns_query(const char *type, const char *name, size_t namelen,
+	      const char *options, char **_result, time_t *_expiry)
+{
+	struct key *rkey;
+	struct user_key_payload *upayload;
+	const struct cred *saved_cred;
+	size_t typelen, desclen;
+	char *desc, *cp;
+	int ret, len;
+
+	kenter("%s,%*.*s,%zu,%s",
+	       type, (int)namelen, (int)namelen, name, namelen, options);
+
+	if (!name || namelen == 0 || !_result)
+		return -EINVAL;
+
+	/* construct the query key description as "[<type>:]<name>" */
+	typelen = 0;
+	desclen = 0;
+	if (type) {
+		typelen = strlen(type);
+		if (typelen < 1)
+			return -EINVAL;
+		desclen += typelen + 1;
+	}
+
+	if (!namelen)
+		namelen = strlen(name);
+	if (namelen < 3)
+		return -EINVAL;
+	desclen += namelen + 1;
+
+	desc = kmalloc(desclen, GFP_KERNEL);
+	if (!desc)
+		return -ENOMEM;
+
+	cp = desc;
+	if (type) {
+		memcpy(cp, type, typelen);
+		cp += typelen;
+		*cp++ = ':';
+	}
+	memcpy(cp, name, namelen);
+	cp += namelen;
+	*cp = '\0';
+
+	if (!options)
+		options = "";
+	kdebug("call request_key(,%s,%s)", desc, options);
+
+	/* make the upcall, using special credentials to prevent the use of
+	 * add_key() to preinstall malicious redirections
+	 */
+	saved_cred = override_creds(dns_resolver_cache);
+	rkey = request_key(&key_type_dns_resolver, desc, options);
+	revert_creds(saved_cred);
+	kfree(desc);
+	if (IS_ERR(rkey)) {
+		ret = PTR_ERR(rkey);
+		goto out;
+	}
+
+	down_read(&rkey->sem);
+	rkey->perm |= KEY_USR_VIEW;
+
+	ret = key_validate(rkey);
+	if (ret < 0)
+		goto put;
+
+	upayload = rcu_dereference_protected(rkey->payload.data,
+					     lockdep_is_held(&rkey->sem));
+	len = upayload->datalen;
+
+	ret = -ENOMEM;
+	*_result = kmalloc(len + 1, GFP_KERNEL);
+	if (!*_result)
+		goto put;
+
+	memcpy(*_result, upayload->data, len + 1);
+	if (_expiry)
+		*_expiry = rkey->expiry;
+
+	ret = len;
+put:
+	up_read(&rkey->sem);
+	key_put(rkey);
+out:
+	kleave(" = %d", ret);
+	return ret;
+}
+EXPORT_SYMBOL(dns_query);
diff --git a/net/dns_resolver/internal.h b/net/dns_resolver/internal.h
new file mode 100644
index 0000000..189ca9e
--- /dev/null
+++ b/net/dns_resolver/internal.h
@@ -0,0 +1,44 @@
+/*
+ *   Copyright (c) 2010 Wang Lei
+ *   Author(s): Wang Lei (wang840925@gmail.com). All Rights Reserved.
+ *
+ *   Internal DNS Rsolver stuff
+ *
+ *   This library is free software; you can redistribute it and/or modify
+ *   it under the terms of the GNU Lesser General Public License as published
+ *   by the Free Software Foundation; either version 2.1 of the License, or
+ *   (at your option) any later version.
+ *
+ *   This library is distributed in the hope that it will be useful,
+ *   but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See
+ *   the GNU Lesser General Public License for more details.
+ *
+ *   You should have received a copy of the GNU Lesser General Public License
+ *   along with this library; if not, write to the Free Software
+ *   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ */
+
+#include <linux/compiler.h>
+#include <linux/kernel.h>
+#include <linux/sched.h>
+
+/*
+ * dns_key.c
+ */
+extern const struct cred *dns_resolver_cache;
+
+/*
+ * debug tracing
+ */
+extern unsigned dns_resolver_debug;
+
+#define	kdebug(FMT, ...)				\
+do {							\
+	if (unlikely(dns_resolver_debug))		\
+		printk(KERN_DEBUG "[%-6.6s] "FMT"\n",	\
+		       current->comm, ##__VA_ARGS__);	\
+} while (0)
+
+#define kenter(FMT, ...) kdebug("==> %s("FMT")", __func__, ##__VA_ARGS__)
+#define kleave(FMT, ...) kdebug("<== %s()"FMT"", __func__, ##__VA_ARGS__)

[PATCH 6/6] DNS: Make AFS go to the DNS for AFSDB records for unknown cells

[David Howells]

From: Wang Lei <wang840925@gmail.com>

Add DNS query support for AFS so that it can get the IP addresses of Volume
Location servers from the DNS using an AFSDB record.

This requires userspace support.  /etc/request-key.conf must be configured to
invoke a helper for dns_resolver type keys with a subtype of "afsdb:" in the
description.

Signed-off-by: Wang Lei <wang840925@gmail.com>
Signed-off-by: David Howells <dhowells@redhat.com>
---

 fs/afs/Kconfig |    1 +
 fs/afs/cell.c  |   40 ++++++++++++++++++++++++++++++----------
 2 files changed, 31 insertions(+), 10 deletions(-)

diff --git a/fs/afs/Kconfig b/fs/afs/Kconfig
index 5c4e61d..8f975f2 100644
--- a/fs/afs/Kconfig
+++ b/fs/afs/Kconfig
@@ -2,6 +2,7 @@ config AFS_FS
 	tristate "Andrew File System support (AFS) (EXPERIMENTAL)"
 	depends on INET && EXPERIMENTAL
 	select AF_RXRPC
+	select DNS_RESOLVER
 	help
 	  If you say Y here, you will get an experimental Andrew File System
 	  driver. It currently only supports unsecured read-only AFS access.
diff --git a/fs/afs/cell.c b/fs/afs/cell.c
index e19c13f..ffea35c 100644
--- a/fs/afs/cell.c
+++ b/fs/afs/cell.c
@@ -13,6 +13,7 @@
 #include <linux/slab.h>
 #include <linux/key.h>
 #include <linux/ctype.h>
+#include <linux/dns_resolver.h>
 #include <linux/sched.h>
 #include <keys/rxrpc-type.h>
 #include "internal.h"
@@ -36,6 +37,8 @@ static struct afs_cell *afs_cell_alloc(const char *name, char *vllist)
 	struct key *key;
 	size_t namelen;
 	char keyname[4 + AFS_MAXCELLNAME + 1], *cp, *dp, *next;
+	char  *dvllist = NULL, *_vllist = NULL;
+	char  delimiter = ':';
 	int ret;
 
 	_enter("%s,%s", name, vllist);
@@ -43,8 +46,10 @@ static struct afs_cell *afs_cell_alloc(const char *name, char *vllist)
 	BUG_ON(!name); /* TODO: want to look up "this cell" in the cache */
 
 	namelen = strlen(name);
-	if (namelen > AFS_MAXCELLNAME)
+	if (namelen > AFS_MAXCELLNAME) {
+		_leave(" = -ENAMETOOLONG");
 		return ERR_PTR(-ENAMETOOLONG);
+	}
 
 	/* allocate and initialise a cell record */
 	cell = kzalloc(sizeof(struct afs_cell) + namelen + 1, GFP_KERNEL);
@@ -64,15 +69,31 @@ static struct afs_cell *afs_cell_alloc(const char *name, char *vllist)
 	INIT_LIST_HEAD(&cell->vl_list);
 	spin_lock_init(&cell->vl_lock);
 
+	/* if the ip address is invalid, try dns query */
+	if (!vllist || strlen(vllist) < 7) {
+		ret = dns_query("afsdb", name, namelen, "ipv4", &dvllist, NULL);
+		if (ret < 0) {
+			_leave(" = %d", ret);
+			return ERR_PTR(ret);
+		}
+		_vllist = dvllist;
+
+		/* change the delimiter for user-space reply */
+		delimiter = ',';
+
+	} else {
+		_vllist = vllist;
+	}
+
 	/* fill in the VL server list from the rest of the string */
 	do {
 		unsigned a, b, c, d;
 
-		next = strchr(vllist, ':');
+		next = strchr(_vllist, delimiter);
 		if (next)
 			*next++ = 0;
 
-		if (sscanf(vllist, "%u.%u.%u.%u", &a, &b, &c, &d) != 4)
+		if (sscanf(_vllist, "%u.%u.%u.%u", &a, &b, &c, &d) != 4)
 			goto bad_address;
 
 		if (a > 255 || b > 255 || c > 255 || d > 255)
@@ -81,7 +102,7 @@ static struct afs_cell *afs_cell_alloc(const char *name, char *vllist)
 		cell->vl_addrs[cell->vl_naddrs++].s_addr =
 			htonl((a << 24) | (b << 16) | (c << 8) | d);
 
-	} while (cell->vl_naddrs < AFS_CELL_MAX_ADDRS && (vllist = next));
+	} while (cell->vl_naddrs < AFS_CELL_MAX_ADDRS && (_vllist = next));
 
 	/* create a key to represent an anonymous user */
 	memcpy(keyname, "afs@", 4);
@@ -110,6 +131,7 @@ bad_address:
 	ret = -EINVAL;
 error:
 	key_put(cell->anonymous_key);
+	kfree(dvllist);
 	kfree(cell);
 	_leave(" = %d", ret);
 	return ERR_PTR(ret);
@@ -201,14 +223,12 @@ int afs_cell_init(char *rootcell)
 	}
 
 	cp = strchr(rootcell, ':');
-	if (!cp) {
-		printk(KERN_ERR "kAFS: no VL server IP addresses specified\n");
-		_leave(" = -EINVAL");
-		return -EINVAL;
-	}
+	if (!cp)
+		_debug("kAFS: no VL server IP addresses specified");
+	else
+		*cp++ = 0;
 
 	/* allocate a cell record for the root cell */
-	*cp++ = 0;
 	new_root = afs_cell_create(rootcell, cp);
 	if (IS_ERR(new_root)) {
 		_leave(" = %ld", PTR_ERR(new_root));

[PATCH 5/6] DNS: Implement option parsing on dns_resolver results

[David Howells]

From: Wang Lei <wang840925-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>

When the dns_resolver upcall program packages results and instantiates its key
with them, the offered data may have a number of options appended to it.  Each
option is of the form:

	#key=value

This implements an option by which the key's expiry time can be set from the
DNS TTL datum:

	#expiry=<nnn>

where <nnn> is a time_t value.

Signed-off-by: Wang Lei <wang840925-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
Signed-off-by: David Howells <dhowells-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
---

 net/dns_resolver/dns_key.c |   85 ++++++++++++++++++++++++++++++++++++++++----
 1 files changed, 78 insertions(+), 7 deletions(-)

diff --git a/net/dns_resolver/dns_key.c b/net/dns_resolver/dns_key.c
index 1b1b411..02c7336 100644
--- a/net/dns_resolver/dns_key.c
+++ b/net/dns_resolver/dns_key.c
@@ -42,6 +42,8 @@ MODULE_PARM_DESC(debug, "DNS Resolver debugging mask");
 
 const struct cred *dns_resolver_cache;
 
+#define	DNS_EXPIRY_OPTION	"expiry_time"
+
 /*
  * Instantiate a user defined key for dns_resolver.
  *
@@ -50,17 +52,26 @@ const struct cred *dns_resolver_cache;
  *
  * If the data contains a '#' characters, then we take the clause after each
  * one to be an option of the form 'key=value'.  The actual data of interest is
- * the string leading up to the first '#'.  For instance:
+ * the string leading up to the first '#'.
+ *
+ * The only option currently supported is the expiry time of the key, which can
+ * be set from the TTL field of the DNS record.  The value should be a time_t
+ * time.
+ *
+ * For instance:
+ *
+ *        "ip1,ip2,...#expiry_time=123"
  *
- *        "ip1,ip2,...#foo=bar"
+ * the expiry time of the data is 123 and the data starts after '#'.
  */
 static int
 dns_resolver_instantiate(struct key *key, const void *_data, size_t datalen)
 {
 	struct user_key_payload *upayload;
+	unsigned long expiry = 0;
 	int ret;
 	size_t result_len = 0;
-	const char *data = _data, *opt;
+	const char *data = _data, *end, *opt;
 
 	kenter("%%%d,%s,'%s',%zu",
 	       key->serial, key->description, data, datalen);
@@ -70,13 +81,65 @@ dns_resolver_instantiate(struct key *key, const void *_data, size_t datalen)
 	datalen--;
 
 	/* deal with any options embedded in the data */
-	opt = memchr(data, '#', datalen);
+	end = data + datalen - 1;
+	opt = memchr(data, '#', datalen - 1);
 	if (!opt) {
-		kdebug("no options currently supported");
-		return -EINVAL;
+		/* no options: the entire data is the result */
+		kdebug("no options");
+		result_len = datalen - 1;
+	} else {
+		result_len = opt - data;
+		opt++;
+		kdebug("options: '%s'", opt);
+		do {
+			const char *next_opt, *eq;
+			int opt_len, opt_nlen, opt_vlen, tmp;
+
+			next_opt = memchr(opt, '#', end - opt) ?: end;
+			opt_len = next_opt - opt;
+			if (!opt_len) {
+				printk(KERN_WARNING
+				       "Empty option to dnsresolver key %d\n",
+				       key->serial);
+				return -EINVAL;
+			}
+
+			eq = memchr(opt, '=', opt_len) ?: end;
+			opt_nlen = eq - opt;
+			eq++;
+			opt_vlen = next_opt - eq; /* will be -1 if no value */
+
+			tmp = opt_vlen >= 0 ? opt_vlen : 0;
+			kdebug("option '%*.*s' val '%*.*s'",
+			       opt_nlen, opt_nlen, opt, tmp, tmp, eq);
+
+			/* see if it's the expiry time */
+			if (opt_nlen == sizeof(DNS_EXPIRY_OPTION) - 1 &&
+			    memcmp(opt, DNS_EXPIRY_OPTION, opt_nlen) == 0) {
+				kdebug("expiry time option");
+				if (opt_vlen <= 0)
+					goto bad_option_value;
+
+				ret = strict_strtoul(eq, 10, &expiry);
+				if (ret < 0)
+					goto bad_option_value;
+				kdebug("expiry time = %lu", expiry);
+				goto next_option;
+			}
+
+		bad_option_value:
+			printk(KERN_WARNING
+			       "Option '%*.*s' to dnsresolver key %d:"
+			       " bad/missing value\n",
+			       opt_nlen, opt_nlen, opt, key->serial);
+			return -EINVAL;
+
+		next_option:
+			opt = next_opt + 1;
+		} while (opt < end);
 	}
 
-	result_len = datalen;
+	kdebug("store result");
 	ret = key_payload_reserve(key, result_len);
 	if (ret < 0)
 		return -EINVAL;
@@ -87,11 +150,19 @@ dns_resolver_instantiate(struct key *key, const void *_data, size_t datalen)
 		return -ENOMEM;
 	}
 
+	/* attach the data */
 	upayload->datalen = result_len;
 	memcpy(upayload->data, data, result_len);
 	upayload->data[result_len] = '\0';
 	rcu_assign_pointer(key->payload.data, upayload);
 
+	/* if we were given an expiry time, then try to apply it */
+	kdebug("expiry %lu [%lu]", expiry, key->expiry);
+	if (expiry && (key->expiry == 0 || expiry < key->expiry)) {
+		kdebug("set expiry to %ld hence", expiry - get_seconds());
+		key->expiry = expiry;
+	}
+
 	kleave(" = 0");
 	return 0;
 }

Re: [PATCH 1/6] KEYS: Authorise keyctl_set_timeout() on a key if we have its authorisation key

[David Howells]

Btw, these are based on the linux-cifs GIT tree.

David