diff options
Diffstat (limited to 'dirmngr/dns-stuff.c')
| -rw-r--r-- | dirmngr/dns-stuff.c | 256 |
1 files changed, 253 insertions, 3 deletions
diff --git a/dirmngr/dns-stuff.c b/dirmngr/dns-stuff.c index 3fa6054d3..c500c34e7 100644 --- a/dirmngr/dns-stuff.c +++ b/dirmngr/dns-stuff.c @@ -1,5 +1,5 @@ /* dns-stuff.c - DNS related code including CERT RR (rfc-4398) - * Copyright (C) 2005, 2006, 2009 Free Software Foundation, Inc. + * Copyright (C) 2003, 2005, 2006, 2009 Free Software Foundation, Inc. * Copyright (C) 2005, 2006, 2009, 2015 Werner Koch * * This file is part of GnuPG. @@ -54,8 +54,11 @@ #include "host2net.h" #include "dns-stuff.h" -/* Not every installation has gotten around to supporting CERTs - yet... */ +/* Not every installation has gotten around to supporting SRVs or + CERTs yet... */ +#ifndef T_SRV +#define T_SRV 33 +#endif #ifndef T_CERT # define T_CERT 37 #endif @@ -588,3 +591,250 @@ get_dns_cert (const char *name, int want_certtype, return gpg_err_make (default_errsource, GPG_ERR_NOT_SUPPORTED); #endif } + +#ifdef USE_DNS_SRV +static int +priosort(const void *a,const void *b) +{ + const struct srventry *sa=a,*sb=b; + if(sa->priority>sb->priority) + return 1; + else if(sa->priority<sb->priority) + return -1; + else + return 0; +} + + +int +getsrv (const char *name,struct srventry **list) +{ + int srvcount=0; + u16 count; + int i, rc; + + *list = NULL; + +#ifdef USE_ADNS + { + adns_state state; + adns_answer *answer = NULL; + + rc = adns_init (&state, adns_if_noerrprint, NULL); + if (rc) + { + log_error ("error initializing adns: %s\n", strerror (errno)); + return -1; + } + + rc = adns_synchronous (state, name, adns_r_srv, adns_qf_quoteok_query, + &answer); + if (rc) + { + log_error ("DNS query failed: %s\n", strerror (errno)); + adns_finish (state); + return -1; + } + if (answer->status != adns_s_ok + || answer->type != adns_r_srv || !answer->nrrs) + { + log_error ("DNS query returned an error or no records: %s (%s)\n", + adns_strerror (answer->status), + adns_errabbrev (answer->status)); + adns_free (answer); + adns_finish (state); + return 0; + } + + for (count = 0; count < answer->nrrs; count++) + { + struct srventry *srv = NULL; + struct srventry *newlist; + + if (strlen (answer->rrs.srvha[count].ha.host) >= MAXDNAME) + { + log_info ("hostname in SRV record too long - skipped\n"); + continue; + } + + newlist = xtryrealloc (*list, (srvcount+1)*sizeof(struct srventry)); + if (!newlist) + goto fail; + *list = newlist; + memset (&(*list)[srvcount], 0, sizeof(struct srventry)); + srv = &(*list)[srvcount]; + srvcount++; + + srv->priority = answer->rrs.srvha[count].priority; + srv->weight = answer->rrs.srvha[count].weight; + srv->port = answer->rrs.srvha[count].port; + strcpy (srv->target, answer->rrs.srvha[count].ha.host); + } + + adns_free (answer); + adns_finish (state); + } +#else /*!USE_ADNS*/ + { + unsigned char answer[2048]; + HEADER *header = (HEADER *)answer; + unsigned char *pt, *emsg; + int r; + u16 dlen; + + r = res_query (name, C_IN, T_SRV, answer, sizeof answer); + if (r < sizeof (HEADER) || r > sizeof answer) + return -1; + if (header->rcode != NOERROR || !(count=ntohs (header->ancount))) + return 0; /* Error or no record found. */ + + emsg = &answer[r]; + pt = &answer[sizeof(HEADER)]; + + /* Skip over the query */ + rc = dn_skipname (pt, emsg); + if (rc == -1) + goto fail; + + pt += rc + QFIXEDSZ; + + while (count-- > 0 && pt < emsg) + { + struct srventry *srv=NULL; + u16 type,class; + struct srventry *newlist; + + newlist = xtryrealloc (*list, (srvcount+1)*sizeof(struct srventry)); + if (!newlist) + goto fail; + *list = newlist; + memset(&(*list)[srvcount],0,sizeof(struct srventry)); + srv=&(*list)[srvcount]; + srvcount++; + + rc = dn_skipname(pt,emsg); /* the name we just queried for */ + if (rc == -1) + goto fail; + pt+=rc; + + /* Truncated message? */ + if((emsg-pt)<16) + goto fail; + + type = buf16_to_u16 (pt); + pt += 2; + /* We asked for SRV and got something else !? */ + if(type!=T_SRV) + goto fail; + + class = buf16_to_u16 (pt); + pt += 2; + /* We asked for IN and got something else !? */ + if(class!=C_IN) + goto fail; + + pt += 4; /* ttl */ + dlen = buf16_to_u16 (pt); + pt += 2; + + srv->priority = buf16_to_ushort (pt); + pt += 2; + srv->weight = buf16_to_ushort (pt); + pt += 2; + srv->port = buf16_to_ushort (pt); + pt += 2; + + /* Get the name. 2782 doesn't allow name compression, but + dn_expand still works to pull the name out of the + packet. */ + rc = dn_expand(answer,emsg,pt,srv->target,MAXDNAME); + if (rc == 1 && srv->target[0] == 0) /* "." */ + { + xfree(*list); + *list = NULL; + return 0; + } + if (rc == -1) + goto fail; + pt += rc; + /* Corrupt packet? */ + if (dlen != rc+6) + goto fail; + } + } +#endif /*!USE_ADNS*/ + + /* Now we have an array of all the srv records. */ + + /* Order by priority */ + qsort(*list,srvcount,sizeof(struct srventry),priosort); + + /* For each priority, move the zero-weighted items first. */ + for (i=0; i < srvcount; i++) + { + int j; + + for (j=i;j < srvcount && (*list)[i].priority == (*list)[j].priority; j++) + { + if((*list)[j].weight==0) + { + /* Swap j with i */ + if(j!=i) + { + struct srventry temp; + + memcpy (&temp,&(*list)[j],sizeof(struct srventry)); + memcpy (&(*list)[j],&(*list)[i],sizeof(struct srventry)); + memcpy (&(*list)[i],&temp,sizeof(struct srventry)); + } + + break; + } + } + } + + /* Run the RFC-2782 weighting algorithm. We don't need very high + quality randomness for this, so regular libc srand/rand is + sufficient. Fixme: It is a bit questionaly to reinitalize srand + - better use a gnupg fucntion for this. */ + srand(time(NULL)*getpid()); + + for (i=0; i < srvcount; i++) + { + int j; + float prio_count=0,chose; + + for (j=i; j < srvcount && (*list)[i].priority == (*list)[j].priority; j++) + { + prio_count+=(*list)[j].weight; + (*list)[j].run_count=prio_count; + } + + chose=prio_count*rand()/RAND_MAX; + + for (j=i;j<srvcount && (*list)[i].priority==(*list)[j].priority;j++) + { + if (chose<=(*list)[j].run_count) + { + /* Swap j with i */ + if(j!=i) + { + struct srventry temp; + + memcpy(&temp,&(*list)[j],sizeof(struct srventry)); + memcpy(&(*list)[j],&(*list)[i],sizeof(struct srventry)); + memcpy(&(*list)[i],&temp,sizeof(struct srventry)); + } + break; + } + } + } + + return srvcount; + + fail: + xfree(*list); + *list=NULL; + return -1; +} +#endif /*USE_DNS_SRV*/ |