From: djm@openbsd.org <djm@openbsd.org>
Date: Tue, 26 Nov 2024 21:23:35 +0000 (+0000)
Subject: upstream: when using RSA keys to sign messages, select the
X-Git-Tag: V_10_0_P1~140
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=d1c1cfc5e4e9b43593d4642810ea8135e4c7db49;p=thirdparty%2Fopenssh-portable.git

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 470b286a3..289f3e728 100644
--- 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,