[PATCH v4 13/17] module: Report signature type to users

[Thomas Weißschuh]

The upcoming CONFIG_MODULE_HASHES will introduce a signature type.
This needs to be handled by callers differently than PKCS7 signatures.

Report the signature type to the caller and let them verify it.

Signed-off-by: Thomas Weißschuh <linux at weissschuh.net>
---
 include/linux/module_signature.h    |  2 +-
 kernel/module/main.c                |  9 +++++++--
 kernel/module_signature.c           | 14 ++++----------
 security/integrity/ima/ima_modsig.c |  8 +++++++-
 4 files changed, 19 insertions(+), 14 deletions(-)

diff --git a/include/linux/module_signature.h b/include/linux/module_signature.h
index 186a55effa30..a45ce3b24403 100644
--- a/include/linux/module_signature.h
+++ b/include/linux/module_signature.h
@@ -41,6 +41,6 @@ struct module_signature {
 };
 
 int mod_split_sig(const void *buf, size_t *buf_len, bool mangled,
-		  size_t *sig_len, const u8 **sig, const char *name);
+		  enum pkey_id_type *sig_type, size_t *sig_len, const u8 **sig, const char *name);
 
 #endif /* _LINUX_MODULE_SIGNATURE_H */
diff --git a/kernel/module/main.c b/kernel/module/main.c
index d65bc300a78c..2a28a0ece809 100644
--- a/kernel/module/main.c
+++ b/kernel/module/main.c
@@ -3348,19 +3348,24 @@ static int module_integrity_check(struct load_info *info, int flags)
 {
 	bool mangled_module = flags & (MODULE_INIT_IGNORE_MODVERSIONS |
 				       MODULE_INIT_IGNORE_VERMAGIC);
+	enum pkey_id_type sig_type;
 	size_t sig_len;
 	const u8 *sig;
 	int err = 0;
 
 	if (IS_ENABLED(CONFIG_MODULE_SIG_POLICY)) {
 		err = mod_split_sig(info->hdr, &info->len, mangled_module,
-				    &sig_len, &sig, "module");
+				    &sig_type, &sig_len, &sig, "module");
 		if (err)
 			return err;
 	}
 
-	if (IS_ENABLED(CONFIG_MODULE_SIG))
+	if (IS_ENABLED(CONFIG_MODULE_SIG) && sig_type == PKEY_ID_PKCS7) {
 		err = module_sig_check(info, sig, sig_len);
+	} else {
+		pr_err("module: not signed with expected PKCS#7 message\n");
+		err = -ENOPKG;
+	}
 
 	if (err)
 		return err;
diff --git a/kernel/module_signature.c b/kernel/module_signature.c
index b2384a73524c..8e0ac9906c9c 100644
--- a/kernel/module_signature.c
+++ b/kernel/module_signature.c
@@ -19,18 +19,11 @@
  * @file_len:	Size of the file to which @ms is appended.
  * @name:	What is being checked. Used for error messages.
  */
-static int mod_check_sig(const struct module_signature *ms, size_t file_len,
-			 const char *name)
+static int mod_check_sig(const struct module_signature *ms, size_t file_len, const char *name)
 {
 	if (be32_to_cpu(ms->sig_len) >= file_len - sizeof(*ms))
 		return -EBADMSG;
 
-	if (ms->id_type != PKEY_ID_PKCS7) {
-		pr_err("%s: not signed with expected PKCS#7 message\n",
-		       name);
-		return -ENOPKG;
-	}
-
 	if (ms->algo != 0 ||
 	    ms->hash != 0 ||
 	    ms->signer_len != 0 ||
@@ -38,7 +31,7 @@ static int mod_check_sig(const struct module_signature *ms, size_t file_len,
 	    ms->__pad[0] != 0 ||
 	    ms->__pad[1] != 0 ||
 	    ms->__pad[2] != 0) {
-		pr_err("%s: PKCS#7 signature info has unexpected non-zero params\n",
+		pr_err("%s: signature info has unexpected non-zero params\n",
 		       name);
 		return -EBADMSG;
 	}
@@ -47,7 +40,7 @@ static int mod_check_sig(const struct module_signature *ms, size_t file_len,
 }
 
 int mod_split_sig(const void *buf, size_t *buf_len, bool mangled,
-		  size_t *sig_len, const u8 **sig, const char *name)
+		  enum pkey_id_type *sig_type, size_t *sig_len, const u8 **sig, const char *name)
 {
 	const unsigned long markerlen = sizeof(MODULE_SIG_STRING) - 1;
 	struct module_signature ms;
@@ -74,6 +67,7 @@ int mod_split_sig(const void *buf, size_t *buf_len, bool mangled,
 	if (ret)
 		return ret;
 
+	*sig_type = ms.id_type;
 	*sig_len = be32_to_cpu(ms.sig_len);
 	modlen -= *sig_len + sizeof(ms);
 	*buf_len = modlen;
diff --git a/security/integrity/ima/ima_modsig.c b/security/integrity/ima/ima_modsig.c
index a57342d39b07..a05008324a10 100644
--- a/security/integrity/ima/ima_modsig.c
+++ b/security/integrity/ima/ima_modsig.c
@@ -41,15 +41,21 @@ int ima_read_modsig(enum ima_hooks func, const void *buf, loff_t buf_len,
 		    struct modsig **modsig)
 {
 	size_t buf_len_sz = buf_len;
+	enum pkey_id_type sig_type;
 	struct modsig *hdr;
 	size_t sig_len;
 	const u8 *sig;
 	int rc;
 
-	rc = mod_split_sig(buf, &buf_len_sz, true, &sig_len, &sig, func_tokens[func]);
+	rc = mod_split_sig(buf, &buf_len_sz, true, &sig_type, &sig_len, &sig, func_tokens[func]);
 	if (rc)
 		return rc;
 
+	if (sig_type != PKEY_ID_PKCS7) {
+		pr_err("%s: not signed with expected PKCS#7 message\n", func_tokens[func]);
+		return -ENOPKG;
+	}
+
 	/* Allocate sig_len additional bytes to hold the raw PKCS#7 data. */
 	hdr = kzalloc(struct_size(hdr, raw_pkcs7, sig_len), GFP_KERNEL);
 	if (!hdr)

-- 
2.52.0