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Return INSECURE, rather than BOGUS when DS proved not to exist.

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Return INSECURE when validating DNS replies which have RRSIGs, but
when a needed DS record in the trust chain is proved not to exist.
It's allowed for a zone to set up DNSKEY and RRSIG records first, then
add a DS later, completing the chain of trust.

Also, since we don't have the infrastructure to track that these
non-validated replies have RRSIGS, don't cache them, so we don't
provide answers with missing RRSIGS from the cache.
This commit is contained in:
Simon Kelley
2015-04-03 21:25:05 +01:00
parent 7aa970e2c7
commit fe3992f9fa
3 changed files with 69 additions and 21 deletions
Download Patch File Download Diff File Expand all files Collapse all files

1
src/dnsmasq.h
View File

@@ -583,6 +583,7 @@ struct hostsfile {
#define STAT_NO_NS 10
#define STAT_NEED_DS_NEG 11
#define STAT_CHASE_CNAME 12
#define STAT_INSECURE_DS 13
#define FREC_NOREBIND 1
#define FREC_CHECKING_DISABLED 2

2
src/dnssec.c
View File

@@ -981,7 +981,7 @@ int dnssec_validate_by_ds(time_t now, struct dns_header *header, size_t plen, ch
/* If we've cached that DS provably doesn't exist, result must be INSECURE */
if (crecp->flags & F_NEG)
return STAT_INSECURE;
return STAT_INSECURE_DS;
/* NOTE, we need to find ONE DNSKEY which matches the DS */
for (valid = 0, j = ntohs(header->ancount); j != 0 && !valid; j--)

73
src/forward.c
View File

@@ -521,7 +521,8 @@ static int forward_query(int udpfd, union mysockaddr *udpaddr,
}
static size_t process_reply(struct dns_header *header, time_t now, struct server *server, size_t n, int check_rebind,
int no_cache, int cache_secure, int ad_reqd, int do_bit, int added_pheader, int check_subnet, union mysockaddr *query_source)
int no_cache, int cache_secure, int bogusanswer, int ad_reqd, int do_bit, int added_pheader,
int check_subnet, union mysockaddr *query_source)
{
unsigned char *pheader, *sizep;
char **sets = 0;
@@ -634,7 +635,7 @@ static size_t process_reply(struct dns_header *header, time_t now, struct server
}
#ifdef HAVE_DNSSEC
if (no_cache && !(header->hb4 & HB4_CD))
if (bogusanswer && !(header->hb4 & HB4_CD))
{
if (!option_bool(OPT_DNSSEC_DEBUG))
{
@@ -786,7 +787,7 @@ void reply_query(int fd, int family, time_t now)
everything is broken */
if (forward->forwardall == 0 || --forward->forwardall == 1 || RCODE(header) != SERVFAIL)
{
int check_rebind = 0, no_cache_dnssec = 0, cache_secure = 0;
int check_rebind = 0, no_cache_dnssec = 0, cache_secure = 0, bogusanswer = 0;
if (option_bool(OPT_NO_REBIND))
check_rebind = !(forward->flags & FREC_NOREBIND);
@@ -819,7 +820,13 @@ void reply_query(int fd, int family, time_t now)
else if (forward->flags & FREC_DS_QUERY)
{
status = dnssec_validate_ds(now, header, n, daemon->namebuff, daemon->keyname, forward->class);
if (status == STAT_NO_DS || status == STAT_NO_NS)
/* Provably no DS, everything below is insecure, even if signatures are offered */
if (status == STAT_NO_DS)
/* We only cache sigs when we've validated a reply.
Avoid caching a reply with sigs if there's a vaildated break in the
DS chain, so we don't return replies from cache missing sigs. */
status = STAT_INSECURE_DS;
else if (status == STAT_NO_NS)
status = STAT_BOGUS;
}
else if (forward->flags & FREC_CHECK_NOSIGN)
@@ -959,7 +966,13 @@ void reply_query(int fd, int family, time_t now)
else if (forward->flags & FREC_DS_QUERY)
{
status = dnssec_validate_ds(now, header, n, daemon->namebuff, daemon->keyname, forward->class);
if (status == STAT_NO_DS || status == STAT_NO_NS)
/* Provably no DS, everything below is insecure, even if signatures are offered */
if (status == STAT_NO_DS)
/* We only cache sigs when we've validated a reply.
Avoid caching a reply with sigs if there's a vaildated break in the
DS chain, so we don't return replies from cache missing sigs. */
status = STAT_INSECURE_DS;
else if (status == STAT_NO_NS)
status = STAT_BOGUS;
}
else if (forward->flags & FREC_CHECK_NOSIGN)
@@ -985,6 +998,17 @@ void reply_query(int fd, int family, time_t now)
}
}
no_cache_dnssec = 0;
if (status == STAT_INSECURE_DS)
{
/* We only cache sigs when we've validated a reply.
Avoid caching a reply with sigs if there's a vaildated break in the
DS chain, so we don't return replies from cache missing sigs. */
status = STAT_INSECURE;
no_cache_dnssec = 1;
}
if (status == STAT_TRUNCATED)
header->hb3 |= HB3_TC;
else
@@ -1002,12 +1026,13 @@ void reply_query(int fd, int family, time_t now)
log_query(F_KEYTAG | F_SECSTAT, "result", NULL, result);
}
no_cache_dnssec = 0;
if (status == STAT_SECURE)
cache_secure = 1;
else if (status == STAT_BOGUS)
{
no_cache_dnssec = 1;
bogusanswer = 1;
}
}
#endif
@@ -1017,7 +1042,7 @@ void reply_query(int fd, int family, time_t now)
else
header->hb4 &= ~HB4_CD;
if ((nn = process_reply(header, now, server, (size_t)n, check_rebind, no_cache_dnssec, cache_secure,
if ((nn = process_reply(header, now, server, (size_t)n, check_rebind, no_cache_dnssec, cache_secure, bogusanswer,
forward->flags & FREC_AD_QUESTION, forward->flags & FREC_DO_QUESTION,
forward->flags & FREC_ADDED_PHEADER, forward->flags & FREC_HAS_SUBNET, &forward->source)))
{
@@ -1420,7 +1445,7 @@ static int do_check_sign(struct frec *forward, int status, time_t now, char *nam
}
}
/* Move toward the root, until we find a signed non-existance of a DS, in which case
/* Move down from the root, until we find a signed non-existance of a DS, in which case
an unsigned answer is OK, or we find a signed DS, in which case there should be
a signature, and the answer is BOGUS */
static int tcp_check_for_unsigned_zone(time_t now, struct dns_header *header, size_t plen, int class, char *name,
@@ -1570,9 +1595,14 @@ static int tcp_key_recurse(time_t now, int status, struct dns_header *header, si
else if (status == STAT_NEED_DS || status == STAT_NEED_DS_NEG)
{
new_status = dnssec_validate_ds(now, header, n, name, keyname, class);
if (status == STAT_NEED_DS && (new_status == STAT_NO_DS || new_status == STAT_NO_NS))
if (status == STAT_NEED_DS)
{
if (new_status == STAT_NO_DS)
new_status = STAT_INSECURE_DS;
else if (new_status == STAT_NO_NS)
new_status = STAT_BOGUS;
}
}
else if (status == STAT_CHASE_CNAME)
new_status = dnssec_chase_cname(now, header, n, name, keyname);
else
@@ -1630,9 +1660,14 @@ static int tcp_key_recurse(time_t now, int status, struct dns_header *header, si
else if (status == STAT_NEED_DS || status == STAT_NEED_DS_NEG)
{
new_status = dnssec_validate_ds(now, header, n, name, keyname, class);
if (status == STAT_NEED_DS && (new_status == STAT_NO_DS || new_status == STAT_NO_NS))
if (status == STAT_NEED_DS)
{
if (new_status == STAT_NO_DS)
new_status = STAT_INSECURE_DS;
else if (new_status == STAT_NO_NS)
new_status = STAT_BOGUS; /* Validated no DS */
}
}
else if (status == STAT_CHASE_CNAME)
new_status = dnssec_chase_cname(now, header, n, name, keyname);
else
@@ -1673,7 +1708,7 @@ unsigned char *tcp_request(int confd, time_t now,
int local_auth = 0;
#endif
int checking_disabled, ad_question, do_bit, added_pheader = 0;
int check_subnet, no_cache_dnssec = 0, cache_secure = 0;
int check_subnet, no_cache_dnssec = 0, cache_secure = 0, bogusanswer = 0;
size_t m;
unsigned short qtype;
unsigned int gotname;
@@ -1941,6 +1976,15 @@ unsigned char *tcp_request(int confd, time_t now,
int status = tcp_key_recurse(now, STAT_TRUNCATED, header, m, 0, daemon->namebuff, daemon->keyname, last_server, &keycount);
char *result;
if (status == STAT_INSECURE_DS)
{
/* We only cache sigs when we've validated a reply.
Avoid caching a reply with sigs if there's a vaildated break in the
DS chain, so we don't return replies from cache missing sigs. */
status = STAT_INSECURE;
no_cache_dnssec = 1;
}
if (keycount == 0)
{
result = "ABANDONED";
@@ -1952,7 +1996,10 @@ unsigned char *tcp_request(int confd, time_t now,
log_query(F_KEYTAG | F_SECSTAT, "result", NULL, result);
if (status == STAT_BOGUS)
{
no_cache_dnssec = 1;
bogusanswer = 1;
}
if (status == STAT_SECURE)
cache_secure = 1;
@@ -1987,7 +2034,7 @@ unsigned char *tcp_request(int confd, time_t now,
#endif
m = process_reply(header, now, last_server, (unsigned int)m,
option_bool(OPT_NO_REBIND) && !norebind, no_cache_dnssec,
option_bool(OPT_NO_REBIND) && !norebind, no_cache_dnssec, bogusanswer,
cache_secure, ad_question, do_bit, added_pheader, check_subnet, &peer_addr);
break;