diff options
| -rw-r--r-- | resolv/nss_dns/dns-host.c | 478 |
1 files changed, 180 insertions, 298 deletions
diff --git a/resolv/nss_dns/dns-host.c b/resolv/nss_dns/dns-host.c index 8e38583e15..b887e77e9c 100644 --- a/resolv/nss_dns/dns-host.c +++ b/resolv/nss_dns/dns-host.c @@ -107,12 +107,19 @@ typedef union querybuf u_char buf[MAXPACKET]; } querybuf; -static enum nss_status getanswer_r (struct resolv_context *ctx, - const querybuf *answer, int anslen, - const char *qname, int qtype, - struct hostent *result, char *buffer, - size_t buflen, int *errnop, int *h_errnop, - int32_t *ttlp, char **canonp); +/* For historic reasons, pointers to IP addresses are char *, so use a + single list type for addresses and host names. */ +#define DYNARRAY_STRUCT ptrlist +#define DYNARRAY_ELEMENT char * +#define DYNARRAY_PREFIX ptrlist_ +#include <malloc/dynarray-skeleton.c> + +static enum nss_status getanswer_r (unsigned char *packet, size_t packetlen, + uint16_t qtype, struct alloc_buffer *abuf, + struct ptrlist *addresses, + struct ptrlist *aliases, + int *errnop, int *h_errnop, int32_t *ttlp); +static void addrsort (struct resolv_context *ctx, char **ap, int num); static enum nss_status getanswer_ptr (unsigned char *packet, size_t packetlen, struct alloc_buffer *abuf, char **hnamep, int *errnop, @@ -184,12 +191,6 @@ gethostbyname3_context (struct resolv_context *ctx, char *buffer, size_t buflen, int *errnop, int *h_errnop, int32_t *ttlp, char **canonp) { - union - { - querybuf *buf; - u_char *ptr; - } host_buffer; - querybuf *orig_host_buffer; char tmp[NS_MAXDNAME]; int size, type, n; const char *cp; @@ -223,10 +224,12 @@ gethostbyname3_context (struct resolv_context *ctx, && (cp = __res_context_hostalias (ctx, name, tmp, sizeof (tmp))) != NULL) name = cp; - host_buffer.buf = orig_host_buffer = (querybuf *) alloca (1024); + unsigned char dns_packet_buffer[1024]; + unsigned char *alt_dns_packet_buffer = dns_packet_buffer; - n = __res_context_search (ctx, name, C_IN, type, host_buffer.buf->buf, - 1024, &host_buffer.ptr, NULL, NULL, NULL, NULL); + n = __res_context_search (ctx, name, C_IN, type, + dns_packet_buffer, sizeof (dns_packet_buffer), + &alt_dns_packet_buffer, NULL, NULL, NULL, NULL); if (n < 0) { switch (errno) @@ -255,12 +258,77 @@ gethostbyname3_context (struct resolv_context *ctx, __set_errno (olderr); } else - status = getanswer_r - (ctx, host_buffer.buf, n, name, type, result, buffer, buflen, - errnop, h_errnop, ttlp, canonp); + { + struct alloc_buffer abuf = alloc_buffer_create (buffer, buflen); - if (host_buffer.buf != orig_host_buffer) - free (host_buffer.buf); + struct ptrlist addresses; + ptrlist_init (&addresses); + struct ptrlist aliases; + ptrlist_init (&aliases); + + status = getanswer_r (alt_dns_packet_buffer, n, type, + &abuf, &addresses, &aliases, + errnop, h_errnop, ttlp); + if (status == NSS_STATUS_SUCCESS) + { + if (ptrlist_has_failed (&addresses) + || ptrlist_has_failed (&aliases)) + { + /* malloc failure. Do not retry using the ERANGE protocol. */ + *errnop = ENOMEM; + *h_errnop = NETDB_INTERNAL; + status = NSS_STATUS_UNAVAIL; + } + + /* Reserve the address and alias arrays in the result + buffer. Both are NULL-terminated, but the first element + of the alias array is stored in h_name, so no extra space + for the NULL terminator is needed there. */ + result->h_addr_list + = alloc_buffer_alloc_array (&abuf, char *, + ptrlist_size (&addresses) + 1); + result->h_aliases + = alloc_buffer_alloc_array (&abuf, char *, + ptrlist_size (&aliases)); + if (alloc_buffer_has_failed (&abuf)) + { + /* Retry using the ERANGE protocol. */ + *errnop = ERANGE; + *h_errnop = NETDB_INTERNAL; + status = NSS_STATUS_TRYAGAIN; + } + else + { + /* Copy the address list and NULL-terminate it. */ + memcpy (result->h_addr_list, ptrlist_begin (&addresses), + ptrlist_size (&addresses) * sizeof (char *)); + result->h_addr_list[ptrlist_size (&addresses)] = NULL; + + /* Sort the address list if requested. */ + if (type == T_A && __resolv_context_sort_count (ctx) > 0) + addrsort (ctx, result->h_addr_list, ptrlist_size (&addresses)); + + /* Copy the aliases, excluding the last one. */ + memcpy (result->h_aliases, ptrlist_begin (&aliases), + (ptrlist_size (&aliases) - 1) * sizeof (char *)); + result->h_aliases[ptrlist_size (&aliases) - 1] = NULL; + + /* The last alias goes into h_name. */ + assert (ptrlist_size (&aliases) >= 1); + result->h_name = ptrlist_end (&aliases)[-1]; + + /* This is also the canonical name. */ + if (canonp != NULL) + *canonp = result->h_name; + } + } + + ptrlist_free (&aliases); + ptrlist_free (&addresses); + } + + if (alt_dns_packet_buffer != dns_packet_buffer) + free (alt_dns_packet_buffer); return status; } @@ -614,314 +682,128 @@ addrsort (struct resolv_context *ctx, char **ap, int num) break; } -static enum nss_status -getanswer_r (struct resolv_context *ctx, - const querybuf *answer, int anslen, const char *qname, int qtype, - struct hostent *result, char *buffer, size_t buflen, - int *errnop, int *h_errnop, int32_t *ttlp, char **canonp) +/* Convert the uncompressed, binary domain name CDNAME into its + textual representation and add it to the end of ALIASES, allocating + space for a copy of the name from ABUF. Skip adding the name if it + is not a valid host name, and return false in that case, otherwise + true. */ +static bool +getanswer_r_store_alias (const unsigned char *cdname, + struct alloc_buffer *abuf, + struct ptrlist *aliases) { - 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]; - 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; - - 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) - { - if (__glibc_unlikely (errno == EMSGSIZE)) - goto too_small; - - n = -1; - } + /* Filter out domain names that are not host names. */ + if (!__res_binary_hnok (cdname)) + return false; + + /* Note: Not NS_MAXCDNAME, so that __ns_name_ntop implicitly checks + for length. */ + char dname[MAXHOSTNAMELEN + 1]; + if (__ns_name_ntop (cdname, dname, sizeof (dname)) < 0) + return false; + /* Do not report an error on allocation failure, instead store NULL + or do nothing. getanswer_r's caller will see NSS_STATUS_SUCCESS + and detect the memory allocation failure or buffer space + exhaustion, and report it accordingly. */ + ptrlist_add (aliases, alloc_buffer_copy_string (abuf, dname)); + return true; +} - if (__glibc_unlikely (n < 0)) - { - *errnop = errno; - *h_errnop = NO_RECOVERY; - return NSS_STATUS_UNAVAIL; - } - if (__glibc_unlikely (__libc_res_hnok (bp) == 0)) +static enum nss_status __attribute__ ((noinline)) +getanswer_r (unsigned char *packet, size_t packetlen, uint16_t qtype, + struct alloc_buffer *abuf, + struct ptrlist *addresses, struct ptrlist *aliases, + int *errnop, int *h_errnop, int32_t *ttlp) +{ + struct ns_rr_cursor c; + if (!__ns_rr_cursor_init (&c, packet, packetlen)) { - 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; - if (qtype == T_A || qtype == T_AAAA) + /* Treat the QNAME just like an alias. Error out if it is not a + valid host name. */ + if (ns_rr_cursor_rcode (&c) == NXDOMAIN + || !getanswer_r_store_alias (ns_rr_cursor_qname (&c), abuf, aliases)) { - /* res_send() has already verified that the query name is the - * same as the one we sent; this just gets the expanded name - * (i.e., with the succeeding search-domain tacked on). - */ - n = strlen (bp) + 1; /* for the \0 */ - if (n >= MAXHOSTNAMELEN) - { - *h_errnop = NO_RECOVERY; - *errnop = ENOENT; - return NSS_STATUS_TRYAGAIN; - } - result->h_name = bp; - bp += n; - linebuflen -= n; - if (linebuflen < 0) - goto too_small; - /* The qname can be abbreviated, but h_name is now absolute. */ - qname = result->h_name; + if (ttlp != NULL) + /* No negative caching. */ + *ttlp = 0; + *h_errnop = HOST_NOT_FOUND; + *errnop = ENOENT; + return NSS_STATUS_NOTFOUND; } - 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; + 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]; - while (ancount-- > 0 && cp < end_of_message && had_error == 0) + for (; ancount > 0; --ancount) { - 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) - { - if (__glibc_unlikely (errno == EMSGSIZE)) - goto too_small; - - n = -1; - } - - if (__glibc_unlikely (n < 0 || __libc_res_hnok (bp) == 0)) - { - ++had_error; - continue; - } - cp += n; /* name */ - - if (__glibc_unlikely (cp + 10 > end_of_message)) + struct ns_rr_wire rr; + if (!__ns_rr_cursor_next (&c, &rr)) { - ++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. */ - - if (end_of_message - cp < n) - { - /* RDATA extends beyond the end of the packet. */ - ++had_error; - continue; - } + /* Skip over records with the wrong class. */ + if (rr.rclass != C_IN) + continue; - if (__glibc_unlikely (class != C_IN)) - { - /* XXX - debug? syslog? */ - cp += n; - continue; /* XXX - had_error++ ? */ - } + /* Update TTL for recognized record types. */ + if ((rr.rtype == T_CNAME || rr.rtype == qtype) + && 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; - - if (ap >= &host_data->aliases[MAX_NR_ALIASES - 1]) - continue; - n = __libc_dn_expand (answer->buf, end_of_message, cp, - tbuf, sizeof tbuf); - if (__glibc_unlikely (n < 0 || __libc_res_hnok (tbuf) == 0)) - { - ++had_error; - continue; - } - cp += n; - /* Store alias. */ - *ap++ = bp; - n = strlen (bp) + 1; /* For the \0. */ - if (__glibc_unlikely (n >= MAXHOSTNAMELEN)) - { - ++had_error; - continue; - } - bp += n; - linebuflen -= 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; } - result->h_name = bp; - bp = __mempcpy (bp, tbuf, n); /* Cannot overflow. */ - linebuflen -= n; - continue; + /* And store the new name as an alias. */ + getanswer_r_store_alias (name_buffer, abuf, aliases); + expected_name = name_buffer; } - - if (__glibc_unlikely (type != qtype)) + else if (rr.rtype == qtype + && __ns_samebinaryname (rr.rname, expected_name) + && rr.rdlength == rrtype_to_rdata_length (qtype)) { - cp += n; - continue; /* XXX - had_error++ ? */ + /* Make a copy of the address and store it. Increase the + alignment to 4, in case there are applications out there + that expect at least this level of address alignment. */ + ptrlist_add (addresses, (char *) alloc_buffer_next (abuf, uint32_t)); + alloc_buffer_copy_bytes (abuf, rr.rdata, rr.rdlength); } - - switch (type) - { - 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; - if (canonp != NULL) - *canonp = bp; - 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: - abort (); - } - if (had_error == 0) - ++haveanswer; } - if (haveanswer > 0) + if (ptrlist_size (addresses) == 0) { - *ap = NULL; - *hap = NULL; - /* - * Note: we sort even if host can take only one address - * in its return structures - should give it the "best" - * address in that case, not some random one - */ - if (haveanswer > 1 && qtype == T_A - && __resolv_context_sort_count (ctx) > 0) - addrsort (ctx, host_data->h_addr_ptrs, haveanswer); - - 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 address record found. */ + if (ttlp != NULL) + /* No caching of negative responses. */ + *ttlp = 0; + *h_errnop = NO_RECOVERY; + *errnop = ENOENT; + return NSS_STATUS_TRYAGAIN; + } + else + { *h_errnop = NETDB_SUCCESS; return NSS_STATUS_SUCCESS; } - no_recovery: - *h_errnop = NO_RECOVERY; - *errnop = ENOENT; - /* Special case here: if the resolver sent a result but it only - contains a CNAME while we are looking for a T_A or T_AAAA record, - we fail with NOTFOUND instead of TRYAGAIN. */ - return ((qtype == T_A || qtype == T_AAAA) && ap != host_data->aliases - ? NSS_STATUS_NOTFOUND : NSS_STATUS_TRYAGAIN); } static enum nss_status |