diff options
Diffstat (limited to 'dns.c')
-rw-r--r-- | dns.c | 398 |
1 files changed, 398 insertions, 0 deletions
@@ -0,0 +1,398 @@ +#include <stdio.h> +#include <netdb.h> +#include <sys/types.h> +#include <netinet/in.h> +#include <arpa/nameser.h> +#include <resolv.h> +#include <errno.h> +extern int res_query(); +extern int res_search(); +#include "ip.h" +#include "ipalloc.h" +#include "fmt.h" +#include "alloc.h" +#include "str.h" +#include "stralloc.h" +#include "dns.h" +#include "case.h" + +static unsigned short getshort(c) unsigned char *c; +{ unsigned short u; u = c[0]; return (u << 8) + c[1]; } + +static union { HEADER hdr; unsigned char buf[PACKETSZ]; } response; +static int responselen; +static unsigned char *responseend; +static unsigned char *responsepos; + +static int numanswers; +static char name[MAXDNAME]; +static struct ip_address ip; +unsigned short pref; + +static stralloc glue = {0}; + +static int (*lookup)() = res_query; + +static int resolve(domain,type) +stralloc *domain; +int type; +{ + int n; + int i; + + errno = 0; + if (!stralloc_copy(&glue,domain)) return DNS_MEM; + if (!stralloc_0(&glue)) return DNS_MEM; + responselen = lookup(glue.s,C_IN,type,response.buf,sizeof(response)); + if (responselen <= 0) + { + if (errno == ECONNREFUSED) return DNS_SOFT; + if (h_errno == TRY_AGAIN) return DNS_SOFT; + return DNS_HARD; + } + if (responselen >= sizeof(response)) + responselen = sizeof(response); + responseend = response.buf + responselen; + responsepos = response.buf + sizeof(HEADER); + n = ntohs(response.hdr.qdcount); + while (n-- > 0) + { + i = dn_expand(response.buf,responseend,responsepos,name,MAXDNAME); + if (i < 0) return DNS_SOFT; + responsepos += i; + i = responseend - responsepos; + if (i < QFIXEDSZ) return DNS_SOFT; + responsepos += QFIXEDSZ; + } + numanswers = ntohs(response.hdr.ancount); + return 0; +} + +static int findname(wanttype) +int wanttype; +{ + unsigned short rrtype; + unsigned short rrdlen; + int i; + + if (numanswers <= 0) return 2; + --numanswers; + if (responsepos == responseend) return DNS_SOFT; + + i = dn_expand(response.buf,responseend,responsepos,name,MAXDNAME); + if (i < 0) return DNS_SOFT; + responsepos += i; + + i = responseend - responsepos; + if (i < 4 + 3 * 2) return DNS_SOFT; + + rrtype = getshort(responsepos); + rrdlen = getshort(responsepos + 8); + responsepos += 10; + + if (rrtype == wanttype) + { + if (dn_expand(response.buf,responseend,responsepos,name,MAXDNAME) < 0) + return DNS_SOFT; + responsepos += rrdlen; + return 1; + } + + responsepos += rrdlen; + return 0; +} + +static int findip(wanttype) +int wanttype; +{ + unsigned short rrtype; + unsigned short rrdlen; + int i; + + if (numanswers <= 0) return 2; + --numanswers; + if (responsepos == responseend) return DNS_SOFT; + + i = dn_expand(response.buf,responseend,responsepos,name,MAXDNAME); + if (i < 0) return DNS_SOFT; + responsepos += i; + + i = responseend - responsepos; + if (i < 4 + 3 * 2) return DNS_SOFT; + + rrtype = getshort(responsepos); + rrdlen = getshort(responsepos + 8); + responsepos += 10; + + if (rrtype == wanttype) + { + if (rrdlen < 4) + return DNS_SOFT; + ip.d[0] = responsepos[0]; + ip.d[1] = responsepos[1]; + ip.d[2] = responsepos[2]; + ip.d[3] = responsepos[3]; + responsepos += rrdlen; + return 1; + } + + responsepos += rrdlen; + return 0; +} + +static int findmx(wanttype) +int wanttype; +{ + unsigned short rrtype; + unsigned short rrdlen; + int i; + + if (numanswers <= 0) return 2; + --numanswers; + if (responsepos == responseend) return DNS_SOFT; + + i = dn_expand(response.buf,responseend,responsepos,name,MAXDNAME); + if (i < 0) return DNS_SOFT; + responsepos += i; + + i = responseend - responsepos; + if (i < 4 + 3 * 2) return DNS_SOFT; + + rrtype = getshort(responsepos); + rrdlen = getshort(responsepos + 8); + responsepos += 10; + + if (rrtype == wanttype) + { + if (rrdlen < 3) + return DNS_SOFT; + pref = (responsepos[0] << 8) + responsepos[1]; + if (dn_expand(response.buf,responseend,responsepos + 2,name,MAXDNAME) < 0) + return DNS_SOFT; + responsepos += rrdlen; + return 1; + } + + responsepos += rrdlen; + return 0; +} + +void dns_init(flagsearch) +int flagsearch; +{ + res_init(); + if (flagsearch) lookup = res_search; +} + +int dns_cname(sa) +stralloc *sa; +{ + int r; + int loop; + for (loop = 0;loop < 10;++loop) + { + if (!sa->len) return loop; + if (sa->s[sa->len - 1] == ']') return loop; + if (sa->s[sa->len - 1] == '.') { --sa->len; continue; } + switch(resolve(sa,T_ANY)) + { + case DNS_MEM: return DNS_MEM; + case DNS_SOFT: return DNS_SOFT; + case DNS_HARD: return loop; + default: + while ((r = findname(T_CNAME)) != 2) + { + if (r == DNS_SOFT) return DNS_SOFT; + if (r == 1) + { + if (!stralloc_copys(sa,name)) return DNS_MEM; + break; + } + } + if (r == 2) return loop; + } + } + return DNS_HARD; /* alias loop */ +} + +#define FMT_IAA 40 + +static int iaafmt(s,ip) +char *s; +struct ip_address *ip; +{ + unsigned int i; + unsigned int len; + len = 0; + i = fmt_ulong(s,(unsigned long) ip->d[3]); len += i; if (s) s += i; + i = fmt_str(s,"."); len += i; if (s) s += i; + i = fmt_ulong(s,(unsigned long) ip->d[2]); len += i; if (s) s += i; + i = fmt_str(s,"."); len += i; if (s) s += i; + i = fmt_ulong(s,(unsigned long) ip->d[1]); len += i; if (s) s += i; + i = fmt_str(s,"."); len += i; if (s) s += i; + i = fmt_ulong(s,(unsigned long) ip->d[0]); len += i; if (s) s += i; + i = fmt_str(s,".in-addr.arpa."); len += i; if (s) s += i; + return len; +} + +int dns_ptr(sa,ip) +stralloc *sa; +struct ip_address *ip; +{ + int r; + + if (!stralloc_ready(sa,iaafmt((char *) 0,ip))) return DNS_MEM; + sa->len = iaafmt(sa->s,ip); + switch(resolve(sa,T_PTR)) + { + case DNS_MEM: return DNS_MEM; + case DNS_SOFT: return DNS_SOFT; + case DNS_HARD: return DNS_HARD; + } + while ((r = findname(T_PTR)) != 2) + { + if (r == DNS_SOFT) return DNS_SOFT; + if (r == 1) + { + if (!stralloc_copys(sa,name)) return DNS_MEM; + return 0; + } + } + return DNS_HARD; +} + +static int dns_ipplus(ia,sa,pref) +ipalloc *ia; +stralloc *sa; +int pref; +{ + int r; + struct ip_mx ix; + + if (!stralloc_copy(&glue,sa)) return DNS_MEM; + if (!stralloc_0(&glue)) return DNS_MEM; + if (glue.s[0]) { + ix.pref = 0; + if (!glue.s[ip_scan(glue.s,&ix.ip)] || !glue.s[ip_scanbracket(glue.s,&ix.ip)]) + { + if (!ipalloc_append(ia,&ix)) return DNS_MEM; + return 0; + } + } + + switch(resolve(sa,T_A)) + { + case DNS_MEM: return DNS_MEM; + case DNS_SOFT: return DNS_SOFT; + case DNS_HARD: return DNS_HARD; + } + while ((r = findip(T_A)) != 2) + { + ix.ip = ip; + ix.pref = pref; + if (r == DNS_SOFT) return DNS_SOFT; + if (r == 1) + if (!ipalloc_append(ia,&ix)) return DNS_MEM; + } + return 0; +} + +int dns_ip(ia,sa) +ipalloc *ia; +stralloc *sa; +{ + if (!ipalloc_readyplus(ia,0)) return DNS_MEM; + ia->len = 0; + return dns_ipplus(ia,sa,0); +} + +int dns_mxip(ia,sa,random) +ipalloc *ia; +stralloc *sa; +unsigned long random; +{ + int r; + struct mx { stralloc sa; unsigned short p; } *mx; + struct ip_mx ix; + int nummx; + int i; + int j; + int flagsoft; + + if (!ipalloc_readyplus(ia,0)) return DNS_MEM; + ia->len = 0; + + if (!stralloc_copy(&glue,sa)) return DNS_MEM; + if (!stralloc_0(&glue)) return DNS_MEM; + if (glue.s[0]) { + ix.pref = 0; + if (!glue.s[ip_scan(glue.s,&ix.ip)] || !glue.s[ip_scanbracket(glue.s,&ix.ip)]) + { + if (!ipalloc_append(ia,&ix)) return DNS_MEM; + return 0; + } + } + + switch(resolve(sa,T_MX)) + { + case DNS_MEM: return DNS_MEM; + case DNS_SOFT: return DNS_SOFT; + case DNS_HARD: return dns_ip(ia,sa); + } + + mx = (struct mx *) alloc(numanswers * sizeof(struct mx)); + if (!mx) return DNS_MEM; + nummx = 0; + + while ((r = findmx(T_MX)) != 2) + { + if (r == DNS_SOFT) { alloc_free(mx); return DNS_SOFT; } + if (r == 1) + { + mx[nummx].p = pref; + mx[nummx].sa.s = 0; + if (!stralloc_copys(&mx[nummx].sa,name)) + { + while (nummx > 0) alloc_free(mx[--nummx].sa.s); + alloc_free(mx); return DNS_MEM; + } + ++nummx; + } + } + + if (!nummx) return dns_ip(ia,sa); /* e.g., CNAME -> A */ + + flagsoft = 0; + while (nummx > 0) + { + unsigned long numsame; + + i = 0; + numsame = 1; + for (j = 1;j < nummx;++j) + if (mx[j].p < mx[i].p) + { + i = j; + numsame = 1; + } + else if (mx[j].p == mx[i].p) + { + ++numsame; + random = random * 69069 + 1; + if ((random / 2) < (2147483647 / numsame)) + i = j; + } + + switch(dns_ipplus(ia,&mx[i].sa,mx[i].p)) + { + case DNS_MEM: case DNS_SOFT: + flagsoft = 1; break; + } + + alloc_free(mx[i].sa.s); + mx[i] = mx[--nummx]; + } + + alloc_free(mx); + return flagsoft; +} |