upstream: Ensure that all returned SSHFP records for the specified host
name and hostkey type match instead of only one. While there, simplify the code somewhat and add some debugging. Based on discussion in bz#3322, ok djm@. OpenBSD-Commit-ID: 0a6a0a476eb7f9dfe8fe2c05a1a395e3e9b22ee4
This commit is contained in:
dtucker@openbsd.org
Darren Tucker
parent
1cc1fd0953
commit
b75a80fa83
58
dns.c
58
dns.c
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@ -1,4 +1,4 @@
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/* $OpenBSD: dns.c,v 1.40 2021/07/05 01:16:46 dtucker Exp $ */
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/* $OpenBSD: dns.c,v 1.41 2021/07/19 03:13:28 dtucker Exp $ */
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/*
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* Copyright (c) 2003 Wesley Griffin. All rights reserved.
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@ -75,6 +75,7 @@ dns_result_totext(unsigned int res)
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/*
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* Read SSHFP parameters from key buffer.
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* Caller must free digest which is allocated by sshkey_fingerprint_raw().
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*/
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static int
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dns_read_key(u_int8_t *algorithm, u_int8_t *digest_type,
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@ -86,32 +87,21 @@ dns_read_key(u_int8_t *algorithm, u_int8_t *digest_type,
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switch (key->type) {
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case KEY_RSA:
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*algorithm = SSHFP_KEY_RSA;
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if (!*digest_type)
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*digest_type = SSHFP_HASH_SHA1;
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break;
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case KEY_DSA:
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*algorithm = SSHFP_KEY_DSA;
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if (!*digest_type)
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*digest_type = SSHFP_HASH_SHA1;
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break;
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case KEY_ECDSA:
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*algorithm = SSHFP_KEY_ECDSA;
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if (!*digest_type)
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*digest_type = SSHFP_HASH_SHA256;
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break;
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case KEY_ED25519:
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*algorithm = SSHFP_KEY_ED25519;
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if (!*digest_type)
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*digest_type = SSHFP_HASH_SHA256;
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break;
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case KEY_XMSS:
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*algorithm = SSHFP_KEY_XMSS;
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if (!*digest_type)
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*digest_type = SSHFP_HASH_SHA256;
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break;
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default:
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*algorithm = SSHFP_KEY_RESERVED; /* 0 */
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*digest_type = SSHFP_HASH_RESERVED; /* 0 */
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}
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switch (*digest_type) {
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@ -133,7 +123,6 @@ dns_read_key(u_int8_t *algorithm, u_int8_t *digest_type,
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} else {
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*digest = NULL;
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*digest_len = 0;
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success = 0;
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}
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return success;
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@ -212,7 +201,6 @@ verify_host_key_dns(const char *hostname, struct sockaddr *address,
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struct rrsetinfo *fingerprints = NULL;
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u_int8_t hostkey_algorithm;
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u_int8_t hostkey_digest_type = SSHFP_HASH_RESERVED;
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u_char *hostkey_digest;
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size_t hostkey_digest_len;
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@ -248,14 +236,6 @@ verify_host_key_dns(const char *hostname, struct sockaddr *address,
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fingerprints->rri_nrdatas);
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}
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/* Initialize default host key parameters */
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if (!dns_read_key(&hostkey_algorithm, &hostkey_digest_type,
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&hostkey_digest, &hostkey_digest_len, hostkey)) {
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error("Error calculating host key fingerprint.");
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freerrset(fingerprints);
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return -1;
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}
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if (fingerprints->rri_nrdatas)
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*flags |= DNS_VERIFY_FOUND;
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@ -271,35 +251,41 @@ verify_host_key_dns(const char *hostname, struct sockaddr *address,
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verbose("Error parsing fingerprint from DNS.");
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continue;
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}
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debug3_f("checking SSHFP type %d fptype %d", dnskey_algorithm,
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dnskey_digest_type);
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if (hostkey_digest_type != dnskey_digest_type) {
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hostkey_digest_type = dnskey_digest_type;
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free(hostkey_digest);
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/* Initialize host key parameters */
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if (!dns_read_key(&hostkey_algorithm,
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&hostkey_digest_type, &hostkey_digest,
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&hostkey_digest_len, hostkey)) {
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/* Calculate host key fingerprint. */
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if (!dns_read_key(&hostkey_algorithm, &dnskey_digest_type,
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&hostkey_digest, &hostkey_digest_len, hostkey)) {
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error("Error calculating key fingerprint.");
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freerrset(fingerprints);
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return -1;
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}
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}
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/* Check if the current key is the same as the given key */
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if (hostkey_algorithm == dnskey_algorithm &&
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hostkey_digest_type == dnskey_digest_type) {
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if (hostkey_digest_len == dnskey_digest_len &&
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timingsafe_bcmp(hostkey_digest, dnskey_digest,
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hostkey_digest_len) == 0)
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hostkey_digest_len == dnskey_digest_len) {
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if (timingsafe_bcmp(hostkey_digest, dnskey_digest,
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hostkey_digest_len) == 0) {
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debug_f("matched SSHFP type %d fptype %d",
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dnskey_algorithm, dnskey_digest_type);
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*flags |= DNS_VERIFY_MATCH;
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} else {
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debug_f("failed SSHFP type %d fptype %d",
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dnskey_algorithm, dnskey_digest_type);
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*flags |= DNS_VERIFY_FAILED;
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}
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}
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free(dnskey_digest);
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free(hostkey_digest); /* from sshkey_fingerprint_raw() */
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}
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free(hostkey_digest); /* from sshkey_fingerprint_raw() */
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freerrset(fingerprints);
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/* If any fingerprint failed to validate, return failure. */
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if (*flags & DNS_VERIFY_FAILED)
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*flags &= ~DNS_VERIFY_MATCH;
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if (*flags & DNS_VERIFY_FOUND)
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if (*flags & DNS_VERIFY_MATCH)
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debug("matching host key fingerprint found in DNS");
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3
dns.h
3
dns.h
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@ -1,4 +1,4 @@
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/* $OpenBSD: dns.h,v 1.18 2018/02/23 15:58:37 markus Exp $ */
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/* $OpenBSD: dns.h,v 1.19 2021/07/19 03:13:28 dtucker Exp $ */
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/*
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* Copyright (c) 2003 Wesley Griffin. All rights reserved.
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@ -50,6 +50,7 @@ enum sshfp_hashes {
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#define DNS_VERIFY_FOUND 0x00000001
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#define DNS_VERIFY_MATCH 0x00000002
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#define DNS_VERIFY_SECURE 0x00000004
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#define DNS_VERIFY_FAILED 0x00000008
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int verify_host_key_dns(const char *, struct sockaddr *,
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struct sshkey *, int *);
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