Check that the public key OID matches the sig alg

Using the rsa_pss_rsae_sha256 sig alg should imply that the key OID is
rsaEncryption. Similarly rsa_pss_pss_sha256 implies the key OID is
rsassaPss. However we did not check this and incorrectly tolerated a key
OID that did not match the sig alg sent by the peer.

Fixes #6611

Reviewed-by: Rich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/6732)

3 files changed, 32 insertions, 10 deletions

diff --git a/ssl/ssl_cert.c b/ssl/ssl_cert.c
index b2b342767c..df5cff79c9 100644
--- a/ssl/ssl_cert.c
+++ b/ssl/ssl_cert.c
@@ -995,22 +995,35 @@ int ssl_ctx_security(const SSL_CTX *ctx, int op, int bits, int nid, void *other)
                              ctx->cert->sec_ex);
 }
 
-const SSL_CERT_LOOKUP *ssl_cert_lookup_by_pkey(const EVP_PKEY *pk, size_t *pidx)
+int ssl_cert_lookup_by_nid(int nid, size_t *pidx)
 {
-    int nid = EVP_PKEY_id(pk);
     size_t i;
 
-    if (nid == NID_undef)
-        return NULL;
-
     for (i = 0; i < OSSL_NELEM(ssl_cert_info); i++) {
         if (ssl_cert_info[i].nid == nid) {
-            if (pidx != NULL)
-                *pidx = i;
-            return &ssl_cert_info[i];
+            *pidx = i;
+            return 1;
         }
     }
-    return NULL;
+
+    return 0;
+}
+
+const SSL_CERT_LOOKUP *ssl_cert_lookup_by_pkey(const EVP_PKEY *pk, size_t *pidx)
+{
+    int nid = EVP_PKEY_id(pk);
+    size_t tmpidx;
+
+    if (nid == NID_undef)
+        return NULL;
+
+    if (!ssl_cert_lookup_by_nid(nid, &tmpidx))
+        return NULL;
+
+    if (pidx != NULL)
+        *pidx = tmpidx;
+
+    return &ssl_cert_info[tmpidx];
 }
 
 const SSL_CERT_LOOKUP *ssl_cert_lookup_by_idx(size_t idx)
diff --git a/ssl/ssl_locl.h b/ssl/ssl_locl.h
index b38052f614..e7258d439a 100644
--- a/ssl/ssl_locl.h
+++ b/ssl/ssl_locl.h
@@ -2288,6 +2288,7 @@ __owur int ssl_security(const SSL *s, int op, int bits, int nid, void *other);
 __owur int ssl_ctx_security(const SSL_CTX *ctx, int op, int bits, int nid,
                             void *other);
 
+__owur int ssl_cert_lookup_by_nid(int nid, size_t *pidx);
 __owur const SSL_CERT_LOOKUP *ssl_cert_lookup_by_pkey(const EVP_PKEY *pk,
                                                       size_t *pidx);
 __owur const SSL_CERT_LOOKUP *ssl_cert_lookup_by_idx(size_t idx);
diff --git a/ssl/t1_lib.c b/ssl/t1_lib.c
index 3c7590c31f..df27ba6b7b 100644
--- a/ssl/t1_lib.c
+++ b/ssl/t1_lib.c
@@ -955,7 +955,7 @@ int tls12_check_peer_sigalg(SSL *s, uint16_t sig, EVP_PKEY *pkey)
     const uint16_t *sent_sigs;
     const EVP_MD *md = NULL;
     char sigalgstr[2];
-    size_t sent_sigslen, i;
+    size_t sent_sigslen, i, cidx;
     int pkeyid = EVP_PKEY_id(pkey);
     const SIGALG_LOOKUP *lu;
 
@@ -986,6 +986,14 @@ int tls12_check_peer_sigalg(SSL *s, uint16_t sig, EVP_PKEY *pkey)
                  SSL_R_WRONG_SIGNATURE_TYPE);
         return 0;
     }
+    /* Check the sigalg is consistent with the key OID */
+    if (!ssl_cert_lookup_by_nid(EVP_PKEY_id(pkey), &cidx)
+            || lu->sig_idx != (int)cidx) {
+        SSLfatal(s, SSL_AD_ILLEGAL_PARAMETER, SSL_F_TLS12_CHECK_PEER_SIGALG,
+                 SSL_R_WRONG_SIGNATURE_TYPE);
+        return 0;
+    }
+
 #ifndef OPENSSL_NO_EC
     if (pkeyid == EVP_PKEY_EC) {