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