[PATCH v5 08/14] module: Move authentication logic into dedicated new file

["Thomas Weißschuh" <linux@weissschuh.net>]

The module authentication functionality will also be used by the
hash-based module authentication. To make it usable even if
CONFIG_MODULE_SIG is disabled, move it to a new file.

Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
---
 kernel/module/auth.c     | 85 +++++++++++++++++++++++++++++++++++++++++++++
 kernel/module/internal.h | 14 ++++++--
 kernel/module/main.c     |  6 ++--
 kernel/module/signing.c  | 90 ++----------------------------------------------
 4 files changed, 103 insertions(+), 92 deletions(-)

diff --git a/kernel/module/auth.c b/kernel/module/auth.c
index 956ac63d9d33..831a13eb0c9b 100644
--- a/kernel/module/auth.c
+++ b/kernel/module/auth.c
@@ -5,10 +5,16 @@
  * Written by David Howells (dhowells@redhat.com)
  */
 
+#include <linux/errno.h>
 #include <linux/export.h>
 #include <linux/module.h>
+#include <linux/module_signature.h>
 #include <linux/moduleparam.h>
+#include <linux/security.h>
+#include <linux/string.h>
 #include <linux/types.h>
+#include <uapi/linux/module.h>
+#include "internal.h"
 
 #undef MODULE_PARAM_PREFIX
 #define MODULE_PARAM_PREFIX "module."
@@ -30,3 +36,82 @@ void set_module_sig_enforced(void)
 {
 	sig_enforce = true;
 }
+
+static int mod_verify_sig(const void *mod, struct load_info *info)
+{
+	struct module_signature ms;
+	size_t sig_len, modlen = info->len;
+	int ret;
+
+	if (modlen <= sizeof(ms))
+		return -EBADMSG;
+
+	memcpy(&ms, mod + (modlen - sizeof(ms)), sizeof(ms));
+
+	ret = mod_check_sig(&ms, modlen, "module");
+	if (ret)
+		return ret;
+
+	sig_len = be32_to_cpu(ms.sig_len);
+	modlen -= sig_len + sizeof(ms);
+	info->len = modlen;
+
+	return module_sig_check(mod, modlen, mod + modlen, sig_len);
+}
+
+int module_auth_check(struct load_info *info, int flags)
+{
+	int err = -ENODATA;
+	const unsigned long markerlen = sizeof(MODULE_SIGNATURE_MARKER) - 1;
+	const char *reason;
+	const void *mod = info->hdr;
+	bool mangled_module = flags & (MODULE_INIT_IGNORE_MODVERSIONS |
+				       MODULE_INIT_IGNORE_VERMAGIC);
+	/*
+	 * Do not allow mangled modules as a module with version information
+	 * removed is no longer the module that was signed.
+	 */
+	if (!mangled_module &&
+	    info->len > markerlen &&
+	    memcmp(mod + info->len - markerlen, MODULE_SIGNATURE_MARKER, markerlen) == 0) {
+		/* We truncate the module to discard the signature */
+		info->len -= markerlen;
+		err = mod_verify_sig(mod, info);
+		if (!err) {
+			info->auth_ok = true;
+			return 0;
+		}
+	}
+
+	/*
+	 * We don't permit modules to be loaded into the trusted kernels
+	 * without a valid signature on them, but if we're not enforcing,
+	 * certain errors are non-fatal.
+	 */
+	switch (err) {
+	case -ENODATA:
+		reason = "unsigned module";
+		break;
+	case -ENOPKG:
+		reason = "module with unsupported crypto";
+		break;
+	case -ENOKEY:
+		reason = "module with unavailable key";
+		break;
+
+	default:
+		/*
+		 * All other errors are fatal, including lack of memory,
+		 * unparseable signatures, and signature check failures --
+		 * even if signatures aren't required.
+		 */
+		return err;
+	}
+
+	if (is_module_sig_enforced()) {
+		pr_notice("Loading of %s is rejected\n", reason);
+		return -EKEYREJECTED;
+	}
+
+	return security_locked_down(LOCKDOWN_MODULE_SIGNATURE);
+}
diff --git a/kernel/module/internal.h b/kernel/module/internal.h
index f8f425b167f1..d923e31a5d8e 100644
--- a/kernel/module/internal.h
+++ b/kernel/module/internal.h
@@ -336,14 +336,24 @@ void module_mark_ro_after_init(const Elf_Ehdr *hdr, Elf_Shdr *sechdrs,
 			       const char *secstrings);
 
 #ifdef CONFIG_MODULE_SIG
-int module_sig_check(struct load_info *info, int flags);
+int module_sig_check(const void *mod, size_t mod_len, const void *sig, size_t sig_len);
 #else /* !CONFIG_MODULE_SIG */
-static inline int module_sig_check(struct load_info *info, int flags)
+static inline int module_sig_check(const void *mod, size_t mod_len,
+				   const void *sig, size_t sig_len)
 {
 	return 0;
 }
 #endif /* !CONFIG_MODULE_SIG */
 
+#ifdef CONFIG_MODULE_AUTH
+int module_auth_check(struct load_info *info, int flags);
+#else /* !CONFIG_MODULE_AUTH */
+static inline int module_auth_check(struct load_info *info, int flags)
+{
+	return 0;
+}
+#endif /* !CONFIG_MODULE_AUTH */
+
 #ifdef CONFIG_DEBUG_KMEMLEAK
 void kmemleak_load_module(const struct module *mod, const struct load_info *info);
 #else /* !CONFIG_DEBUG_KMEMLEAK */
diff --git a/kernel/module/main.c b/kernel/module/main.c
index cd8a74df117e..55a010383a8d 100644
--- a/kernel/module/main.c
+++ b/kernel/module/main.c
@@ -3428,8 +3428,8 @@ static int load_module(struct load_info *info, const char __user *uargs,
 	char *after_dashes;
 
 	/*
-	 * Do the signature check (if any) first. All that
-	 * the signature check needs is info->len, it does
+	 * Do the authentication checks (if any) first. All that
+	 * the authentication checks need is info->len, it does
 	 * not need any of the section info. That can be
 	 * set up later. This will minimize the chances
 	 * of a corrupt module causing problems before
@@ -3439,7 +3439,7 @@ static int load_module(struct load_info *info, const char __user *uargs,
 	 * off the sig length at the end of the module, making
 	 * checks against info->len more correct.
 	 */
-	err = module_sig_check(info, flags);
+	err = module_auth_check(info, flags);
 	if (err)
 		goto free_copy;
 
diff --git a/kernel/module/signing.c b/kernel/module/signing.c
index 07a786723221..a49317e3c66f 100644
--- a/kernel/module/signing.c
+++ b/kernel/module/signing.c
@@ -5,98 +5,14 @@
  * Written by David Howells (dhowells@redhat.com)
  */
 
-#include <linux/kernel.h>
-#include <linux/errno.h>
-#include <linux/module.h>
-#include <linux/module_signature.h>
-#include <linux/string.h>
+#include <linux/types.h>
 #include <linux/verification.h>
-#include <linux/security.h>
-#include <crypto/public_key.h>
-#include <uapi/linux/module.h>
 #include "internal.h"
 
-/*
- * Verify the signature on a module.
- */
-static int mod_verify_sig(const void *mod, struct load_info *info)
+int module_sig_check(const void *mod, size_t mod_len, const void *sig, size_t sig_len)
 {
-	struct module_signature ms;
-	size_t sig_len, modlen = info->len;
-	int ret;
-
-	if (modlen <= sizeof(ms))
-		return -EBADMSG;
-
-	memcpy(&ms, mod + (modlen - sizeof(ms)), sizeof(ms));
-
-	ret = mod_check_sig(&ms, modlen, "module");
-	if (ret)
-		return ret;
-
-	sig_len = be32_to_cpu(ms.sig_len);
-	modlen -= sig_len + sizeof(ms);
-	info->len = modlen;
-
-	return verify_pkcs7_signature(mod, modlen, mod + modlen, sig_len,
+	return verify_pkcs7_signature(mod, mod_len, sig, sig_len,
 				      VERIFY_USE_SECONDARY_KEYRING,
 				      VERIFYING_MODULE_SIGNATURE,
 				      NULL, NULL);
 }
-
-int module_sig_check(struct load_info *info, int flags)
-{
-	int err = -ENODATA;
-	const unsigned long markerlen = sizeof(MODULE_SIGNATURE_MARKER) - 1;
-	const char *reason;
-	const void *mod = info->hdr;
-	bool mangled_module = flags & (MODULE_INIT_IGNORE_MODVERSIONS |
-				       MODULE_INIT_IGNORE_VERMAGIC);
-	/*
-	 * Do not allow mangled modules as a module with version information
-	 * removed is no longer the module that was signed.
-	 */
-	if (!mangled_module &&
-	    info->len > markerlen &&
-	    memcmp(mod + info->len - markerlen, MODULE_SIGNATURE_MARKER, markerlen) == 0) {
-		/* We truncate the module to discard the signature */
-		info->len -= markerlen;
-		err = mod_verify_sig(mod, info);
-		if (!err) {
-			info->auth_ok = true;
-			return 0;
-		}
-	}
-
-	/*
-	 * We don't permit modules to be loaded into the trusted kernels
-	 * without a valid signature on them, but if we're not enforcing,
-	 * certain errors are non-fatal.
-	 */
-	switch (err) {
-	case -ENODATA:
-		reason = "unsigned module";
-		break;
-	case -ENOPKG:
-		reason = "module with unsupported crypto";
-		break;
-	case -ENOKEY:
-		reason = "module with unavailable key";
-		break;
-
-	default:
-		/*
-		 * All other errors are fatal, including lack of memory,
-		 * unparseable signatures, and signature check failures --
-		 * even if signatures aren't required.
-		 */
-		return err;
-	}
-
-	if (is_module_sig_enforced()) {
-		pr_notice("Loading of %s is rejected\n", reason);
-		return -EKEYREJECTED;
-	}
-
-	return security_locked_down(LOCKDOWN_MODULE_SIGNATURE);
-}

-- 
2.54.0