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commit 6ca53a2453598804a2559a548a08424fca96434a
Author: Florian Weimer <fweimer@redhat.com>
Date: Mon Jan 21 09:26:41 2019 +0100
resolv: Do not send queries for non-host-names in nss_dns [BZ #24112]
Before this commit, nss_dns would send a query which did not contain a
host name as the query name (such as invalid\032name.example.com) and
then reject the answer in getanswer_r and gaih_getanswer_slice, using
a check based on res_hnok. With this commit, no query is sent, and a
host-not-found error is returned to NSS without network interaction.
diff --git a/resolv/nss_dns/dns-host.c b/resolv/nss_dns/dns-host.c
index 1e85e4f08ffc8600..e697d9103797341b 100644
--- a/resolv/nss_dns/dns-host.c
+++ b/resolv/nss_dns/dns-host.c
@@ -273,11 +273,26 @@ gethostbyname3_context (struct resolv_context *ctx,
return status;
}
+/* Verify that the name looks like a host name. There is no point in
+ sending a query which will not produce a usable name in the
+ response. */
+static enum nss_status
+check_name (const char *name, int *h_errnop)
+{
+ if (res_hnok (name))
+ return NSS_STATUS_SUCCESS;
+ *h_errnop = HOST_NOT_FOUND;
+ return NSS_STATUS_NOTFOUND;
+}
+
enum nss_status
_nss_dns_gethostbyname2_r (const char *name, int af, struct hostent *result,
char *buffer, size_t buflen, int *errnop,
int *h_errnop)
{
+ enum nss_status status = check_name (name, h_errnop);
+ if (status != NSS_STATUS_SUCCESS)
+ return status;
return _nss_dns_gethostbyname3_r (name, af, result, buffer, buflen, errnop,
h_errnop, NULL, NULL);
}
@@ -288,6 +303,9 @@ _nss_dns_gethostbyname_r (const char *name, struct hostent *result,
char *buffer, size_t buflen, int *errnop,
int *h_errnop)
{
+ enum nss_status status = check_name (name, h_errnop);
+ if (status != NSS_STATUS_SUCCESS)
+ return status;
struct resolv_context *ctx = __resolv_context_get ();
if (ctx == NULL)
{
@@ -295,7 +313,7 @@ _nss_dns_gethostbyname_r (const char *name, struct hostent *result,
*h_errnop = NETDB_INTERNAL;
return NSS_STATUS_UNAVAIL;
}
- enum nss_status status = NSS_STATUS_NOTFOUND;
+ status = NSS_STATUS_NOTFOUND;
if (res_use_inet6 ())
status = gethostbyname3_context (ctx, name, AF_INET6, result, buffer,
buflen, errnop, h_errnop, NULL, NULL);
@@ -312,6 +330,9 @@ _nss_dns_gethostbyname4_r (const char *name, struct gaih_addrtuple **pat,
char *buffer, size_t buflen, int *errnop,
int *herrnop, int32_t *ttlp)
{
+ enum nss_status status = check_name (name, herrnop);
+ if (status != NSS_STATUS_SUCCESS)
+ return status;
struct resolv_context *ctx = __resolv_context_get ();
if (ctx == NULL)
{
@@ -346,7 +367,6 @@ _nss_dns_gethostbyname4_r (const char *name, struct gaih_addrtuple **pat,
int ans2p_malloced = 0;
int olderr = errno;
- enum nss_status status;
int n = __res_context_search (ctx, name, C_IN, T_QUERY_A_AND_AAAA,
host_buffer.buf->buf, 2048, &host_buffer.ptr,
&ans2p, &nans2p, &resplen2, &ans2p_malloced);