- jakob@cvs.openbsd.org 2003/11/12 16:39:58

     [dns.c dns.h readconf.c ssh_config.5 sshconnect.c]
     update SSHFP validation. ok markus@

1 files changed, 28 insertions, 40 deletions

diff --git a/dns.c b/dns.c
index 2fff1b802..2342b6609 100644
--- a/dns.c
+++ b/dns.c
@@ -1,4 +1,4 @@
-/*      $OpenBSD: dns.c,v 1.7 2003/10/14 19:42:10 jakob Exp $   */
+/*      $OpenBSD: dns.c,v 1.8 2003/11/12 16:39:58 jakob Exp $   */
 
 /*
  * Copyright (c) 2003 Wesley Griffin. All rights reserved.
@@ -43,7 +43,7 @@
 #include "uuencode.h"
 
 extern char *__progname;
-RCSID("$OpenBSD: dns.c,v 1.7 2003/10/14 19:42:10 jakob Exp $");
+RCSID("$OpenBSD: dns.c,v 1.8 2003/11/12 16:39:58 jakob Exp $");
 
 #ifndef LWRES
 static const char *errset_text[] = {
@@ -83,7 +83,7 @@ dns_result_totext(unsigned int error)
  */
 static int
 dns_read_key(u_int8_t *algorithm, u_int8_t *digest_type,
-    u_char **digest, u_int *digest_len, Key *key)
+    u_char **digest, u_int *digest_len, const Key *key)
 {
         int success = 0;
 
@@ -145,16 +145,15 @@ dns_read_rdata(u_int8_t *algorithm, u_int8_t *digest_type,
 
 /*
  * Verify the given hostname, address and host key using DNS.
- * Returns 0 if key verifies or -1 if key does NOT verify
+ * Returns 0 if lookup succeeds, -1 otherwise 
  */
 int
 verify_host_key_dns(const char *hostname, struct sockaddr *address,
-    Key *hostkey)
+    const Key *hostkey, int *flags)
 {
         int counter;
         int result;
         struct rrsetinfo *fingerprints = NULL;
-        int failures = 0;
 
         u_int8_t hostkey_algorithm;
         u_int8_t hostkey_digest_type;
@@ -166,6 +165,7 @@ verify_host_key_dns(const char *hostname, struct sockaddr *address,
         u_char *dnskey_digest;
         u_int dnskey_digest_len;
 
+        *flags = 0;
 
         debug3("verify_hostkey_dns");
         if (hostkey == NULL)
@@ -175,28 +175,29 @@ verify_host_key_dns(const char *hostname, struct sockaddr *address,
             DNS_RDATATYPE_SSHFP, 0, &fingerprints);
         if (result) {
                 verbose("DNS lookup error: %s", dns_result_totext(result));
-                return DNS_VERIFY_ERROR;
+                return -1;
         }
 
-#ifdef DNSSEC
-        /* Only accept validated answers */
-        if (!fingerprints->rri_flags & RRSET_VALIDATED) {
-                error("Ignored unvalidated fingerprint from DNS.");
-                freerrset(fingerprints);
-                return DNS_VERIFY_ERROR;
+        if (fingerprints->rri_flags & RRSET_VALIDATED) {
+                *flags |= DNS_VERIFY_SECURE;
+                debug("found %d secure fingerprints in DNS",
+                    fingerprints->rri_nrdatas);
+        } else {
+                debug("found %d insecure fingerprints in DNS",
+                    fingerprints->rri_nrdatas);
         }
-#endif
-
-        debug("found %d fingerprints in DNS", fingerprints->rri_nrdatas);
 
         /* Initialize host key parameters */
         if (!dns_read_key(&hostkey_algorithm, &hostkey_digest_type,
             &hostkey_digest, &hostkey_digest_len, hostkey)) {
                 error("Error calculating host key fingerprint.");
                 freerrset(fingerprints);
-                return DNS_VERIFY_ERROR;
+                return -1;
         }
 
+        if (fingerprints->rri_nrdatas)
+                *flags |= DNS_VERIFY_FOUND;
+
         for (counter = 0 ; counter < fingerprints->rri_nrdatas ; counter++)  {
                 /*
                  * Extract the key from the answer. Ignore any badly
@@ -218,35 +219,22 @@ verify_host_key_dns(const char *hostname, struct sockaddr *address,
                             memcmp(hostkey_digest, dnskey_digest,
                             hostkey_digest_len) == 0) {
 
-                                /* Matching algoritm and digest. */
-                                freerrset(fingerprints);
-                                debug("matching host key fingerprint found in DNS");
-                                return DNS_VERIFY_OK;
-                        } else {
-                                /* Correct algorithm but bad digest */
-                                debug("verify_hostkey_dns: failed");
-                                failures++;
+                                *flags |= DNS_VERIFY_MATCH;
                         }
                 }
         }
 
         freerrset(fingerprints);
 
-        if (failures) {
-                error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
-                error("@    WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED!     @");
-                error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
-                error("IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!");
-                error("Someone could be eavesdropping on you right now (man-in-the-middle attack)!");
-                error("It is also possible that the %s host key has just been changed.",
-                    key_type(hostkey));
-                error("Please contact your system administrator.");
-                return DNS_VERIFY_FAILED;
-        }
-
-        debug("fingerprints found in DNS, but none of them matched");
+        if (*flags & DNS_VERIFY_FOUND)
+                if (*flags & DNS_VERIFY_MATCH)
+                        debug("matching host key fingerprint found in DNS");
+                else
+                        debug("mismatching host key fingerprint found in DNS");
+        else
+                debug("no host key fingerprint found in DNS");
 
-        return DNS_VERIFY_ERROR;
+        return 0;
 }
 
 
@@ -254,7 +242,7 @@ verify_host_key_dns(const char *hostname, struct sockaddr *address,
  * Export the fingerprint of a key as a DNS resource record
  */
 int
-export_dns_rr(const char *hostname, Key *key, FILE *f, int generic)
+export_dns_rr(const char *hostname, const Key *key, FILE *f, int generic)
 {
         u_int8_t rdata_pubkey_algorithm = 0;
         u_int8_t rdata_digest_type = SSHFP_HASH_SHA1;