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resolv: Do not send queries for non-host-names in nss_dns [BZ #24112]

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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.

(cherry picked from commit 6ca53a2453)
This commit is contained in:
Florian Weimer 2019-01-21 09:26:41 +01:00
parent 8e92ca5dd7
commit 37edf1d3f8
2 changed files with 31 additions and 2 deletions
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9
ChangeLog
View File

@ -1,3 +1,12 @@
2019-01-18 Florian Weimer <fweimer@redhat.com>
[BZ #24112]
resolv: Do not send queries for non-host-names in nss_dns.
* resolv/nss_dns/dns-host.c (check_name): New function.
(_nss_dns_gethostbyname2_r): Use it.
(_nss_dns_gethostbyname_r): Likewise.
(_nss_dns_gethostbyname4_r): Likewise.
2019-01-21 Florian Weimer <fweimer@redhat.com>
* resolv/inet_addr.c: Reformat to GNU style.

24
resolv/nss_dns/dns-host.c
View File

@ -274,11 +274,26 @@ 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);
}
@ -289,6 +304,9 @@ _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)
{
@ -296,7 +314,7 @@ _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);
@ -313,6 +331,9 @@ _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)
{
@ -347,7 +368,6 @@ _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);