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authorBen Lindstrom <mouring@eviladmin.org>2002-08-01 01:21:56 +0000
committerBen Lindstrom <mouring@eviladmin.org>2002-08-01 01:21:56 +0000
commit3ed6640532ea53bc37182262141c9e917a448025 (patch)
tree88ad1d4bbb9cd865c154f24ad12feafd7e302ccd /sshconnect.c
parent18d2b5d399a6ee97c65a058c14054fd2da2b891a (diff)
- markus@cvs.openbsd.org 2002/07/24 16:11:18
[hostfile.c hostfile.h sshconnect.c] print out all known keys for a host if we get a unknown host key, see discussion at http://marc.theaimsgroup.com/?t=101069210100016&r=1&w=4 the ssharp mitm tool attacks users in a similar way, so i'd like to pointed out again: A MITM attack is always possible if the ssh client prints: The authenticity of host 'bla' can't be established. (protocol version 2 with pubkey authentication allows you to detect MITM attacks)
Diffstat (limited to 'sshconnect.c')
-rw-r--r--sshconnect.c73
1 files changed, 69 insertions, 4 deletions
diff --git a/sshconnect.c b/sshconnect.c
index 9f8458dc..8599684e 100644
--- a/sshconnect.c
+++ b/sshconnect.c
@@ -13,7 +13,7 @@
*/
#include "includes.h"
-RCSID("$OpenBSD: sshconnect.c,v 1.131 2002/07/12 13:29:09 itojun Exp $");
+RCSID("$OpenBSD: sshconnect.c,v 1.132 2002/07/24 16:11:18 markus Exp $");
#include <openssl/bn.h>
@@ -46,6 +46,8 @@ extern uid_t original_effective_uid;
#define INET6_ADDRSTRLEN 46
#endif
+static int show_other_keys(const char *, Key *);
+
/*
* Connect to the given ssh server using a proxy command.
*/
@@ -494,7 +496,7 @@ check_host_key(char *host, struct sockaddr *hostaddr, Key *host_key,
int salen;
char ntop[NI_MAXHOST];
char msg[1024];
- int len, host_line, ip_line;
+ int len, host_line, ip_line, has_keys;
const char *host_file = NULL, *ip_file = NULL;
/*
@@ -638,14 +640,19 @@ check_host_key(char *host, struct sockaddr *hostaddr, Key *host_key,
"have requested strict checking.", type, host);
goto fail;
} else if (options.strict_host_key_checking == 2) {
+ has_keys = show_other_keys(host, host_key);
/* The default */
fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX);
snprintf(msg, sizeof(msg),
"The authenticity of host '%.200s (%s)' can't be "
- "established.\n"
+ "established%s\n"
"%s key fingerprint is %s.\n"
"Are you sure you want to continue connecting "
- "(yes/no)? ", host, ip, type, fp);
+ "(yes/no)? ",
+ host, ip,
+ has_keys ? ",\nbut keys of different type are already "
+ "known for this host." : ".",
+ type, fp);
xfree(fp);
if (!confirm(msg))
goto fail;
@@ -748,6 +755,9 @@ check_host_key(char *host, struct sockaddr *hostaddr, Key *host_key,
* accept the authentication.
*/
break;
+ case HOST_FOUND:
+ fatal("internal error");
+ break;
}
if (options.check_host_ip && host_status != HOST_CHANGED &&
@@ -859,3 +869,58 @@ ssh_put_password(char *password)
memset(padded, 0, size);
xfree(padded);
}
+
+static int
+show_key_from_file(const char *file, const char *host, int keytype)
+{
+ Key *found;
+ char *fp;
+ int line, ret;
+
+ found = key_new(keytype);
+ if ((ret = lookup_key_in_hostfile_by_type(file, host,
+ keytype, found, &line))) {
+ fp = key_fingerprint(found, SSH_FP_MD5, SSH_FP_HEX);
+ log("WARNING: %s key found for host %s\n"
+ "in file %s line %d with\n"
+ "%s key fingerprint %s.",
+ key_type(found), host, file, line,
+ key_type(found), fp);
+ xfree(fp);
+ }
+ key_free(found);
+ return (ret);
+}
+
+/* print all known host keys for a given host, but skip keys of given type */
+static int
+show_other_keys(const char *host, Key *key)
+{
+ int type[] = { KEY_RSA1, KEY_RSA, KEY_DSA, -1};
+ int i, found = 0;
+
+ for (i = 0; type[i] != -1; i++) {
+ if (type[i] == key->type)
+ continue;
+ if (type[i] != KEY_RSA1 &&
+ show_key_from_file(options.user_hostfile2, host, type[i])) {
+ found = 1;
+ continue;
+ }
+ if (type[i] != KEY_RSA1 &&
+ show_key_from_file(options.system_hostfile2, host, type[i])) {
+ found = 1;
+ continue;
+ }
+ if (show_key_from_file(options.user_hostfile, host, type[i])) {
+ found = 1;
+ continue;
+ }
+ if (show_key_from_file(options.system_hostfile, host, type[i])) {
+ found = 1;
+ continue;
+ }
+ debug2("no key of type %d for host %s", type[i], host);
+ }
+ return (found);
+}