/***
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 <http://www.gnu.org/licenses/>.
***/
#ifdef HAVE_GCRYPT
#include <gcrypt.h>
#endif
#include "alloc-util.h"
#include "dns-domain.h"
#include "hexdecoct.h"
#include "resolved-dns-dnssec.h"
#include "resolved-dns-packet.h"
#include "string-table.h"
#define VERIFY_RRS_MAX 256
#define MAX_KEY_SIZE (32*1024)
/* Permit a maximum clock skew of 1h 10min. This should be enough to deal with DST confusion */
#define SKEW_MAX (1*USEC_PER_HOUR + 10*USEC_PER_MINUTE)
/* Maximum number of NSEC3 iterations we'll do. RFC5155 says 2500 shall be the maximum useful value */
#define NSEC3_ITERATIONS_MAX 2500
/*
* The DNSSEC Chain of trust:
*
* Normal RRs are protected via RRSIG RRs in combination with DNSKEY RRs, all in the same zone
* DNSKEY RRs are either protected like normal RRs, or via a DS from a zone "higher" up the tree
* DS RRs are protected like normal RRs
*
* Example chain:
* Normal RR → RRSIG/DNSKEY+ → DS → RRSIG/DNSKEY+ → DS → ... → DS → RRSIG/DNSKEY+ → DS
*/
uint16_t dnssec_keytag(DnsResourceRecord *dnskey, bool mask_revoke) {
const uint8_t *p;
uint32_t sum, f;
size_t i;
/* The algorithm from RFC 4034, Appendix B. */
assert(dnskey);
assert(dnskey->key->type == DNS_TYPE_DNSKEY);
f = (uint32_t) dnskey->dnskey.flags;
if (mask_revoke)
f &= ~DNSKEY_FLAG_REVOKE;
sum = f + ((((uint32_t) dnskey->dnskey.protocol) << 8) + (uint32_t) dnskey->dnskey.algorithm);
p = dnskey->dnskey.key;
for (i = 0; i < dnskey->dnskey.key_size; i++)
sum += (i & 1) == 0 ? (uint32_t) p[i] << 8 : (uint32_t) p[i];
sum += (sum >> 16) & UINT32_C(0xFFFF);
return sum & UINT32_C(0xFFFF);
}
int dnssec_canonicalize(const char *n, char *buffer, size_t buffer_max) {
size_t c = 0;
int r;
/* Converts the specified hostname into DNSSEC canonicalized
* form. */
if (buffer_max < 2)
return -ENOBUFS;
for (;;) {
r = dns_label_unescape(&n, buffer, buffer_max);
if (r < 0)
return r;
if (r == 0)
break;
if (buffer_max < (size_t) r + 2)
return -ENOBUFS;
/* The DNSSEC canonical form is not clear on what to
* do with dots appearing in labels, the way DNS-SD
* does it. Refuse it for now. */
if (memchr(buffer, '.', r))
return -EINVAL;
ascii_strlower_n(buffer, (size_t) r);
buffer[r] = '.';
buffer += r + 1;
c += r + 1;
buffer_max -= r + 1;
}
if (c <= 0) {
/* Not even a single label: this is the root domain name */
assert(buffer_max > 2);
buffer[0] = '.';
buffer[1] = 0;
return 1;
}
return (int) c;
}
#ifdef HAVE_GCRYPT
static void initialize_libgcrypt(void) {
const char *p;
if (gcry_control(GCRYCTL_INITIALIZATION_FINISHED_P))
return;
p = gcry_check_version("1.4.5");
assert(p);
gcry_control(GCRYCTL_DISABLE_SECMEM);
gcry_control(GCRYCTL_INITIALIZATION_FINISHED, 0);
}
static int rr_compare(const void *a, const void *b) {
DnsResourceRecord **x = (DnsResourceRecord**) a, **y = (DnsResourceRecord**) b;
size_t m;
int r;
/* Let's order the RRs according to RFC 4034, Section 6.3 */
assert(x);
assert(*x);
assert((*x)->wire_format);
assert(y);
assert(*y);
assert((*y)->wire_format);
m = MIN(DNS_RESOURCE_RECORD_RDATA_SIZE(*x), DNS_RESOURCE_RECORD_RDATA_SIZE(*y));
r = memcmp(DNS_RESOURCE_RECORD_RDATA(*x), DNS_RESOURCE_RECORD_RDATA(*y), m);
if (r != 0)
return r;
if (DNS_RESOURCE_RECORD_RDATA_SIZE(*x) < DNS_RESOURCE_RECORD_RDATA_SIZE(*y))
return -1;
else if (DNS_RESOURCE_RECORD_RDATA_SIZE(*x) > DNS_RESOURCE_RECORD_RDATA_SIZE(*y))
return 1;
return 0;
}
static int dnssec_rsa_verify_raw(
const char *hash_algorithm,
const void *signature, size_t signature_size,
const void *data, size_t data_size,
const void *exponent, size_t exponent_size,
const void *modulus, size_t modulus_size) {
gcry_sexp_t public_key_sexp = NULL, data_sexp = NULL, signature_sexp = NULL;
gcry_mpi_t n = NULL, e = NULL, s = NULL;
gcry_error_t ge;
int r;
assert(hash_algorithm);
ge = gcry_mpi_scan(&s, GCRYMPI_FMT_USG, signature, signature_size, NULL);
if (ge != 0) {
r = -EIO;
goto finish;
}
ge = gcry_mpi_scan(&e, GCRYMPI_FMT_USG, exponent, exponent_size, NULL);
if (ge != 0) {
r = -EIO;
goto finish;
}
ge = gcry_mpi_scan(&n, GCRYMPI_FMT_USG, modulus, modulus_size, NULL);
if (ge != 0) {
r = -EIO;
goto finish;
}
ge = gcry_sexp_build(&signature_sexp,
NULL,
"(sig-val (rsa (s %m)))",
s);
if (ge != 0) {
r = -EIO;
goto finish;
}
ge = gcry_sexp_build(&data_sexp,
NULL,
"(data (flags pkcs1) (hash %s %b))",
hash_algorithm,
(int) data_size,
data);
if (ge != 0) {
r = -EIO;
goto finish;
}
ge = gcry_sexp_build(&public_key_sexp,
NULL,
"(public-key (rsa (n %m) (e %m)))",
n,
e);
if (ge != 0) {
r = -EIO;
goto finish;
}
ge = gcry_pk_verify(signature_sexp, data_sexp, public_key_sexp);
if (gpg_err_code(ge) == GPG_ERR_BAD_SIGNATURE)
r = 0;
else if (ge != 0) {
log_debug("RSA signature check failed: %s", gpg_strerror(ge));
r = -EIO;
} else
r = 1;
finish:
if (e)
gcry_mpi_release(e);
if (n)
gcry_mpi_release(n);
if (s)
gcry_mpi_release(s);
if (public_key_sexp)
gcry_sexp_release(public_key_sexp);
if (signature_sexp)
gcry_sexp_release(signature_sexp);
if (data_sexp)
gcry_sexp_release(data_sexp);
return r;
}
static int dnssec_rsa_verify(
const char *hash_algorithm,
const void *hash, size_t hash_size,
DnsResourceRecord *rrsig,
DnsResourceRecord *dnskey) {
size_t exponent_size, modulus_size;
void *exponent, *modulus;
assert(hash_algorithm);
assert(hash);
assert(hash_size > 0);
assert(rrsig);
assert(dnskey);
if (*(uint8_t*) dnskey->dnskey.key == 0) {
/* exponent is > 255 bytes long */
exponent = (uint8_t*) dnskey->dnskey.key + 3;
exponent_size =
((size_t) (((uint8_t*) dnskey->dnskey.key)[1]) << 8) |
((size_t) ((uint8_t*) dnskey->dnskey.key)[2]);
if (exponent_size < 256)
return -EINVAL;
if (3 + exponent_size >= dnskey->dnskey.key_size)
return -EINVAL;
modulus = (uint8_t*) dnskey->dnskey.key + 3 + exponent_size;
modulus_size = dnskey->dnskey.key_size - 3 - exponent_size;
} else {
/* exponent is <= 255 bytes long */
exponent = (uint8_t*) dnskey->dnskey.key + 1;
exponent_size = (size_t) ((uint8_t*) dnskey->dnskey.key)[0];
if (exponent_size <= 0)
return -EINVAL;
if (1 + exponent_size >= dnskey->dnskey.key_size)
return -EINVAL;
modulus = (uint8_t*) dnskey->dnskey.key + 1 + exponent_size;
modulus_size = dnskey->dnskey.key_size - 1 - exponent_size;
}
return dnssec_rsa_verify_raw(
hash_algorithm,
rrsig->rrsig.signature, rrsig->rrsig.signature_size,
hash, hash_size,
exponent, exponent_size,
modulus, modulus_size);
}
static int dnssec_ecdsa_verify_raw(
const char *hash_algorithm,
const char *curve,
const void *signature_r, size_t signature_r_size,
const void *signature_s, size_t signature_s_size,
const void *data, size_t data_size,
const void *key, size_t key_size) {
gcry_sexp_t public_key_sexp = NULL, data_sexp = NULL, signature_sexp = NULL;
gcry_mpi_t q = NULL, r = NULL, s = NULL;
gcry_error_t ge;
int k;
assert(hash_algorithm);
ge = gcry_mpi_scan(&r, GCRYMPI_FMT_USG, signature_r, signature_r_size, NULL);
if (ge != 0) {
k = -EIO;
goto finish;
}
ge = gcry_mpi_scan(&s, GCRYMPI_FMT_USG, signature_s, signature_s_size, NULL);
if (ge != 0) {
k = -EIO;
goto finish;
}
ge = gcry_mpi_scan(&q, GCRYMPI_FMT_USG, key, key_size, NULL);
if (ge != 0) {
k = -EIO;
goto finish;
}
ge = gcry_sexp_build(&signature_sexp,
NULL,
"(sig-val (ecdsa (r %m) (s %m)))",
r,
s);
if (ge != 0) {
k = -EIO;
goto finish;
}
ge = gcry_sexp_build(&data_sexp,
NULL,
"(data (flags rfc6979) (hash %s %b))",
hash_algorithm,
(int) data_size,
data);
if (ge != 0) {
k = -EIO;
goto finish;
}
ge = gcry_sexp_build(&public_key_sexp,
NULL,
"(public-key (ecc (curve %s) (q %m)))",
curve,
q);
if (ge != 0) {
k = -EIO;
goto finish;
}
ge = gcry_pk_verify(signature_sexp, data_sexp, public_key_sexp);
if (gpg_err_code(ge) == GPG_ERR_BAD_SIGNATURE)
k = 0;
else if (ge != 0) {
log_debug("ECDSA signature check failed: %s", gpg_strerror(ge));
k = -EIO;
} else
k = 1;
finish:
if (r)
gcry_mpi_release(r);
if (s)
gcry_mpi_release(s);
if (q)
gcry_mpi_release(q);
if (public_key_sexp)
gcry_sexp_release(public_key_sexp);
if (signature_sexp)
gcry_sexp_release(signature_sexp);
if (data_sexp)
gcry_sexp_release(data_sexp);
return k;
}
static int dnssec_ecdsa_verify(
const char *hash_algorithm,
int algorithm,
const void *hash, size_t hash_size,
DnsResourceRecord *rrsig,
DnsResourceRecord *dnskey) {
const char *curve;
size_t key_size;
uint8_t *q;
assert(hash);
assert(hash_size);
assert(rrsig);
assert(dnskey);
if (algorithm == DNSSEC_ALGORITHM_ECDSAP256SHA256) {
key_size = 32;
curve = "NIST P-256";
} else if (algorithm == DNSSEC_ALGORITHM_ECDSAP384SHA384) {
key_size = 48;
curve = "NIST P-384";
} else
return -EOPNOTSUPP;
if (dnskey->dnskey.key_size != key_size * 2)
return -EINVAL;
if (rrsig->rrsig.signature_size != key_size * 2)
return -EINVAL;
q = alloca(key_size*2 + 1);
q[0] = 0x04; /* Prepend 0x04 to indicate an uncompressed key */
memcpy(q+1, dnskey->dnskey.key, key_size*2);
return dnssec_ecdsa_verify_raw(
hash_algorithm,
curve,
rrsig->rrsig.signature, key_size,
(uint8_t*) rrsig->rrsig.signature + key_size, key_size,
hash, hash_size,
q, key_size*2+1);
}
static void md_add_uint8(gcry_md_hd_t md, uint8_t v) {
gcry_md_write(md, &v, sizeof(v));
}
static void md_add_uint16(gcry_md_hd_t md, uint16_t v) {
v = htobe16(v);
gcry_md_write(md, &v, sizeof(v));
}
static void md_add_uint32(gcry_md_hd_t md, uint32_t v) {
v = htobe32(v);
gcry_md_write(md, &v, sizeof(v));
}
static int dnssec_rrsig_prepare(DnsResourceRecord *rrsig) {
int n_key_labels, n_signer_labels;
const char *name;
int r;
/* Checks whether the specified RRSIG RR is somewhat valid, and initializes the .n_skip_labels_source and
* .n_skip_labels_signer fields so that we can use them later on. */
assert(rrsig);
assert(rrsig->key->type == DNS_TYPE_RRSIG);
/* Check if this RRSIG RR is already prepared */
if (rrsig->n_skip_labels_source != (unsigned) -1)
return 0;
if (rrsig->rrsig.inception > rrsig->rrsig.expiration)
return -EINVAL;
name = DNS_RESOURCE_KEY_NAME(rrsig->key);
n_key_labels = dns_name_count_labels(name);
if (n_key_labels < 0)
return n_key_labels;
if (rrsig->rrsig.labels > n_key_labels)
return -EINVAL;
n_signer_labels = dns_name_count_labels(rrsig->rrsig.signer);
if (n_signer_labels < 0)
return n_signer_labels;
if (n_signer_labels > rrsig->rrsig.labels)
return -EINVAL;
r = dns_name_skip(name, n_key_labels - n_signer_labels, &name);
if (r < 0)
return r;
if (r == 0)
return -EINVAL;
/* Check if the signer is really a suffix of us */
r = dns_name_equal(name, rrsig->rrsig.signer);
if (r < 0)
return r;
if (r == 0)
return -EINVAL;
rrsig->n_skip_labels_source = n_key_labels - rrsig->rrsig.labels;
rrsig->n_skip_labels_signer = n_key_labels - n_signer_labels;
return 0;
}
static int dnssec_rrsig_expired(DnsResourceRecord *rrsig, usec_t realtime) {
usec_t expiration, inception, skew;
assert(rrsig);
assert(rrsig->key->type == DNS_TYPE_RRSIG);
if (realtime == USEC_INFINITY)
realtime = now(CLOCK_REALTIME);
expiration = rrsig->rrsig.expiration * USEC_PER_SEC;
inception = rrsig->rrsig.inception * USEC_PER_SEC;
/* Consider inverted validity intervals as expired */
if (inception > expiration)
return true;
/* Permit a certain amount of clock skew of 10% of the valid
* time range. This takes inspiration from unbound's
* resolver. */
skew = (expiration - inception) / 10;
if (skew > SKEW_MAX)
skew = SKEW_MAX;
if (inception < skew)
inception = 0;
else
inception -= skew;
if (expiration + skew < expiration)
expiration = USEC_INFINITY;
else
expiration += skew;
return realtime < inception || realtime > expiration;
}
static int algorithm_to_gcrypt_md(uint8_t algorithm) {
/* Translates a DNSSEC signature algorithm into a gcrypt
* digest identifier.
*
* Note that we implement all algorithms listed as "Must
* implement" and "Recommended to Implement" in RFC6944. We
* don't implement any algorithms that are listed as
* "Optional" or "Must Not Implement". Specifically, we do not
* implement RSAMD5, DSASHA1, DH, DSA-NSEC3-SHA1, and
* GOST-ECC. */
switch (algorithm) {
case DNSSEC_ALGORITHM_RSASHA1:
case DNSSEC_ALGORITHM_RSASHA1_NSEC3_SHA1:
return GCRY_MD_SHA1;
case DNSSEC_ALGORITHM_RSASHA256:
case DNSSEC_ALGORITHM_ECDSAP256SHA256:
return GCRY_MD_SHA256;
case DNSSEC_ALGORITHM_ECDSAP384SHA384:
return GCRY_MD_SHA384;
case DNSSEC_ALGORITHM_RSASHA512:
return GCRY_MD_SHA512;
default:
return -EOPNOTSUPP;
}
}
static void dnssec_fix_rrset_ttl(
DnsResourceRecord *list[],
unsigned n,
DnsResourceRecord *rrsig,
usec_t realtime) {
unsigned k;
assert(list);
assert(n > 0);
assert(rrsig);
for (k = 0; k < n; k++) {
DnsResourceRecord *rr = list[k];
/* Pick the TTL as the minimum of the RR's TTL, the
* RR's original TTL according to the RRSIG and the
* RRSIG's own TTL, see RFC 4035, Section 5.3.3 */
rr->ttl = MIN3(rr->ttl, rrsig->rrsig.original_ttl, rrsig->ttl);
rr->expiry = rrsig->rrsig.expiration * USEC_PER_SEC;
/* Copy over information about the signer and wildcard source of synthesis */
rr->n_skip_labels_source = rrsig->n_skip_labels_source;
rr->n_skip_labels_signer = rrsig->n_skip_labels_signer;
}
rrsig->expiry = rrsig->rrsig.expiration * USEC_PER_SEC;
}
int dnssec_verify_rrset(
DnsAnswer *a,
const DnsResourceKey *key,
DnsResourceRecord *rrsig,
DnsResourceRecord *dnskey,
usec_t realtime,
DnssecResult *result) {
uint8_t wire_format_name[DNS_WIRE_FOMAT_HOSTNAME_MAX];
DnsResourceRecord **list, *rr;
const char *source, *name;
gcry_md_hd_t md = NULL;
int r, md_algorithm;
size_t k, n = 0;
size_t hash_size;
void *hash;
bool wildcard;
assert(key);
assert(rrsig);
assert(dnskey);
assert(result);
assert(rrsig->key->type == DNS_TYPE_RRSIG);
assert(dnskey->key->type == DNS_TYPE_DNSKEY);
/* Verifies the the RRSet matching the specified "key" in "a",
* using the signature "rrsig" and the key "dnskey". It's
* assumed the RRSIG and DNSKEY match. */
md_algorithm = algorithm_to_gcrypt_md(rrsig->rrsig.algorithm);
if (md_algorithm == -EOPNOTSUPP) {
*result = DNSSEC_UNSUPPORTED_ALGORITHM;
return 0;
}
if (md_algorithm < 0)
return md_algorithm;
r = dnssec_rrsig_prepare(rrsig);
if (r == -EINVAL) {
*result = DNSSEC_INVALID;
return r;
}
if (r < 0)
return r;
r = dnssec_rrsig_expired(rrsig, realtime);
if (r < 0)
return r;
if (r > 0) {
*result = DNSSEC_SIGNATURE_EXPIRED;
return 0;
}
name = DNS_RESOURCE_KEY_NAME(key);
/* Some keys may only appear signed in the zone apex, and are invalid anywhere else. (SOA, NS...) */
if (dns_type_apex_only(rrsig->rrsig.type_covered)) {
r = dns_name_equal(rrsig->rrsig.signer, name);
if (r < 0)
return r;
if (r == 0) {
*result = DNSSEC_INVALID;
return 0;
}
}
/* OTOH DS RRs may not appear in the zone apex, but are valid everywhere else. */
if (rrsig->rrsig.type_covered == DNS_TYPE_DS) {
r = dns_name_equal(rrsig->rrsig.signer, name);
if (r < 0)
return r;
if (r > 0) {
*result = DNSSEC_INVALID;
return 0;
}
}
/* Determine the "Source of Synthesis" and whether this is a wildcard RRSIG */
r = dns_name_suffix(name, rrsig->rrsig.labels, &source);
if (r < 0)
return r;
if (r > 0 && !dns_type_may_wildcard(rrsig->rrsig.type_covered)) {
/* We refuse to validate NSEC3 or SOA RRs that are synthesized from wildcards */
*result = DNSSEC_INVALID;
return 0;
}
if (r == 1) {
/* If we stripped a single label, then let's see if that maybe was "*". If so, we are not really
* synthesized from a wildcard, we are the wildcard itself. Treat that like a normal name. */
r = dns_name_startswith(name, "*");
if (r < 0)
return r;
if (r > 0)
source = name;
wildcard = r == 0;
} else
wildcard = r > 0;
/* Collect all relevant RRs in a single array, so that we can look at the RRset */
list = newa(DnsResourceRecord *, dns_answer_size(a));
DNS_ANSWER_FOREACH(rr, a) {
r = dns_resource_key_equal(key, rr->key);
if (r < 0)
return r;
if (r == 0)
continue;
/* We need the wire format for ordering, and digest calculation */
r = dns_resource_record_to_wire_format(rr, true);
if (r < 0)
return r;
list[n++] = rr;
if (n > VERIFY_RRS_MAX)
return -E2BIG;
}
if (n <= 0)
return -ENODATA;
/* Bring the RRs into canonical order */
qsort_safe(list, n, sizeof(DnsResourceRecord*), rr_compare);
/* OK, the RRs are now in canonical order. Let's calculate the digest */
initialize_libgcrypt();
hash_size = gcry_md_get_algo_dlen(md_algorithm);
assert(hash_size > 0);
gcry_md_open(&md, md_algorithm, 0);
if (!md)
return -EIO;
md_add_uint16(md, rrsig->rrsig.type_covered);
md_add_uint8(md, rrsig->rrsig.algorithm);
md_add_uint8(md, rrsig->rrsig.labels);
md_add_uint32(md, rrsig->rrsig.original_ttl);
md_add_uint32(md, rrsig->rrsig.expiration);
md_add_uint32(md, rrsig->rrsig.inception);
md_add_uint16(md, rrsig->rrsig.key_tag);
r = dns_name_to_wire_format(rrsig->rrsig.signer, wire_format_name, sizeof(wire_format_name), true);
if (r < 0)
goto finish;
gcry_md_write(md, wire_format_name, r);
/* Convert the source of synthesis into wire format */
r = dns_name_to_wire_format(source, wire_format_name, sizeof(wire_format_name), true);
if (r < 0)
goto finish;
for (k = 0; k < n; k++) {
size_t l;
rr = list[k];
/* Hash the source of synthesis. If this is a wildcard, then prefix it with the *. label */
if (wildcard)
gcry_md_write(md, (uint8_t[]) { 1, '*'}, 2);
gcry_md_write(md, wire_format_name, r);
md_add_uint16(md, rr->key->type);
md_add_uint16(md, rr->key->class);
md_add_uint32(md, rrsig->rrsig.original_ttl);
l = DNS_RESOURCE_RECORD_RDATA_SIZE(rr);
assert(l <= 0xFFFF);
md_add_uint16(md, (uint16_t) l);
gcry_md_write(md, DNS_RESOURCE_RECORD_RDATA(rr), l);
}
hash = gcry_md_read(md, 0);
if (!hash) {
r = -EIO;
goto finish;
}
switch (rrsig->rrsig.algorithm) {
case DNSSEC_ALGORITHM_RSASHA1:
case DNSSEC_ALGORITHM_RSASHA1_NSEC3_SHA1:
case DNSSEC_ALGORITHM_RSASHA256:
case DNSSEC_ALGORITHM_RSASHA512:
r = dnssec_rsa_verify(
gcry_md_algo_name(md_algorithm),
hash, hash_size,
rrsig,
dnskey);
break;
case DNSSEC_ALGORITHM_ECDSAP256SHA256:
case DNSSEC_ALGORITHM_ECDSAP384SHA384:
r = dnssec_ecdsa_verify(
gcry_md_algo_name(md_algorithm),
rrsig->rrsig.algorithm,
hash, hash_size,
rrsig,
dnskey);
break;
}
if (r < 0)
goto finish;
/* Now, fix the ttl, expiry, and remember the synthesizing source and the signer */
if (r > 0)
dnssec_fix_rrset_ttl(list, n, rrsig, realtime);
if (r == 0)
*result = DNSSEC_INVALID;
else if (wildcard)
*result = DNSSEC_VALIDATED_WILDCARD;
else
*result = DNSSEC_VALIDATED;
r = 0;
finish:
gcry_md_close(md);
return r;
}
int dnssec_rrsig_match_dnskey(DnsResourceRecord *rrsig, DnsResourceRecord *dnskey, bool revoked_ok) {
assert(rrsig);
assert(dnskey);
/* Checks if the specified DNSKEY RR matches the key used for
* the signature in the specified RRSIG RR */
if (rrsig->key->type != DNS_TYPE_RRSIG)
return -EINVAL;
if (dnskey->key->type != DNS_TYPE_DNSKEY)
return 0;
if (dnskey->key->class != rrsig->key->class)
return 0;
if ((dnskey->dnskey.flags & DNSKEY_FLAG_ZONE_KEY) == 0)
return 0;
if (!revoked_ok && (dnskey->dnskey.flags & DNSKEY_FLAG_REVOKE))
return 0;
if (dnskey->dnskey.protocol != 3)
return 0;
if (dnskey->dnskey.algorithm != rrsig->rrsig.algorithm)
return 0;
if (dnssec_keytag(dnskey, false) != rrsig->rrsig.key_tag)
return 0;
return dns_name_equal(DNS_RESOURCE_KEY_NAME(dnskey->key), rrsig->rrsig.signer);
}
int dnssec_key_match_rrsig(const DnsResourceKey *key, DnsResourceRecord *rrsig) {
assert(key);
assert(rrsig);
/* Checks if the specified RRSIG RR protects the RRSet of the specified RR key. */
if (rrsig->key->type != DNS_TYPE_RRSIG)
return 0;
if (rrsig->key->class != key->class)
return 0;
if (rrsig->rrsig.type_covered != key->type)
return 0;
return dns_name_equal(DNS_RESOURCE_KEY_NAME(rrsig->key), DNS_RESOURCE_KEY_NAME(key));
}
int dnssec_verify_rrset_search(
DnsAnswer *a,
const DnsResourceKey *key,
DnsAnswer *validated_dnskeys,
usec_t realtime,
DnssecResult *result,
DnsResourceRecord **ret_rrsig) {
bool found_rrsig = false, found_invalid = false, found_expired_rrsig = false, found_unsupported_algorithm = false;
DnsResourceRecord *rrsig;
int r;
assert(key);
assert(result);
/* Verifies all RRs from "a" that match the key "key" against DNSKEYs in "validated_dnskeys" */
if (!a || a->n_rrs <= 0)
return -ENODATA;
/* Iterate through each RRSIG RR. */
DNS_ANSWER_FOREACH(rrsig, a) {
DnsResourceRecord *dnskey;
DnsAnswerFlags flags;
/* Is this an RRSIG RR that applies to RRs matching our key? */
r = dnssec_key_match_rrsig(key, rrsig);
if (r < 0)
return r;
if (r == 0)
continue;
found_rrsig = true;
/* Look for a matching key */
DNS_ANSWER_FOREACH_FLAGS(dnskey, flags, validated_dnskeys) {
DnssecResult one_result;
if ((flags & DNS_ANSWER_AUTHENTICATED) == 0)
continue;
/* Is this a DNSKEY RR that matches they key of our RRSIG? */
r = dnssec_rrsig_match_dnskey(rrsig, dnskey, false);
if (r < 0)
return r;
if (r == 0)
continue;
/* Take the time here, if it isn't set yet, so
* that we do all validations with the same
* time. */
if (realtime == USEC_INFINITY)
realtime = now(CLOCK_REALTIME);
/* Yay, we found a matching RRSIG with a matching
* DNSKEY, awesome. Now let's verify all entries of
* the RRSet against the RRSIG and DNSKEY
* combination. */
r = dnssec_verify_rrset(a, key, rrsig, dnskey, realtime, &one_result);
if (r < 0)
return r;
switch (one_result) {
case DNSSEC_VALIDATED:
case DNSSEC_VALIDATED_WILDCARD:
/* Yay, the RR has been validated,
* return immediately, but fix up the expiry */
if (ret_rrsig)
*ret_rrsig = rrsig;
*result = one_result;
return 0;
case DNSSEC_INVALID:
/* If the signature is invalid, let's try another
key and/or signature. After all they
key_tags and stuff are not unique, and
might be shared by multiple keys. */
found_invalid = true;
continue;
case DNSSEC_UNSUPPORTED_ALGORITHM:
/* If the key algorithm is
unsupported, try another
RRSIG/DNSKEY pair, but remember we
encountered this, so that we can
return a proper error when we
encounter nothing better. */
found_unsupported_algorithm = true;
continue;
case DNSSEC_SIGNATURE_EXPIRED:
/* If the signature is expired, try
another one, but remember it, so
that we can return this */
found_expired_rrsig = true;
continue;
default:
assert_not_reached("Unexpected DNSSEC validation result");
}
}
}
if (found_expired_rrsig)
*result = DNSSEC_SIGNATURE_EXPIRED;
else if (found_unsupported_algorithm)
*result = DNSSEC_UNSUPPORTED_ALGORITHM;
else if (found_invalid)
*result = DNSSEC_INVALID;
else if (found_rrsig)
*result = DNSSEC_MISSING_KEY;
else
*result = DNSSEC_NO_SIGNATURE;
if (ret_rrsig)
*ret_rrsig = NULL;
return 0;
}
int dnssec_has_rrsig(DnsAnswer *a, const DnsResourceKey *key) {
DnsResourceRecord *rr;
int r;
/* Checks whether there's at least one RRSIG in 'a' that proctects RRs of the specified key */
DNS_ANSWER_FOREACH(rr, a) {
r = dnssec_key_match_rrsig(key, rr);
if (r < 0)
return r;
if (r > 0)
return 1;
}
return 0;
}
static int digest_to_gcrypt_md(uint8_t algorithm) {
/* Translates a DNSSEC digest algorithm into a gcrypt digest identifier */
switch (algorithm) {
case DNSSEC_DIGEST_SHA1:
return GCRY_MD_SHA1;
case DNSSEC_DIGEST_SHA256:
return GCRY_MD_SHA256;
case DNSSEC_DIGEST_SHA384:
return GCRY_MD_SHA384;
default:
return -EOPNOTSUPP;
}
}
int dnssec_verify_dnskey_by_ds(DnsResourceRecord *dnskey, DnsResourceRecord *ds, bool mask_revoke) {
char owner_name[DNSSEC_CANONICAL_HOSTNAME_MAX];
gcry_md_hd_t md = NULL;
size_t hash_size;
int md_algorithm, r;
void *result;
assert(dnskey);
assert(ds);
/* Implements DNSKEY verification by a DS, according to RFC 4035, section 5.2 */
if (dnskey->key->type != DNS_TYPE_DNSKEY)
return -EINVAL;
if (ds->key->type != DNS_TYPE_DS)
return -EINVAL;
if ((dnskey->dnskey.flags & DNSKEY_FLAG_ZONE_KEY) == 0)
return -EKEYREJECTED;
if (!mask_revoke && (dnskey->dnskey.flags & DNSKEY_FLAG_REVOKE))
return -EKEYREJECTED;
if (dnskey->dnskey.protocol != 3)
return -EKEYREJECTED;
if (dnskey->dnskey.algorithm != ds->ds.algorithm)
return 0;
if (dnssec_keytag(dnskey, mask_revoke) != ds->ds.key_tag)
return 0;
initialize_libgcrypt();
md_algorithm = digest_to_gcrypt_md(ds->ds.digest_type);
if (md_algorithm < 0)
return md_algorithm;
hash_size = gcry_md_get_algo_dlen(md_algorithm);
assert(hash_size > 0);
if (ds->ds.digest_size != hash_size)
return 0;
r = dnssec_canonicalize(DNS_RESOURCE_KEY_NAME(dnskey->key), owner_name, sizeof(owner_name));
if (r < 0)
return r;
gcry_md_open(&md, md_algorithm, 0);
if (!md)
return -EIO;
gcry_md_write(md, owner_name, r);
if (mask_revoke)
md_add_uint16(md, dnskey->dnskey.flags & ~DNSKEY_FLAG_REVOKE);
else
md_add_uint16(md, dnskey->dnskey.flags);
md_add_uint8(md, dnskey->dnskey.protocol);
md_add_uint8(md, dnskey->dnskey.algorithm);
gcry_md_write(md, dnskey->dnskey.key, dnskey->dnskey.key_size);
result = gcry_md_read(md, 0);
if (!result) {
r = -EIO;
goto finish;
}
r = memcmp(result, ds->ds.digest, ds->ds.digest_size) != 0;
finish:
gcry_md_close(md);
return r;
}
int dnssec_verify_dnskey_by_ds_search(DnsResourceRecord *dnskey, DnsAnswer *validated_ds) {
DnsResourceRecord *ds;
DnsAnswerFlags flags;
int r;
assert(dnskey);
if (dnskey->key->type != DNS_TYPE_DNSKEY)
return 0;
DNS_ANSWER_FOREACH_FLAGS(ds, flags, validated_ds) {
if ((flags & DNS_ANSWER_AUTHENTICATED) == 0)
continue;
if (ds->key->type != DNS_TYPE_DS)
continue;
if (ds->key->class != dnskey->key->class)
continue;
r = dns_name_equal(DNS_RESOURCE_KEY_NAME(dnskey->key), DNS_RESOURCE_KEY_NAME(ds->key));
if (r < 0)
return r;
if (r == 0)
continue;
r = dnssec_verify_dnskey_by_ds(dnskey, ds, false);
if (IN_SET(r, -EKEYREJECTED, -EOPNOTSUPP))
return 0; /* The DNSKEY is revoked or otherwise invalid, or we don't support the digest algorithm */
if (r < 0)
return r;
if (r > 0)
return 1;
}
return 0;
}
static int nsec3_hash_to_gcrypt_md(uint8_t algorithm) {
/* Translates a DNSSEC NSEC3 hash algorithm into a gcrypt digest identifier */
switch (algorithm) {
case NSEC3_ALGORITHM_SHA1:
return GCRY_MD_SHA1;
default:
return -EOPNOTSUPP;
}
}
int dnssec_nsec3_hash(DnsResourceRecord *nsec3, const char *name, void *ret) {
uint8_t wire_format[DNS_WIRE_FOMAT_HOSTNAME_MAX];
gcry_md_hd_t md = NULL;
size_t hash_size;
int algorithm;
void *result;
unsigned k;
int r;
assert(nsec3);
assert(name);
assert(ret);
if (nsec3->key->type != DNS_TYPE_NSEC3)
return -EINVAL;
if (nsec3->nsec3.iterations > NSEC3_ITERATIONS_MAX) {
log_debug("Ignoring NSEC3 RR %s with excessive number of iterations.", dns_resource_record_to_string(nsec3));
return -EOPNOTSUPP;
}
algorithm = nsec3_hash_to_gcrypt_md(nsec3->nsec3.algorithm);
if (algorithm < 0)
return algorithm;
initialize_libgcrypt();
hash_size = gcry_md_get_algo_dlen(algorithm);
assert(hash_size > 0);
if (nsec3->nsec3.next_hashed_name_size != hash_size)
return -EINVAL;
r = dns_name_to_wire_format(name, wire_format, sizeof(wire_format), true);
if (r < 0)
return r;
gcry_md_open(&md, algorithm, 0);
if (!md)
return -EIO;
gcry_md_write(md, wire_format, r);
gcry_md_write(md, nsec3->nsec3.salt, nsec3->nsec3.salt_size);
result = gcry_md_read(md, 0);
if (!result) {
r = -EIO;
goto finish;
}
for (k = 0; k < nsec3->nsec3.iterations; k++) {
uint8_t tmp[hash_size];
memcpy(tmp, result, hash_size);
gcry_md_reset(md);
gcry_md_write(md, tmp, hash_size);
gcry_md_write(md, nsec3->nsec3.salt, nsec3->nsec3.salt_size);
result = gcry_md_read(md, 0);
if (!result) {
r = -EIO;
goto finish;
}
}
memcpy(ret, result, hash_size);
r = (int) hash_size;
finish:
gcry_md_close(md);
return r;
}
static int nsec3_is_good(DnsResourceRecord *rr, DnsResourceRecord *nsec3) {
const char *a, *b;
int r;
assert(rr);
if (rr->key->type != DNS_TYPE_NSEC3)
return 0;
/* RFC 5155, Section 8.2 says we MUST ignore NSEC3 RRs with flags != 0 or 1 */
if (!IN_SET(rr->nsec3.flags, 0, 1))
return 0;
/* Ignore NSEC3 RRs whose algorithm we don't know */
if (nsec3_hash_to_gcrypt_md(rr->nsec3.algorithm) < 0)
return 0;
/* Ignore NSEC3 RRs with an excessive number of required iterations */
if (rr->nsec3.iterations > NSEC3_ITERATIONS_MAX)
return 0;
/* Ignore NSEC3 RRs generated from wildcards. If these NSEC3 RRs weren't correctly signed we can't make this
* check (since rr->n_skip_labels_source is -1), but that's OK, as we won't trust them anyway in that case. */
if (rr->n_skip_labels_source != 0 && rr->n_skip_labels_source != (unsigned) -1)
return 0;
/* Ignore NSEC3 RRs that are located anywhere else than one label below the zone */
if (rr->n_skip_labels_signer != 1 && rr->n_skip_labels_signer != (unsigned) -1)
return 0;
if (!nsec3)
return 1;
/* If a second NSEC3 RR is specified, also check if they are from the same zone. */
if (nsec3 == rr) /* Shortcut */
return 1;
if (rr->key->class != nsec3->key->class)
return 0;
if (rr->nsec3.algorithm != nsec3->nsec3.algorithm)
return 0;
if (rr->nsec3.iterations != nsec3->nsec3.iterations)
return 0;
if (rr->nsec3.salt_size != nsec3->nsec3.salt_size)
return 0;
if (memcmp(rr->nsec3.salt, nsec3->nsec3.salt, rr->nsec3.salt_size) != 0)
return 0;
a = DNS_RESOURCE_KEY_NAME(rr->key);
r = dns_name_parent(&a); /* strip off hash */
if (r < 0)
return r;
if (r == 0)
return 0;
b = DNS_RESOURCE_KEY_NAME(nsec3->key);
r = dns_name_parent(&b); /* strip off hash */
if (r < 0)
return r;
if (r == 0)
return 0;
/* Make sure both have the same parent */
return dns_name_equal(a, b);
}
static int nsec3_hashed_domain_format(const uint8_t *hashed, size_t hashed_size, const char *zone, char **ret) {
_cleanup_free_ char *l = NULL;
char *j;
assert(hashed);
assert(hashed_size > 0);
assert(zone);
assert(ret);
l = base32hexmem(hashed, hashed_size, false);
if (!l)
return -ENOMEM;
j = strjoin(l, ".", zone, NULL);
if (!j)
return -ENOMEM;
*ret = j;
return (int) hashed_size;
}
static int nsec3_hashed_domain_make(DnsResourceRecord *nsec3, const char *domain, const char *zone, char **ret) {
uint8_t hashed[DNSSEC_HASH_SIZE_MAX];
int hashed_size;
assert(nsec3);
assert(domain);
assert(zone);
assert(ret);
hashed_size = dnssec_nsec3_hash(nsec3, domain, hashed);
if (hashed_size < 0)
return hashed_size;
return nsec3_hashed_domain_format(hashed, (size_t) hashed_size, zone, ret);
}
/* See RFC 5155, Section 8
* First try to find a NSEC3 record that matches our query precisely, if that fails, find the closest
* enclosure. Secondly, find a proof that there is no closer enclosure and either a proof that there
* is no wildcard domain as a direct descendant of the closest enclosure, or find an NSEC3 record that
* matches the wildcard domain.
*
* Based on this we can prove either the existence of the record in @key, or NXDOMAIN or NODATA, or
* that there is no proof either way. The latter is the case if a the proof of non-existence of a given
* name uses an NSEC3 record with the opt-out bit set. Lastly, if we are given insufficient NSEC3 records
* to conclude anything we indicate this by returning NO_RR. */
static int dnssec_test_nsec3(DnsAnswer *answer, DnsResourceKey *key, DnssecNsecResult *result, bool *authenticated, uint32_t *ttl) {
_cleanup_free_ char *next_closer_domain = NULL, *wildcard_domain = NULL;
const char *zone, *p, *pp = NULL, *wildcard;
DnsResourceRecord *rr, *enclosure_rr, *zone_rr, *wildcard_rr = NULL;
DnsAnswerFlags flags;
int hashed_size, r;
bool a, no_closer = false, no_wildcard = false, optout = false;
assert(key);
assert(result);
/* First step, find the zone name and the NSEC3 parameters of the zone.
* it is sufficient to look for the longest common suffix we find with
* any NSEC3 RR in the response. Any NSEC3 record will do as all NSEC3
* records from a given zone in a response must use the same
* parameters. */
zone = DNS_RESOURCE_KEY_NAME(key);
for (;;) {
DNS_ANSWER_FOREACH_FLAGS(zone_rr, flags, answer) {
r = nsec3_is_good(zone_rr, NULL);
if (r < 0)
return r;
if (r == 0)
continue;
r = dns_name_equal_skip(DNS_RESOURCE_KEY_NAME(zone_rr->key), 1, zone);
if (r < 0)
return r;
if (r > 0)
goto found_zone;
}
/* Strip one label from the front */
r = dns_name_parent(&zone);
if (r < 0)
return r;
if (r == 0)
break;
}
*result = DNSSEC_NSEC_NO_RR;
return 0;
found_zone:
/* Second step, find the closest encloser NSEC3 RR in 'answer' that matches 'key' */
p = DNS_RESOURCE_KEY_NAME(key);
for (;;) {
_cleanup_free_ char *hashed_domain = NULL;
hashed_size = nsec3_hashed_domain_make(zone_rr, p, zone, &hashed_domain);
if (hashed_size == -EOPNOTSUPP) {
*result = DNSSEC_NSEC_UNSUPPORTED_ALGORITHM;
return 0;
}
if (hashed_size < 0)
return hashed_size;
DNS_ANSWER_FOREACH_FLAGS(enclosure_rr, flags, answer) {
r = nsec3_is_good(enclosure_rr, zone_rr);
if (r < 0)
return r;
if (r == 0)
continue;
if (enclosure_rr->nsec3.next_hashed_name_size != (size_t) hashed_size)
continue;
r = dns_name_equal(DNS_RESOURCE_KEY_NAME(enclosure_rr->key), hashed_domain);
if (r < 0)
return r;
if (r > 0) {
a = flags & DNS_ANSWER_AUTHENTICATED;
goto found_closest_encloser;
}
}
/* We didn't find the closest encloser with this name,
* but let's remember this domain name, it might be
* the next closer name */
pp = p;
/* Strip one label from the front */
r = dns_name_parent(&p);
if (r < 0)
return r;
if (r == 0)
break;
}
*result = DNSSEC_NSEC_NO_RR;
return 0;
found_closest_encloser:
/* We found a closest encloser in 'p'; next closer is 'pp' */
if (!pp) {
/* We have an exact match! If we area looking for a DS RR, then we must insist that we got the NSEC3 RR
* from the parent. Otherwise the one from the child. Do so, by checking whether SOA and NS are
* appropriately set. */
if (key->type == DNS_TYPE_DS) {
if (bitmap_isset(enclosure_rr->nsec3.types, DNS_TYPE_SOA))
return -EBADMSG;
} else {
if (bitmap_isset(enclosure_rr->nsec3.types, DNS_TYPE_NS) &&
!bitmap_isset(enclosure_rr->nsec3.types, DNS_TYPE_SOA))
return -EBADMSG;
}
/* No next closer NSEC3 RR. That means there's a direct NSEC3 RR for our key. */
if (bitmap_isset(enclosure_rr->nsec3.types, key->type))
*result = DNSSEC_NSEC_FOUND;
else if (bitmap_isset(enclosure_rr->nsec3.types, DNS_TYPE_CNAME))
*result = DNSSEC_NSEC_CNAME;
else
*result = DNSSEC_NSEC_NODATA;
if (authenticated)
*authenticated = a;
if (ttl)
*ttl = enclosure_rr->ttl;
return 0;
}
/* Ensure this is not a DNAME domain, see RFC5155, section 8.3. */
if (bitmap_isset(enclosure_rr->nsec3.types, DNS_TYPE_DNAME))
return -EBADMSG;
/* Ensure that this data is from the delegated domain
* (i.e. originates from the "lower" DNS server), and isn't
* just glue records (i.e. doesn't originate from the "upper"
* DNS server). */
if (bitmap_isset(enclosure_rr->nsec3.types, DNS_TYPE_NS) &&
!bitmap_isset(enclosure_rr->nsec3.types, DNS_TYPE_SOA))
return -EBADMSG;
/* Prove that there is no next closer and whether or not there is a wildcard domain. */
wildcard = strjoina("*.", p);
r = nsec3_hashed_domain_make(enclosure_rr, wildcard, zone, &wildcard_domain);
if (r < 0)
return r;
if (r != hashed_size)
return -EBADMSG;
r = nsec3_hashed_domain_make(enclosure_rr, pp, zone, &next_closer_domain);
if (r < 0)
return r;
if (r != hashed_size)
return -EBADMSG;
DNS_ANSWER_FOREACH_FLAGS(rr, flags, answer) {
_cleanup_free_ char *next_hashed_domain = NULL;
r = nsec3_is_good(rr, zone_rr);
if (r < 0)
return r;
if (r == 0)
continue;
r = nsec3_hashed_domain_format(rr->nsec3.next_hashed_name, rr->nsec3.next_hashed_name_size, zone, &next_hashed_domain);
if (r < 0)
return r;
r = dns_name_between(DNS_RESOURCE_KEY_NAME(rr->key), next_closer_domain, next_hashed_domain);
if (r < 0)
return r;
if (r > 0) {
if (rr->nsec3.flags & 1)
optout = true;
a = a && (flags & DNS_ANSWER_AUTHENTICATED);
no_closer = true;
}
r = dns_name_equal(DNS_RESOURCE_KEY_NAME(rr->key), wildcard_domain);
if (r < 0)
return r;
if (r > 0) {
a = a && (flags & DNS_ANSWER_AUTHENTICATED);
wildcard_rr = rr;
}
r = dns_name_between(DNS_RESOURCE_KEY_NAME(rr->key), wildcard_domain, next_hashed_domain);
if (r < 0)
return r;
if (r > 0) {
if (rr->nsec3.flags & 1)
/* This only makes sense if we have a wildcard delegation, which is
* very unlikely, see RFC 4592, Section 4.2, but we cannot rely on
* this not happening, so hence cannot simply conclude NXDOMAIN as
* we would wish */
optout = true;
a = a && (flags & DNS_ANSWER_AUTHENTICATED);
no_wildcard = true;
}
}
if (wildcard_rr && no_wildcard)
return -EBADMSG;
if (!no_closer) {
*result = DNSSEC_NSEC_NO_RR;
return 0;
}
if (wildcard_rr) {
/* A wildcard exists that matches our query. */
if (optout)
/* This is not specified in any RFC to the best of my knowledge, but
* if the next closer enclosure is covered by an opt-out NSEC3 RR
* it means that we cannot prove that the source of synthesis is
* correct, as there may be a closer match. */
*result = DNSSEC_NSEC_OPTOUT;
else if (bitmap_isset(wildcard_rr->nsec3.types, key->type))
*result = DNSSEC_NSEC_FOUND;
else if (bitmap_isset(wildcard_rr->nsec3.types, DNS_TYPE_CNAME))
*result = DNSSEC_NSEC_CNAME;
else
*result = DNSSEC_NSEC_NODATA;
} else {
if (optout)
/* The RFC only specifies that we have to care for optout for NODATA for
* DS records. However, children of an insecure opt-out delegation should
* also be considered opt-out, rather than verified NXDOMAIN.
* Note that we do not require a proof of wildcard non-existence if the
* next closer domain is covered by an opt-out, as that would not provide
* any additional information. */
*result = DNSSEC_NSEC_OPTOUT;
else if (no_wildcard)
*result = DNSSEC_NSEC_NXDOMAIN;
else {
*result = DNSSEC_NSEC_NO_RR;
return 0;
}
}
if (authenticated)
*authenticated = a;
if (ttl)
*ttl = enclosure_rr->ttl;
return 0;
}
static int dnssec_nsec_wildcard_equal(DnsResourceRecord *rr, const char *name) {
char label[DNS_LABEL_MAX];
const char *n;
int r;
assert(rr);
assert(rr->key->type == DNS_TYPE_NSEC);
/* Checks whether the specified RR has a name beginning in "*.", and if the rest is a suffix of our name */
if (rr->n_skip_labels_source != 1)
return 0;
n = DNS_RESOURCE_KEY_NAME(rr->key);
r = dns_label_unescape(&n, label, sizeof(label));
if (r <= 0)
return r;
if (r != 1 || label[0] != '*')
return 0;
return dns_name_endswith(name, n);
}
static int dnssec_nsec_in_path(DnsResourceRecord *rr, const char *name) {
const char *nn, *common_suffix;
int r;
assert(rr);
assert(rr->key->type == DNS_TYPE_NSEC);
/* Checks whether the specified nsec RR indicates that name is an empty non-terminal (ENT)
*
* A couple of examples:
*
* NSEC bar → waldo.foo.bar: indicates that foo.bar exists and is an ENT
* NSEC waldo.foo.bar → yyy.zzz.xoo.bar: indicates that xoo.bar and zzz.xoo.bar exist and are ENTs
* NSEC yyy.zzz.xoo.bar → bar: indicates pretty much nothing about ENTs
*/
/* First, determine parent of next domain. */
nn = rr->nsec.next_domain_name;
r = dns_name_parent(&nn);
if (r <= 0)
return r;
/* If the name we just determined is not equal or child of the name we are interested in, then we can't say
* anything at all. */
r = dns_name_endswith(nn, name);
if (r <= 0)
return r;
/* If the name we we are interested in is not a prefix of the common suffix of the NSEC RR's owner and next domain names, then we can't say anything either. */
r = dns_name_common_suffix(DNS_RESOURCE_KEY_NAME(rr->key), rr->nsec.next_domain_name, &common_suffix);
if (r < 0)
return r;
return dns_name_endswith(name, common_suffix);
}
static int dnssec_nsec_from_parent_zone(DnsResourceRecord *rr, const char *name) {
int r;
assert(rr);
assert(rr->key->type == DNS_TYPE_NSEC);
/* Checks whether this NSEC originates to the parent zone or the child zone. */
r = dns_name_parent(&name);
if (r <= 0)
return r;
r = dns_name_equal(name, DNS_RESOURCE_KEY_NAME(rr->key));
if (r <= 0)
return r;
/* DNAME, and NS without SOA is an indication for a delegation. */
if (bitmap_isset(rr->nsec.types, DNS_TYPE_DNAME))
return 1;
if (bitmap_isset(rr->nsec.types, DNS_TYPE_NS) && !bitmap_isset(rr->nsec.types, DNS_TYPE_SOA))
return 1;
return 0;
}
static int dnssec_nsec_covers(DnsResourceRecord *rr, const char *name) {
const char *common_suffix, *p;
int r;
assert(rr);
assert(rr->key->type == DNS_TYPE_NSEC);
/* Checks whether the "Next Closer" is witin the space covered by the specified RR. */
r = dns_name_common_suffix(DNS_RESOURCE_KEY_NAME(rr->key), rr->nsec.next_domain_name, &common_suffix);
if (r < 0)
return r;
for (;;) {
p = name;
r = dns_name_parent(&name);
if (r < 0)
return r;
if (r == 0)
return 0;
r = dns_name_equal(name, common_suffix);
if (r < 0)
return r;
if (r > 0)
break;
}
/* p is now the "Next Closer". */
return dns_name_between(DNS_RESOURCE_KEY_NAME(rr->key), p, rr->nsec.next_domain_name);
}
static int dnssec_nsec_covers_wildcard(DnsResourceRecord *rr, const char *name) {
const char *common_suffix, *wc;
int r;
assert(rr);
assert(rr->key->type == DNS_TYPE_NSEC);
/* Checks whether the "Wildcard at the Closest Encloser" is within the space covered by the specified
* RR. Specifically, checks whether 'name' has the common suffix of the NSEC RR's owner and next names as
* suffix, and whether the NSEC covers the name generated by that suffix prepended with an asterisk label.
*
* NSEC bar → waldo.foo.bar: indicates that *.bar and *.foo.bar do not exist
* NSEC waldo.foo.bar → yyy.zzz.xoo.bar: indicates that *.xoo.bar and *.zzz.xoo.bar do not exist (and more ...)
* NSEC yyy.zzz.xoo.bar → bar: indicates that a number of wildcards don#t exist either...
*/
r = dns_name_common_suffix(DNS_RESOURCE_KEY_NAME(rr->key), rr->nsec.next_domain_name, &common_suffix);
if (r < 0)
return r;
/* If the common suffix is not shared by the name we are interested in, it has nothing to say for us. */
r = dns_name_endswith(name, common_suffix);
if (r <= 0)
return r;
wc = strjoina("*.", common_suffix, NULL);
return dns_name_between(DNS_RESOURCE_KEY_NAME(rr->key), wc, rr->nsec.next_domain_name);
}
int dnssec_nsec_test(DnsAnswer *answer, DnsResourceKey *key, DnssecNsecResult *result, bool *authenticated, uint32_t *ttl) {
bool have_nsec3 = false, covering_rr_authenticated = false, wildcard_rr_authenticated = false;
DnsResourceRecord *rr, *covering_rr = NULL, *wildcard_rr = NULL;
DnsAnswerFlags flags;
const char *name;
int r;
assert(key);
assert(result);
/* Look for any NSEC/NSEC3 RRs that say something about the specified key. */
name = DNS_RESOURCE_KEY_NAME(key);
DNS_ANSWER_FOREACH_FLAGS(rr, flags, answer) {
if (rr->key->class != key->class)
continue;
have_nsec3 = have_nsec3 || (rr->key->type == DNS_TYPE_NSEC3);
if (rr->key->type != DNS_TYPE_NSEC)
continue;
/* The following checks only make sense for NSEC RRs that are not expanded from a wildcard */
r = dns_resource_record_is_synthetic(rr);
if (r < 0)
return r;
if (r > 0)
continue;
/* Check if this is a direct match. If so, we have encountered a NODATA case */
r = dns_name_equal(DNS_RESOURCE_KEY_NAME(rr->key), name);
if (r < 0)
return r;
if (r == 0) {
/* If it's not a direct match, maybe it's a wild card match? */
r = dnssec_nsec_wildcard_equal(rr, name);
if (r < 0)
return r;
}
if (r > 0) {
if (key->type == DNS_TYPE_DS) {
/* If we look for a DS RR and the server sent us the NSEC RR of the child zone
* we have a problem. For DS RRs we want the NSEC RR from the parent */
if (bitmap_isset(rr->nsec.types, DNS_TYPE_SOA))
continue;
} else {
/* For all RR types, ensure that if NS is set SOA is set too, so that we know
* we got the child's NSEC. */
if (bitmap_isset(rr->nsec.types, DNS_TYPE_NS) &&
!bitmap_isset(rr->nsec.types, DNS_TYPE_SOA))
continue;
}
if (bitmap_isset(rr->nsec.types, key->type))
*result = DNSSEC_NSEC_FOUND;
else if (bitmap_isset(rr->nsec.types, DNS_TYPE_CNAME))
*result = DNSSEC_NSEC_CNAME;
else
*result = DNSSEC_NSEC_NODATA;
if (authenticated)
*authenticated = flags & DNS_ANSWER_AUTHENTICATED;
if (ttl)
*ttl = rr->ttl;
return 0;
}
/* Check if the name we are looking for is an empty non-terminal within the owner or next name
* of the NSEC RR. */
r = dnssec_nsec_in_path(rr, name);
if (r < 0)
return r;
if (r > 0) {
*result = DNSSEC_NSEC_NODATA;
if (authenticated)
*authenticated = flags & DNS_ANSWER_AUTHENTICATED;
if (ttl)
*ttl = rr->ttl;
return 0;
}
/* The following two "covering" checks, are not useful if the NSEC is from the parent */
r = dnssec_nsec_from_parent_zone(rr, name);
if (r < 0)
return r;
if (r > 0)
continue;
/* Check if this NSEC RR proves the absence of an explicit RR under this name */
r = dnssec_nsec_covers(rr, name);
if (r < 0)
return r;
if (r > 0 && (!covering_rr || !covering_rr_authenticated)) {
covering_rr = rr;
covering_rr_authenticated = flags & DNS_ANSWER_AUTHENTICATED;
}
/* Check if this NSEC RR proves the absence of a wildcard RR under this name */
r = dnssec_nsec_covers_wildcard(rr, name);
if (r < 0)
return r;
if (r > 0 && (!wildcard_rr || !wildcard_rr_authenticated)) {
wildcard_rr = rr;
wildcard_rr_authenticated = flags & DNS_ANSWER_AUTHENTICATED;
}
}
if (covering_rr && wildcard_rr) {
/* If we could prove that neither the name itself, nor the wildcard at the closest encloser exists, we
* proved the NXDOMAIN case. */
*result = DNSSEC_NSEC_NXDOMAIN;
if (authenticated)
*authenticated = covering_rr_authenticated && wildcard_rr_authenticated;
if (ttl)
*ttl = MIN(covering_rr->ttl, wildcard_rr->ttl);
return 0;
}
/* OK, this was not sufficient. Let's see if NSEC3 can help. */
if (have_nsec3)
return dnssec_test_nsec3(answer, key, result, authenticated, ttl);
/* No approproate NSEC RR found, report this. */
*result = DNSSEC_NSEC_NO_RR;
return 0;
}
static int dnssec_nsec_test_enclosed(DnsAnswer *answer, uint16_t type, const char *name, const char *zone, bool *authenticated) {
DnsResourceRecord *rr;
DnsAnswerFlags flags;
int r;
assert(name);
assert(zone);
/* Checks whether there's an NSEC/NSEC3 that proves that the specified 'name' is non-existing in the specified
* 'zone'. The 'zone' must be a suffix of the 'name'. */
DNS_ANSWER_FOREACH_FLAGS(rr, flags, answer) {
bool found = false;
if (rr->key->type != type && type != DNS_TYPE_ANY)
continue;
switch (rr->key->type) {
case DNS_TYPE_NSEC:
/* We only care for NSEC RRs from the indicated zone */
r = dns_resource_record_is_signer(rr, zone);
if (r < 0)
return r;
if (r == 0)
continue;
r = dns_name_between(DNS_RESOURCE_KEY_NAME(rr->key), name, rr->nsec.next_domain_name);
if (r < 0)
return r;
found = r > 0;
break;
case DNS_TYPE_NSEC3: {
_cleanup_free_ char *hashed_domain = NULL, *next_hashed_domain = NULL;
/* We only care for NSEC3 RRs from the indicated zone */
r = dns_resource_record_is_signer(rr, zone);
if (r < 0)
return r;
if (r == 0)
continue;
r = nsec3_is_good(rr, NULL);
if (r < 0)
return r;
if (r == 0)
break;
/* Format the domain we are testing with the NSEC3 RR's hash function */
r = nsec3_hashed_domain_make(
rr,
name,
zone,
&hashed_domain);
if (r < 0)
return r;
if ((size_t) r != rr->nsec3.next_hashed_name_size)
break;
/* Format the NSEC3's next hashed name as proper domain name */
r = nsec3_hashed_domain_format(
rr->nsec3.next_hashed_name,
rr->nsec3.next_hashed_name_size,
zone,
&next_hashed_domain);
if (r < 0)
return r;
r = dns_name_between(DNS_RESOURCE_KEY_NAME(rr->key), hashed_domain, next_hashed_domain);
if (r < 0)
return r;
found = r > 0;
break;
}
default:
continue;
}
if (found) {
if (authenticated)
*authenticated = flags & DNS_ANSWER_AUTHENTICATED;
return 1;
}
}
return 0;
}
static int dnssec_test_positive_wildcard_nsec3(
DnsAnswer *answer,
const char *name,
const char *source,
const char *zone,
bool *authenticated) {
const char *next_closer = NULL;
int r;
/* Run a positive NSEC3 wildcard proof. Specifically:
*
* A proof that the the "next closer" of the generating wildcard does not exist.
*
* Note a key difference between the NSEC3 and NSEC versions of the proof. NSEC RRs don't have to exist for
* empty non-transients. NSEC3 RRs however have to. This means it's sufficient to check if the next closer name
* exists for the NSEC3 RR and we are done.
*
* To prove that a.b.c.d.e.f is rightfully synthesized from a wildcard *.d.e.f all we have to check is that
* c.d.e.f does not exist. */
for (;;) {
next_closer = name;
r = dns_name_parent(&name);
if (r < 0)
return r;
if (r == 0)
return 0;
r = dns_name_equal(name, source);
if (r < 0)
return r;
if (r > 0)
break;
}
return dnssec_nsec_test_enclosed(answer, DNS_TYPE_NSEC3, next_closer, zone, authenticated);
}
static int dnssec_test_positive_wildcard_nsec(
DnsAnswer *answer,
const char *name,
const char *source,
const char *zone,
bool *_authenticated) {
bool authenticated = true;
int r;
/* Run a positive NSEC wildcard proof. Specifically:
*
* A proof that there's neither a wildcard name nor a non-wildcard name that is a suffix of the name "name" and
* a prefix of the synthesizing source "source" in the zone "zone".
*
* See RFC 5155, Section 8.8 and RFC 4035, Section 5.3.4
*
* Note that if we want to prove that a.b.c.d.e.f is rightfully synthesized from a wildcard *.d.e.f, then we
* have to prove that none of the following exist:
*
* 1) a.b.c.d.e.f
* 2) *.b.c.d.e.f
* 3) b.c.d.e.f
* 4) *.c.d.e.f
* 5) c.d.e.f
*
*/
for (;;) {
_cleanup_free_ char *wc = NULL;
bool a = false;
/* Check if there's an NSEC or NSEC3 RR that proves that the mame we determined is really non-existing,
* i.e between the owner name and the next name of an NSEC RR. */
r = dnssec_nsec_test_enclosed(answer, DNS_TYPE_NSEC, name, zone, &a);
if (r <= 0)
return r;
authenticated = authenticated && a;
/* Strip one label off */
r = dns_name_parent(&name);
if (r <= 0)
return r;
/* Did we reach the source of synthesis? */
r = dns_name_equal(name, source);
if (r < 0)
return r;
if (r > 0) {
/* Successful exit */
*_authenticated = authenticated;
return 1;
}
/* Safety check, that the source of synthesis is still our suffix */
r = dns_name_endswith(name, source);
if (r < 0)
return r;
if (r == 0)
return -EBADMSG;
/* Replace the label we stripped off with an asterisk */
wc = strappend("*.", name);
if (!wc)
return -ENOMEM;
/* And check if the proof holds for the asterisk name, too */
r = dnssec_nsec_test_enclosed(answer, DNS_TYPE_NSEC, wc, zone, &a);
if (r <= 0)
return r;
authenticated = authenticated && a;
/* In the next iteration we'll check the non-asterisk-prefixed version */
}
}
int dnssec_test_positive_wildcard(
DnsAnswer *answer,
const char *name,
const char *source,
const char *zone,
bool *authenticated) {
int r;
assert(name);
assert(source);
assert(zone);
assert(authenticated);
r = dns_answer_contains_zone_nsec3(answer, zone);
if (r < 0)
return r;
if (r > 0)
return dnssec_test_positive_wildcard_nsec3(answer, name, source, zone, authenticated);
else
return dnssec_test_positive_wildcard_nsec(answer, name, source, zone, authenticated);
}
#else
int dnssec_verify_rrset(
DnsAnswer *a,
const DnsResourceKey *key,
DnsResourceRecord *rrsig,
DnsResourceRecord *dnskey,
usec_t realtime,
DnssecResult *result) {
return -EOPNOTSUPP;
}
int dnssec_rrsig_match_dnskey(DnsResourceRecord *rrsig, DnsResourceRecord *dnskey, bool revoked_ok) {
return -EOPNOTSUPP;
}
int dnssec_key_match_rrsig(const DnsResourceKey *key, DnsResourceRecord *rrsig) {
return -EOPNOTSUPP;
}
int dnssec_verify_rrset_search(
DnsAnswer *a,
const DnsResourceKey *key,
DnsAnswer *validated_dnskeys,
usec_t realtime,
DnssecResult *result,
DnsResourceRecord **ret_rrsig) {
return -EOPNOTSUPP;
}
int dnssec_has_rrsig(DnsAnswer *a, const DnsResourceKey *key) {
return -EOPNOTSUPP;
}
int dnssec_verify_dnskey_by_ds(DnsResourceRecord *dnskey, DnsResourceRecord *ds, bool mask_revoke) {
return -EOPNOTSUPP;
}
int dnssec_verify_dnskey_by_ds_search(DnsResourceRecord *dnskey, DnsAnswer *validated_ds) {
return -EOPNOTSUPP;
}
int dnssec_nsec3_hash(DnsResourceRecord *nsec3, const char *name, void *ret) {
return -EOPNOTSUPP;
}
int dnssec_nsec_test(DnsAnswer *answer, DnsResourceKey *key, DnssecNsecResult *result, bool *authenticated, uint32_t *ttl) {
return -EOPNOTSUPP;
}
int dnssec_test_positive_wildcard(
DnsAnswer *answer,
const char *name,
const char *source,
const char *zone,
bool *authenticated) {
return -EOPNOTSUPP;
}
#endif
static const char* const dnssec_result_table[_DNSSEC_RESULT_MAX] = {
[DNSSEC_VALIDATED] = "validated",
[DNSSEC_VALIDATED_WILDCARD] = "validated-wildcard",
[DNSSEC_INVALID] = "invalid",
[DNSSEC_SIGNATURE_EXPIRED] = "signature-expired",
[DNSSEC_UNSUPPORTED_ALGORITHM] = "unsupported-algorithm",
[DNSSEC_NO_SIGNATURE] = "no-signature",
[DNSSEC_MISSING_KEY] = "missing-key",
[DNSSEC_UNSIGNED] = "unsigned",
[DNSSEC_FAILED_AUXILIARY] = "failed-auxiliary",
[DNSSEC_NSEC_MISMATCH] = "nsec-mismatch",
[DNSSEC_INCOMPATIBLE_SERVER] = "incompatible-server",
};
DEFINE_STRING_TABLE_LOOKUP(dnssec_result, DnssecResult);
static const char* const dnssec_verdict_table[_DNSSEC_VERDICT_MAX] = {
[DNSSEC_SECURE] = "secure",
[DNSSEC_INSECURE] = "insecure",
[DNSSEC_BOGUS] = "bogus",
[DNSSEC_INDETERMINATE] = "indeterminate",
};
DEFINE_STRING_TABLE_LOOKUP(dnssec_verdict, DnssecVerdict);