From 65d5eb9eddabb4fc22faf1e40c6372ef848696d6 Mon Sep 17 00:00:00 2001
From: djm <djm@openbsd.org>
Date: Thu, 6 Jan 2022 22:00:18 +0000
Subject: [PATCH] make ssh-keysign use the requested signature algorithm and
 not the default for the keytype. Part of unbreaking hostbased auth for
 RSA/SHA2 keys. ok markus@

---
 usr.bin/ssh/ssh-keysign.c | 29 ++++++++++++++++++++---------
 1 file changed, 20 insertions(+), 9 deletions(-)

diff --git a/usr.bin/ssh/ssh-keysign.c b/usr.bin/ssh/ssh-keysign.c
index 1d7807ac651..ade85522ddd 100644
--- a/usr.bin/ssh/ssh-keysign.c
+++ b/usr.bin/ssh/ssh-keysign.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: ssh-keysign.c,v 1.69 2021/11/13 17:26:13 deraadt Exp $ */
+/* $OpenBSD: ssh-keysign.c,v 1.70 2022/01/06 22:00:18 djm Exp $ */
 /*
  * Copyright (c) 2002 Markus Friedl.  All rights reserved.
  *
@@ -57,7 +57,7 @@
 extern char *__progname;
 
 static int
-valid_request(struct passwd *pw, char *host, struct sshkey **ret,
+valid_request(struct passwd *pw, char *host, struct sshkey **ret, char **pkalgp,
     u_char *data, size_t datalen)
 {
 	struct sshbuf *b;
@@ -70,6 +70,8 @@ valid_request(struct passwd *pw, char *host, struct sshkey **ret,
 
 	if (ret != NULL)
 		*ret = NULL;
+	if (pkalgp != NULL)
+		*pkalgp = NULL;
 	fail = 0;
 
 	if ((b = sshbuf_from(data, datalen)) == NULL)
@@ -120,8 +122,6 @@ valid_request(struct passwd *pw, char *host, struct sshkey **ret,
 		fail++;
 	} else if (key->type != pktype)
 		fail++;
-	free(pkalg);
-	free(pkblob);
 
 	/* client host name, handle trailing dot */
 	if ((r = sshbuf_get_cstring(b, &p, &len)) != 0)
@@ -152,8 +152,19 @@ valid_request(struct passwd *pw, char *host, struct sshkey **ret,
 
 	if (fail)
 		sshkey_free(key);
-	else if (ret != NULL)
-		*ret = key;
+	else {
+		if (ret != NULL) {
+			*ret = key;
+			key = NULL;
+		}
+		if (pkalgp != NULL) {
+			*pkalgp = pkalg;
+			pkalg = NULL;
+		}
+	}
+	sshkey_free(key);
+	free(pkalg);
+	free(pkblob);
 
 	return (fail ? -1 : 0);
 }
@@ -168,7 +179,7 @@ main(int argc, char **argv)
 	struct passwd *pw;
 	int r, key_fd[NUM_KEYTYPES], i, found, version = 2, fd;
 	u_char *signature, *data, rver;
-	char *host, *fp;
+	char *host, *fp, *pkalg;
 	size_t slen, dlen;
 
 	if (pledge("stdio rpath getpw dns id", NULL) != 0)
@@ -258,7 +269,7 @@ main(int argc, char **argv)
 
 	if ((r = sshbuf_get_string(b, &data, &dlen)) != 0)
 		fatal_r(r, "%s: buffer error", __progname);
-	if (valid_request(pw, host, &key, data, dlen) < 0)
+	if (valid_request(pw, host, &key, &pkalg, data, dlen) < 0)
 		fatal("%s: not a valid request", __progname);
 	free(host);
 
@@ -279,7 +290,7 @@ main(int argc, char **argv)
 	}
 
 	if ((r = sshkey_sign(keys[i], &signature, &slen, data, dlen,
-	    NULL, NULL, NULL, 0)) != 0)
+	    pkalg, NULL, NULL, 0)) != 0)
 		fatal_r(r, "%s: sshkey_sign failed", __progname);
 	free(data);
 
-- 
2.20.1