[PATCH 2/4] ima: export new IMA functions for signature verification

Vivek Goyal
2013-03-15T20:36:23Z

Export IMA functions so that other subsystems can use IMA for file
signature verification.

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
---
include/linux/ima.h | 24 +++++++++++++++++++-
include/linux/integrity.h | 7 ++++++
security/integrity/ima/ima_api.c | 16 +++++++++++++
security/integrity/ima/ima_appraise.c | 39 +++++++++++++++++++++++++++++++++
4 files changed, 85 insertions(+), 1 deletions(-)

diff --git a/include/linux/ima.h b/include/linux/ima.h
index 86c361e..846e784 100644
--- a/include/linux/ima.h
+++ b/include/linux/ima.h
@@ -11,6 +11,7 @@
#define _LINUX_IMA_H

#include <linux/fs.h>
+#include <linux/integrity.h>
struct linux_binprm;

#ifdef CONFIG_IMA
@@ -19,7 +20,8 @@ extern int ima_file_check(struct file *file, int mask);
extern void ima_file_free(struct file *file);
extern int ima_file_mmap(struct file *file, unsigned long prot);
extern int ima_module_check(struct file *file);
-
+extern int ima_file_signature_alloc(struct file *file, char **sig);
+extern int ima_signature_type(char *sig, enum evm_ima_xattr_type *sig_type);
#else
static inline int ima_bprm_check(struct linux_binprm *bprm)
{
@@ -46,6 +48,18 @@ static inline int ima_module_check(struct file *file)
return 0;
}

+static inline int ima_file_signature_alloc(struct file *file, char **sig)
+{
+ return -EOPNOTSUPP;
+}
+
+static inline int ima_signature_type(char *sig,
+ enum evm_ima_xattr_type *sig_type)
+{
+ return -EOPNOTSUPP;
+}
+
+
#endif /* CONFIG_IMA_H */

#ifdef CONFIG_IMA_APPRAISE
@@ -53,6 +67,7 @@ extern void ima_inode_post_setattr(struct dentry *dentry);
extern int ima_inode_setxattr(struct dentry *dentry, const char *xattr_name,
const void *xattr_value, size_t xattr_value_len);
extern int ima_inode_removexattr(struct dentry *dentry, const char *xattr_name);
+extern int ima_appraise_file(struct file *file, char *sig, unsigned int siglen);
#else
static inline void ima_inode_post_setattr(struct dentry *dentry)
{
@@ -72,5 +87,12 @@ static inline int ima_inode_removexattr(struct dentry *dentry,
{
return 0;
}
+
+static inline int ima_appraise_file(struct file *file, char *sig,
+ unsigned int siglen)
+{
+ return -EOPNOTSUPP;
+}
+
#endif /* CONFIG_IMA_APPRAISE_H */
#endif /* _LINUX_IMA_H */
diff --git a/include/linux/integrity.h b/include/linux/integrity.h
index 66c5fe9..0aa1b42 100644
--- a/include/linux/integrity.h
+++ b/include/linux/integrity.h
@@ -20,6 +20,13 @@ enum integrity_status {
INTEGRITY_UNKNOWN,
};

+enum evm_ima_xattr_type {
+ IMA_XATTR_DIGEST = 0x01,
+ EVM_XATTR_HMAC,
+ EVM_IMA_XATTR_DIGSIG,
+ EVM_IMA_XATTR_DIGSIG_ASYMMETRIC,
+};
+
/* List of EVM protected security xattrs */
#ifdef CONFIG_INTEGRITY
extern struct integrity_iint_cache *integrity_inode_get(struct inode *inode);
diff --git a/security/integrity/ima/ima_api.c b/security/integrity/ima/ima_api.c
index 1c03e8f..cb23538 100644
--- a/security/integrity/ima/ima_api.c
+++ b/security/integrity/ima/ima_api.c
@@ -254,3 +254,19 @@ const char *ima_d_path(struct path *path, char **pathbuf)
}
return pathname;
}
+
+/*
+ * Get ima signature.
+ */
+int ima_file_signature_alloc(struct file *file, char **sig)
+{
+ struct dentry *dentry = file->f_dentry;
+
+ return vfs_getxattr_alloc(dentry, XATTR_NAME_IMA, sig, 0, GFP_NOFS);
+}
+
+int ima_signature_type(char *sig, enum evm_ima_xattr_type *sig_type)
+{
+ *sig_type = ((struct evm_ima_xattr_data *)sig)->type;
+ return 0;
+}
diff --git a/security/integrity/ima/ima_appraise.c b/security/integrity/ima/ima_appraise.c
index 9bc0723..4e44874 100644
--- a/security/integrity/ima/ima_appraise.c
+++ b/security/integrity/ima/ima_appraise.c
@@ -108,6 +108,45 @@ static void ima_cache_flags(struct integrity_iint_cache *iint, int func)
}

/*
+ * Appraise a file with a given signature
+ * sig: signature
+ * siglen: length of signature
+ *
+ * Returns 0 on successful appraisal, error otherwise.
+ */
+int ima_appraise_file(struct file *file, char *sig, unsigned int siglen)
+{
+ struct evm_ima_xattr_data *xattr_value;
+ int ret = 0, rc;
+ /* FIX Me. retrieve hash algo from sig */
+ char digest[SHA1_DIGEST_SIZE];
+
+ xattr_value = (struct evm_ima_xattr_data*) sig;
+ ret = ima_calc_file_hash(file, digest);
+ if (ret)
+ return ret;
+
+ switch (xattr_value->type) {
+ case IMA_XATTR_DIGEST:
+ rc = memcmp(xattr_value->digest, digest, SHA1_DIGEST_SIZE);
+ if (!rc)
+ ret = -EKEYREJECTED;
+ break;
+ case EVM_IMA_XATTR_DIGSIG:
+ case EVM_IMA_XATTR_DIGSIG_ASYMMETRIC:
+ return integrity_digsig_verify(xattr_value->type,
+ INTEGRITY_KEYRING_IMA,
+ xattr_value->digest, siglen - 1,
+ digest, SHA1_DIGEST_SIZE);
+ default:
+ ret = -EBADMSG;
+ break;
+ }
+
+ return ret;
+}
+
+/*
* ima_appraise_measurement - appraise file measurement
*
* Call evm_verifyxattr() to verify the integrity of 'security.ima'.
--
1.7.7.6