5 files changed, 74 insertions, 16 deletions

diff --git a/crypto/asymmetric_keys/pkcs7_parser.h b/crypto/asymmetric_keys/pkcs7_parser.h
index 91949f92bc72..efc7dc9b8f9c 100644
--- a/crypto/asymmetric_keys/pkcs7_parser.h
+++ b/crypto/asymmetric_keys/pkcs7_parser.h
@@ -23,6 +23,7 @@ struct pkcs7_signed_info {
         struct x509_certificate *signer; /* Signing certificate (in msg->certs) */
         unsigned index;
         bool trusted;
+        bool unsupported_crypto;        /* T if not usable due to missing crypto */
 
         /* Message digest - the digest of the Content Data (or NULL) */
         const void      *msgdigest;
diff --git a/crypto/asymmetric_keys/pkcs7_trust.c b/crypto/asymmetric_keys/pkcs7_trust.c
index 09197e50fa82..8bd474e5e706 100644
--- a/crypto/asymmetric_keys/pkcs7_trust.c
+++ b/crypto/asymmetric_keys/pkcs7_trust.c
@@ -35,6 +35,11 @@ static int pkcs7_validate_trust_one(struct pkcs7_message *pkcs7,
 
         kenter(",%u,", sinfo->index);
 
+        if (sinfo->unsupported_crypto) {
+                kleave(" = -ENOPKG [cached]");
+                return -ENOPKG;
+        }
+
         for (x509 = sinfo->signer; x509; x509 = x509->signer) {
                 if (x509->seen) {
                         if (x509->verified) {
@@ -139,24 +144,28 @@ int pkcs7_validate_trust(struct pkcs7_message *pkcs7,
 {
         struct pkcs7_signed_info *sinfo;
         struct x509_certificate *p;
-        int cached_ret = 0, ret;
+        int cached_ret = -ENOKEY;
+        int ret;
 
         for (p = pkcs7->certs; p; p = p->next)
                 p->seen = false;
 
         for (sinfo = pkcs7->signed_infos; sinfo; sinfo = sinfo->next) {
                 ret = pkcs7_validate_trust_one(pkcs7, sinfo, trust_keyring);
-                if (ret < 0) {
-                        if (ret == -ENOPKG) {
+                switch (ret) {
+                case -ENOKEY:
+                        continue;
+                case -ENOPKG:
+                        if (cached_ret == -ENOKEY)
                                 cached_ret = -ENOPKG;
-                        } else if (ret == -ENOKEY) {
-                                if (cached_ret == 0)
-                                        cached_ret = -ENOKEY;
-                        } else {
-                                return ret;
-                        }
+                        continue;
+                case 0:
+                        *_trusted |= sinfo->trusted;
+                        cached_ret = 0;
+                        continue;
+                default:
+                        return ret;
                 }
-                *_trusted |= sinfo->trusted;
         }
 
         return cached_ret;
diff --git a/crypto/asymmetric_keys/pkcs7_verify.c b/crypto/asymmetric_keys/pkcs7_verify.c
index 57e90fa17f2b..bd264052f751 100644
--- a/crypto/asymmetric_keys/pkcs7_verify.c
+++ b/crypto/asymmetric_keys/pkcs7_verify.c
@@ -181,7 +181,7 @@ static int pkcs7_verify_sig_chain(struct pkcs7_message *pkcs7,
                 x509->seen = true;
                 ret = x509_get_sig_params(x509);
                 if (ret < 0)
-                        return ret;
+                        goto maybe_missing_crypto_in_x509;
 
                 pr_debug("- issuer %s\n", x509->issuer);
                 if (x509->authority)
@@ -203,7 +203,7 @@ static int pkcs7_verify_sig_chain(struct pkcs7_message *pkcs7,
 
                         ret = x509_check_signature(x509->pub, x509);
                         if (ret < 0)
-                                return ret;
+                                goto maybe_missing_crypto_in_x509;
                         x509->signer = x509;
                         pr_debug("- self-signed\n");
                         return 0;
@@ -245,6 +245,17 @@ static int pkcs7_verify_sig_chain(struct pkcs7_message *pkcs7,
                 x509 = p;
                 might_sleep();
         }
+
+maybe_missing_crypto_in_x509:
+        /* Just prune the certificate chain at this point if we lack some
+         * crypto module to go further.  Note, however, we don't want to set
+         * sinfo->missing_crypto as the signed info block may still be
+         * validatable against an X.509 cert lower in the chain that we have a
+         * trusted copy of.
+         */
+        if (ret == -ENOPKG)
+                return 0;
+        return ret;
 }
 
 /*
@@ -286,11 +297,33 @@ static int pkcs7_verify_one(struct pkcs7_message *pkcs7,
 /**
  * pkcs7_verify - Verify a PKCS#7 message
  * @pkcs7: The PKCS#7 message to be verified
+ *
+ * Verify a PKCS#7 message is internally consistent - that is, the data digest
+ * matches the digest in the AuthAttrs and any signature in the message or one
+ * of the X.509 certificates it carries that matches another X.509 cert in the
+ * message can be verified.
+ *
+ * This does not look to match the contents of the PKCS#7 message against any
+ * external public keys.
+ *
+ * Returns, in order of descending priority:
+ *
+ *  (*) -EKEYREJECTED if a signature failed to match for which we found an
+ *      appropriate X.509 certificate, or:
+ *
+ *  (*) -EBADMSG if some part of the message was invalid, or:
+ *
+ *  (*) -ENOPKG if none of the signature chains are verifiable because suitable
+ *      crypto modules couldn't be found, or:
+ *
+ *  (*) 0 if all the signature chains that don't incur -ENOPKG can be verified
+ *      (note that a signature chain may be of zero length), or:
  */
 int pkcs7_verify(struct pkcs7_message *pkcs7)
 {
         struct pkcs7_signed_info *sinfo;
         struct x509_certificate *x509;
+        int enopkg = -ENOPKG;
         int ret, n;
 
         kenter("");
@@ -306,12 +339,17 @@ int pkcs7_verify(struct pkcs7_message *pkcs7)
         for (sinfo = pkcs7->signed_infos; sinfo; sinfo = sinfo->next) {
                 ret = pkcs7_verify_one(pkcs7, sinfo);
                 if (ret < 0) {
+                        if (ret == -ENOPKG) {
+                                sinfo->unsupported_crypto = true;
+                                continue;
+                        }
                         kleave(" = %d", ret);
                         return ret;
                 }
+                enopkg = 0;
         }
 
-        kleave(" = 0");
-        return 0;
+        kleave(" = %d", enopkg);
+        return enopkg;
 }
 EXPORT_SYMBOL_GPL(pkcs7_verify);
diff --git a/crypto/asymmetric_keys/x509_parser.h b/crypto/asymmetric_keys/x509_parser.h
index 0e8d59b010fb..4e1a384901ed 100644
--- a/crypto/asymmetric_keys/x509_parser.h
+++ b/crypto/asymmetric_keys/x509_parser.h
@@ -38,6 +38,7 @@ struct x509_certificate {
         bool            seen;                   /* Infinite recursion prevention */
         bool            verified;
         bool            trusted;
+        bool            unsupported_crypto;     /* T if can't be verified due to missing crypto */
 };
 
 /*
diff --git a/crypto/asymmetric_keys/x509_public_key.c b/crypto/asymmetric_keys/x509_public_key.c
index c60905c3f4d2..1d9a4c555376 100644
--- a/crypto/asymmetric_keys/x509_public_key.c
+++ b/crypto/asymmetric_keys/x509_public_key.c
@@ -115,6 +115,8 @@ int x509_get_sig_params(struct x509_certificate *cert)
 
         pr_devel("==>%s()\n", __func__);
 
+        if (cert->unsupported_crypto)
+                return -ENOPKG;
         if (cert->sig.rsa.s)
                 return 0;
 
@@ -127,8 +129,13 @@ int x509_get_sig_params(struct x509_certificate *cert)
          * big the hash operational data will be.
          */
         tfm = crypto_alloc_shash(hash_algo_name[cert->sig.pkey_hash_algo], 0, 0);
-        if (IS_ERR(tfm))
-                return (PTR_ERR(tfm) == -ENOENT) ? -ENOPKG : PTR_ERR(tfm);
+        if (IS_ERR(tfm)) {
+                if (PTR_ERR(tfm) == -ENOENT) {
+                        cert->unsupported_crypto = true;
+                        return -ENOPKG;
+                }
+                return PTR_ERR(tfm);
+        }
 
         desc_size = crypto_shash_descsize(tfm) + sizeof(*desc);
         digest_size = crypto_shash_digestsize(tfm);
@@ -175,6 +182,8 @@ int x509_check_signature(const struct public_key *pub,
                 return ret;
 
         ret = public_key_verify_signature(pub, &cert->sig);
+        if (ret == -ENOPKG)
+                cert->unsupported_crypto = true;
         pr_debug("Cert Verification: %d\n", ret);
         return ret;
 }