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https://sourceware.org/git/glibc.git
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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>
This commit is contained in:
Florian Weimer
parent
0dcc43e998
commit
e32547d661
@ -69,6 +69,7 @@
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* --Copyright--
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*/
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#include <alloc_buffer.h>
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#include <assert.h>
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#include <ctype.h>
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#include <errno.h>
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@ -116,10 +117,9 @@ static enum nss_status getanswer_r (struct resolv_context *ctx,
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struct hostent *result, char *buffer,
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size_t buflen, int *errnop, int *h_errnop,
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int map, int32_t *ttlp, char **canonp);
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static enum nss_status getanswer_ptr (const querybuf *answer, int anslen,
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const char *qname,
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struct hostent *result, char *buffer,
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size_t buflen, int *errnop,
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static enum nss_status getanswer_ptr (unsigned char *packet, size_t packetlen,
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struct alloc_buffer *abuf,
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char **hnamep, int *errnop,
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int *h_errnop, int32_t *ttlp);
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static enum nss_status gaih_getanswer (const querybuf *answer1, int anslen1,
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@ -456,36 +456,21 @@ _nss_dns_gethostbyaddr2_r (const void *addr, socklen_t len, int af,
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static const u_char tunnelled[] = { 0,0, 0,0, 0,0, 0,0, 0,0, 0,0 };
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static const u_char v6local[] = { 0,0, 0,1 };
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const u_char *uaddr = (const u_char *)addr;
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struct host_data
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{
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char *aliases[MAX_NR_ALIASES];
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unsigned char host_addr[16]; /* IPv4 or IPv6 */
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char *h_addr_ptrs[MAX_NR_ADDRS + 1];
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char linebuffer[0];
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} *host_data = (struct host_data *) buffer;
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union
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{
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querybuf *buf;
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u_char *ptr;
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} host_buffer;
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querybuf *orig_host_buffer;
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char qbuf[MAXDNAME+1], *qp = NULL;
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size_t size;
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int n, status;
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int olderr = errno;
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uintptr_t pad = -(uintptr_t) buffer % __alignof__ (struct host_data);
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buffer += pad;
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buflen = buflen > pad ? buflen - pad : 0;
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if (__glibc_unlikely (buflen < sizeof (struct host_data)))
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{
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*errnop = ERANGE;
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*h_errnop = NETDB_INTERNAL;
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return NSS_STATUS_TRYAGAIN;
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}
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host_data = (struct host_data *) buffer;
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/* Prepare the allocation buffer. Store the pointer array first, to
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benefit from buffer alignment. */
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struct alloc_buffer abuf = alloc_buffer_create (buffer, buflen);
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char **address_array = alloc_buffer_alloc_array (&abuf, char *, 2);
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if (address_array == NULL)
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{
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*errnop = ERANGE;
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*h_errnop = NETDB_INTERNAL;
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return NSS_STATUS_TRYAGAIN;
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}
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struct resolv_context *ctx = __resolv_context_get ();
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if (ctx == NULL)
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@ -529,8 +514,6 @@ _nss_dns_gethostbyaddr2_r (const void *addr, socklen_t len, int af,
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return NSS_STATUS_UNAVAIL;
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}
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host_buffer.buf = orig_host_buffer = (querybuf *) alloca (1024);
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switch (af)
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{
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case AF_INET:
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@ -554,35 +537,52 @@ _nss_dns_gethostbyaddr2_r (const void *addr, socklen_t len, int af,
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break;
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}
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n = __res_context_query (ctx, qbuf, C_IN, T_PTR, host_buffer.buf->buf,
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1024, &host_buffer.ptr, NULL, NULL, NULL, NULL);
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unsigned char dns_packet_buffer[1024];
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unsigned char *alt_dns_packet_buffer = dns_packet_buffer;
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n = __res_context_query (ctx, qbuf, C_IN, T_PTR,
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dns_packet_buffer, sizeof (dns_packet_buffer),
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&alt_dns_packet_buffer,
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NULL, NULL, NULL, NULL);
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if (n < 0)
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{
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*h_errnop = h_errno;
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__set_errno (olderr);
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if (host_buffer.buf != orig_host_buffer)
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free (host_buffer.buf);
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if (alt_dns_packet_buffer != dns_packet_buffer)
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free (alt_dns_packet_buffer);
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__resolv_context_put (ctx);
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return errno == ECONNREFUSED ? NSS_STATUS_UNAVAIL : NSS_STATUS_NOTFOUND;
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}
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status = getanswer_ptr (host_buffer.buf, n, qbuf, result,
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buffer, buflen, errnop, h_errnop, ttlp);
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if (host_buffer.buf != orig_host_buffer)
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free (host_buffer.buf);
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if (status != NSS_STATUS_SUCCESS)
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{
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__resolv_context_put (ctx);
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return status;
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}
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status = getanswer_ptr (alt_dns_packet_buffer, n,
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&abuf, &result->h_name, errnop, h_errnop, ttlp);
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if (alt_dns_packet_buffer != dns_packet_buffer)
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free (alt_dns_packet_buffer);
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__resolv_context_put (ctx);
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if (status != NSS_STATUS_SUCCESS)
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return status;
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/* result->h_name has already been set by getanswer_ptr. */
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result->h_addrtype = af;
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result->h_length = len;
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memcpy (host_data->host_addr, addr, len);
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host_data->h_addr_ptrs[0] = (char *) host_data->host_addr;
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host_data->h_addr_ptrs[1] = NULL;
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/* Increase the alignment to 4, in case there are applications out
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there that expect at least this level of address alignment. */
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address_array[0] = (char *) alloc_buffer_next (&abuf, uint32_t);
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alloc_buffer_copy_bytes (&abuf, uaddr, len);
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address_array[1] = NULL;
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/* This check also covers allocation failure in getanswer_ptr. */
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if (alloc_buffer_has_failed (&abuf))
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{
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*errnop = ERANGE;
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*h_errnop = NETDB_INTERNAL;
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return NSS_STATUS_TRYAGAIN;
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}
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result->h_addr_list = address_array;
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result->h_aliases = &address_array[1]; /* Points to NULL. */
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*h_errnop = NETDB_SUCCESS;
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__resolv_context_put (ctx);
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return NSS_STATUS_SUCCESS;
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}
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libc_hidden_def (_nss_dns_gethostbyaddr2_r)
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@ -961,287 +961,86 @@ getanswer_r (struct resolv_context *ctx,
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}
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static enum nss_status
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getanswer_ptr (const querybuf *answer, int anslen, const char *qname,
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struct hostent *result, char *buffer, size_t buflen,
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getanswer_ptr (unsigned char *packet, size_t packetlen,
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struct alloc_buffer *abuf, char **hnamep,
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int *errnop, int *h_errnop, int32_t *ttlp)
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{
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struct host_data
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{
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char *aliases[MAX_NR_ALIASES];
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unsigned char host_addr[16]; /* IPv4 or IPv6 */
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char *h_addr_ptrs[0];
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} *host_data;
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int linebuflen;
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const HEADER *hp;
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const u_char *end_of_message, *cp;
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int n, ancount, qdcount;
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int haveanswer, had_error;
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char *bp, **ap, **hap;
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char tbuf[MAXDNAME];
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const char *tname;
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u_char packtmp[NS_MAXCDNAME];
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uintptr_t pad = -(uintptr_t) buffer % __alignof__ (struct host_data);
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buffer += pad;
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buflen = buflen > pad ? buflen - pad : 0;
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if (__glibc_unlikely (buflen < sizeof (struct host_data)))
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{
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/* The buffer is too small. */
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too_small:
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*errnop = ERANGE;
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*h_errnop = NETDB_INTERNAL;
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return NSS_STATUS_TRYAGAIN;
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}
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host_data = (struct host_data *) buffer;
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linebuflen = buflen - sizeof (struct host_data);
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if (buflen - sizeof (struct host_data) != linebuflen)
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linebuflen = INT_MAX;
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tname = qname;
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result->h_name = NULL;
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end_of_message = answer->buf + anslen;
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/*
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* find first satisfactory answer
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*/
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hp = &answer->hdr;
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ancount = ntohs (hp->ancount);
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qdcount = ntohs (hp->qdcount);
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cp = answer->buf + HFIXEDSZ;
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if (__glibc_unlikely (qdcount != 1))
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struct ns_rr_cursor c;
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if (!__ns_rr_cursor_init (&c, packet, packetlen))
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{
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/* This should not happen because __res_context_query already
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perfroms response validation. */
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*h_errnop = NO_RECOVERY;
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return NSS_STATUS_UNAVAIL;
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}
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if (sizeof (struct host_data) + (ancount + 1) * sizeof (char *) >= buflen)
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goto too_small;
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bp = (char *) &host_data->h_addr_ptrs[ancount + 1];
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linebuflen -= (ancount + 1) * sizeof (char *);
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int ancount = ns_rr_cursor_ancount (&c);
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const unsigned char *expected_name = ns_rr_cursor_qname (&c);
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/* expected_name may be updated to point into this buffer. */
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unsigned char name_buffer[NS_MAXCDNAME];
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n = __ns_name_unpack (answer->buf, end_of_message, cp,
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packtmp, sizeof packtmp);
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if (n != -1 && __ns_name_ntop (packtmp, bp, linebuflen) == -1)
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while (ancount > 0)
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{
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if (__glibc_unlikely (errno == EMSGSIZE))
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goto too_small;
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n = -1;
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}
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if (__glibc_unlikely (n < 0))
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{
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*errnop = errno;
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*h_errnop = NO_RECOVERY;
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return NSS_STATUS_UNAVAIL;
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}
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if (__glibc_unlikely (__libc_res_dnok (bp) == 0))
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{
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errno = EBADMSG;
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*errnop = EBADMSG;
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*h_errnop = NO_RECOVERY;
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return NSS_STATUS_UNAVAIL;
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}
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cp += n + QFIXEDSZ;
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ap = host_data->aliases;
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*ap = NULL;
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result->h_aliases = host_data->aliases;
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hap = host_data->h_addr_ptrs;
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*hap = NULL;
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result->h_addr_list = host_data->h_addr_ptrs;
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haveanswer = 0;
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had_error = 0;
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while (ancount-- > 0 && cp < end_of_message && had_error == 0)
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{
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int type, class;
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n = __ns_name_unpack (answer->buf, end_of_message, cp,
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packtmp, sizeof packtmp);
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if (n != -1 && __ns_name_ntop (packtmp, bp, linebuflen) == -1)
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struct ns_rr_wire rr;
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if (!__ns_rr_cursor_next (&c, &rr))
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{
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if (__glibc_unlikely (errno == EMSGSIZE))
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goto too_small;
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n = -1;
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*h_errnop = NO_RECOVERY;
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return NSS_STATUS_UNAVAIL;
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}
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if (__glibc_unlikely (n < 0 || __libc_res_dnok (bp) == 0))
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/* Skip over records with the wrong class. */
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if (rr.rclass != C_IN)
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continue;
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/* Update TTL for known record types. */
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if ((rr.rtype == T_CNAME || rr.rtype == T_PTR)
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&& ttlp != NULL && *ttlp > rr.ttl)
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*ttlp = rr.ttl;
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if (rr.rtype == T_CNAME)
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{
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++had_error;
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continue;
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}
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cp += n; /* name */
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if (__glibc_unlikely (cp + 10 > end_of_message))
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{
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++had_error;
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continue;
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}
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NS_GET16 (type, cp);
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NS_GET16 (class, cp);
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int32_t ttl;
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NS_GET32 (ttl, cp);
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NS_GET16 (n, cp); /* RDATA length. */
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if (end_of_message - cp < n)
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{
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/* RDATA extends beyond the end of the packet. */
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++had_error;
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continue;
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}
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if (__glibc_unlikely (class != C_IN))
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{
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/* XXX - debug? syslog? */
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cp += n;
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continue; /* XXX - had_error++ ? */
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}
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if (type == T_CNAME)
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{
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/* A CNAME could also have a TTL entry. */
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if (ttlp != NULL && ttl < *ttlp)
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*ttlp = ttl;
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n = __libc_dn_expand (answer->buf, end_of_message, cp,
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tbuf, sizeof tbuf);
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if (__glibc_unlikely (n < 0 || __libc_res_dnok (tbuf) == 0))
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/* NB: No check for owner name match, based on historic
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precedent. Record the CNAME target as the new expected
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name. */
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int n = __ns_name_unpack (c.begin, c.end, rr.rdata,
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name_buffer, sizeof (name_buffer));
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if (n < 0)
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{
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++had_error;
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continue;
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*h_errnop = NO_RECOVERY;
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return NSS_STATUS_UNAVAIL;
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}
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cp += n;
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/* Get canonical name. */
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n = strlen (tbuf) + 1; /* For the \0. */
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if (__glibc_unlikely (n > linebuflen))
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goto too_small;
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if (__glibc_unlikely (n >= MAXHOSTNAMELEN))
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{
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++had_error;
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continue;
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}
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tname = bp;
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bp = __mempcpy (bp, tbuf, n); /* Cannot overflow. */
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linebuflen -= n;
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continue;
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expected_name = name_buffer;
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}
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switch (type)
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else if (rr.rtype == T_PTR
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&& __ns_samebinaryname (rr.rname, expected_name))
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{
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case T_PTR:
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if (__glibc_unlikely (__strcasecmp (tname, bp) != 0))
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/* Decompress the target of the PTR record. This is the
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host name we are looking for. We can only use it if it
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is syntactically valid. Historically, only one host name
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is returned here. If the recursive resolver performs DNS
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record rotation, the returned host name is essentially
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random, which is why multiple PTR records are rarely
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used. Use MAXHOSTNAMELEN instead of NS_MAXCDNAME for
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additional length checking. */
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char hname[MAXHOSTNAMELEN + 1];
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if (__ns_name_unpack (c.begin, c.end, rr.rdata,
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name_buffer, sizeof (name_buffer)) < 0
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|| !__res_binary_hnok (expected_name)
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|| __ns_name_ntop (name_buffer, hname, sizeof (hname)) < 0)
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{
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cp += n;
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continue; /* XXX - had_error++ ? */
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*h_errnop = NO_RECOVERY;
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return NSS_STATUS_UNAVAIL;
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}
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n = __ns_name_unpack (answer->buf, end_of_message, cp,
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packtmp, sizeof packtmp);
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if (n != -1 && __ns_name_ntop (packtmp, bp, linebuflen) == -1)
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{
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if (__glibc_unlikely (errno == EMSGSIZE))
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goto too_small;
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n = -1;
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}
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if (__glibc_unlikely (n < 0 || __libc_res_hnok (bp) == 0))
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{
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++had_error;
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break;
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}
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if (ttlp != NULL && ttl < *ttlp)
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*ttlp = ttl;
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/* bind would put multiple PTR records as aliases, but we don't do
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that. */
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result->h_name = bp;
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*h_errnop = NETDB_SUCCESS;
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/* Successful allocation is checked by the caller. */
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*hnamep = alloc_buffer_copy_string (abuf, hname);
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return NSS_STATUS_SUCCESS;
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case T_A:
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case T_AAAA:
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if (__glibc_unlikely (__strcasecmp (result->h_name, bp) != 0))
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{
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cp += n;
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continue; /* XXX - had_error++ ? */
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}
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/* Stop parsing at a record whose length is incorrect. */
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if (n != rrtype_to_rdata_length (type))
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{
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++had_error;
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break;
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}
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/* Skip records of the wrong type. */
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if (n != result->h_length)
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{
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cp += n;
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continue;
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}
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if (!haveanswer)
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{
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int nn;
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/* We compose a single hostent out of the entire chain of
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entries, so the TTL of the hostent is essentially the lowest
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TTL in the chain. */
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if (ttlp != NULL && ttl < *ttlp)
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*ttlp = ttl;
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result->h_name = bp;
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nn = strlen (bp) + 1; /* for the \0 */
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bp += nn;
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linebuflen -= nn;
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}
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/* Provide sufficient alignment for both address
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families. */
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enum { align = 4 };
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_Static_assert ((align % __alignof__ (struct in_addr)) == 0,
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"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;
|
||||
/* No PTR record found. */
|
||||
if (ttlp != NULL)
|
||||
/* No caching of negative responses. */
|
||||
*ttlp = 0;
|
||||
|
||||
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;
|
||||
}
|
||||
|
||||
*h_errnop = NETDB_SUCCESS;
|
||||
return NSS_STATUS_SUCCESS;
|
||||
}
|
||||
no_recovery:
|
||||
*h_errnop = NO_RECOVERY;
|
||||
*errnop = ENOENT;
|
||||
return NSS_STATUS_TRYAGAIN;
|
||||
|
||||
Loading…
Reference in New Issue
Block a user