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resolved: rework dnssec validation results

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This adds a new validation result DNSSEC_UNSUPPORTED_ALGORITHM which is
returned when we encounter an unsupported crypto algorithm when trying
to validate RRSIG/DNSKEY combinations. Previously we'd return ENOTSUPP
in this case, but it's better to consider this a non-error DNSSEC
validation result, since our reaction to this case needs to be more like
in cases such as expired or missing keys: we need to keep continue
validation looking for another RRSIG/DNSKEY combination that works
better for us.

This also reworks how dnssec_validate_rrsig_search() propagates errors
from dnssec_validate_rrsig(). Previously, errors such as unsupported
algorithms or expired signatures would not be propagated, but simply be
returned as "missing-key".
This commit is contained in:
Lennart Poettering 2015-12-11 13:55:26 +01:00
parent 79e2493138
commit 203f1b35d9
2 changed files with 58 additions and 18 deletions
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66
src/resolve/resolved-dns-dnssec.c
View File

@ -295,8 +295,10 @@ int dnssec_verify_rrset(
* using the signature "rrsig" and the key "dnskey". It's
* assumed the RRSIG and DNSKEY match. */
if (!dnssec_algorithm_supported(rrsig->rrsig.algorithm))
return -EOPNOTSUPP;
if (!dnssec_algorithm_supported(rrsig->rrsig.algorithm)) {
*result = DNSSEC_UNSUPPORTED_ALGORITHM;
return 0;
}
if (a->n_rrs > VERIFY_RRS_MAX)
return -E2BIG;
@ -508,7 +510,7 @@ int dnssec_verify_rrset_search(
usec_t realtime,
DnssecResult *result) {
bool found_rrsig = false, found_dnskey = false;
bool found_rrsig = false, found_invalid = false, found_expired_rrsig = false, found_unsupported_algorithm = false;
DnsResourceRecord *rrsig;
int r;
@ -524,6 +526,7 @@ int dnssec_verify_rrset_search(
DNS_ANSWER_FOREACH(rrsig, a) {
DnsResourceRecord *dnskey;
/* Is this an RRSIG RR that applies to RRs matching our key? */
r = dnssec_key_match_rrsig(key, rrsig);
if (r < 0)
return r;
@ -536,14 +539,13 @@ int dnssec_verify_rrset_search(
DNS_ANSWER_FOREACH(dnskey, validated_dnskeys) {
DnssecResult one_result;
/* Is this a DNSKEY RR that matches they key of our RRSIG? */
r = dnssec_rrsig_match_dnskey(rrsig, dnskey);
if (r < 0)
return r;
if (r == 0)
continue;
found_dnskey = true;
/* Take the time here, if it isn't set yet, so
* that we do all validations with the same
* time. */
@ -556,22 +558,53 @@ int dnssec_verify_rrset_search(
* combination. */
r = dnssec_verify_rrset(a, key, rrsig, dnskey, realtime, &one_result);
if (r < 0 && r != EOPNOTSUPP)
if (r < 0)
return r;
if (one_result == DNSSEC_VALIDATED) {
switch (one_result) {
case DNSSEC_VALIDATED:
/* Yay, the RR has been validated,
* return immediately. */
*result = DNSSEC_VALIDATED;
return 0;
}
/* If the signature is invalid, or done using
an unsupported algorithm, 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. */
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_dnskey)
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;
@ -756,10 +789,11 @@ DEFINE_STRING_TABLE_LOOKUP(dnssec_mode, DnssecMode);
static const char* const dnssec_result_table[_DNSSEC_RESULT_MAX] = {
[DNSSEC_VALIDATED] = "validated",
[DNSSEC_INVALID] = "invalid",
[DNSSEC_UNSIGNED] = "unsigned",
[DNSSEC_SIGNATURE_EXPIRED] = "signature-expired",
[DNSSEC_UNSUPPORTED_ALGORITHM] = "unsupported-algorithm",
[DNSSEC_NO_SIGNATURE] = "no-signature",
[DNSSEC_MISSING_KEY] = "missing-key",
[DNSSEC_SIGNATURE_EXPIRED] = "signature-expired",
[DNSSEC_UNSIGNED] = "unsigned",
[DNSSEC_FAILED_AUXILIARY] = "failed-auxiliary",
};
DEFINE_STRING_TABLE_LOOKUP(dnssec_result, DnssecResult);

10
src/resolve/resolved-dns-dnssec.h
View File

@ -43,12 +43,18 @@ enum DnssecMode {
};
enum DnssecResult {
/* These four are returned by dnssec_verify_rrset() */
DNSSEC_VALIDATED,
DNSSEC_INVALID,
DNSSEC_UNSIGNED,
DNSSEC_SIGNATURE_EXPIRED,
DNSSEC_UNSUPPORTED_ALGORITHM,
/* These two are added by dnssec_verify_rrset_search() */
DNSSEC_NO_SIGNATURE,
DNSSEC_MISSING_KEY,
DNSSEC_SIGNATURE_EXPIRED,
/* These two are added by the DnsTransaction logic */
DNSSEC_UNSIGNED,
DNSSEC_FAILED_AUXILIARY,
_DNSSEC_RESULT_MAX,
_DNSSEC_RESULT_INVALID = -1