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-rw-r--r--src/resolv/async_resolv.c113
-rw-r--r--src/resolv/async_resolv.h4
-rw-r--r--src/resolv/async_resolv_utils.c9
3 files changed, 123 insertions, 3 deletions
diff --git a/src/resolv/async_resolv.c b/src/resolv/async_resolv.c
index f93612440..85c4d99a4 100644
--- a/src/resolv/async_resolv.c
+++ b/src/resolv/async_resolv.c
@@ -62,7 +62,21 @@
#endif
#define DNS__16BIT(p) (((p)[0] << 8) | (p)[1])
+
+/*
+ * Macro DNS__32BIT reads a network long (32 bit) given in network
+ * byte order, and returns its value as an unsigned int. Copied
+ * from c-ares source code.
+ */
+#define DNS__32BIT(p) ((unsigned int) \
+ (((unsigned int)((unsigned char)(p)[0]) << 24U) | \
+ ((unsigned int)((unsigned char)(p)[1]) << 16U) | \
+ ((unsigned int)((unsigned char)(p)[2]) << 8U) | \
+ ((unsigned int)((unsigned char)(p)[3]))))
+
#define DNS_HEADER_ANCOUNT(h) DNS__16BIT((h) + 6)
+#define DNS_RR_LEN(r) DNS__16BIT((r) + 8)
+#define DNS_RR_TTL(r) DNS__32BIT((r) + 4)
#define RESOLV_TIMEOUTMS 2000
@@ -1572,6 +1586,7 @@ struct getsrv_state {
/* parsed data returned by ares */
struct ares_srv_reply *reply_list;
+ uint32_t ttl;
int status;
int timeouts;
int retrying;
@@ -1607,6 +1622,7 @@ resolv_getsrv_send(TALLOC_CTX *mem_ctx, struct tevent_context *ev,
state->resolv_ctx = ctx;
state->query = query;
state->reply_list = NULL;
+ state->ttl = 0;
state->status = 0;
state->timeouts = 0;
state->retrying = 0;
@@ -1624,6 +1640,92 @@ resolv_getsrv_send(TALLOC_CTX *mem_ctx, struct tevent_context *ev,
return req;
}
+/*
+ * Implemented based on http://tools.ietf.org/html/rfc2181#section-5
+ *
+ * Especially:
+ * 5.2. TTLs of RRs in an RRSet
+ * Consequently the use of differing TTLs in an RRSet is hereby
+ * deprecated, the TTLs of all RRs in an RRSet must be the same.
+ * ...
+ * Should an authoritative source send such a malformed RRSet, the
+ * client should treat the RRs for all purposes as if all TTLs in the
+ * RRSet had been set to the value of the lowest TTL in the RRSet.
+ *
+ * On success, returns true and sets the TTL in the _ttl parameter. On
+ * failure, returns false and _ttl is undefined.
+ */
+static bool
+resolv_get_ttl(const unsigned char *abuf, const int alen, uint32_t *_ttl)
+{
+ const unsigned char *aptr;
+ int ret;
+ char *name = NULL;
+ long len;
+ uint32_t ttl = 0;
+ uint32_t rr_ttl;
+ unsigned int rr_len;
+ unsigned int ancount;
+ unsigned int i;
+
+ /* Read the number of RRs and then skip past the header */
+ if (alen < NS_HFIXEDSZ) {
+ return false;
+ }
+
+ ancount = DNS_HEADER_ANCOUNT(abuf);
+ if (ancount == 0) {
+ return false;
+ }
+
+ aptr = abuf + NS_HFIXEDSZ;
+
+ /* We only care about len from the question data,
+ * so that we can move past hostname */
+ ret = ares_expand_name(aptr, abuf, alen, &name, &len);
+ ares_free_string(name);
+ if (ret != ARES_SUCCESS) {
+ return false;
+ }
+
+ /* Skip past the question */
+ aptr += len + NS_QFIXEDSZ;
+ if (aptr > abuf + alen) {
+ return false;
+ }
+
+ /* Examine each RR in turn and read the lowest TTL */
+ for (i = 0; i < ancount; i++) {
+ /* Decode the RR up to the data field. */
+ ret = ares_expand_name(aptr, abuf, alen, &name, &len);
+ ares_free_string(name);
+ if (ret != ARES_SUCCESS) {
+ return false;
+ }
+
+ aptr += len;
+ if (aptr + NS_RRFIXEDSZ > abuf + alen) {
+ return false;
+ }
+
+ rr_len = DNS_RR_LEN(aptr);
+ rr_ttl = DNS_RR_TTL(aptr);
+ if (aptr + rr_len > abuf + alen) {
+ return false;
+ }
+ aptr += NS_RRFIXEDSZ + rr_len;
+
+ if (ttl > 0) {
+ ttl = MIN(ttl, rr_ttl);
+ } else {
+ ttl = rr_ttl; /* special-case for first TTL */
+ }
+ }
+
+ *_ttl = ttl;
+ return true;
+}
+
static void
resolv_getsrv_done(void *arg, int status, int timeouts, unsigned char *abuf, int alen)
{
@@ -1631,6 +1733,7 @@ resolv_getsrv_done(void *arg, int status, int timeouts, unsigned char *abuf, int
struct tevent_req *req;
struct getsrv_state *state;
int ret;
+ bool ok;
struct ares_srv_reply *reply_list;
if (rreq->rwatch == NULL) {
@@ -1671,6 +1774,10 @@ resolv_getsrv_done(void *arg, int status, int timeouts, unsigned char *abuf, int
goto fail;
}
state->reply_list = reply_list;
+ ok = resolv_get_ttl(abuf, alen, &state->ttl);
+ if (ok == false) {
+ state->ttl = RESOLV_DEFAULT_TTL;
+ }
tevent_req_done(req);
return;
@@ -1682,7 +1789,8 @@ fail:
int
resolv_getsrv_recv(TALLOC_CTX *mem_ctx, struct tevent_req *req, int *status,
- int *timeouts, struct ares_srv_reply **reply_list)
+ int *timeouts, struct ares_srv_reply **reply_list,
+ uint32_t *ttl)
{
struct getsrv_state *state = tevent_req_data(req, struct getsrv_state);
@@ -1692,6 +1800,9 @@ resolv_getsrv_recv(TALLOC_CTX *mem_ctx, struct tevent_req *req, int *status,
*timeouts = state->timeouts;
if (reply_list)
*reply_list = talloc_steal(mem_ctx, state->reply_list);
+ if (ttl) {
+ *ttl = state->ttl;
+ }
TEVENT_REQ_RETURN_ON_ERROR(req);
diff --git a/src/resolv/async_resolv.h b/src/resolv/async_resolv.h
index 919ba370b..9b08f12ae 100644
--- a/src/resolv/async_resolv.h
+++ b/src/resolv/async_resolv.h
@@ -144,7 +144,8 @@ int resolv_getsrv_recv(TALLOC_CTX *mem_ctx,
struct tevent_req *req,
int *status,
int *timeouts,
- struct ares_srv_reply **reply_list);
+ struct ares_srv_reply **reply_list,
+ uint32_t *ttl);
/* This is an implementation of section "Usage rules" of RFC 2782 */
int
@@ -187,6 +188,7 @@ resolv_discover_srv_send(TALLOC_CTX *mem_ctx,
errno_t resolv_discover_srv_recv(TALLOC_CTX *mem_ctx,
struct tevent_req *req,
struct ares_srv_reply **_reply_list,
+ uint32_t *_ttl,
char **_dns_domain);
#endif /* __ASYNC_RESOLV_H__ */
diff --git a/src/resolv/async_resolv_utils.c b/src/resolv/async_resolv_utils.c
index c5ae5f9d4..250681717 100644
--- a/src/resolv/async_resolv_utils.c
+++ b/src/resolv/async_resolv_utils.c
@@ -162,6 +162,7 @@ struct resolv_discover_srv_state {
int domain_index;
struct ares_srv_reply *reply_list;
+ uint32_t ttl;
};
static errno_t resolv_discover_srv_next_domain(struct tevent_req *req);
@@ -272,7 +273,8 @@ static void resolv_discover_srv_done(struct tevent_req *subreq)
req = tevent_req_callback_data(subreq, struct tevent_req);
state = tevent_req_data(req, struct resolv_discover_srv_state);
- ret = resolv_getsrv_recv(state, subreq, &status, NULL, &state->reply_list);
+ ret = resolv_getsrv_recv(state, subreq, &status, NULL,
+ &state->reply_list, &state->ttl);
talloc_zfree(subreq);
if (ret != EOK) {
DEBUG(SSSDBG_OP_FAILURE, "SRV query failed [%d]: %s\n",
@@ -307,6 +309,7 @@ done:
errno_t resolv_discover_srv_recv(TALLOC_CTX *mem_ctx,
struct tevent_req *req,
struct ares_srv_reply **_reply_list,
+ uint32_t *_ttl,
char **_dns_domain)
{
struct resolv_discover_srv_state *state = NULL;
@@ -331,5 +334,9 @@ errno_t resolv_discover_srv_recv(TALLOC_CTX *mem_ctx,
*_reply_list = talloc_steal(mem_ctx, state->reply_list);
}
+ if (*_ttl) {
+ *_ttl = state->ttl;
+ }
+
return EOK;
}
generated by cgit (git 2.34.1) at 2024-11-11 08:15:33 +0000