From dad96236271dcb55963b9fe8385f7812e71e67f7 Mon Sep 17 00:00:00 2001
From: Markus Friedl <markus@cvs.openbsd.org>
Date: Thu, 23 Jan 2003 13:50:28 +0000
Subject: ssh-add -c, prompt user for confirmation (using ssh-askpass) when
 private agent key is used; with djm@; test by dugsong@, djm@; ok deraadt@

---
 usr.bin/ssh/ssh-agent.c | 54 +++++++++++++++++++++++++++++++++++++++++--------
 1 file changed, 46 insertions(+), 8 deletions(-)

(limited to 'usr.bin/ssh/ssh-agent.c')

diff --git a/usr.bin/ssh/ssh-agent.c b/usr.bin/ssh/ssh-agent.c
index bbe9ae0b8ac..49ed36b12ae 100644
--- a/usr.bin/ssh/ssh-agent.c
+++ b/usr.bin/ssh/ssh-agent.c
@@ -35,7 +35,7 @@
 
 #include "includes.h"
 #include <sys/queue.h>
-RCSID("$OpenBSD: ssh-agent.c,v 1.106 2003/01/21 18:14:36 marc Exp $");
+RCSID("$OpenBSD: ssh-agent.c,v 1.107 2003/01/23 13:50:27 markus Exp $");
 
 #include <openssl/evp.h>
 #include <openssl/md5.h>
@@ -50,6 +50,8 @@ RCSID("$OpenBSD: ssh-agent.c,v 1.106 2003/01/21 18:14:36 marc Exp $");
 #include "authfd.h"
 #include "compat.h"
 #include "log.h"
+#include "readpass.h"
+#include "misc.h"
 
 #ifdef SMARTCARD
 #include "scard.h"
@@ -77,6 +79,7 @@ typedef struct identity {
 	Key *key;
 	char *comment;
 	u_int death;
+	u_int confirm;
 } Identity;
 
 typedef struct {
@@ -158,6 +161,30 @@ lookup_identity(Key *key, int version)
 	return (NULL);
 }
 
+/* Check confirmation of keysign request */
+static int
+confirm_key(Identity *id)
+{
+	char *p, prompt[1024];
+	int ret = -1;
+
+	p = key_fingerprint(id->key, SSH_FP_MD5, SSH_FP_HEX);
+	snprintf(prompt, sizeof(prompt), "Allow use of key %s?\n"
+	    "Key fingerprint %s.", id->comment, p);
+	xfree(p);
+	p = read_passphrase(prompt, RP_ALLOW_EOF);
+	if (p != NULL) {
+		/*
+		 * Accept empty responses and responses consisting 
+		 * of the word "yes" as affirmative.
+		 */
+		if (*p == '\0' || *p == '\n' || strcasecmp(p, "yes") == 0)
+			ret = 0;
+		xfree(p);
+	}
+	return (ret);
+}
+
 /* send list of supported public keys to 'client' */
 static void
 process_request_identities(SocketEntry *e, int version)
@@ -221,7 +248,7 @@ process_authentication_challenge1(SocketEntry *e)
 		goto failure;
 
 	id = lookup_identity(key, 1);
-	if (id != NULL) {
+	if (id != NULL && (!id->confirm || confirm_key(id) == 0)) {
 		Key *private = id->key;
 		/* Decrypt the challenge using the private key. */
 		if (rsa_private_decrypt(challenge, challenge, private->rsa) <= 0)
@@ -281,7 +308,7 @@ process_sign_request2(SocketEntry *e)
 	key = key_from_blob(blob, blen);
 	if (key != NULL) {
 		Identity *id = lookup_identity(key, 2);
-		if (id != NULL)
+		if (id != NULL && (!id->confirm || confirm_key(id) == 0))
 			ok = key_sign(id->key, &signature, &slen, data, dlen);
 	}
 	key_free(key);
@@ -401,7 +428,7 @@ static void
 process_add_identity(SocketEntry *e, int version)
 {
 	Idtab *tab = idtab_lookup(version);
-	int type, success = 0, death = 0;
+	int type, success = 0, death = 0, confirm = 0;
 	char *type_name, *comment;
 	Key *k = NULL;
 
@@ -463,6 +490,9 @@ process_add_identity(SocketEntry *e, int version)
 		case SSH_AGENT_CONSTRAIN_LIFETIME:
 			death = time(NULL) + buffer_get_int(&e->request);
 			break;
+		case SSH_AGENT_CONSTRAIN_CONFIRM:
+			confirm = 1;
+			break;
 		default:
 			break;
 		}
@@ -474,6 +504,7 @@ process_add_identity(SocketEntry *e, int version)
 		id->key = k;
 		id->comment = comment;
 		id->death = death;
+		id->confirm = confirm;
 		TAILQ_INSERT_TAIL(&tab->idlist, id, next);
 		/* Increment the number of identities. */
 		tab->nentries++;
@@ -558,6 +589,7 @@ process_add_smartcard_key (SocketEntry *e)
 			id->key = k;
 			id->comment = xstrdup("smartcard key");
 			id->death = 0;
+			id->confirm = 0;
 			TAILQ_INSERT_TAIL(&tab->idlist, id, next);
 			tab->nentries++;
 			success = 1;
@@ -938,7 +970,8 @@ usage(void)
 int
 main(int ac, char **av)
 {
-	int sock, c_flag = 0, d_flag = 0, k_flag = 0, s_flag = 0, ch, nalloc;
+	int c_flag = 0, d_flag = 0, k_flag = 0, s_flag = 0;
+	int sock, fd,  ch, nalloc;
 	char *shell, *format, *pidstr, *agentsocket = NULL;
 	fd_set *readsetp = NULL, *writesetp = NULL;
 	struct sockaddr_un sunaddr;
@@ -1106,9 +1139,14 @@ main(int ac, char **av)
 	}
 
 	(void)chdir("/");
-	close(0);
-	close(1);
-	close(2);
+	if ((fd = open(_PATH_DEVNULL, O_RDWR, 0)) != -1) {
+		/* XXX might close listen socket */
+		(void)dup2(fd, STDIN_FILENO);
+		(void)dup2(fd, STDOUT_FILENO);
+		(void)dup2(fd, STDERR_FILENO);
+		if (fd > 2)
+			close(fd);
+	}
 
 	/* deny core dumps, since memory contains unencrypted private keys */
 	rlim.rlim_cur = rlim.rlim_max = 0;
-- 
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