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gnupg/dirmngr/dns-stuff.c
Werner Koch 304566d332
dirmngr: Add option --standard-resolver. 
* dirmngr/dirmngr.c (oStandardResolver): New constant.
(opts): New option --standard-resolver.
(parse_rereadable_options): Set option.
* dirmngr/dns-stuff.c: Refactor all code to support the new option.
(standard_resolver): New var.
(enable_standard_resolver, standard_resolver_p): New func.
* dirmngr/http.c (connect_server): Remove USE_DNS_SRV build
conditional.
* dirmngr/ks-engine-hkp.c (map_host): Ditto.
* dirmngr/server.c (cmd_getinfo) <dnsinfo>: Take care of new option
* configure.ac (HAVE_ADNS_IF_TORMODE): Remove var ADNSLIB.  ac_define
USE_ADNS in the adns checking code.  Remove options --disable-dns-srv
and --disable-dns-cert.  Always look for the system resolver.  Print
warning if no system resolver was found.
(USE_DNS_CERT, USE_DNS_SRV): Remove ac_defines.
(HAVE_SYSTEM_RESOLVER): New ac_define.
(USE_DNS_SRV): Remove am_conditional; not used anyway.
--

This option allows for runtime switching to the system's standard
resolver.  This is mainly useful to work around possible bugs in the
optional resolver libraries (as of now ADNS).  Note that on Windows
there is no code to use systems's resolver and thus for full
functionality dirmngr must be build with a separate resolver.

This patch also does way with configure options to disable the use of
CERT and SRV records.

Signed-off-by: Werner Koch <wk@gnupg.org>
2016-12-01 16:40:32 +01:00

1492 lines
38 KiB
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/* dns-stuff.c - DNS related code including CERT RR (rfc-4398)
* Copyright (C) 2003, 2005, 2006, 2009 Free Software Foundation, Inc.
* Copyright (C) 2005, 2006, 2009, 2015. 2016 Werner Koch
*
* This file is part of GnuPG.
*
* This file is free software; you can redistribute it and/or modify
* it under the terms of either
*
* - the GNU Lesser General Public License as published by the Free
* Software Foundation; either version 3 of the License, or (at
* your option) any later version.
*
* or
*
* - the GNU General Public License as published by the Free
* Software Foundation; either version 2 of the License, or (at
* your option) any later version.
*
* or both in parallel, as here.
*
* This file is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, see <https://www.gnu.org/licenses/>.
*/
#include <config.h>
#include <sys/types.h>
#ifdef HAVE_W32_SYSTEM
# ifdef HAVE_WINSOCK2_H
# include <winsock2.h>
# endif
# include <windows.h>
#else
# if HAVE_SYSTEM_RESOLVER
# include <netinet/in.h>
# include <arpa/nameser.h>
# include <resolv.h>
# endif
# include <netdb.h>
#endif
#include <string.h>
#include <unistd.h>
#ifdef USE_ADNS
# include <adns.h>
#endif
#if !defined(HAVE_GETADDRINFO) && !defined(USE_ADNS)
# error Either getaddrinfo or the ADNS library is required.
#endif
#ifdef WITHOUT_NPTH /* Give the Makefile a chance to build without Pth. */
# undef USE_NPTH
#endif
#ifdef USE_NPTH
# include <npth.h>
#endif
#include "util.h"
#include "host2net.h"
#include "dns-stuff.h"
#ifdef USE_NPTH
# define my_unprotect() npth_unprotect ()
# define my_protect() npth_protect ()
#else
# define my_unprotect() do { } while(0)
# define my_protect() do { } while(0)
#endif
/* We allow the use of 0 instead of AF_UNSPEC - check this assumption. */
#if AF_UNSPEC != 0
# error AF_UNSPEC does not have the value 0
#endif
/* Windows does not support the AI_ADDRCONFIG flag - use zero instead. */
#ifndef AI_ADDRCONFIG
# define AI_ADDRCONFIG 0
#endif
/* Provide a replacement function for older ADNS versions. */
#ifndef HAVE_ADNS_FREE
# define adns_free(a) free ((a))
#endif
/* 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
/* ADNS has no support for CERT yet. */
#define my_adns_r_cert 37
/* The default nameserver used with ADNS in Tor mode. */
#define DEFAULT_NAMESERVER "8.8.8.8"
/* If set force the use of the standard resolver. */
static int standard_resolver;
/* If set Tor mode shall be used. */
static int tor_mode;
/* A string with the nameserver IP address used with Tor.
(40 should be sufficient for v6 but we add some extra for a scope.) */
static char tor_nameserver[40+20];
/* A string to hold the credentials presented to Tor. */
#ifdef USE_ADNS
static char tor_credentials[50];
#endif
/* Calling this function with YES set to True forces the use of the
* standard resolver even if dirmngr has been built with support for
* an alternative resolver. */
void
enable_standard_resolver (int yes)
{
standard_resolver = yes;
}
/* Return true if the standard resolver is used. */
int
standard_resolver_p (void)
{
return standard_resolver;
}
/* Sets the module in Tor mode. Returns 0 is this is possible or an
error code. */
gpg_error_t
enable_dns_tormode (int new_circuit)
{
(void) new_circuit;
#ifdef USE_ADNS
# if HAVE_ADNS_IF_TORMODE
if (!*tor_credentials || new_circuit)
{
static unsigned int counter;
gpgrt_snprintf (tor_credentials, sizeof tor_credentials,
"dirmngr-%lu:p%u",
(unsigned long)getpid (), counter);
counter++;
}
tor_mode = 1;
return 0;
# endif
#endif
return gpg_error (GPG_ERR_NOT_IMPLEMENTED);
}
/* Change the default IP address of the nameserver to IPADDR. The
address needs to be a numerical IP address and will be used for the
next DNS query. Note that this is only used in Tor mode. */
void
set_dns_nameserver (const char *ipaddr)
{
strncpy (tor_nameserver, ipaddr? ipaddr : DEFAULT_NAMESERVER,
sizeof tor_nameserver -1);
tor_nameserver[sizeof tor_nameserver -1] = 0;
}
/* Free an addressinfo linked list as returned by resolve_dns_name. */
void
free_dns_addrinfo (dns_addrinfo_t ai)
{
while (ai)
{
dns_addrinfo_t next = ai->next;
xfree (ai);
ai = next;
}
}
static gpg_error_t
map_eai_to_gpg_error (int ec)
{
gpg_error_t err;
switch (ec)
{
case EAI_AGAIN: err = gpg_error (GPG_ERR_EAGAIN); break;
case EAI_BADFLAGS: err = gpg_error (GPG_ERR_INV_FLAG); break;
case EAI_FAIL: err = gpg_error (GPG_ERR_SERVER_FAILED); break;
case EAI_MEMORY: err = gpg_error (GPG_ERR_ENOMEM); break;
#ifdef EAI_NODATA
case EAI_NODATA: err = gpg_error (GPG_ERR_NO_DATA); break;
#endif
case EAI_NONAME: err = gpg_error (GPG_ERR_NO_NAME); break;
case EAI_SERVICE: err = gpg_error (GPG_ERR_NOT_SUPPORTED); break;
case EAI_FAMILY: err = gpg_error (GPG_ERR_EAFNOSUPPORT); break;
case EAI_SOCKTYPE: err = gpg_error (GPG_ERR_ESOCKTNOSUPPORT); break;
#ifndef HAVE_W32_SYSTEM
# ifdef EAI_ADDRFAMILY
case EAI_ADDRFAMILY:err = gpg_error (GPG_ERR_EADDRNOTAVAIL); break;
# endif
case EAI_SYSTEM: err = gpg_error_from_syserror (); break;
#endif
default: err = gpg_error (GPG_ERR_UNKNOWN_ERRNO); break;
}
return err;
}
#ifdef USE_ADNS
static gpg_error_t
map_adns_status_to_gpg_error (adns_status status)
{
gpg_err_code_t ec;
switch (status)
{
/* case adns_s_netunreach: ec = GPG_ERR_ENETUNREACH; break; */
default: ec = GPG_ERR_GENERAL; break;
}
return gpg_error (ec);
}
#endif /*USE_ADNS*/
#ifdef USE_ADNS
/* Init ADNS and store the new state at R_STATE. Returns 0 on
success; prints an error message and returns an error code on
failure. */
static gpg_error_t
my_adns_init (adns_state *r_state)
{
gpg_error_t err = 0;
int ret;
if (tor_mode)
{
char *cfgstr;
if (!*tor_nameserver)
set_dns_nameserver (NULL);
cfgstr = xtryasprintf ("nameserver %s\n"
"options adns_tormode adns_sockscred:%s",
tor_nameserver, tor_credentials);
if (!cfgstr)
err = gpg_error_from_syserror ();
else
{
ret = adns_init_strcfg (r_state, adns_if_debug /*adns_if_noerrprint*/, NULL, cfgstr);
if (ret)
err = gpg_error_from_errno (ret);
xfree (cfgstr);
}
}
else
{
ret = adns_init (r_state, adns_if_noerrprint, NULL);
if (ret)
err = gpg_error_from_errno (ret);
}
if (err)
{
log_error ("error initializing adns: %s\n", gpg_strerror (err));
return err;
}
return 0;
}
#endif /*USE_ADNS*/
#ifdef USE_ADNS
/* Resolve a name using the ADNS library. See resolve_dns_name for
the description. */
static gpg_error_t
resolve_name_adns (const char *name, unsigned short port,
int want_family, int want_socktype,
dns_addrinfo_t *r_dai, char **r_canonname)
{
gpg_error_t err = 0;
int ret;
dns_addrinfo_t daihead = NULL;
dns_addrinfo_t dai;
adns_state state;
adns_answer *answer = NULL;
int count;
(void)want_family;
*r_dai = NULL;
if (r_canonname)
*r_canonname = NULL;
if (want_socktype != SOCK_STREAM && want_socktype != SOCK_DGRAM)
return gpg_error (GPG_ERR_ESOCKTNOSUPPORT);
err = my_adns_init (&state);
if (err)
return err;
my_unprotect ();
ret = adns_synchronous (state, name, adns_r_addr,
adns_qf_quoteok_query, &answer);
my_protect ();
if (ret)
{
err = gpg_error (gpg_err_code_from_errno (ret));
log_error ("DNS query failed: %s\n", gpg_strerror (err));
goto leave;
}
err = gpg_error (GPG_ERR_NOT_FOUND);
if (answer->status != adns_s_ok || answer->type != adns_r_addr)
{
err = map_adns_status_to_gpg_error (answer->status);
if (gpg_err_code (err) == GPG_ERR_GENERAL)
err = gpg_error (GPG_ERR_NOT_FOUND);
log_error ("DNS query returned an error: %s (%s)\n",
adns_strerror (answer->status),
adns_errabbrev (answer->status));
goto leave;
}
if (r_canonname && answer->cname)
{
*r_canonname = xtrystrdup (answer->cname);
if (!*r_canonname)
{
err = gpg_error_from_syserror ();
goto leave;
}
}
for (count = 0; count < answer->nrrs; count++)
{
int len;
adns_rr_addr *addr;
len = answer->rrs.addr[count].len;
addr = &answer->rrs.addr[count];
if (addr->addr.sa.sa_family != AF_INET6
&& addr->addr.sa.sa_family != AF_INET)
continue;
dai = xtrymalloc (sizeof *dai + len - 1);
if (!dai)
{
err = gpg_error_from_syserror ();
goto leave;
}
dai->family = addr->addr.sa.sa_family;
dai->socktype = want_socktype == SOCK_STREAM? SOCK_STREAM : SOCK_DGRAM;
dai->protocol = want_socktype == SOCK_STREAM? IPPROTO_TCP : IPPROTO_UDP;
dai->addrlen = len;
memcpy (dai->addr, &addr->addr.sa, len);
((struct sockaddr_in *) dai->addr)->sin_port = htons (port);
dai->next = daihead;
daihead = dai;
err = 0;
}
leave:
adns_free (answer);
adns_finish (state);
if (err)
{
if (r_canonname)
{
xfree (*r_canonname);
*r_canonname = NULL;
}
free_dns_addrinfo (daihead);
}
else
*r_dai = daihead;
return err;
}
#endif /*USE_ADNS*/
/* Resolve a name using the standard system function. */
static gpg_error_t
resolve_name_standard (const char *name, unsigned short port,
int want_family, int want_socktype,
dns_addrinfo_t *r_dai, char **r_canonname)
{
gpg_error_t err = 0;
dns_addrinfo_t daihead = NULL;
dns_addrinfo_t dai;
struct addrinfo *aibuf = NULL;
struct addrinfo hints, *ai;
char portstr[21];
int ret;
*r_dai = NULL;
if (r_canonname)
*r_canonname = NULL;
memset (&hints, 0, sizeof hints);
hints.ai_family = want_family;
hints.ai_socktype = want_socktype;
hints.ai_flags = AI_ADDRCONFIG;
if (r_canonname)
hints.ai_flags |= AI_CANONNAME;
if (port)
snprintf (portstr, sizeof portstr, "%hu", port);
else
*portstr = 0;
/* We can't use the the AI_IDN flag because that does the conversion
using the current locale. However, GnuPG always used UTF-8. To
support IDN we would need to make use of the libidn API. */
ret = getaddrinfo (name, *portstr? portstr : NULL, &hints, &aibuf);
if (ret)
{
aibuf = NULL;
err = map_eai_to_gpg_error (ret);
if (gpg_err_code (err) == GPG_ERR_NO_NAME)
{
/* There seems to be a bug in the glibc getaddrinfo function
if the CNAME points to a long list of A and AAAA records
in which case the function return NO_NAME. Let's do the
CNAME redirection again. */
char *cname;
if (get_dns_cname (name, &cname))
goto leave; /* Still no success. */
ret = getaddrinfo (cname, *portstr? portstr : NULL, &hints, &aibuf);
xfree (cname);
if (ret)
{
aibuf = NULL;
err = map_eai_to_gpg_error (ret);
goto leave;
}
err = 0; /* Yep, now it worked. */
}
else
goto leave;
}
if (r_canonname && aibuf && aibuf->ai_canonname)
{
*r_canonname = xtrystrdup (aibuf->ai_canonname);
if (!*r_canonname)
{
err = gpg_error_from_syserror ();
goto leave;
}
}
for (ai = aibuf; ai; ai = ai->ai_next)
{
if (ai->ai_family != AF_INET6 && ai->ai_family != AF_INET)
continue;
dai = xtrymalloc (sizeof *dai + ai->ai_addrlen - 1);
dai->family = ai->ai_family;
dai->socktype = ai->ai_socktype;
dai->protocol = ai->ai_protocol;
dai->addrlen = ai->ai_addrlen;
memcpy (dai->addr, ai->ai_addr, ai->ai_addrlen);
dai->next = daihead;
daihead = dai;
}
leave:
if (aibuf)
freeaddrinfo (aibuf);
if (err)
{
if (r_canonname)
{
xfree (*r_canonname);
*r_canonname = NULL;
}
free_dns_addrinfo (daihead);
}
else
*r_dai = daihead;
return err;
}
/* Resolve an address using the standard system function. */
static gpg_error_t
resolve_addr_standard (const struct sockaddr *addr, int addrlen,
unsigned int flags, char **r_name)
{
gpg_error_t err;
int ec;
char *buffer, *p;
int buflen;
*r_name = NULL;
buflen = NI_MAXHOST;
buffer = xtrymalloc (buflen + 2 + 1);
if (!buffer)
return gpg_error_from_syserror ();
if ((flags & DNS_NUMERICHOST) || tor_mode)
ec = EAI_NONAME;
else
ec = getnameinfo (addr, addrlen, buffer, buflen, NULL, 0, NI_NAMEREQD);
if (!ec && *buffer == '[')
ec = EAI_FAIL; /* A name may never start with a bracket. */
else if (ec == EAI_NONAME)
{
p = buffer;
if (addr->sa_family == AF_INET6 && (flags & DNS_WITHBRACKET))
{
*p++ = '[';
buflen -= 2;
}
ec = getnameinfo (addr, addrlen, p, buflen, NULL, 0, NI_NUMERICHOST);
if (!ec && addr->sa_family == AF_INET6 && (flags & DNS_WITHBRACKET))
strcat (buffer, "]");
}
if (ec)
err = map_eai_to_gpg_error (ec);
else
{
p = xtryrealloc (buffer, strlen (buffer)+1);
if (!p)
err = gpg_error_from_syserror ();
else
{
buffer = p;
err = 0;
}
}
if (err)
xfree (buffer);
else
*r_name = buffer;
return err;
}
/* This a wrapper around getaddrinfo with slightly different semantics.
NAME is the name to resolve.
PORT is the requested port or 0.
WANT_FAMILY is either 0 (AF_UNSPEC), AF_INET6, or AF_INET4.
WANT_SOCKETTYPE is either SOCK_STREAM or SOCK_DGRAM.
On success the result is stored in a linked list with the head
stored at the address R_AI; the caller must call gpg_addrinfo_free
on this. If R_CANONNAME is not NULL the official name of the host
is stored there as a malloced string; if that name is not available
NULL is stored. */
gpg_error_t
resolve_dns_name (const char *name, unsigned short port,
int want_family, int want_socktype,
dns_addrinfo_t *r_ai, char **r_canonname)
{
#ifdef USE_ADNS
if (!standard_resolver)
return resolve_name_adns (name, port, want_family, want_socktype,
r_ai, r_canonname);
#endif
return resolve_name_standard (name, port, want_family, want_socktype,
r_ai, r_canonname);
}
gpg_error_t
resolve_dns_addr (const struct sockaddr *addr, int addrlen,
unsigned int flags, char **r_name)
{
return resolve_addr_standard (addr, addrlen, flags, r_name);
}
/* Check whether NAME is an IP address. Returns true if it is either
an IPv6 or IPv4 numerical address. */
int
is_ip_address (const char *name)
{
const char *s;
int ndots, dblcol, n;
if (*name == '[')
return 1; /* yes: A legal DNS name may not contain this character;
this mut be bracketed v6 address. */
if (*name == '.')
return 0; /* No. A leading dot is not a valid IP address. */
/* Check whether this is a v6 address. */
ndots = n = dblcol = 0;
for (s=name; *s; s++)
{
if (*s == ':')
{
ndots++;
if (s[1] == ':')
{
ndots++;
if (dblcol)
return 0; /* No: Only one "::" allowed. */
dblcol++;
if (s[1])
s++;
}
n = 0;
}
else if (*s == '.')
goto legacy;
else if (!strchr ("0123456789abcdefABCDEF", *s))
return 0; /* No: Not a hex digit. */
else if (++n > 4)
return 0; /* To many digits in a group. */
}
if (ndots > 7)
return 0; /* No: Too many colons. */
else if (ndots > 1)
return 1; /* Yes: At least 2 colons indicate an v6 address. */
legacy:
/* Check whether it is legacy IP address. */
ndots = n = 0;
for (s=name; *s; s++)
{
if (*s == '.')
{
if (s[1] == '.')
return 0; /* No: Douple dot. */
if (atoi (s+1) > 255)
return 0; /* No: Ipv4 byte value too large. */
ndots++;
n = 0;
}
else if (!strchr ("0123456789", *s))
return 0; /* No: Not a digit. */
else if (++n > 3)
return 0; /* No: More than 3 digits. */
}
return !!(ndots == 3);
}
/* Return true if NAME is an onion address. */
int
is_onion_address (const char *name)
{
size_t len;
len = name? strlen (name) : 0;
if (len < 8 || strcmp (name + len - 6, ".onion"))
return 0;
/* Note that we require at least 2 characters before the suffix. */
return 1; /* Yes. */
}
#ifdef USE_ADNS
/* ADNS version of get_dns_cert. */
static gpg_error_t
get_dns_cert_adns (const char *name, int want_certtype,
void **r_key, size_t *r_keylen,
unsigned char **r_fpr, size_t *r_fprlen, char **r_url)
{
gpg_error_t err;
int ret;
adns_state state;
adns_answer *answer = NULL;
unsigned int ctype;
int count;
err = my_adns_init (&state);
if (err)
return err;
my_unprotect ();
ret = adns_synchronous (state, name,
(adns_r_unknown
| (want_certtype < DNS_CERTTYPE_RRBASE
? my_adns_r_cert
: (want_certtype - DNS_CERTTYPE_RRBASE))),
adns_qf_quoteok_query, &answer);
my_protect ();
if (ret)
{
err = gpg_error (gpg_err_code_from_errno (ret));
/* log_error ("DNS query failed: %s\n", gpg_strerror (err)); */
adns_finish (state);
return err;
}
if (answer->status != adns_s_ok)
{
/* log_error ("DNS query returned an error: %s (%s)\n", */
/* adns_strerror (answer->status), */
/* adns_errabbrev (answer->status)); */
err = map_adns_status_to_gpg_error (answer->status);
if (gpg_err_code (err) == GPG_ERR_GENERAL)
err = gpg_error (GPG_ERR_NOT_FOUND);
goto leave;
}
err = gpg_error (GPG_ERR_NOT_FOUND);
for (count = 0; count < answer->nrrs; count++)
{
int datalen = answer->rrs.byteblock[count].len;
const unsigned char *data = answer->rrs.byteblock[count].data;
/* First check for our generic RR hack. */
if (datalen
&& want_certtype >= DNS_CERTTYPE_RRBASE
&& ((want_certtype - DNS_CERTTYPE_RRBASE)
== (answer->type & ~adns_r_unknown)))
{
/* Found the requested record - return it. */
*r_key = xtrymalloc (datalen);
if (!*r_key)
err = gpg_error_from_syserror ();
else
{
memcpy (*r_key, data, datalen);
*r_keylen = datalen;
err = 0;
}
goto leave;
}
if (datalen < 5)
continue; /* Truncated CERT record - skip. */
ctype = buf16_to_uint (data);
/* (key tag and algorithm fields are not required.) */
data += 5;
datalen -= 5;
if (want_certtype && want_certtype != ctype)
; /* Not of the requested certtype. */
else if (ctype == DNS_CERTTYPE_PGP && datalen >= 11 && r_key && r_keylen)
{
/* CERT type is PGP. Gpg checks for a minimum length of 11,
thus we do the same. */
*r_key = xtrymalloc (datalen);
if (!*r_key)
err = gpg_error_from_syserror ();
else
{
memcpy (*r_key, data, datalen);
*r_keylen = datalen;
err = 0;
}
goto leave;
}
else if (ctype == DNS_CERTTYPE_IPGP && datalen && datalen < 1023
&& datalen >= data[0] + 1 && r_fpr && r_fprlen && r_url)
{
/* CERT type is IPGP. We made sure that the data is
plausible and that the caller requested this
information. */
*r_fprlen = data[0];
if (*r_fprlen)
{
*r_fpr = xtrymalloc (*r_fprlen);
if (!*r_fpr)
{
err = gpg_error_from_syserror ();
goto leave;
}
memcpy (*r_fpr, data + 1, *r_fprlen);
}
else
*r_fpr = NULL;
if (datalen > *r_fprlen + 1)
{
*r_url = xtrymalloc (datalen - (*r_fprlen + 1) + 1);
if (!*r_url)
{
err = gpg_error_from_syserror ();
xfree (*r_fpr);
*r_fpr = NULL;
goto leave;
}
memcpy (*r_url,
data + (*r_fprlen + 1), datalen - (*r_fprlen + 1));
(*r_url)[datalen - (*r_fprlen + 1)] = '\0';
}
else
*r_url = NULL;
err = 0;
goto leave;
}
}
leave:
adns_free (answer);
adns_finish (state);
return err;
}
#endif /*!USE_ADNS */
/* Standard resolver version of get_dns_cert. */
static gpg_error_t
get_dns_cert_standard (const char *name, int want_certtype,
void **r_key, size_t *r_keylen,
unsigned char **r_fpr, size_t *r_fprlen, char **r_url)
{
#ifdef HAVE_SYSTEM_RESOLVER
gpg_error_t err;
unsigned char *answer;
int r;
u16 count;
/* Allocate a 64k buffer which is the limit for an DNS response. */
answer = xtrymalloc (65536);
if (!answer)
return gpg_error_from_syserror ();
err = gpg_error (GPG_ERR_NOT_FOUND);
r = res_query (name, C_IN,
(want_certtype < DNS_CERTTYPE_RRBASE
? T_CERT
: (want_certtype - DNS_CERTTYPE_RRBASE)),
answer, 65536);
/* Not too big, not too small, no errors and at least 1 answer. */
if (r >= sizeof (HEADER) && r <= 65536
&& (((HEADER *)(void *) answer)->rcode) == NOERROR
&& (count = ntohs (((HEADER *)(void *) answer)->ancount)))
{
int rc;
unsigned char *pt, *emsg;
emsg = &answer[r];
pt = &answer[sizeof (HEADER)];
/* Skip over the query */
rc = dn_skipname (pt, emsg);
if (rc == -1)
{
err = gpg_error (GPG_ERR_INV_OBJ);
goto leave;
}
pt += rc + QFIXEDSZ;
/* There are several possible response types for a CERT request.
We're interested in the PGP (a key) and IPGP (a URI) types.
Skip all others. TODO: A key is better than a URI since
we've gone through all this bother to fetch it, so favor that
if we have both PGP and IPGP? */
while (count-- > 0 && pt < emsg)
{
u16 type, class, dlen, ctype;
rc = dn_skipname (pt, emsg); /* the name we just queried for */
if (rc == -1)
{
err = gpg_error (GPG_ERR_INV_OBJ);
goto leave;
}
pt += rc;
/* Truncated message? 15 bytes takes us to the point where
we start looking at the ctype. */
if ((emsg - pt) < 15)
break;
type = buf16_to_u16 (pt);
pt += 2;
class = buf16_to_u16 (pt);
pt += 2;
if (class != C_IN)
break;
/* ttl */
pt += 4;
/* data length */
dlen = buf16_to_u16 (pt);
pt += 2;
/* Check the type and parse. */
if (want_certtype >= DNS_CERTTYPE_RRBASE
&& type == (want_certtype - DNS_CERTTYPE_RRBASE)
&& r_key)
{
*r_key = xtrymalloc (dlen);
if (!*r_key)
err = gpg_error_from_syserror ();
else
{
memcpy (*r_key, pt, dlen);
*r_keylen = dlen;
err = 0;
}
goto leave;
}
else if (want_certtype >= DNS_CERTTYPE_RRBASE)
{
/* We did not found the requested RR. */
pt += dlen;
}
else if (type == T_CERT)
{
/* We got a CERT type. */
ctype = buf16_to_u16 (pt);
pt += 2;
/* Skip the CERT key tag and algo which we don't need. */
pt += 3;
dlen -= 5;
/* 15 bytes takes us to here */
if (want_certtype && want_certtype != ctype)
; /* Not of the requested certtype. */
else if (ctype == DNS_CERTTYPE_PGP && dlen && r_key && r_keylen)
{
/* PGP type */
*r_key = xtrymalloc (dlen);
if (!*r_key)
err = gpg_error_from_syserror ();
else
{
memcpy (*r_key, pt, dlen);
*r_keylen = dlen;
err = 0;
}
goto leave;
}
else if (ctype == DNS_CERTTYPE_IPGP
&& dlen && dlen < 1023 && dlen >= pt[0] + 1)
{
/* IPGP type */
*r_fprlen = pt[0];
if (*r_fprlen)
{
*r_fpr = xtrymalloc (*r_fprlen);
if (!*r_fpr)
{
err = gpg_error_from_syserror ();
goto leave;
}
memcpy (*r_fpr, &pt[1], *r_fprlen);
}
else
*r_fpr = NULL;
if (dlen > *r_fprlen + 1)
{
*r_url = xtrymalloc (dlen - (*r_fprlen + 1) + 1);
if (!*r_fpr)
{
err = gpg_error_from_syserror ();
xfree (*r_fpr);
*r_fpr = NULL;
goto leave;
}
memcpy (*r_url, &pt[*r_fprlen + 1],
dlen - (*r_fprlen + 1));
(*r_url)[dlen - (*r_fprlen + 1)] = '\0';
}
else
*r_url = NULL;
err = 0;
goto leave;
}
/* No subtype matches, so continue with the next answer. */
pt += dlen;
}
else
{
/* Not a requested type - might be a CNAME. Try next item. */
pt += dlen;
}
}
}
leave:
xfree (answer);
return err;
#else /*!HAVE_SYSTEM_RESOLVER*/
(void)name;
(void)want_certtype;
(void)r_key;
(void)r_keylen;
(void)r_fpr;
(void)r_fprlen;
(void)r_url;
return gpg_error (GPG_ERR_NOT_SUPPORTED);
#endif /*!HAVE_SYSTEM_RESOLVER*/
}
/* Returns 0 on success or an error code. If a PGP CERT record was
found, the malloced data is returned at (R_KEY, R_KEYLEN) and
the other return parameters are set to NULL/0. If an IPGP CERT
record was found the fingerprint is stored as an allocated block at
R_FPR and its length at R_FPRLEN; an URL is is allocated as a
string and returned at R_URL. If WANT_CERTTYPE is 0 this function
returns the first CERT found with a supported type; it is expected
that only one CERT record is used. If WANT_CERTTYPE is one of the
supported certtypes only records with this certtype are considered
and the first found is returned. (R_KEY,R_KEYLEN) are optional. */
gpg_error_t
get_dns_cert (const char *name, int want_certtype,
void **r_key, size_t *r_keylen,
unsigned char **r_fpr, size_t *r_fprlen, char **r_url)
{
if (r_key)
*r_key = NULL;
if (r_keylen)
*r_keylen = 0;
*r_fpr = NULL;
*r_fprlen = 0;
*r_url = NULL;
#ifdef USE_ADNS
if (!standard_resolver)
return get_dns_cert_adns (name, want_certtype, r_key, r_keylen,
r_fpr, r_fprlen, r_url);
#endif /*!USE_ADNS */
return get_dns_cert_standard (name, want_certtype, r_key, r_keylen,
r_fpr, r_fprlen, r_url);
}
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;
}
#ifdef USE_ADNS
/* ADNS based helper for getsrv. */
static int
getsrv_adns (const char *name, struct srventry **list)
{
int srvcount = 0;
u16 count;
int rc;
adns_state state;
adns_answer *answer = NULL;
if (my_adns_init (&state))
return -1;
my_unprotect ();
rc = adns_synchronous (state, name, adns_r_srv, adns_qf_quoteok_query,
&answer);
my_protect ();
if (rc)
{
log_error ("DNS query failed: %s\n", strerror (rc));
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) >= sizeof srv->target)
{
log_info ("hostname in SRV record too long - skipped\n");
continue;
}
newlist = xtryrealloc (*list, (srvcount+1)*sizeof(struct srventry));
if (!newlist)
{
xfree (*list);
*list = NULL;
return -1;
}
*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);
return srvcount;
}
#endif /*USE_ADNS*/
/* Standard resolver based helper for getsrv. */
static int
getsrv_standard (const char *name, struct srventry **list)
{
#ifdef HAVE_SYSTEM_RESOLVER
union {
unsigned char ans[2048];
HEADER header[1];
} res;
unsigned char *answer = res.ans;
HEADER *header = res.header;
unsigned char *pt, *emsg;
int r, rc;
u16 dlen;
int srvcount=0;
u16 count;
/* Do not allow a query using the standard resolver in Tor mode. */
if (tor_mode)
return -1;
my_unprotect ();
r = res_query (name, C_IN, T_SRV, answer, sizeof answer);
my_protect ();
if (r < sizeof (HEADER) || r > sizeof answer
|| 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, sizeof srv->target);
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;
}
return srvcount;
fail:
xfree (*list);
*list = NULL;
return -1;
#else /*!HAVE_SYSTEM_RESOLVER*/
(void)name;
(void)list;
return -1;
#endif /*!HAVE_SYSTEM_RESOLVER*/
}
int
getsrv (const char *name, struct srventry **list)
{
int srvcount;
int i;
*list = NULL;
if (0)
;
#ifdef USE_ADNS
else if (!standard_resolver)
srvcount = getsrv_adns (name, list);
#endif /*!USE_ADNS*/
else
srvcount = getsrv_standard (name, list);
if (srvcount <= 0)
return srvcount;
/* 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. */
{
static int done;
if (!done)
{
done = 1;
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;
}
#ifdef USE_ADNS
/* ADNS version of get_dns_cname. */
gpg_error_t
get_dns_cname_adns (const char *name, char **r_cname)
{
gpg_error_t err;
int rc;
adns_state state;
adns_answer *answer = NULL;
if (my_adns_init (&state))
return gpg_error (GPG_ERR_GENERAL);
my_unprotect ();
rc = adns_synchronous (state, name, adns_r_cname, adns_qf_quoteok_query,
&answer);
my_protect ();
if (rc)
{
err = gpg_error (gpg_err_code_from_errno (rc));
log_error ("DNS query failed: %s\n", gpg_strerror (err));
adns_finish (state);
return err;
}
if (answer->status != adns_s_ok
|| answer->type != adns_r_cname || answer->nrrs != 1)
{
err = map_adns_status_to_gpg_error (answer->status);
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 err;
}
*r_cname = xtrystrdup (answer->rrs.str[0]);
if (!*r_cname)
err = gpg_error_from_syserror ();
else
err = 0;
adns_free (answer);
adns_finish (state);
return err;
}
#endif /*USE_ADNS*/
/* Standard resolver version of get_dns_cname. */
gpg_error_t
get_dns_cname_standard (const char *name, char **r_cname)
{
#ifdef HAVE_SYSTEM_RESOLVER
gpg_error_t err;
int rc;
union {
unsigned char ans[2048];
HEADER header[1];
} res;
unsigned char *answer = res.ans;
HEADER *header = res.header;
unsigned char *pt, *emsg;
int r;
char *cname;
int cnamesize = 1025;
u16 count;
/* Do not allow a query using the standard resolver in Tor mode. */
if (tor_mode)
return -1;
r = res_query (name, C_IN, T_CERT, answer, sizeof answer);
if (r < sizeof (HEADER) || r > sizeof answer)
return gpg_error (GPG_ERR_SERVER_FAILED);
if (header->rcode != NOERROR || !(count=ntohs (header->ancount)))
return gpg_error (GPG_ERR_NO_NAME); /* Error or no record found. */
if (count != 1)
return gpg_error (GPG_ERR_SERVER_FAILED);
emsg = &answer[r];
pt = &answer[sizeof(HEADER)];
rc = dn_skipname (pt, emsg);
if (rc == -1)
return gpg_error (GPG_ERR_SERVER_FAILED);
pt += rc + QFIXEDSZ;
if (pt >= emsg)
return gpg_error (GPG_ERR_SERVER_FAILED);
rc = dn_skipname (pt, emsg);
if (rc == -1)
return gpg_error (GPG_ERR_SERVER_FAILED);
pt += rc + 2 + 2 + 4;
if (pt+2 >= emsg)
return gpg_error (GPG_ERR_SERVER_FAILED);
pt += 2; /* Skip rdlen */
cname = xtrymalloc (cnamesize);
if (!cname)
return gpg_error_from_syserror ();
rc = dn_expand (answer, emsg, pt, cname, cnamesize -1);
if (rc == -1)
{
xfree (cname);
return gpg_error (GPG_ERR_SERVER_FAILED);
}
*r_cname = xtryrealloc (cname, strlen (cname)+1);
if (!*r_cname)
{
err = gpg_error_from_syserror ();
xfree (cname);
return err;
}
return 0;
#else /*!HAVE_SYSTEM_RESOLVER*/
(void)name;
(void)r_cname;
return -1;
#endif /*!HAVE_SYSTEM_RESOLVER*/
}
gpg_error_t
get_dns_cname (const char *name, char **r_cname)
{
*r_cname = NULL;
#ifdef USE_ADNS
if (!standard_resolver)
return get_dns_cname_adns (name, r_cname);
#endif /*!USE_ADNS*/
return get_dns_cname_standard (name, r_cname);
}
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