diff options
Diffstat (limited to 'src/c-ares/ares_parse_a_reply.c')
| -rw-r--r-- | src/c-ares/ares_parse_a_reply.c | 264 |
1 files changed, 264 insertions, 0 deletions
diff --git a/src/c-ares/ares_parse_a_reply.c b/src/c-ares/ares_parse_a_reply.c new file mode 100644 index 00000000..0422bd38 --- /dev/null +++ b/src/c-ares/ares_parse_a_reply.c @@ -0,0 +1,264 @@ + +/* Copyright 1998 by the Massachusetts Institute of Technology. + * + * Permission to use, copy, modify, and distribute this + * software and its documentation for any purpose and without + * fee is hereby granted, provided that the above copyright + * notice appear in all copies and that both that copyright + * notice and this permission notice appear in supporting + * documentation, and that the name of M.I.T. not be used in + * advertising or publicity pertaining to distribution of the + * software without specific, written prior permission. + * M.I.T. makes no representations about the suitability of + * this software for any purpose. It is provided "as is" + * without express or implied warranty. + */ + +#include "ares_setup.h" + +#ifdef HAVE_NETINET_IN_H +# include <netinet/in.h> +#endif +#ifdef HAVE_NETDB_H +# include <netdb.h> +#endif +#ifdef HAVE_ARPA_INET_H +# include <arpa/inet.h> +#endif +#ifdef HAVE_ARPA_NAMESER_H +# include <arpa/nameser.h> +#else +# include "nameser.h" +#endif +#ifdef HAVE_ARPA_NAMESER_COMPAT_H +# include <arpa/nameser_compat.h> +#endif + +#ifdef HAVE_STRINGS_H +# include <strings.h> +#endif + +#ifdef HAVE_LIMITS_H +# include <limits.h> +#endif + +#include "ares.h" +#include "ares_dns.h" +#include "ares_private.h" + +int ares_parse_a_reply(const unsigned char *abuf, int alen, + struct hostent **host, + struct ares_addrttl *addrttls, int *naddrttls) +{ + unsigned int qdcount, ancount; + int status, i, rr_type, rr_class, rr_len, rr_ttl, naddrs; + int cname_ttl = INT_MAX; /* the TTL imposed by the CNAME chain */ + int naliases; + long len; + const unsigned char *aptr; + char *hostname, *rr_name, *rr_data, **aliases; + struct in_addr *addrs; + struct hostent *hostent; + const int max_addr_ttls = (addrttls && naddrttls) ? *naddrttls : 0; + + /* Set *host to NULL for all failure cases. */ + if (host) + *host = NULL; + /* Same with *naddrttls. */ + if (naddrttls) + *naddrttls = 0; + + /* Give up if abuf doesn't have room for a header. */ + if (alen < HFIXEDSZ) + return ARES_EBADRESP; + + /* Fetch the question and answer count from the header. */ + qdcount = DNS_HEADER_QDCOUNT(abuf); + ancount = DNS_HEADER_ANCOUNT(abuf); + if (qdcount != 1) + return ARES_EBADRESP; + + /* Expand the name from the question, and skip past the question. */ + aptr = abuf + HFIXEDSZ; + status = ares__expand_name_for_response(aptr, abuf, alen, &hostname, &len); + if (status != ARES_SUCCESS) + return status; + if (aptr + len + QFIXEDSZ > abuf + alen) + { + ares_free(hostname); + return ARES_EBADRESP; + } + aptr += len + QFIXEDSZ; + + if (host) + { + /* Allocate addresses and aliases; ancount gives an upper bound for + both. */ + addrs = ares_malloc(ancount * sizeof(struct in_addr)); + if (!addrs) + { + ares_free(hostname); + return ARES_ENOMEM; + } + aliases = ares_malloc((ancount + 1) * sizeof(char *)); + if (!aliases) + { + ares_free(hostname); + ares_free(addrs); + return ARES_ENOMEM; + } + } + else + { + addrs = NULL; + aliases = NULL; + } + + naddrs = 0; + naliases = 0; + + /* Examine each answer resource record (RR) in turn. */ + for (i = 0; i < (int)ancount; i++) + { + /* Decode the RR up to the data field. */ + status = ares__expand_name_for_response(aptr, abuf, alen, &rr_name, &len); + if (status != ARES_SUCCESS) + break; + aptr += len; + if (aptr + RRFIXEDSZ > abuf + alen) + { + ares_free(rr_name); + status = ARES_EBADRESP; + break; + } + rr_type = DNS_RR_TYPE(aptr); + rr_class = DNS_RR_CLASS(aptr); + rr_len = DNS_RR_LEN(aptr); + rr_ttl = DNS_RR_TTL(aptr); + aptr += RRFIXEDSZ; + if (aptr + rr_len > abuf + alen) + { + ares_free(rr_name); + status = ARES_EBADRESP; + break; + } + + if (rr_class == C_IN && rr_type == T_A + && rr_len == sizeof(struct in_addr) + && strcasecmp(rr_name, hostname) == 0) + { + if (addrs) + { + if (aptr + sizeof(struct in_addr) > abuf + alen) + { /* LCOV_EXCL_START: already checked above */ + ares_free(rr_name); + status = ARES_EBADRESP; + break; + } /* LCOV_EXCL_STOP */ + memcpy(&addrs[naddrs], aptr, sizeof(struct in_addr)); + } + if (naddrs < max_addr_ttls) + { + struct ares_addrttl * const at = &addrttls[naddrs]; + if (aptr + sizeof(struct in_addr) > abuf + alen) + { /* LCOV_EXCL_START: already checked above */ + ares_free(rr_name); + status = ARES_EBADRESP; + break; + } /* LCOV_EXCL_STOP */ + memcpy(&at->ipaddr, aptr, sizeof(struct in_addr)); + at->ttl = rr_ttl; + } + naddrs++; + status = ARES_SUCCESS; + } + + if (rr_class == C_IN && rr_type == T_CNAME) + { + /* Record the RR name as an alias. */ + if (aliases) + aliases[naliases] = rr_name; + else + ares_free(rr_name); + naliases++; + + /* Decode the RR data and replace the hostname with it. */ + status = ares__expand_name_for_response(aptr, abuf, alen, &rr_data, + &len); + if (status != ARES_SUCCESS) + break; + ares_free(hostname); + hostname = rr_data; + + /* Take the min of the TTLs we see in the CNAME chain. */ + if (cname_ttl > rr_ttl) + cname_ttl = rr_ttl; + } + else + ares_free(rr_name); + + aptr += rr_len; + if (aptr > abuf + alen) + { /* LCOV_EXCL_START: already checked above */ + status = ARES_EBADRESP; + break; + } /* LCOV_EXCL_STOP */ + } + + if (status == ARES_SUCCESS && naddrs == 0 && naliases == 0) + /* the check for naliases to be zero is to make sure CNAME responses + don't get caught here */ + status = ARES_ENODATA; + if (status == ARES_SUCCESS) + { + /* We got our answer. */ + if (naddrttls) + { + const int n = naddrs < max_addr_ttls ? naddrs : max_addr_ttls; + for (i = 0; i < n; i++) + { + /* Ensure that each A TTL is no larger than the CNAME TTL. */ + if (addrttls[i].ttl > cname_ttl) + addrttls[i].ttl = cname_ttl; + } + *naddrttls = n; + } + if (aliases) + aliases[naliases] = NULL; + if (host) + { + /* Allocate memory to build the host entry. */ + hostent = ares_malloc(sizeof(struct hostent)); + if (hostent) + { + hostent->h_addr_list = ares_malloc((naddrs + 1) * sizeof(char *)); + if (hostent->h_addr_list) + { + /* Fill in the hostent and return successfully. */ + hostent->h_name = hostname; + hostent->h_aliases = aliases; + hostent->h_addrtype = AF_INET; + hostent->h_length = sizeof(struct in_addr); + for (i = 0; i < naddrs; i++) + hostent->h_addr_list[i] = (char *) &addrs[i]; + hostent->h_addr_list[naddrs] = NULL; + if (!naddrs && addrs) + ares_free(addrs); + *host = hostent; + return ARES_SUCCESS; + } + ares_free(hostent); + } + status = ARES_ENOMEM; + } + } + if (aliases) + { + for (i = 0; i < naliases; i++) + ares_free(aliases[i]); + ares_free(aliases); + } + ares_free(addrs); + ares_free(hostname); + return status; +} |