[PATCH 2/6] pki: Use SHA-2 for session ID signing with ECDSA keys

[Alan Dunn <amdunn@xxxxxxxxx>]

Previously, SHA-1 was used always.

BUG: https://red.libssh.org/issues/148

Signed-off-by: Alan Dunn <amdunn@xxxxxxxxx>
---
 src/pki.c |   59 +++++++++++++++++++++++++++++++++++++++++++++++------------
 1 file changed, 47 insertions(+), 12 deletions(-)

diff --git a/src/pki.c b/src/pki.c
index b8d0d6b..c88fb48 100644
--- a/src/pki.c
+++ b/src/pki.c
@@ -33,6 +33,7 @@
 
 #include "config.h"
 
+#include <assert.h>
 #include <errno.h>
 #include <ctype.h>
 #include <stdio.h>
@@ -1299,6 +1300,11 @@ int ssh_pki_signature_verify_blob(ssh_session session,
 
         evp(key->ecdsa_nid, digest, dlen, ehash, &elen);
 
+#ifdef DEBUG_CRYPTO
+        ssh_print_hexa("Hash to be verified with ecdsa",
+                       ehash, elen);
+#endif
+
         rc = pki_signature_verify(session,
                                   sig,
                                   key,
@@ -1365,6 +1371,10 @@ ssh_string ssh_pki_do_sign(ssh_session session,
         evp_update(ctx, buffer_get_rest(sigbuf), buffer_get_rest_len(sigbuf));
         evp_final(ctx, ehash, &elen);
 
+#ifdef DEBUG_CRYPTO
+        ssh_print_hexa("Hash being signed", ehash, elen);
+#endif
+
         sig = pki_do_sign(privkey, ehash, elen);
 #endif
     } else {
@@ -1458,10 +1468,8 @@ ssh_string ssh_srv_pki_do_sign_sessionid(ssh_session session,
                                          const ssh_key privkey)
 {
     struct ssh_crypto_struct *crypto;
-    unsigned char hash[SHA_DIGEST_LEN] = {0};
     ssh_signature sig;
     ssh_string sig_blob;
-    SHACTX ctx;
     int rc;
 
     if (session == NULL || privkey == NULL || !ssh_key_is_private(privkey)) {
@@ -1470,24 +1478,51 @@ ssh_string ssh_srv_pki_do_sign_sessionid(ssh_session session,
     crypto = session->next_crypto ? session->next_crypto :
                                        session->current_crypto;
 
-    ctx = sha1_init();
-    if (ctx == NULL) {
-        return NULL;
-    }
     if (crypto->secret_hash == NULL){
         ssh_set_error(session,SSH_FATAL,"Missing secret_hash");
         return NULL;
     }
-    sha1_update(ctx, crypto->secret_hash, crypto->digest_len);
-    sha1_final(hash, ctx);
+
+    if (privkey->type == SSH_KEYTYPE_ECDSA) {
+#ifdef HAVE_ECC
+        unsigned char ehash[EVP_DIGEST_LEN] = {0};
+        uint32_t elen;
+
+        evp(privkey->ecdsa_nid, crypto->secret_hash, crypto->digest_len,
+            ehash, &elen);
 
 #ifdef DEBUG_CRYPTO
-    ssh_print_hexa("Hash being signed", hash, SHA_DIGEST_LEN);
+        ssh_print_hexa("Hash being signed", ehash, elen);
 #endif
 
-    sig = pki_do_sign_sessionid(privkey, hash, SHA_DIGEST_LEN);
-    if (sig == NULL) {
-        return NULL;
+        sig = pki_do_sign_sessionid(privkey, ehash, elen);
+        if (sig == NULL) {
+            return NULL;
+        }
+#else
+        /* If ECC is not supported, the privkey type shouldn't be
+           ECDSA */
+        assert(0);
+#endif
+    } else {
+        unsigned char hash[SHA_DIGEST_LEN] = {0};
+        SHACTX ctx;
+
+        ctx = sha1_init();
+        if (ctx == NULL) {
+            return NULL;
+        }
+        sha1_update(ctx, crypto->secret_hash, crypto->digest_len);
+        sha1_final(hash, ctx);
+
+#ifdef DEBUG_CRYPTO
+        ssh_print_hexa("Hash being signed", hash, SHA_DIGEST_LEN);
+#endif
+
+        sig = pki_do_sign_sessionid(privkey, hash, SHA_DIGEST_LEN);
+        if (sig == NULL) {
+            return NULL;
+        }
     }
 
     rc = ssh_pki_export_signature_blob(sig, &sig_blob);
-- 
1.7.9.5