upstream commit

pass negotiated signing algorithm though to
sshkey_verify() and check that the negotiated algorithm matches the type in
the signature (only matters for RSA SHA1/SHA2 sigs). ok markus@

OpenBSD-Commit-ID: 735fb15bf4adc060d3bee9d047a4bcaaa81b1af9

1 files changed, 5 insertions, 3 deletions

diff --git a/monitor.c b/monitor.c
index a0ad9857d..5b8f0ef65 100644
--- a/monitor.c
+++ b/monitor.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: monitor.c,v 1.175 2017/10/05 15:52:03 djm Exp $ */
+/* $OpenBSD: monitor.c,v 1.176 2017/12/18 02:25:15 djm Exp $ */
 /*
  * Copyright 2002 Niels Provos <provos@citi.umich.edu>
  * Copyright 2002 Markus Friedl <markus@openbsd.org>
@@ -1339,12 +1339,14 @@ mm_answer_keyverify(int sock, struct sshbuf *m)
 {
         struct sshkey *key;
         u_char *signature, *data, *blob;
+        char *sigalg;
         size_t signaturelen, datalen, bloblen;
         int r, ret, valid_data = 0, encoded_ret;
 
         if ((r = sshbuf_get_string(m, &blob, &bloblen)) != 0 ||
             (r = sshbuf_get_string(m, &signature, &signaturelen)) != 0 ||
-            (r = sshbuf_get_string(m, &data, &datalen)) != 0)
+            (r = sshbuf_get_string(m, &data, &datalen)) != 0 ||
+            (r = sshbuf_get_cstring(m, &sigalg, NULL)) != 0)
                 fatal("%s: buffer error: %s", __func__, ssh_err(r));
 
         if (hostbased_cuser == NULL || hostbased_chost == NULL ||
@@ -1373,7 +1375,7 @@ mm_answer_keyverify(int sock, struct sshbuf *m)
                 fatal("%s: bad signature data blob", __func__);
 
         ret = sshkey_verify(key, signature, signaturelen, data, datalen,
-            active_state->compat);
+            sigalg, active_state->compat);
         debug3("%s: %s %p signature %s", __func__, auth_method, key,
             (ret == 0) ? "verified" : "unverified");
         auth2_record_key(authctxt, ret == 0, key);