pki: Support RSA SHA2 signatures of sessionid for server

This involves mostly creation of host keys proofs but needs
to follow the same procedure as the client authentication
signatures.

At the same time, the SHA2 extension is enabled in the pkd
so we are able to atomicaly provide correct signatures and
pass tests.

Signed-off-by: Jakub Jelen <jjelen@redhat.com>
Reviewed-by: Andreas Schneider <asn@cryptomilk.org>

1 files changed, 13 insertions, 24 deletions

diff --git a/src/pki_crypto.c b/src/pki_crypto.c
index 524cc0ff..8e1e16ad 100644
--- a/src/pki_crypto.c
+++ b/src/pki_crypto.c
@@ -1236,26 +1236,6 @@ static ssh_string _RSA_do_sign_hash(const unsigned char *digest,
     return sig_blob;
 }
 
-/**
- * @internal
- *
- * @brief Compute a digital signature.
- *
- * @param[in]  digest    The message digest.
- *
- * @param[in]  dlen      The length of the digest.
- *
- * @param[in]  privkey   The private rsa key to use for signing.
- *
- * @return               A newly allocated rsa sig blob or NULL on error.
- */
-static ssh_string _RSA_do_sign(const unsigned char *digest,
-                                    int dlen,
-                                    RSA *privkey)
-{
-    return _RSA_do_sign_hash(digest, dlen, privkey, SSH_DIGEST_AUTO);
-}
-
 static ssh_string pki_dsa_signature_to_blob(const ssh_signature sig)
 {
     char buffer[40] = { 0 };
@@ -1813,16 +1793,24 @@ ssh_signature pki_do_sign_hash(const ssh_key privkey,
 }
 
 #ifdef WITH_SERVER
-ssh_signature pki_do_sign_sessionid(const ssh_key key,
-                                    const unsigned char *hash,
-                                    size_t hlen)
+ssh_signature pki_do_sign_sessionid_hash(const ssh_key key,
+                                         const unsigned char *hash,
+                                         size_t hlen,
+                                         enum ssh_digest_e hash_type)
 {
     ssh_signature sig;
 
+    /* Only RSA supports different signature algorithm types now */
+    if (key->type != SSH_KEYTYPE_RSA && hash_type != SSH_DIGEST_AUTO) {
+        SSH_LOG(SSH_LOG_WARN, "Incompatible signature algorithm passed");
+        return NULL;
+    }
+
     sig = ssh_signature_new();
     if (sig == NULL) {
         return NULL;
     }
+
     sig->type = key->type;
     sig->type_c = key->type_c;
 
@@ -1836,7 +1824,8 @@ ssh_signature pki_do_sign_sessionid(const ssh_key key,
             break;
         case SSH_KEYTYPE_RSA:
         case SSH_KEYTYPE_RSA1:
-            sig->rsa_sig = _RSA_do_sign(hash, hlen, key->rsa);
+            sig->type_c = ssh_key_signature_to_char(key->type, hash_type);
+            sig->rsa_sig = _RSA_do_sign_hash(hash, hlen, key->rsa, hash_type);
             if (sig->rsa_sig == NULL) {
                 ssh_signature_free(sig);
                 return NULL;