From 675a7e60aeb91bda719ae30abb1ecbb853b8f7ea Mon Sep 17 00:00:00 2001 From: Eric Andersen Date: Thu, 30 Nov 2000 19:57:33 +0000 Subject: Some cleanups from W. Greathouse (and a few of my own) --- libc/inet/resolv.c | 234 ++++++++++++++++++++++++++++++++++------------------- 1 file changed, 152 insertions(+), 82 deletions(-) (limited to 'libc/inet/resolv.c') diff --git a/libc/inet/resolv.c b/libc/inet/resolv.c index 718d71a0d..7abc9b506 100644 --- a/libc/inet/resolv.c +++ b/libc/inet/resolv.c @@ -7,6 +7,31 @@ * modify it under the terms of the GNU Library General Public * License as published by the Free Software Foundation; either * version 2 of the License, or (at your option) any later version. + * + * 5-Oct-2000 W. Greathouse wgreathouse@smva.com + * Fix memory leak and memory corruption. + * -- Every name resolution resulted in + * a new parse of resolv.conf and new + * copy of nameservers allocated by + * strdup. + * -- Every name resolution resulted in + * a new read of resolv.conf without + * resetting index from prior read... + * resulting in exceeding array bounds. + * + * Limit nameservers read from resolv.conf + * + * Add "search" domains from resolv.conf + * + * Some systems will return a security + * signature along with query answer for + * dynamic DNS entries. + * -- skip/ignore this answer + * + * Include arpa/nameser.h for defines. + * + * General cleanup + * */ #include @@ -21,11 +46,13 @@ #include #include #include +#include -#define DNS_SERVICE 53 #define MAX_RECURSE 5 #define REPLY_TIMEOUT 10 #define MAX_RETRIES 15 +#define MAX_SERVERS 3 +#define MAX_SEARCH 4 #undef DEBUG #ifdef DEBUG @@ -37,7 +64,7 @@ #ifdef L_encodeh int encode_header(struct resolv_header *h, unsigned char *dest, int maxlen) { - if (maxlen < 12) + if (maxlen < HFIXEDSZ) return -1; dest[0] = (h->id & 0xff00) >> 8; @@ -55,7 +82,7 @@ int encode_header(struct resolv_header *h, unsigned char *dest, int maxlen) dest[10] = (h->arcount & 0xff00) >> 8; dest[11] = (h->arcount & 0x00ff) >> 0; - return 12; + return HFIXEDSZ; } #endif @@ -75,7 +102,7 @@ int decode_header(unsigned char *data, struct resolv_header *h) h->nscount = (data[8] << 8) | data[9]; h->arcount = (data[10] << 8) | data[11]; - return 12; + return HFIXEDSZ; } #endif @@ -129,7 +156,10 @@ int decode_dotted(const unsigned char *data, int offset, if (!data) return -1; - while ((measure && total++), (l = data[offset++])) { + while ((l = data[offset++])) { + + if (measure && total++) + break; if ((l & 0xc0) == (0xc0)) { if (measure) @@ -217,7 +247,7 @@ int decode_question(unsigned char *message, int offset, char temp[256]; int i; - i = decode_dotted(message, offset, temp, 256); + i = decode_dotted(message, offset, temp, sizeof(temp)); if (i < 0) return i; @@ -256,7 +286,7 @@ int encode_answer(struct resolv_answer *a, unsigned char *dest, int maxlen) dest += i; maxlen -= i; - if (maxlen < (10 + a->rdlength)) + if (maxlen < (RRFIXEDSZ+a->rdlength)) return -1; *dest++ = (a->atype & 0xff00) >> 8; @@ -271,7 +301,7 @@ int encode_answer(struct resolv_answer *a, unsigned char *dest, int maxlen) *dest++ = (a->rdlength & 0x00ff) >> 0; memcpy(dest, a->rdata, a->rdlength); - return i + 10 + a->rdlength; + return i + RRFIXEDSZ + a->rdlength; } #endif @@ -282,7 +312,7 @@ int decode_answer(unsigned char *message, int offset, char temp[256]; int i; - i = decode_dotted(message, offset, temp, 256); + i = decode_dotted(message, offset, temp, sizeof(temp)); if (i < 0) return i; @@ -299,11 +329,11 @@ int decode_answer(unsigned char *message, int offset, a->rdlength = (message[0] << 8) | message[1]; message += 2; a->rdata = message; - a->rdoffset = offset + i + 10; + a->rdoffset = offset + i + RRFIXEDSZ; DPRINTF("i=%d,rdlength=%d\n", i, a->rdlength); - return i + 10 + a->rdlength; + return i + RRFIXEDSZ + a->rdlength; } #endif @@ -385,7 +415,7 @@ int form_query(int id, const char *name, int type, unsigned char *packet, q.dotted = (char *) name; q.qtype = type; - q.qclass = 1 /*CLASS_IN */ ; + q.qclass = C_IN; /* CLASS_IN */ i = encode_header(&h, packet, maxlen); if (i < 0) @@ -411,9 +441,7 @@ int dns_lookup(const char *name, int type, int nscount, const char **nsip, unsigned char **outpacket, struct resolv_answer *a) { static int id = 1; - int i, j, len; - int fd; - int pos; + int i, j, len, fd, pos; static int ns = 0; struct sockaddr_in sa; int oldalarm; @@ -421,17 +449,17 @@ int dns_lookup(const char *name, int type, int nscount, const char **nsip, struct resolv_header h; struct resolv_question q; int retries = 0; - unsigned char *packet = malloc(512); + unsigned char * packet = malloc(PACKETSZ); + unsigned char * lookup = malloc(MAXDNAME); + int variant = 0; + extern int searchdomains; + extern const char * searchdomain[MAX_SEARCH]; - if (!packet) - goto fail1; + if (!packet || !lookup || !nscount) + goto fail; DPRINTF("Looking up type %d answer for '%s'\n", type, name); - - if (!nscount) - goto fail1; - ns %= nscount; fd = -1; @@ -444,10 +472,9 @@ int dns_lookup(const char *name, int type, int nscount, const char **nsip, fd = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP); if (fd == -1) - goto fail2; - + goto fail; - memset(packet, 0, 512); + memset(packet, 0, PACKETSZ); memset(&h, 0, sizeof(h)); h.id = ++id; @@ -456,25 +483,32 @@ int dns_lookup(const char *name, int type, int nscount, const char **nsip, DPRINTF("encoding header\n"); - i = encode_header(&h, packet, 512); + i = encode_header(&h, packet, PACKETSZ); if (i < 0) - goto fail3; + goto fail; - q.dotted = (char *) name; + strncpy(lookup,name,MAXDNAME); + if (variant < searchdomains) + { + strncat(lookup,".", MAXDNAME); + strncat(lookup,searchdomain[variant], MAXDNAME); + } + DPRINTF("lookup name: %s\n", lookup); + q.dotted = (char *)lookup; q.qtype = type; - q.qclass = 1 /*CLASS_IN */ ; + q.qclass = C_IN; /* CLASS_IN */ - j = encode_question(&q, packet + i, 512 - i); + j = encode_question(&q, packet+i, PACKETSZ-i); if (j < 0) - goto fail3; + goto fail; len = i + j; DPRINTF("On try %d, sending query to port %d of machine %s\n", - retries, DNS_SERVICE, nsip[ns]); + retries, NAMESERVER_PORT, nsip[ns]); sa.sin_family = AF_INET; - sa.sin_port = htons(DNS_SERVICE); + sa.sin_port = htons(NAMESERVER_PORT); sa.sin_addr.s_addr = inet_addr(nsip[ns]); if (connect(fd, (struct sockaddr *) &sa, sizeof(sa)) == -1) { @@ -483,7 +517,7 @@ int dns_lookup(const char *name, int type, int nscount, const char **nsip, goto tryall; } else /* retry */ - break; + continue; } DPRINTF("Transmitting packet of length %d, id=%d, qr=%d\n", @@ -495,7 +529,7 @@ int dns_lookup(const char *name, int type, int nscount, const char **nsip, oldalarm = alarm(REPLY_TIMEOUT); oldhandler = signal(SIGALRM, dns_catch_signal); - i = recv(fd, packet, 512, 0); + i = recv(fd, packet, PACKETSZ, 0); alarm(0); signal(SIGALRM, oldhandler); @@ -508,7 +542,7 @@ int dns_lookup(const char *name, int type, int nscount, const char **nsip, to next nameserver on queue */ goto again; - if (i < 12) + if (i < HFIXEDSZ) /* too short ! */ goto again; @@ -528,10 +562,10 @@ int dns_lookup(const char *name, int type, int nscount, const char **nsip, if ((h.rcode) || (h.ancount < 1)) { /* negative result, not present */ - goto tryall; + goto again; } - pos = 12; + pos = HFIXEDSZ; for (j = 0; j < h.qdcount; j++) { DPRINTF("Skipping question %d at %d\n", j, pos); @@ -543,11 +577,21 @@ int dns_lookup(const char *name, int type, int nscount, const char **nsip, } DPRINTF("Decoding answer at pos %d\n", pos); - i = decode_answer(packet, pos, a); + for (j=0;jatype != T_SIG) + break; + + DPRINTF("skipping T_SIG %d\n", i); + free(a->dotted); + pos += i; } DPRINTF("Answer name = |%s|\n", a->dotted); @@ -564,28 +608,37 @@ int dns_lookup(const char *name, int type, int nscount, const char **nsip, tryall: /* if there are other nameservers, give them a go, otherwise return with error */ - if (retries >= nscount) - break; + variant = 0; + if (retries >= nscount*(searchdomains+1)) + goto fail; + again: - ns = (ns + 1) % nscount; - continue; + /* if there are searchdomains, try them or fallback as passed */ + if (variant < searchdomains) { + /* next search */ + variant++; + } else { + /* next server, first search */ + ns = (ns + 1) % nscount; + variant = 0; + } } - - - fail3: - close(fd); - fail2: - free(packet); - fail1: +fail: + if (fd != -1) + close(fd); + if (lookup) + free(lookup); + if (packet) + free(packet); return -1; } #endif #ifdef L_resolveaddress -int resolve_address(const char *address, - int nscount, const char **nsip, struct in_addr *in) +int resolve_address(const char *address, int nscount, + const char **nsip, struct in_addr *in) { unsigned char *packet; struct resolv_answer a; @@ -596,19 +649,19 @@ int resolve_address(const char *address, if (!address || !in) return -1; - strcpy(temp, address); + strncpy(temp, address, sizeof(temp)); for (;;) { - i = dns_lookup(temp, 1, nscount, nsip, &packet, &a); + i = dns_lookup(temp, T_A, nscount, nsip, &packet, &a); if (i < 0) return -1; free(a.dotted); - if (a.atype == 5) { /* CNAME */ - i = decode_dotted(packet, a.rdoffset, temp, 256); + if (a.atype == T_CNAME) { /* CNAME */ + i = decode_dotted(packet, a.rdoffset, temp, sizeof(temp)); free(packet); if (i < 0) @@ -616,7 +669,7 @@ int resolve_address(const char *address, if (++nest > MAX_RECURSE) return -1; continue; - } else if (a.atype == 1) { /* ADDRESS */ + } else if (a.atype == T_A) { /* ADDRESS */ free(packet); break; } else { @@ -626,7 +679,7 @@ int resolve_address(const char *address, } if (in) - memcpy(in, a.rdata, 4); + memcpy(in, a.rdata, INADDRSZ); /* IPv4 T_A */ return 0; } @@ -647,33 +700,33 @@ int resolve_mailbox(const char *address, return -1; /* look up mail exchange */ - i = dns_lookup(address, 15, nscount, nsip, &packet, &a); + i = dns_lookup(address, T_MX, nscount, nsip, &packet, &a); - strcpy(temp, address); + strncpy(temp, address, sizeof(temp)); if (i >= 0) { - i = decode_dotted(packet, a.rdoffset + 2, temp, 256); + i = decode_dotted(packet, a.rdoffset+2, temp, sizeof(temp)); free(packet); } for (;;) { - i = dns_lookup(temp, 1, nscount, nsip, &packet, &a); + i = dns_lookup(temp, T_A, nscount, nsip, &packet, &a); if (i < 0) return -1; free(a.dotted); - if (a.atype == 5) { /* CNAME */ - i = decode_dotted(packet, a.rdoffset, temp, 256); + if (a.atype == T_CNAME) { /* CNAME */ + i = decode_dotted(packet, a.rdoffset, temp, sizeof(temp)); free(packet); if (i < 0) return i; if (++nest > MAX_RECURSE) return -1; continue; - } else if (a.atype == 1) { /* ADDRESS */ + } else if (a.atype == T_A) { /* ADDRESS */ free(packet); break; } else { @@ -683,19 +736,23 @@ int resolve_mailbox(const char *address, } if (in) - memcpy(in, a.rdata, 4); + memcpy(in, a.rdata, INADDRSZ); /* IPv4 */ return 0; } #endif extern int nameservers; -extern const char *nameserver[3]; +extern const char * nameserver[MAX_SERVERS]; +extern int searchdomains; +extern const char * searchdomain[MAX_SEARCH]; #ifdef L_opennameservers int nameservers; -const char * nameserver[3]; +const char * nameserver[MAX_SERVERS]; +int searchdomains; +const char * searchdomain[MAX_SEARCH]; int open_nameservers() { @@ -703,14 +760,27 @@ int open_nameservers() char **arg; int i; + if (nameservers > 0) + return 0; + if ((fp = fopen("/etc/resolv.conf", "r"))) { - if ((arg = cfgfind(fp, "nameserver"))) { - for (i = 1; arg[i]; i++) { + if (0 != (arg = cfgfind(fp, "nameserver"))) { + for (i=1; arg[i] && nameservers <= MAX_SERVERS; i++) { nameserver[nameservers++] = strdup(arg[i]); + DPRINTF("adding nameserver %s\n",arg[i]); + } + } + if (0 != (arg = cfgfind(fp, "search"))) { + for (i=1; arg[i] && searchdomains <= MAX_SEARCH; i++) { + searchdomain[searchdomains++] = strdup(arg[i]); + DPRINTF("adding search %s\n",arg[i]); } } fclose(fp); + } else { + DPRINTF("failed to open resolv.conf\n"); } + DPRINTF("nameservers = %d\n", nameservers); return 0; } #endif @@ -720,7 +790,7 @@ void close_nameservers(void) { while (nameservers > 0) - free(nameserver[--nameservers]); + free((void*)nameserver[--nameservers]); } #endif @@ -787,12 +857,12 @@ struct hostent *gethostbyname(const char *name) if (i < 0) return 0; - strcpy(namebuf, a.dotted); + strncpy(namebuf, a.dotted, sizeof(namebuf)); free(a.dotted); - if (a.atype == 5) { /* CNAME */ - i = decode_dotted(packet, a.rdoffset, namebuf, 256); + if (a.atype == T_CNAME) { /* CNAME */ + i = decode_dotted(packet, a.rdoffset, namebuf, sizeof(namebuf)); free(packet); if (i < 0) @@ -800,7 +870,7 @@ struct hostent *gethostbyname(const char *name) if (++nest > MAX_RECURSE) return 0; continue; - } else if (a.atype == 1) { /* ADDRESS */ + } else if (a.atype == T_A) { /* ADDRESS */ memcpy(&in, a.rdata, sizeof(in)); h.h_name = namebuf; h.h_addrtype = AF_INET; @@ -850,16 +920,16 @@ struct hostent *gethostbyaddr(const char *addr, int len, int type) for (;;) { - i = dns_lookup(namebuf, 12, nameservers, nameserver, &packet, &a); + i = dns_lookup(namebuf, T_PTR, nameservers, nameserver, &packet, &a); if (i < 0) return 0; - strcpy(namebuf, a.dotted); + strncpy(namebuf, a.dotted, sizeof(namebuf)); free(a.dotted); - if (a.atype == 5) { /* CNAME */ - i = decode_dotted(packet, a.rdoffset, namebuf, 256); + if (a.atype == T_CNAME) { /* CNAME */ + i = decode_dotted(packet, a.rdoffset, namebuf, sizeof(namebuf)); free(packet); if (i < 0) @@ -867,8 +937,8 @@ struct hostent *gethostbyaddr(const char *addr, int len, int type) if (++nest > MAX_RECURSE) return 0; continue; - } else if (a.atype == 12) { /* ADDRESS */ - i = decode_dotted(packet, a.rdoffset, namebuf, 256); + } else if (a.atype == T_PTR) { /* ADDRESS */ + i = decode_dotted(packet, a.rdoffset, namebuf, sizeof(namebuf)); free(packet); h.h_name = namebuf; -- cgit v1.2.3