upstream: Accept the host key fingerprint as a synonym for "yes"

when accepting an unknown host key.  This allows you to paste a fingerprint
obtained out of band into the yes/no prompt and have the client do the
comparison for you.  ok markus@ djm@

OpenBSD-Commit-ID: 3c47d10b9f43d3d345e044fd9ec09709583a2767

1 files changed, 11 insertions, 8 deletions

diff --git a/sshconnect.c b/sshconnect.c
index 1a5f6a4c8..955671b4e 100644
--- a/sshconnect.c
+++ b/sshconnect.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: sshconnect.c,v 1.311 2019/01/19 21:36:38 djm Exp $ */
+/* $OpenBSD: sshconnect.c,v 1.312 2019/01/24 17:00:29 dtucker Exp $ */
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -563,22 +563,24 @@ ssh_connect(struct ssh *ssh, const char *host, struct addrinfo *addrs,
 
 /* defaults to 'no' */
 static int
-confirm(const char *prompt)
+confirm(const char *prompt, const char *fingerprint)
 {
         const char *msg, *again = "Please type 'yes' or 'no': ";
+        const char *again_fp = "Please type 'yes', 'no' or the fingerprint: ";
         char *p;
         int ret = -1;
 
         if (options.batch_mode)
                 return 0;
-        for (msg = prompt;;msg = again) {
+        for (msg = prompt;;msg = fingerprint ? again_fp : again) {
                 p = read_passphrase(msg, RP_ECHO);
                 if (p == NULL)
                         return 0;
                 p[strcspn(p, "\n")] = '\0';
                 if (p[0] == '\0' || strcasecmp(p, "no") == 0)
                         ret = 0;
-                else if (strcasecmp(p, "yes") == 0)
+                else if (strcasecmp(p, "yes") == 0 || (fingerprint != NULL &&
+                    strcasecmp(p, fingerprint) == 0))
                         ret = 1;
                 free(p);
                 if (ret != -1)
@@ -706,7 +708,7 @@ check_host_key(char *hostname, struct sockaddr *hostaddr, u_short port,
         char msg[1024];
         const char *type;
         const struct hostkey_entry *host_found, *ip_found;
-        int len, cancelled_forwarding = 0;
+        int len, cancelled_forwarding = 0, confirmed;
         int local = sockaddr_is_local(hostaddr);
         int r, want_cert = sshkey_is_cert(host_key), host_ip_differ = 0;
         int hostkey_trusted = 0; /* Known or explicitly accepted by user */
@@ -881,14 +883,15 @@ check_host_key(char *hostname, struct sockaddr *hostaddr, u_short port,
                             "established%s\n"
                             "%s key fingerprint is %s.%s%s\n%s"
                             "Are you sure you want to continue connecting "
-                            "(yes/no)? ",
+                            "(yes/no/[fingerprint])? ",
                             host, ip, msg1, type, fp,
                             options.visual_host_key ? "\n" : "",
                             options.visual_host_key ? ra : "",
                             msg2);
                         free(ra);
+                        confirmed = confirm(msg, fp);
                         free(fp);
-                        if (!confirm(msg))
+                        if (!confirmed)
                                 goto fail;
                         hostkey_trusted = 1; /* user explicitly confirmed */
                 }
@@ -1082,7 +1085,7 @@ check_host_key(char *hostname, struct sockaddr *hostaddr, u_short port,
                     SSH_STRICT_HOSTKEY_ASK) {
                         strlcat(msg, "\nAre you sure you want "
                             "to continue connecting (yes/no)? ", sizeof(msg));
-                        if (!confirm(msg))
+                        if (!confirm(msg, NULL))
                                 goto fail;
                 } else if (options.strict_host_key_checking !=
                     SSH_STRICT_HOSTKEY_OFF) {