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glibc/SOURCES/glibc-upstream-2.34-323.patch

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commit 32e5db37684ffcbc6ae34fcc6cdcf28670506baa
Author: Florian Weimer <fweimer@redhat.com>
Date: Tue Aug 30 10:02:49 2022 +0200
nss_dns: Rewrite _nss_dns_gethostbyaddr2_r and getanswer_ptr
The simplification takes advantage of the split from getanswer_r.
It fixes various aliases issues, and optimizes NSS buffer usage.
The new DNS packet parsing helpers are used, too.
Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
(cherry picked from commit e32547d661a43da63368e488b6cfa9c53b4dcf92)
diff --git a/resolv/nss_dns/dns-host.c b/resolv/nss_dns/dns-host.c
index a6bf73a091968358..2cd7170f20b60588 100644
--- a/resolv/nss_dns/dns-host.c
+++ b/resolv/nss_dns/dns-host.c
@@ -70,6 +70,7 @@
* --Copyright--
*/
+#include <alloc_buffer.h>
#include <assert.h>
#include <ctype.h>
#include <errno.h>
@@ -117,10 +118,9 @@ static enum nss_status getanswer_r (struct resolv_context *ctx,
struct hostent *result, char *buffer,
size_t buflen, int *errnop, int *h_errnop,
int map, int32_t *ttlp, char **canonp);
-static enum nss_status getanswer_ptr (const querybuf *answer, int anslen,
- const char *qname,
- struct hostent *result, char *buffer,
- size_t buflen, int *errnop,
+static enum nss_status getanswer_ptr (unsigned char *packet, size_t packetlen,
+ struct alloc_buffer *abuf,
+ char **hnamep, int *errnop,
int *h_errnop, int32_t *ttlp);
static enum nss_status gaih_getanswer (const querybuf *answer1, int anslen1,
@@ -457,36 +457,21 @@ _nss_dns_gethostbyaddr2_r (const void *addr, socklen_t len, int af,
static const u_char tunnelled[] = { 0,0, 0,0, 0,0, 0,0, 0,0, 0,0 };
static const u_char v6local[] = { 0,0, 0,1 };
const u_char *uaddr = (const u_char *)addr;
- struct host_data
- {
- char *aliases[MAX_NR_ALIASES];
- unsigned char host_addr[16]; /* IPv4 or IPv6 */
- char *h_addr_ptrs[MAX_NR_ADDRS + 1];
- char linebuffer[0];
- } *host_data = (struct host_data *) buffer;
- union
- {
- querybuf *buf;
- u_char *ptr;
- } host_buffer;
- querybuf *orig_host_buffer;
char qbuf[MAXDNAME+1], *qp = NULL;
size_t size;
int n, status;
int olderr = errno;
- uintptr_t pad = -(uintptr_t) buffer % __alignof__ (struct host_data);
- buffer += pad;
- buflen = buflen > pad ? buflen - pad : 0;
-
- if (__glibc_unlikely (buflen < sizeof (struct host_data)))
- {
- *errnop = ERANGE;
- *h_errnop = NETDB_INTERNAL;
- return NSS_STATUS_TRYAGAIN;
- }
-
- host_data = (struct host_data *) buffer;
+ /* Prepare the allocation buffer. Store the pointer array first, to
+ benefit from buffer alignment. */
+ struct alloc_buffer abuf = alloc_buffer_create (buffer, buflen);
+ char **address_array = alloc_buffer_alloc_array (&abuf, char *, 2);
+ if (address_array == NULL)
+ {
+ *errnop = ERANGE;
+ *h_errnop = NETDB_INTERNAL;
+ return NSS_STATUS_TRYAGAIN;
+ }
struct resolv_context *ctx = __resolv_context_get ();
if (ctx == NULL)
@@ -530,8 +515,6 @@ _nss_dns_gethostbyaddr2_r (const void *addr, socklen_t len, int af,
return NSS_STATUS_UNAVAIL;
}
- host_buffer.buf = orig_host_buffer = (querybuf *) alloca (1024);
-
switch (af)
{
case AF_INET:
@@ -555,35 +538,52 @@ _nss_dns_gethostbyaddr2_r (const void *addr, socklen_t len, int af,
break;
}
- n = __res_context_query (ctx, qbuf, C_IN, T_PTR, host_buffer.buf->buf,
- 1024, &host_buffer.ptr, NULL, NULL, NULL, NULL);
+ unsigned char dns_packet_buffer[1024];
+ unsigned char *alt_dns_packet_buffer = dns_packet_buffer;
+ n = __res_context_query (ctx, qbuf, C_IN, T_PTR,
+ dns_packet_buffer, sizeof (dns_packet_buffer),
+ &alt_dns_packet_buffer,
+ NULL, NULL, NULL, NULL);
if (n < 0)
{
*h_errnop = h_errno;
__set_errno (olderr);
- if (host_buffer.buf != orig_host_buffer)
- free (host_buffer.buf);
+ if (alt_dns_packet_buffer != dns_packet_buffer)
+ free (alt_dns_packet_buffer);
__resolv_context_put (ctx);
return errno == ECONNREFUSED ? NSS_STATUS_UNAVAIL : NSS_STATUS_NOTFOUND;
}
- status = getanswer_ptr (host_buffer.buf, n, qbuf, result,
- buffer, buflen, errnop, h_errnop, ttlp);
- if (host_buffer.buf != orig_host_buffer)
- free (host_buffer.buf);
+ status = getanswer_ptr (alt_dns_packet_buffer, n,
+ &abuf, &result->h_name, errnop, h_errnop, ttlp);
+
+ if (alt_dns_packet_buffer != dns_packet_buffer)
+ free (alt_dns_packet_buffer);
+ __resolv_context_put (ctx);
+
if (status != NSS_STATUS_SUCCESS)
- {
- __resolv_context_put (ctx);
- return status;
- }
+ return status;
+ /* result->h_name has already been set by getanswer_ptr. */
result->h_addrtype = af;
result->h_length = len;
- memcpy (host_data->host_addr, addr, len);
- host_data->h_addr_ptrs[0] = (char *) host_data->host_addr;
- host_data->h_addr_ptrs[1] = NULL;
+ /* Increase the alignment to 4, in case there are applications out
+ there that expect at least this level of address alignment. */
+ address_array[0] = (char *) alloc_buffer_next (&abuf, uint32_t);
+ alloc_buffer_copy_bytes (&abuf, uaddr, len);
+ address_array[1] = NULL;
+
+ /* This check also covers allocation failure in getanswer_ptr. */
+ if (alloc_buffer_has_failed (&abuf))
+ {
+ *errnop = ERANGE;
+ *h_errnop = NETDB_INTERNAL;
+ return NSS_STATUS_TRYAGAIN;
+ }
+ result->h_addr_list = address_array;
+ result->h_aliases = &address_array[1]; /* Points to NULL. */
+
*h_errnop = NETDB_SUCCESS;
- __resolv_context_put (ctx);
return NSS_STATUS_SUCCESS;
}
libc_hidden_def (_nss_dns_gethostbyaddr2_r)
@@ -962,287 +962,86 @@ getanswer_r (struct resolv_context *ctx,
}
static enum nss_status
-getanswer_ptr (const querybuf *answer, int anslen, const char *qname,
- struct hostent *result, char *buffer, size_t buflen,
+getanswer_ptr (unsigned char *packet, size_t packetlen,
+ struct alloc_buffer *abuf, char **hnamep,
int *errnop, int *h_errnop, int32_t *ttlp)
{
- struct host_data
- {
- char *aliases[MAX_NR_ALIASES];
- unsigned char host_addr[16]; /* IPv4 or IPv6 */
- char *h_addr_ptrs[0];
- } *host_data;
- int linebuflen;
- const HEADER *hp;
- const u_char *end_of_message, *cp;
- int n, ancount, qdcount;
- int haveanswer, had_error;
- char *bp, **ap, **hap;
- char tbuf[MAXDNAME];
- const char *tname;
- u_char packtmp[NS_MAXCDNAME];
- uintptr_t pad = -(uintptr_t) buffer % __alignof__ (struct host_data);
- buffer += pad;
- buflen = buflen > pad ? buflen - pad : 0;
- if (__glibc_unlikely (buflen < sizeof (struct host_data)))
- {
- /* The buffer is too small. */
- too_small:
- *errnop = ERANGE;
- *h_errnop = NETDB_INTERNAL;
- return NSS_STATUS_TRYAGAIN;
- }
- host_data = (struct host_data *) buffer;
- linebuflen = buflen - sizeof (struct host_data);
- if (buflen - sizeof (struct host_data) != linebuflen)
- linebuflen = INT_MAX;
-
- tname = qname;
- result->h_name = NULL;
- end_of_message = answer->buf + anslen;
-
- /*
- * find first satisfactory answer
- */
- hp = &answer->hdr;
- ancount = ntohs (hp->ancount);
- qdcount = ntohs (hp->qdcount);
- cp = answer->buf + HFIXEDSZ;
- if (__glibc_unlikely (qdcount != 1))
- {
- *h_errnop = NO_RECOVERY;
- return NSS_STATUS_UNAVAIL;
- }
- if (sizeof (struct host_data) + (ancount + 1) * sizeof (char *) >= buflen)
- goto too_small;
- bp = (char *) &host_data->h_addr_ptrs[ancount + 1];
- linebuflen -= (ancount + 1) * sizeof (char *);
-
- n = __ns_name_unpack (answer->buf, end_of_message, cp,
- packtmp, sizeof packtmp);
- if (n != -1 && __ns_name_ntop (packtmp, bp, linebuflen) == -1)
+ struct ns_rr_cursor c;
+ if (!__ns_rr_cursor_init (&c, packet, packetlen))
{
- if (__glibc_unlikely (errno == EMSGSIZE))
- goto too_small;
-
- n = -1;
- }
-
- if (__glibc_unlikely (n < 0))
- {
- *errnop = errno;
- *h_errnop = NO_RECOVERY;
- return NSS_STATUS_UNAVAIL;
- }
- if (__glibc_unlikely (__libc_res_dnok (bp) == 0))
- {
- errno = EBADMSG;
- *errnop = EBADMSG;
+ /* This should not happen because __res_context_query already
+ perfroms response validation. */
*h_errnop = NO_RECOVERY;
return NSS_STATUS_UNAVAIL;
}
- cp += n + QFIXEDSZ;
+ int ancount = ns_rr_cursor_ancount (&c);
+ const unsigned char *expected_name = ns_rr_cursor_qname (&c);
+ /* expected_name may be updated to point into this buffer. */
+ unsigned char name_buffer[NS_MAXCDNAME];
- ap = host_data->aliases;
- *ap = NULL;
- result->h_aliases = host_data->aliases;
- hap = host_data->h_addr_ptrs;
- *hap = NULL;
- result->h_addr_list = host_data->h_addr_ptrs;
- haveanswer = 0;
- had_error = 0;
-
- while (ancount-- > 0 && cp < end_of_message && had_error == 0)
+ while (ancount > 0)
{
- int type, class;
-
- n = __ns_name_unpack (answer->buf, end_of_message, cp,
- packtmp, sizeof packtmp);
- if (n != -1 && __ns_name_ntop (packtmp, bp, linebuflen) == -1)
+ struct ns_rr_wire rr;
+ if (!__ns_rr_cursor_next (&c, &rr))
{
- if (__glibc_unlikely (errno == EMSGSIZE))
- goto too_small;
-
- n = -1;
- }
-
- if (__glibc_unlikely (n < 0 || __libc_res_dnok (bp) == 0))
- {
- ++had_error;
- continue;
- }
- cp += n; /* name */
-
- if (__glibc_unlikely (cp + 10 > end_of_message))
- {
- ++had_error;
- continue;
+ *h_errnop = NO_RECOVERY;
+ return NSS_STATUS_UNAVAIL;
}
- NS_GET16 (type, cp);
- NS_GET16 (class, cp);
- int32_t ttl;
- NS_GET32 (ttl, cp);
- NS_GET16 (n, cp); /* RDATA length. */
+ /* Skip over records with the wrong class. */
+ if (rr.rclass != C_IN)
+ continue;
- if (end_of_message - cp < n)
- {
- /* RDATA extends beyond the end of the packet. */
- ++had_error;
- continue;
- }
-
- if (__glibc_unlikely (class != C_IN))
- {
- /* XXX - debug? syslog? */
- cp += n;
- continue; /* XXX - had_error++ ? */
- }
+ /* Update TTL for known record types. */
+ if ((rr.rtype == T_CNAME || rr.rtype == T_PTR)
+ && ttlp != NULL && *ttlp > rr.ttl)
+ *ttlp = rr.ttl;
- if (type == T_CNAME)
+ if (rr.rtype == T_CNAME)
{
- /* A CNAME could also have a TTL entry. */
- if (ttlp != NULL && ttl < *ttlp)
- *ttlp = ttl;
-
- n = __libc_dn_expand (answer->buf, end_of_message, cp,
- tbuf, sizeof tbuf);
- if (__glibc_unlikely (n < 0 || __libc_res_dnok (tbuf) == 0))
- {
- ++had_error;
- continue;
- }
- cp += n;
- /* Get canonical name. */
- n = strlen (tbuf) + 1; /* For the \0. */
- if (__glibc_unlikely (n > linebuflen))
- goto too_small;
- if (__glibc_unlikely (n >= MAXHOSTNAMELEN))
+ /* NB: No check for owner name match, based on historic
+ precedent. Record the CNAME target as the new expected
+ name. */
+ int n = __ns_name_unpack (c.begin, c.end, rr.rdata,
+ name_buffer, sizeof (name_buffer));
+ if (n < 0)
{
- ++had_error;
- continue;
+ *h_errnop = NO_RECOVERY;
+ return NSS_STATUS_UNAVAIL;
}
- tname = bp;
- bp = __mempcpy (bp, tbuf, n); /* Cannot overflow. */
- linebuflen -= n;
- continue;
+ expected_name = name_buffer;
}
-
- switch (type)
+ else if (rr.rtype == T_PTR
+ && __ns_samebinaryname (rr.rname, expected_name))
{
- case T_PTR:
- if (__glibc_unlikely (__strcasecmp (tname, bp) != 0))
- {
- cp += n;
- continue; /* XXX - had_error++ ? */
- }
-
- n = __ns_name_unpack (answer->buf, end_of_message, cp,
- packtmp, sizeof packtmp);
- if (n != -1 && __ns_name_ntop (packtmp, bp, linebuflen) == -1)
- {
- if (__glibc_unlikely (errno == EMSGSIZE))
- goto too_small;
-
- n = -1;
- }
-
- if (__glibc_unlikely (n < 0 || __libc_res_hnok (bp) == 0))
+ /* Decompress the target of the PTR record. This is the
+ host name we are looking for. We can only use it if it
+ is syntactically valid. Historically, only one host name
+ is returned here. If the recursive resolver performs DNS
+ record rotation, the returned host name is essentially
+ random, which is why multiple PTR records are rarely
+ used. Use MAXHOSTNAMELEN instead of NS_MAXCDNAME for
+ additional length checking. */
+ char hname[MAXHOSTNAMELEN + 1];
+ if (__ns_name_unpack (c.begin, c.end, rr.rdata,
+ name_buffer, sizeof (name_buffer)) < 0
+ || !__res_binary_hnok (expected_name)
+ || __ns_name_ntop (name_buffer, hname, sizeof (hname)) < 0)
{
- ++had_error;
- break;
+ *h_errnop = NO_RECOVERY;
+ return NSS_STATUS_UNAVAIL;
}
- if (ttlp != NULL && ttl < *ttlp)
- *ttlp = ttl;
- /* bind would put multiple PTR records as aliases, but we don't do
- that. */
- result->h_name = bp;
- *h_errnop = NETDB_SUCCESS;
+ /* Successful allocation is checked by the caller. */
+ *hnamep = alloc_buffer_copy_string (abuf, hname);
return NSS_STATUS_SUCCESS;
- case T_A:
- case T_AAAA:
- if (__glibc_unlikely (__strcasecmp (result->h_name, bp) != 0))
- {
- cp += n;
- continue; /* XXX - had_error++ ? */
- }
-
- /* Stop parsing at a record whose length is incorrect. */
- if (n != rrtype_to_rdata_length (type))
- {
- ++had_error;
- break;
- }
-
- /* Skip records of the wrong type. */
- if (n != result->h_length)
- {
- cp += n;
- continue;
- }
- if (!haveanswer)
- {
- int nn;
-
- /* We compose a single hostent out of the entire chain of
- entries, so the TTL of the hostent is essentially the lowest
- TTL in the chain. */
- if (ttlp != NULL && ttl < *ttlp)
- *ttlp = ttl;
- result->h_name = bp;
- nn = strlen (bp) + 1; /* for the \0 */
- bp += nn;
- linebuflen -= nn;
- }
-
- /* Provide sufficient alignment for both address
- families. */
- enum { align = 4 };
- _Static_assert ((align % __alignof__ (struct in_addr)) == 0,
- "struct in_addr alignment");
- _Static_assert ((align % __alignof__ (struct in6_addr)) == 0,
- "struct in6_addr alignment");
- {
- char *new_bp = PTR_ALIGN_UP (bp, align);
- linebuflen -= new_bp - bp;
- bp = new_bp;
- }
-
- if (__glibc_unlikely (n > linebuflen))
- goto too_small;
- bp = __mempcpy (*hap++ = bp, cp, n);
- cp += n;
- linebuflen -= n;
- break;
- default:
- cp += n;
- continue; /* XXX - had_error++ ? */
}
- if (had_error == 0)
- ++haveanswer;
}
- if (haveanswer > 0)
- {
- *ap = NULL;
- *hap = NULL;
-
- if (result->h_name == NULL)
- {
- n = strlen (qname) + 1; /* For the \0. */
- if (n > linebuflen)
- goto too_small;
- if (n >= MAXHOSTNAMELEN)
- goto no_recovery;
- result->h_name = bp;
- bp = __mempcpy (bp, qname, n); /* Cannot overflow. */
- linebuflen -= n;
- }
+ /* No PTR record found. */
+ if (ttlp != NULL)
+ /* No caching of negative responses. */
+ *ttlp = 0;
- *h_errnop = NETDB_SUCCESS;
- return NSS_STATUS_SUCCESS;
- }
- no_recovery:
*h_errnop = NO_RECOVERY;
*errnop = ENOENT;
return NSS_STATUS_TRYAGAIN;