/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
/***
This file is part of systemd.
Copyright 2015 Lennart Poettering
systemd is free software; you can redistribute it and/or modify it
under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 2.1 of the License, or
(at your option) any later version.
systemd is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
along with systemd; If not, see .
***/
#include
#include "alloc-util.h"
#include "conf-files.h"
#include "def.h"
#include "dns-domain.h"
#include "fd-util.h"
#include "fileio.h"
#include "hexdecoct.h"
#include "parse-util.h"
#include "resolved-dns-trust-anchor.h"
#include "resolved-dns-dnssec.h"
#include "set.h"
#include "string-util.h"
#include "strv.h"
static const char trust_anchor_dirs[] = CONF_PATHS_NULSTR("dnssec-trust-anchors.d");
/* The DS RR from https://data.iana.org/root-anchors/root-anchors.xml, retrieved December 2015 */
static const uint8_t root_digest[] =
{ 0x49, 0xAA, 0xC1, 0x1D, 0x7B, 0x6F, 0x64, 0x46, 0x70, 0x2E, 0x54, 0xA1, 0x60, 0x73, 0x71, 0x60,
0x7A, 0x1A, 0x41, 0x85, 0x52, 0x00, 0xFD, 0x2C, 0xE1, 0xCD, 0xDE, 0x32, 0xF2, 0x4E, 0x8F, 0xB5 };
static bool dns_trust_anchor_knows_domain_positive(DnsTrustAnchor *d, const char *name) {
assert(d);
/* Returns true if there's an entry for the specified domain
* name in our trust anchor */
return
hashmap_contains(d->positive_by_key, &DNS_RESOURCE_KEY_CONST(DNS_CLASS_IN, DNS_TYPE_DNSKEY, name)) ||
hashmap_contains(d->positive_by_key, &DNS_RESOURCE_KEY_CONST(DNS_CLASS_IN, DNS_TYPE_DS, name));
}
static int dns_trust_anchor_add_builtin(DnsTrustAnchor *d) {
_cleanup_(dns_resource_record_unrefp) DnsResourceRecord *rr = NULL;
_cleanup_(dns_answer_unrefp) DnsAnswer *answer = NULL;
int r;
assert(d);
r = hashmap_ensure_allocated(&d->positive_by_key, &dns_resource_key_hash_ops);
if (r < 0)
return r;
/* Only add the built-in trust anchor if there's neither a DS
* nor a DNSKEY defined for the root domain. That way users
* have an easy way to override the root domain DS/DNSKEY
* data. */
if (dns_trust_anchor_knows_domain_positive(d, "."))
return 0;
/* Add the RR from https://data.iana.org/root-anchors/root-anchors.xml */
rr = dns_resource_record_new_full(DNS_CLASS_IN, DNS_TYPE_DS, "");
if (!rr)
return -ENOMEM;
rr->ds.key_tag = 19036;
rr->ds.algorithm = DNSSEC_ALGORITHM_RSASHA256;
rr->ds.digest_type = DNSSEC_DIGEST_SHA256;
rr->ds.digest_size = sizeof(root_digest);
rr->ds.digest = memdup(root_digest, rr->ds.digest_size);
if (!rr->ds.digest)
return -ENOMEM;
answer = dns_answer_new(1);
if (!answer)
return -ENOMEM;
r = dns_answer_add(answer, rr, 0, DNS_ANSWER_AUTHENTICATED);
if (r < 0)
return r;
r = hashmap_put(d->positive_by_key, rr->key, answer);
if (r < 0)
return r;
answer = NULL;
return 0;
}
static int dns_trust_anchor_load_positive(DnsTrustAnchor *d, const char *path, unsigned line, const char *s) {
_cleanup_(dns_resource_record_unrefp) DnsResourceRecord *rr = NULL;
_cleanup_free_ char *domain = NULL, *class = NULL, *type = NULL;
_cleanup_(dns_answer_unrefp) DnsAnswer *answer = NULL;
DnsAnswer *old_answer = NULL;
const char *p = s;
int r;
assert(d);
assert(line);
r = extract_first_word(&p, &domain, NULL, EXTRACT_QUOTES);
if (r < 0)
return log_warning_errno(r, "Unable to parse domain in line %s:%u: %m", path, line);
if (!dns_name_is_valid(domain)) {
log_warning("Domain name %s is invalid, at line %s:%u, ignoring line.", domain, path, line);
return -EINVAL;
}
r = extract_many_words(&p, NULL, 0, &class, &type, NULL);
if (r < 0)
return log_warning_errno(r, "Unable to parse class and type in line %s:%u: %m", path, line);
if (r != 2) {
log_warning("Missing class or type in line %s:%u", path, line);
return -EINVAL;
}
if (!strcaseeq(class, "IN")) {
log_warning("RR class %s is not supported, ignoring line %s:%u.", class, path, line);
return -EINVAL;
}
if (strcaseeq(type, "DS")) {
_cleanup_free_ char *key_tag = NULL, *algorithm = NULL, *digest_type = NULL, *digest = NULL;
_cleanup_free_ void *dd = NULL;
uint16_t kt;
int a, dt;
size_t l;
r = extract_many_words(&p, NULL, 0, &key_tag, &algorithm, &digest_type, &digest, NULL);
if (r < 0) {
log_warning_errno(r, "Failed to parse DS parameters on line %s:%u: %m", path, line);
return -EINVAL;
}
if (r != 4) {
log_warning("Missing DS parameters on line %s:%u", path, line);
return -EINVAL;
}
r = safe_atou16(key_tag, &kt);
if (r < 0)
return log_warning_errno(r, "Failed to parse DS key tag %s on line %s:%u: %m", key_tag, path, line);
a = dnssec_algorithm_from_string(algorithm);
if (a < 0) {
log_warning("Failed to parse DS algorithm %s on line %s:%u", algorithm, path, line);
return -EINVAL;
}
dt = dnssec_digest_from_string(digest_type);
if (dt < 0) {
log_warning("Failed to parse DS digest type %s on line %s:%u", digest_type, path, line);
return -EINVAL;
}
r = unhexmem(digest, strlen(digest), &dd, &l);
if (r < 0) {
log_warning("Failed to parse DS digest %s on line %s:%u", digest, path, line);
return -EINVAL;
}
rr = dns_resource_record_new_full(DNS_CLASS_IN, DNS_TYPE_DS, domain);
if (!rr)
return log_oom();
rr->ds.key_tag = kt;
rr->ds.algorithm = a;
rr->ds.digest_type = dt;
rr->ds.digest_size = l;
rr->ds.digest = dd;
dd = NULL;
} else if (strcaseeq(type, "DNSKEY")) {
_cleanup_free_ char *flags = NULL, *protocol = NULL, *algorithm = NULL, *key = NULL;
_cleanup_free_ void *k = NULL;
uint16_t f;
size_t l;
int a;
r = extract_many_words(&p, NULL, 0, &flags, &protocol, &algorithm, &key, NULL);
if (r < 0)
return log_warning_errno(r, "Failed to parse DNSKEY parameters on line %s:%u: %m", path, line);
if (r != 4) {
log_warning("Missing DNSKEY parameters on line %s:%u", path, line);
return -EINVAL;
}
if (!streq(protocol, "3")) {
log_warning("DNSKEY Protocol is not 3 on line %s:%u", path, line);
return -EINVAL;
}
r = safe_atou16(flags, &f);
if (r < 0)
return log_warning_errno(r, "Failed to parse DNSKEY flags field %s on line %s:%u", flags, path, line);
if ((f & DNSKEY_FLAG_ZONE_KEY) == 0) {
log_warning("DNSKEY lacks zone key bit set on line %s:%u", path, line);
return -EINVAL;
}
if ((f & DNSKEY_FLAG_REVOKE)) {
log_warning("DNSKEY is already revoked on line %s:%u", path, line);
return -EINVAL;
}
a = dnssec_algorithm_from_string(algorithm);
if (a < 0) {
log_warning("Failed to parse DNSKEY algorithm %s on line %s:%u", algorithm, path, line);
return -EINVAL;
}
r = unbase64mem(key, strlen(key), &k, &l);
if (r < 0)
return log_warning_errno(r, "Failed to parse DNSKEY key data %s on line %s:%u", key, path, line);
rr = dns_resource_record_new_full(DNS_CLASS_IN, DNS_TYPE_DNSKEY, domain);
if (!rr)
return log_oom();
rr->dnskey.flags = f;
rr->dnskey.protocol = 3;
rr->dnskey.algorithm = a;
rr->dnskey.key_size = l;
rr->dnskey.key = k;
k = NULL;
} else {
log_warning("RR type %s is not supported, ignoring line %s:%u.", type, path, line);
return -EINVAL;
}
if (!isempty(p)) {
log_warning("Trailing garbage on line %s:%u, ignoring line.", path, line);
return -EINVAL;
}
r = hashmap_ensure_allocated(&d->positive_by_key, &dns_resource_key_hash_ops);
if (r < 0)
return log_oom();
old_answer = hashmap_get(d->positive_by_key, rr->key);
answer = dns_answer_ref(old_answer);
r = dns_answer_add_extend(&answer, rr, 0, DNS_ANSWER_AUTHENTICATED);
if (r < 0)
return log_error_errno(r, "Failed to add trust anchor RR: %m");
r = hashmap_replace(d->positive_by_key, rr->key, answer);
if (r < 0)
return log_error_errno(r, "Failed to add answer to trust anchor: %m");
old_answer = dns_answer_unref(old_answer);
answer = NULL;
return 0;
}
static int dns_trust_anchor_load_negative(DnsTrustAnchor *d, const char *path, unsigned line, const char *s) {
_cleanup_free_ char *domain = NULL;
const char *p = s;
int r;
assert(d);
assert(line);
r = extract_first_word(&p, &domain, NULL, EXTRACT_QUOTES);
if (r < 0)
return log_warning_errno(r, "Unable to parse line %s:%u: %m", path, line);
if (!dns_name_is_valid(domain)) {
log_warning("Domain name %s is invalid, at line %s:%u, ignoring line.", domain, path, line);
return -EINVAL;
}
if (!isempty(p)) {
log_warning("Trailing garbage at line %s:%u, ignoring line.", path, line);
return -EINVAL;
}
r = set_ensure_allocated(&d->negative_by_name, &dns_name_hash_ops);
if (r < 0)
return log_oom();
r = set_put(d->negative_by_name, domain);
if (r < 0)
return log_oom();
if (r > 0)
domain = NULL;
return 0;
}
static int dns_trust_anchor_load_files(
DnsTrustAnchor *d,
const char *suffix,
int (*loader)(DnsTrustAnchor *d, const char *path, unsigned n, const char *line)) {
_cleanup_strv_free_ char **files = NULL;
char **f;
int r;
assert(d);
assert(suffix);
assert(loader);
r = conf_files_list_nulstr(&files, suffix, NULL, trust_anchor_dirs);
if (r < 0)
return log_error_errno(r, "Failed to enumerate %s trust anchor files: %m", suffix);
STRV_FOREACH(f, files) {
_cleanup_fclose_ FILE *g = NULL;
char line[LINE_MAX];
unsigned n = 0;
g = fopen(*f, "r");
if (!g) {
if (errno == ENOENT)
continue;
log_warning_errno(errno, "Failed to open %s: %m", *f);
continue;
}
FOREACH_LINE(line, g, log_warning_errno(errno, "Failed to read %s, ignoring: %m", *f)) {
char *l;
n++;
l = strstrip(line);
if (isempty(l))
continue;
if (*l == ';')
continue;
(void) loader(d, *f, n, l);
}
}
return 0;
}
static void dns_trust_anchor_dump(DnsTrustAnchor *d) {
DnsAnswer *a;
Iterator i;
assert(d);
if (hashmap_isempty(d->positive_by_key))
log_info("No positive trust anchors defined.");
else {
log_info("Positive Trust Anchors:");
HASHMAP_FOREACH(a, d->positive_by_key, i) {
DnsResourceRecord *rr;
DNS_ANSWER_FOREACH(rr, a)
log_info("%s", dns_resource_record_to_string(rr));
}
}
if (set_isempty(d->negative_by_name))
log_info("No negative trust anchors defined.");
else {
char *n;
log_info("Negative trust anchors:");
SET_FOREACH(n, d->negative_by_name, i)
log_info("%s%s", n, endswith(n, ".") ? "" : ".");
}
}
int dns_trust_anchor_load(DnsTrustAnchor *d) {
int r;
assert(d);
/* If loading things from disk fails, we don't consider this fatal */
(void) dns_trust_anchor_load_files(d, ".positive", dns_trust_anchor_load_positive);
(void) dns_trust_anchor_load_files(d, ".negative", dns_trust_anchor_load_negative);
/* However, if the built-in DS fails, then we have a problem. */
r = dns_trust_anchor_add_builtin(d);
if (r < 0)
return log_error_errno(r, "Failed to add trust anchor built-in: %m");
dns_trust_anchor_dump(d);
return 0;
}
void dns_trust_anchor_flush(DnsTrustAnchor *d) {
DnsAnswer *a;
assert(d);
while ((a = hashmap_steal_first(d->positive_by_key)))
dns_answer_unref(a);
d->positive_by_key = hashmap_free(d->positive_by_key);
d->negative_by_name = set_free_free(d->negative_by_name);
}
int dns_trust_anchor_lookup_positive(DnsTrustAnchor *d, const DnsResourceKey *key, DnsAnswer **ret) {
DnsAnswer *a;
assert(d);
assert(key);
assert(ret);
/* We only serve DS and DNSKEY RRs. */
if (!IN_SET(key->type, DNS_TYPE_DS, DNS_TYPE_DNSKEY))
return 0;
a = hashmap_get(d->positive_by_key, key);
if (!a)
return 0;
*ret = dns_answer_ref(a);
return 1;
}
int dns_trust_anchor_lookup_negative(DnsTrustAnchor *d, const char *name) {
assert(d);
assert(name);
return set_contains(d->negative_by_name, name);
}
static int dns_trust_anchor_remove_revoked(DnsTrustAnchor *d, DnsResourceRecord *rr) {
_cleanup_(dns_answer_unrefp) DnsAnswer *new_answer = NULL;
DnsAnswer *old_answer;
int r;
old_answer = hashmap_get(d->positive_by_key, rr->key);
if (!old_answer)
return 0;
new_answer = dns_answer_ref(old_answer);
r = dns_answer_remove_by_rr(&new_answer, rr);
if (r <= 0)
return r;
/* We found the key! Warn the user */
log_struct(LOG_WARNING,
LOG_MESSAGE_ID(SD_MESSAGE_DNSSEC_TRUST_ANCHOR_REVOKED),
LOG_MESSAGE("DNSSEC Trust anchor %s has been revoked. Please update the trust anchor, or upgrade your operating system."), strna(dns_resource_record_to_string(rr)),
"TRUST_ANCHOR=%s", dns_resource_record_to_string(rr),
NULL);
if (dns_answer_size(new_answer) <= 0) {
assert_se(hashmap_remove(d->positive_by_key, rr->key) == old_answer);
dns_answer_unref(old_answer);
return 1;
}
r = hashmap_replace(d->positive_by_key, new_answer->items[0].rr->key, new_answer);
if (r < 0)
return r;
new_answer = NULL;
dns_answer_unref(old_answer);
return 1;
}
static int dns_trust_anchor_check_revoked_one(DnsTrustAnchor *d, DnsResourceRecord *revoked_dnskey) {
DnsAnswer *a;
int r;
assert(d);
assert(revoked_dnskey);
assert(revoked_dnskey->key->type == DNS_TYPE_DNSKEY);
assert(revoked_dnskey->dnskey.flags & DNSKEY_FLAG_REVOKE);
a = hashmap_get(d->positive_by_key, revoked_dnskey->key);
if (a) {
DnsResourceRecord *anchor;
/* First, look for the precise DNSKEY in our trust anchor database */
DNS_ANSWER_FOREACH(anchor, a) {
if (anchor->dnskey.protocol != revoked_dnskey->dnskey.protocol)
continue;
if (anchor->dnskey.algorithm != revoked_dnskey->dnskey.algorithm)
continue;
if (anchor->dnskey.key_size != revoked_dnskey->dnskey.key_size)
continue;
if (((anchor->dnskey.flags ^ revoked_dnskey->dnskey.flags) | DNSKEY_FLAG_REVOKE) != DNSKEY_FLAG_REVOKE)
continue;
if (memcmp(anchor->dnskey.key, revoked_dnskey->dnskey.key, anchor->dnskey.key_size) != 0)
continue;
dns_trust_anchor_remove_revoked(d, anchor);
break;
}
}
a = hashmap_get(d->positive_by_key, &DNS_RESOURCE_KEY_CONST(revoked_dnskey->key->class, DNS_TYPE_DS, DNS_RESOURCE_KEY_NAME(revoked_dnskey->key)));
if (a) {
DnsResourceRecord *anchor;
/* Second, look for DS RRs matching this DNSKEY in our trust anchor database */
DNS_ANSWER_FOREACH(anchor, a) {
r = dnssec_verify_dnskey(revoked_dnskey, anchor, true);
if (r < 0)
return r;
if (r == 0)
continue;
dns_trust_anchor_remove_revoked(d, anchor);
break;
}
}
return 0;
}
int dns_trust_anchor_check_revoked(DnsTrustAnchor *d, DnsAnswer *rrs, const DnsResourceKey *key) {
DnsResourceRecord *dnskey;
int r;
assert(d);
assert(key);
/* Looks for self-signed DNSKEY RRs in "rrs" that have been revoked. */
if (key->type != DNS_TYPE_DNSKEY)
return 0;
DNS_ANSWER_FOREACH(dnskey, rrs) {
DnsResourceRecord *rrsig;
DnssecResult result;
r = dns_resource_key_equal(key, dnskey->key);
if (r < 0)
return r;
if (r == 0)
continue;
/* Is this DNSKEY revoked? */
if ((dnskey->dnskey.flags & DNSKEY_FLAG_REVOKE) == 0)
continue;
/* Could this be interesting to us at all? If not,
* there's no point in looking for and verifying a
* self-signed RRSIG. */
if (!dns_trust_anchor_knows_domain_positive(d, DNS_RESOURCE_KEY_NAME(dnskey->key)))
continue;
/* Look for a self-signed RRSIG */
DNS_ANSWER_FOREACH(rrsig, rrs) {
if (rrsig->key->type != DNS_TYPE_RRSIG)
continue;
r = dnssec_rrsig_match_dnskey(rrsig, dnskey, true);
if (r < 0)
return r;
if (r == 0)
continue;
r = dnssec_verify_rrset(rrs, key, rrsig, dnskey, USEC_INFINITY, &result);
if (r < 0)
return r;
if (result != DNSSEC_VALIDATED)
continue;
/* Bingo! Now, act! */
r = dns_trust_anchor_check_revoked_one(d, dnskey);
if (r < 0)
return r;
}
}
return 0;
}