lib: Reject peer keys of another algorithmtestingbe

The openssl_dhe_derive() function decoded the peer public key from the
wire with d2i_PUBKEY() and handed it straight to
EVP_PKEY_derive_set_peer(). A peer offering a key of a type other than
the one negotiated was only caught inside OpenSSL. This aborts in
OpenSSL debug builds, which tripped integration.

Now we check the decoded key type against the type of the local key
pair first.

Signed-off-by: Dimitri Staessens <dimitri@ouroboros.rocks>
Signed-off-by: Sander Vrijders <sander@ouroboros.rocks>

1 files changed, 8 insertions, 2 deletions

diff --git a/src/lib/crypt/openssl.c b/src/lib/crypt/openssl.c
index 1ee2318e..9c488b9d 100644
--- a/src/lib/crypt/openssl.c
+++ b/src/lib/crypt/openssl.c
@@ -1057,8 +1057,9 @@ int openssl_dhe_derive(EVP_PKEY * pkp,
                        int        kdf,
                        uint8_t *  s)
 {
-        uint8_t *  pos;
-        EVP_PKEY * pub;
+        uint8_t *    pos;
+        EVP_PKEY *   pub;
+        const char * name;
 
         assert(pkp != NULL);
         assert(pk.data != NULL);
@@ -1070,6 +1071,11 @@ int openssl_dhe_derive(EVP_PKEY * pkp,
         if (pub == NULL)
                 goto fail_decode;
 
+        /* A peer key of another type must not reach the derivation */
+        name = EVP_PKEY_get0_type_name(pkp);
+        if (name == NULL || EVP_PKEY_is_a(pub, name) != 1)
+                goto fail_derive;
+
         if (__openssl_dhe_derive(pkp, pub, pk, kdf, s) < 0)
                 goto fail_derive;