upstream: when using RSA keys to sign messages, select the

signature algorithm based on the requested hash algorithm ("-Ohashalg=xxx").

This allows using something other than rsa-sha2-512, which may not
be supported on all signing backends, e.g. some smartcards only
support SHA256.

Patch from Morten Linderud; ok markus@

OpenBSD-Commit-ID: 246353fac24e92629263996558c6788348363ad7

diff --git a/sshsig.c b/sshsig.c
index 470b286a3a982875a48a5262b7057c4710b17fed..289f3e72897e22fb743370ffa7e6f73bd72c0741 100644 (file)
--- a/sshsig.c
+++ b/sshsig.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: sshsig.c,v 1.35 2024/03/08 22:16:32 djm Exp $ */
+/* $OpenBSD: sshsig.c,v 1.36 2024/11/26 21:23:35 djm Exp $ */
 /*
  * Copyright (c) 2019 Google LLC
  *
@@ -190,8 +190,13 @@ sshsig_wrap_sign(struct sshkey *key, const char *hashalg,
        }
 
        /* If using RSA keys then default to a good signature algorithm */
-       if (sshkey_type_plain(key->type) == KEY_RSA)
+       if (sshkey_type_plain(key->type) == KEY_RSA) {
                sign_alg = RSA_SIGN_ALG;
+               if (strcmp(hashalg, "sha256") == 0)
+                       sign_alg = "rsa-sha2-256";
+               else if (strcmp(hashalg, "sha512") == 0)
+                       sign_alg = "rsa-sha2-512";
+       }
 
        if (signer != NULL) {
                if ((r = signer(key, &sig, &slen,