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From:   Michal Suchanek <msuchanek@suse.de>
To:     keyrings@vger.kernel.org
Cc:     Michal Suchanek <msuchanek@suse.de>,
        Michael Ellerman <mpe@ellerman.id.au>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Paul Mackerras <paulus@samba.org>,
        Heiko Carstens <hca@linux.ibm.com>,
        Vasily Gorbik <gor@linux.ibm.com>,
        Christian Borntraeger <borntraeger@de.ibm.com>,
        Alexander Gordeev <agordeev@linux.ibm.com>,
        David Howells <dhowells@redhat.com>,
        Luis Chamberlain <mcgrof@kernel.org>,
        Jessica Yu <jeyu@kernel.org>, Rob Herring <robh@kernel.org>,
        Lakshmi Ramasubramanian <nramas@linux.microsoft.com>,
        Thiago Jung Bauermann <bauerman@linux.ibm.com>,
        Hari Bathini <hbathini@linux.ibm.com>,
        Frank van der Linden <fllinden@amazon.com>,
        linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org,
        linux-s390@vger.kernel.org
Subject: [PATCH 1/3] s390/kexec_file: Don't opencode appended signature verification.
Date:   Wed,  3 Nov 2021 15:27:06 +0100
Message-Id: <90b0c526962c7c835efddeaf5d70f6f5962287e0.1635948742.git.msuchanek@suse.de>
In-Reply-To: <cover.1635948742.git.msuchanek@suse.de>
References: <cover.1635948742.git.msuchanek@suse.de>
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Module verification already implements appeded signature verification.

Reuse it for kexec_file.

Signed-off-by: Michal Suchanek <msuchanek@suse.de>
---
 arch/s390/kernel/machine_kexec_file.c | 33 ++++-----------------------
 include/linux/verification.h          |  3 +++
 kernel/module-internal.h              |  2 --
 kernel/module.c                       |  4 +++-
 kernel/module_signing.c               | 24 +++++++++++--------
 5 files changed, 25 insertions(+), 41 deletions(-)

diff --git a/arch/s390/kernel/machine_kexec_file.c b/arch/s390/kernel/machine_kexec_file.c
index f9e4baa64b67..634e641cd8aa 100644
--- a/arch/s390/kernel/machine_kexec_file.c
+++ b/arch/s390/kernel/machine_kexec_file.c
@@ -23,11 +23,10 @@ const struct kexec_file_ops * const kexec_file_loaders[] = {
 };
 
 #ifdef CONFIG_KEXEC_SIG
-int s390_verify_sig(const char *kernel, unsigned long kernel_len)
+int s390_verify_sig(const char *kernel, unsigned long length)
 {
+	size_t kernel_len = length;
 	const unsigned long marker_len = sizeof(MODULE_SIG_STRING) - 1;
-	struct module_signature *ms;
-	unsigned long sig_len;
 
 	/* Skip signature verification when not secure IPLed. */
 	if (!ipl_secure_flag)
@@ -41,32 +40,8 @@ int s390_verify_sig(const char *kernel, unsigned long kernel_len)
 		return -EKEYREJECTED;
 	kernel_len -= marker_len;
 
-	ms = (void *)kernel + kernel_len - sizeof(*ms);
-	kernel_len -= sizeof(*ms);
-
-	sig_len = be32_to_cpu(ms->sig_len);
-	if (sig_len >= kernel_len)
-		return -EKEYREJECTED;
-	kernel_len -= sig_len;
-
-	if (ms->id_type != PKEY_ID_PKCS7)
-		return -EKEYREJECTED;
-
-	if (ms->algo != 0 ||
-	    ms->hash != 0 ||
-	    ms->signer_len != 0 ||
-	    ms->key_id_len != 0 ||
-	    ms->__pad[0] != 0 ||
-	    ms->__pad[1] != 0 ||
-	    ms->__pad[2] != 0) {
-		return -EBADMSG;
-	}
-
-	return verify_pkcs7_signature(kernel, kernel_len,
-				      kernel + kernel_len, sig_len,
-				      VERIFY_USE_PLATFORM_KEYRING,
-				      VERIFYING_MODULE_SIGNATURE,
-				      NULL, NULL);
+	return verify_appended_signature(kernel, &kernel_len, VERIFY_USE_PLATFORM_KEYRING,
+					"kexec_file");
 }
 #endif /* CONFIG_KEXEC_SIG */
 
diff --git a/include/linux/verification.h b/include/linux/verification.h
index a655923335ae..c1cf0582012a 100644
--- a/include/linux/verification.h
+++ b/include/linux/verification.h
@@ -60,5 +60,8 @@ extern int verify_pefile_signature(const void *pebuf, unsigned pelen,
 				   enum key_being_used_for usage);
 #endif
 
+int verify_appended_signature(const void *data, size_t *len, struct key *trusted_keys,
+			      const char *what);
+
 #endif /* CONFIG_SYSTEM_DATA_VERIFICATION */
 #endif /* _LINUX_VERIFY_PEFILE_H */
diff --git a/kernel/module-internal.h b/kernel/module-internal.h
index 33783abc377b..80461e14bf29 100644
--- a/kernel/module-internal.h
+++ b/kernel/module-internal.h
@@ -27,5 +27,3 @@ struct load_info {
 		unsigned int sym, str, mod, vers, info, pcpu;
 	} index;
 };
-
-extern int mod_verify_sig(const void *mod, struct load_info *info);
diff --git a/kernel/module.c b/kernel/module.c
index 5c26a76e800b..137b3661be75 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -57,6 +57,7 @@
 #include <linux/bsearch.h>
 #include <linux/dynamic_debug.h>
 #include <linux/audit.h>
+#include <linux/verification.h>
 #include <uapi/linux/module.h>
 #include "module-internal.h"
 
@@ -2894,7 +2895,8 @@ static int module_sig_check(struct load_info *info, int flags)
 	    memcmp(mod + info->len - markerlen, MODULE_SIG_STRING, markerlen) == 0) {
 		/* We truncate the module to discard the signature */
 		info->len -= markerlen;
-		err = mod_verify_sig(mod, info);
+		err = verify_appended_signature(mod, &info->len,
+						VERIFY_USE_SECONDARY_KEYRING, "module");
 		if (!err) {
 			info->sig_ok = true;
 			return 0;
diff --git a/kernel/module_signing.c b/kernel/module_signing.c
index 8723ae70ea1f..f492e410564d 100644
--- a/kernel/module_signing.c
+++ b/kernel/module_signing.c
@@ -14,13 +14,19 @@
 #include <crypto/public_key.h>
 #include "module-internal.h"
 
-/*
- * Verify the signature on a module.
+/**
+ * verify_appended_signature - Verify the signature on a module with the
+ * signature marker stripped.
+ * @data: The data to be verified
+ * @len: Size of @data.
+ * @trusted_keys: Keyring to use for verification
+ * @what: Informational string for log messages
  */
-int mod_verify_sig(const void *mod, struct load_info *info)
+int verify_appended_signature(const void *data, size_t *len,
+			      struct key *trusted_keys, const char *what)
 {
 	struct module_signature ms;
-	size_t sig_len, modlen = info->len;
+	size_t sig_len, modlen = *len;
 	int ret;
 
 	pr_devel("==>%s(,%zu)\n", __func__, modlen);
@@ -28,18 +34,18 @@ int mod_verify_sig(const void *mod, struct load_info *info)
 	if (modlen <= sizeof(ms))
 		return -EBADMSG;
 
-	memcpy(&ms, mod + (modlen - sizeof(ms)), sizeof(ms));
+	memcpy(&ms, data + (modlen - sizeof(ms)), sizeof(ms));
 
-	ret = mod_check_sig(&ms, modlen, "module");
+	ret = mod_check_sig(&ms, modlen, what);
 	if (ret)
 		return ret;
 
 	sig_len = be32_to_cpu(ms.sig_len);
 	modlen -= sig_len + sizeof(ms);
-	info->len = modlen;
+	*len = modlen;
 
-	return verify_pkcs7_signature(mod, modlen, mod + modlen, sig_len,
-				      VERIFY_USE_SECONDARY_KEYRING,
+	return verify_pkcs7_signature(data, modlen, data + modlen, sig_len,
+				      trusted_keys,
 				      VERIFYING_MODULE_SIGNATURE,
 				      NULL, NULL);
 }
-- 
2.31.1