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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-27 12:06:34 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-27 12:06:34 +0000
commit5e61585d76ae77fd5e9e96ebabb57afa4d74880d (patch)
tree2b467823aaeebc7ef8bc9e3cabe8074eaef1666d /src/dns/dns_lookup.c
parentInitial commit. (diff)
downloadpostfix-5e61585d76ae77fd5e9e96ebabb57afa4d74880d.tar.xz
postfix-5e61585d76ae77fd5e9e96ebabb57afa4d74880d.zip
Adding upstream version 3.5.24.upstream/3.5.24upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'src/dns/dns_lookup.c')
-rw-r--r--src/dns/dns_lookup.c1216
1 files changed, 1216 insertions, 0 deletions
diff --git a/src/dns/dns_lookup.c b/src/dns/dns_lookup.c
new file mode 100644
index 0000000..c5f7ad9
--- /dev/null
+++ b/src/dns/dns_lookup.c
@@ -0,0 +1,1216 @@
+/*++
+/* NAME
+/* dns_lookup 3
+/* SUMMARY
+/* domain name service lookup
+/* SYNOPSIS
+/* #include <dns.h>
+/*
+/* int dns_lookup(name, type, rflags, list, fqdn, why)
+/* const char *name;
+/* unsigned type;
+/* unsigned rflags;
+/* DNS_RR **list;
+/* VSTRING *fqdn;
+/* VSTRING *why;
+/*
+/* int dns_lookup_l(name, rflags, list, fqdn, why, lflags, ltype, ...)
+/* const char *name;
+/* unsigned rflags;
+/* DNS_RR **list;
+/* VSTRING *fqdn;
+/* VSTRING *why;
+/* int lflags;
+/* unsigned ltype;
+/*
+/* int dns_lookup_v(name, rflags, list, fqdn, why, lflags, ltype)
+/* const char *name;
+/* unsigned rflags;
+/* DNS_RR **list;
+/* VSTRING *fqdn;
+/* VSTRING *why;
+/* int lflags;
+/* unsigned *ltype;
+/* AUXILIARY FUNCTIONS
+/* extern int var_dns_ncache_ttl_fix;
+/*
+/* int dns_lookup_r(name, type, rflags, list, fqdn, why, rcode)
+/* const char *name;
+/* unsigned type;
+/* unsigned rflags;
+/* DNS_RR **list;
+/* VSTRING *fqdn;
+/* VSTRING *why;
+/* int *rcode;
+/*
+/* int dns_lookup_rl(name, rflags, list, fqdn, why, rcode, lflags,
+/* ltype, ...)
+/* const char *name;
+/* unsigned rflags;
+/* DNS_RR **list;
+/* VSTRING *fqdn;
+/* VSTRING *why;
+/* int *rcode;
+/* int lflags;
+/* unsigned ltype;
+/*
+/* int dns_lookup_rv(name, rflags, list, fqdn, why, rcode, lflags,
+/* ltype)
+/* const char *name;
+/* unsigned rflags;
+/* DNS_RR **list;
+/* VSTRING *fqdn;
+/* VSTRING *why;
+/* int *rcode;
+/* int lflags;
+/* unsigned *ltype;
+/*
+/* int dns_lookup_x(name, type, rflags, list, fqdn, why, rcode, lflags)
+/* const char *name;
+/* unsigned type;
+/* unsigned rflags;
+/* DNS_RR **list;
+/* VSTRING *fqdn;
+/* VSTRING *why;
+/* int *rcode;
+/* unsigned lflags;
+/* DESCRIPTION
+/* dns_lookup() looks up DNS resource records. When requested to
+/* look up data other than type CNAME, it will follow a limited
+/* number of CNAME indirections. All result names (including
+/* null terminator) will fit a buffer of size DNS_NAME_LEN.
+/* All name results are validated by \fIvalid_hostname\fR();
+/* an invalid name is reported as a DNS_INVAL result, while
+/* malformed replies are reported as transient errors.
+/*
+/* dns_lookup_l() and dns_lookup_v() allow the user to specify
+/* a list of resource types.
+/*
+/* dns_lookup_x, dns_lookup_r(), dns_lookup_rl() and dns_lookup_rv()
+/* accept or return additional information.
+/*
+/* The var_dns_ncache_ttl_fix variable controls a workaround
+/* for res_search(3) implementations that break the
+/* DNS_REQ_FLAG_NCACHE_TTL feature. The workaround does not
+/* support EDNS0 or DNSSEC, but it should be sufficient for
+/* DNSBL/DNSWL lookups.
+/* INPUTS
+/* .ad
+/* .fi
+/* .IP name
+/* The name to be looked up in the domain name system.
+/* This name must pass the valid_hostname() test; it
+/* must not be an IP address.
+/* .IP type
+/* The resource record type to be looked up (T_A, T_MX etc.).
+/* .IP rflags
+/* Resolver flags. These are a bitwise OR of:
+/* .RS
+/* .IP RES_DEBUG
+/* Print debugging information.
+/* .IP RES_DNSRCH
+/* Search local domain and parent domains.
+/* .IP RES_DEFNAMES
+/* Append local domain to unqualified names.
+/* .IP RES_USE_DNSSEC
+/* Request DNSSEC validation. This flag is silently ignored
+/* when the system stub resolver API, resolver(3), does not
+/* implement DNSSEC.
+/* Automatically turns on the RES_TRUSTAD flag on systems that
+/* support this flag (this behavior will be more configurable
+/* in a later release).
+/* .RE
+/* .IP lflags
+/* Flags that control the operation of the dns_lookup*()
+/* functions. DNS_REQ_FLAG_NONE requests no special processing.
+/* Otherwise, specify one or more of the following:
+/* .RS
+/* .IP DNS_REQ_FLAG_STOP_INVAL
+/* This flag is used by dns_lookup_l() and dns_lookup_v().
+/* Invoke dns_lookup() for the resource types in the order as
+/* specified, and return when dns_lookup() returns DNS_INVAL.
+/* .IP DNS_REQ_FLAG_STOP_NULLMX
+/* This flag is used by dns_lookup_l() and dns_lookup_v().
+/* Invoke dns_lookup() for the resource types in the order as
+/* specified, and return when dns_lookup() returns DNS_NULLMX.
+/* .IP DNS_REQ_FLAG_STOP_MX_POLICY
+/* This flag is used by dns_lookup_l() and dns_lookup_v().
+/* Invoke dns_lookup() for the resource types in the order as
+/* specified, and return when dns_lookup() returns DNS_POLICY
+/* for an MX query.
+/* .IP DNS_REQ_FLAG_STOP_OK
+/* This flag is used by dns_lookup_l() and dns_lookup_v().
+/* Invoke dns_lookup() for the resource types in the order as
+/* specified, and return when dns_lookup() returns DNS_OK.
+/* .IP DNS_REQ_FLAG_NCACHE_TTL
+/* When the lookup result status is DNS_NOTFOUND, return the
+/* SOA record(s) from the authority section in the reply, if
+/* available. The per-record reply TTL specifies how long the
+/* DNS_NOTFOUND answer is valid. The caller should pass the
+/* record(s) to dns_rr_free().
+/* Logs a warning if the RES_DNSRCH or RES_DEFNAMES resolver
+/* flags are set, and disables those flags.
+/* .RE
+/* .IP ltype
+/* The resource record types to be looked up. In the case of
+/* dns_lookup_l(), this is a null-terminated argument list.
+/* In the case of dns_lookup_v(), this is a null-terminated
+/* integer array.
+/* OUTPUTS
+/* .ad
+/* .fi
+/* .IP list
+/* A null pointer, or a pointer to a variable that receives a
+/* list of requested resource records.
+/* .IP fqdn
+/* A null pointer, or storage for the fully-qualified domain
+/* name found for \fIname\fR.
+/* .IP why
+/* A null pointer, or storage for the reason for failure.
+/* .IP rcode
+/* Pointer to storage for the reply RCODE value. This gives
+/* more detailed information than DNS_FAIL, DNS_RETRY, etc.
+/* DIAGNOSTICS
+/* If DNSSEC validation is requested but the response is not
+/* DNSSEC validated, dns_lookup() will send a one-time probe
+/* query as configured with the \fBdnssec_probe\fR configuration
+/* parameter, and will log a warning when the probe response
+/* was not DNSSEC validated.
+/* .PP
+/* dns_lookup() returns one of the following codes and sets the
+/* \fIwhy\fR argument accordingly:
+/* .IP DNS_OK
+/* The DNS query succeeded.
+/* .IP DNS_POLICY
+/* The DNS query succeeded, but the answer did not pass the
+/* policy filter.
+/* .IP DNS_NOTFOUND
+/* The DNS query succeeded; the requested information was not found.
+/* .IP DNS_NULLMX
+/* The DNS query succeeded; the requested service is unavailable.
+/* This is returned when the list argument is not a null
+/* pointer, and an MX lookup result contains a null server
+/* name (so-called "nullmx" record).
+/* .IP DNS_INVAL
+/* The DNS query succeeded; the result failed the valid_hostname() test.
+/*
+/* NOTE: the valid_hostname() test is skipped for results that
+/* the caller suppresses explicitly. For example, when the
+/* caller requests MX record lookup but specifies a null
+/* resource record list argument, no syntax check will be done
+/* for MX server names.
+/* .IP DNS_RETRY
+/* The query failed, or the reply was malformed.
+/* The problem is considered transient.
+/* .IP DNS_FAIL
+/* The query failed.
+/* BUGS
+/* dns_lookup() implements a subset of all possible resource types:
+/* CNAME, MX, A, and some records with similar formatting requirements.
+/* It is unwise to specify the T_ANY wildcard resource type.
+/*
+/* It takes a surprising amount of code to accomplish what appears
+/* to be a simple task. Later versions of the mail system may implement
+/* their own DNS client software.
+/* SEE ALSO
+/* dns_rr(3) resource record memory and list management
+/* LICENSE
+/* .ad
+/* .fi
+/* The Secure Mailer license must be distributed with this software.
+/* AUTHOR(S)
+/* Wietse Venema
+/* IBM T.J. Watson Research
+/* P.O. Box 704
+/* Yorktown Heights, NY 10598, USA
+/*
+/* Wietse Venema
+/* Google, Inc.
+/* 111 8th Avenue
+/* New York, NY 10011, USA
+/*--*/
+
+/* System library. */
+
+#include <sys_defs.h>
+#include <netdb.h>
+#include <string.h>
+#include <ctype.h>
+
+/* Utility library. */
+
+#include <mymalloc.h>
+#include <vstring.h>
+#include <msg.h>
+#include <valid_hostname.h>
+#include <stringops.h>
+
+/* Global library. */
+
+#include <mail_params.h>
+
+/* DNS library. */
+
+#define LIBDNS_INTERNAL
+#include "dns.h"
+
+/* Local stuff. */
+
+ /*
+ * Structure to keep track of things while decoding a name server reply.
+ */
+#define DEF_DNS_REPLY_SIZE 4096 /* in case we're using TCP */
+#define MAX_DNS_REPLY_SIZE 65536 /* in case we're using TCP */
+#define MAX_DNS_QUERY_SIZE 2048 /* XXX */
+
+typedef struct DNS_REPLY {
+ unsigned char *buf; /* raw reply data */
+ size_t buf_len; /* reply buffer length */
+ int rcode; /* unfiltered reply code */
+ int dnssec_ad; /* DNSSEC AD bit */
+ int query_count; /* number of queries */
+ int answer_count; /* number of answers */
+ int auth_count; /* number of authority records */
+ unsigned char *query_start; /* start of query data */
+ unsigned char *answer_start; /* start of answer data */
+ unsigned char *end; /* first byte past reply */
+} DNS_REPLY;
+
+ /*
+ * Test/set primitives to determine if the reply buffer contains a server
+ * response. We use this when the caller requests DNS_REQ_FLAG_NCACHE_TTL,
+ * and the DNS server replies that the requested record does not exist.
+ */
+#define TEST_HAVE_DNS_REPLY_PACKET(r) ((r)->end > (r)->buf)
+#define SET_HAVE_DNS_REPLY_PACKET(r, l) ((r)->end = (r)->buf + (l))
+#define SET_NO_DNS_REPLY_PACKET(r) ((r)->end = (r)->buf)
+
+#define INET_ADDR_LEN 4 /* XXX */
+#define INET6_ADDR_LEN 16 /* XXX */
+
+ /*
+ * To improve postscreen's whitelisting support, we need to know how long a
+ * DNSBL "not found" answer is valid. The 2010 implementation assumed it was
+ * valid for 3600 seconds. That is too long by 2015 standards.
+ *
+ * Instead of guessing, Postfix 3.1 and later implement RFC 2308 (DNS NCACHE),
+ * where a DNS server provides the TTL of a "not found" response as the TTL
+ * of an SOA record in the authority section.
+ *
+ * Unfortunately, the res_search() and res_query() API gets in the way. These
+ * functions overload their result value, the server reply length, and
+ * return -1 when the requested record does not exist. With libbind-based
+ * implementations, the server response is still available in an application
+ * buffer, thanks to the promise that res_query() and res_search() invoke
+ * res_send(), which returns the full server response even if the requested
+ * record does not exist.
+ *
+ * If this promise is broken (for example, res_search() does not call
+ * res_send(), but some non-libbind implementation that updates the
+ * application buffer only when the requested record exists), then we have a
+ * way out by setting the var_dns_ncache_ttl_fix variable. This enables a
+ * limited res_query() clone that should be sufficient for DNSBL / DNSWL
+ * lookups.
+ *
+ * The libunbound API does not comingle the reply length and reply status
+ * information, but that will have to wait until it is safe to make
+ * libunbound a mandatory dependency for Postfix.
+ */
+#ifdef HAVE_RES_SEND
+
+/* dns_res_query - a res_query() clone that can return negative replies */
+
+static int dns_res_query(const char *name, int class, int type,
+ unsigned char *answer, int anslen)
+{
+ unsigned char msg_buf[MAX_DNS_QUERY_SIZE];
+ HEADER *reply_header = (HEADER *) answer;
+ int len;
+
+ /*
+ * Differences with res_query() from libbind:
+ *
+ * - This function returns a positive server reply length not only in case
+ * of success, but in all cases where a server reply is available that
+ * passes the preliminary checks in res_send().
+ *
+ * - This function clears h_errno in case of success. The caller must use
+ * h_errno instead of the return value to decide if the lookup was
+ * successful.
+ *
+ * - No support for EDNS0 and DNSSEC (including turning off EDNS0 after
+ * error). That should be sufficient for DNS reputation lookups where the
+ * reply contains a small number of IP addresses. TXT records are out of
+ * scope for this workaround.
+ */
+ reply_header->rcode = NOERROR;
+
+#define NO_MKQUERY_DATA_BUF ((unsigned char *) 0)
+#define NO_MKQUERY_DATA_LEN ((int) 0)
+#define NO_MKQUERY_NEWRR ((unsigned char *) 0)
+
+ if ((len = res_mkquery(QUERY, name, class, type, NO_MKQUERY_DATA_BUF,
+ NO_MKQUERY_DATA_LEN, NO_MKQUERY_NEWRR,
+ msg_buf, sizeof(msg_buf))) < 0) {
+ SET_H_ERRNO(NO_RECOVERY);
+ if (msg_verbose)
+ msg_info("res_mkquery() failed");
+ return (len);
+ } else if ((len = res_send(msg_buf, len, answer, anslen)) < 0) {
+ SET_H_ERRNO(TRY_AGAIN);
+ if (msg_verbose)
+ msg_info("res_send() failed");
+ return (len);
+ } else {
+ switch (reply_header->rcode) {
+ case NXDOMAIN:
+ SET_H_ERRNO(HOST_NOT_FOUND);
+ break;
+ case NOERROR:
+ if (reply_header->ancount != 0)
+ SET_H_ERRNO(0);
+ else
+ SET_H_ERRNO(NO_DATA);
+ break;
+ case SERVFAIL:
+ SET_H_ERRNO(TRY_AGAIN);
+ break;
+ default:
+ SET_H_ERRNO(NO_RECOVERY);
+ break;
+ }
+ return (len);
+ }
+}
+
+#endif
+
+/* dns_res_search - res_search() that can return negative replies */
+
+static int dns_res_search(const char *name, int class, int type,
+ unsigned char *answer, int anslen, int keep_notfound)
+{
+ int len;
+
+ /*
+ * Differences with res_search() from libbind:
+ *
+ * - With a non-zero keep_notfound argument, this function returns a
+ * positive server reply length not only in case of success, but also in
+ * case of a "notfound" reply status. The keep_notfound argument is
+ * usually zero, which allows us to avoid an unnecessary memset() call in
+ * the most common use case.
+ *
+ * - This function clears h_errno in case of success. The caller must use
+ * h_errno instead of the return value to decide if a lookup was
+ * successful.
+ */
+#define NOT_FOUND_H_ERRNO(he) ((he) == HOST_NOT_FOUND || (he) == NO_DATA)
+
+ if (keep_notfound)
+ /* Prepare for returning a null-padded server reply. */
+ memset(answer, 0, anslen);
+ len = res_search(name, class, type, answer, anslen);
+ /* Begin API creep workaround. */
+ if (len < 0 && h_errno == 0) {
+ SET_H_ERRNO(TRY_AGAIN);
+ msg_warn("res_query(\"%s\", %d, %d, %p, %d) returns %d with h_errno==0"
+ " -- setting h_errno=TRY_AGAIN",
+ name, class, type, answer, anslen, len);
+ }
+ /* End API creep workaround. */
+ if (len > 0) {
+ SET_H_ERRNO(0);
+ } else if (keep_notfound && NOT_FOUND_H_ERRNO(h_errno)) {
+ /* Expect to return a null-padded server reply. */
+ len = anslen;
+ }
+ return (len);
+}
+
+/* dns_query - query name server and pre-parse the reply */
+
+static int dns_query(const char *name, int type, unsigned flags,
+ DNS_REPLY *reply, VSTRING *why, unsigned lflags)
+{
+ HEADER *reply_header;
+ int len;
+ unsigned long saved_options;
+ int keep_notfound = (lflags & DNS_REQ_FLAG_NCACHE_TTL);
+
+ /*
+ * Initialize the reply buffer.
+ */
+ if (reply->buf == 0) {
+ reply->buf = (unsigned char *) mymalloc(DEF_DNS_REPLY_SIZE);
+ reply->buf_len = DEF_DNS_REPLY_SIZE;
+ }
+
+ /*
+ * Initialize the name service.
+ */
+ if ((_res.options & RES_INIT) == 0 && res_init() < 0) {
+ if (why)
+ vstring_strcpy(why, "Name service initialization failure");
+ return (DNS_FAIL);
+ }
+
+ /*
+ * Set search options: debugging, parent domain search, append local
+ * domain. Do not allow the user to control other features.
+ */
+#define USER_FLAGS (RES_DEBUG | RES_DNSRCH | RES_DEFNAMES | RES_USE_DNSSEC)
+
+ if ((flags & USER_FLAGS) != flags)
+ msg_panic("dns_query: bad flags: %d", flags);
+
+ /*
+ * Set extra options that aren't exposed to the application.
+ */
+#define XTRA_FLAGS (RES_USE_EDNS0 | RES_TRUSTAD)
+
+ if (DNS_WANT_DNSSEC_VALIDATION(flags))
+ flags |= (RES_USE_EDNS0 | RES_TRUSTAD);
+
+ /*
+ * Can't append domains: we need the right SOA TTL.
+ */
+#define APPEND_DOMAIN_FLAGS (RES_DNSRCH | RES_DEFNAMES)
+
+ if (keep_notfound && (flags & APPEND_DOMAIN_FLAGS)) {
+ msg_warn("negative caching disables RES_DEFNAMES and RES_DNSRCH");
+ flags &= ~APPEND_DOMAIN_FLAGS;
+ }
+
+ /*
+ * Save and restore resolver options that we overwrite, to avoid
+ * surprising behavior in other code that also invokes the resolver.
+ */
+#define SAVE_FLAGS (USER_FLAGS | XTRA_FLAGS)
+
+ saved_options = (_res.options & SAVE_FLAGS);
+
+ /*
+ * Perform the lookup. Claim that the information cannot be found if and
+ * only if the name server told us so.
+ */
+ for (;;) {
+ _res.options &= ~saved_options;
+ _res.options |= flags;
+ if (keep_notfound && var_dns_ncache_ttl_fix) {
+#ifdef HAVE_RES_SEND
+ len = dns_res_query((char *) name, C_IN, type, reply->buf,
+ reply->buf_len);
+#else
+ var_dns_ncache_ttl_fix = 0;
+ msg_warn("system library does not support %s=yes"
+ " -- ignoring this setting", VAR_DNS_NCACHE_TTL_FIX);
+ len = dns_res_search((char *) name, C_IN, type, reply->buf,
+ reply->buf_len, keep_notfound);
+#endif
+ } else {
+ len = dns_res_search((char *) name, C_IN, type, reply->buf,
+ reply->buf_len, keep_notfound);
+ }
+ _res.options &= ~flags;
+ _res.options |= saved_options;
+ reply_header = (HEADER *) reply->buf;
+ reply->rcode = reply_header->rcode;
+ if ((reply->dnssec_ad = !!reply_header->ad) != 0)
+ DNS_SEC_STATS_SET(DNS_SEC_FLAG_AVAILABLE);
+ if (h_errno != 0) {
+ if (why)
+ vstring_sprintf(why, "Host or domain name not found. "
+ "Name service error for name=%s type=%s: %s",
+ name, dns_strtype(type), dns_strerror(h_errno));
+ if (msg_verbose)
+ msg_info("dns_query: %s (%s): %s",
+ name, dns_strtype(type), dns_strerror(h_errno));
+ switch (h_errno) {
+ case NO_RECOVERY:
+ return (DNS_FAIL);
+ case HOST_NOT_FOUND:
+ case NO_DATA:
+ if (keep_notfound)
+ break;
+ SET_NO_DNS_REPLY_PACKET(reply);
+ return (DNS_NOTFOUND);
+ default:
+ return (DNS_RETRY);
+ }
+ } else {
+ if (msg_verbose)
+ msg_info("dns_query: %s (%s): OK", name, dns_strtype(type));
+ }
+
+ if (reply_header->tc == 0 || reply->buf_len >= MAX_DNS_REPLY_SIZE)
+ break;
+ reply->buf = (unsigned char *)
+ myrealloc((void *) reply->buf, 2 * reply->buf_len);
+ reply->buf_len *= 2;
+ }
+
+ /*
+ * Future proofing. If this reaches the panic call, then some code change
+ * introduced a bug.
+ */
+ if (len < 0)
+ msg_panic("dns_query: bad length %d (h_errno=%s)",
+ len, dns_strerror(h_errno));
+
+ /*
+ * Paranoia.
+ */
+ if (len > reply->buf_len) {
+ msg_warn("reply length %d > buffer length %d for name=%s type=%s",
+ len, (int) reply->buf_len, name, dns_strtype(type));
+ len = reply->buf_len;
+ }
+
+ /*
+ * Initialize the reply structure. Some structure members are filled on
+ * the fly while the reply is being parsed.
+ */
+ SET_HAVE_DNS_REPLY_PACKET(reply, len);
+ reply->query_start = reply->buf + sizeof(HEADER);
+ reply->answer_start = 0;
+ reply->query_count = ntohs(reply_header->qdcount);
+ reply->answer_count = ntohs(reply_header->ancount);
+ reply->auth_count = ntohs(reply_header->nscount);
+ if (msg_verbose > 1)
+ msg_info("dns_query: reply len=%d ancount=%d nscount=%d",
+ len, reply->answer_count, reply->auth_count);
+
+ /*
+ * Future proofing. If this reaches the panic call, then some code change
+ * introduced a bug.
+ */
+ if (h_errno == 0) {
+ return (DNS_OK);
+ } else if (keep_notfound) {
+ return (DNS_NOTFOUND);
+ } else {
+ msg_panic("dns_query: unexpected reply status: %s",
+ dns_strerror(h_errno));
+ }
+}
+
+/* dns_skip_query - skip query data in name server reply */
+
+static int dns_skip_query(DNS_REPLY *reply)
+{
+ int query_count = reply->query_count;
+ unsigned char *pos = reply->query_start;
+ int len;
+
+ /*
+ * For each query, skip over the domain name and over the fixed query
+ * data.
+ */
+ while (query_count-- > 0) {
+ if (pos >= reply->end)
+ return DNS_RETRY;
+ len = dn_skipname(pos, reply->end);
+ if (len < 0)
+ return (DNS_RETRY);
+ pos += len + QFIXEDSZ;
+ }
+ reply->answer_start = pos;
+ return (DNS_OK);
+}
+
+/* dns_get_fixed - extract fixed data from resource record */
+
+static int dns_get_fixed(unsigned char *pos, DNS_FIXED *fixed)
+{
+ GETSHORT(fixed->type, pos);
+ GETSHORT(fixed->class, pos);
+ GETLONG(fixed->ttl, pos);
+ GETSHORT(fixed->length, pos);
+
+ if (fixed->class != C_IN) {
+ msg_warn("dns_get_fixed: bad class: %u", fixed->class);
+ return (DNS_RETRY);
+ }
+ return (DNS_OK);
+}
+
+/* valid_rr_name - validate hostname in resource record */
+
+static int valid_rr_name(const char *name, const char *location,
+ unsigned type, DNS_REPLY *reply)
+{
+ char temp[DNS_NAME_LEN];
+ char *query_name;
+ int len;
+ char *gripe;
+ int result;
+
+ /*
+ * People aren't supposed to specify numeric names where domain names are
+ * required, but it "works" with some mailers anyway, so people complain
+ * when software doesn't bend over backwards.
+ */
+#define PASS_NAME 1
+#define REJECT_NAME 0
+
+ if (valid_hostaddr(name, DONT_GRIPE)) {
+ result = PASS_NAME;
+ gripe = "numeric domain name";
+ } else if (!valid_hostname(name, DO_GRIPE | DO_WILDCARD)) {
+ result = REJECT_NAME;
+ gripe = "malformed domain name";
+ } else {
+ result = PASS_NAME;
+ gripe = 0;
+ }
+
+ /*
+ * If we have a gripe, show some context, including the name used in the
+ * query and the type of reply that we're looking at.
+ */
+ if (gripe) {
+ len = dn_expand(reply->buf, reply->end, reply->query_start,
+ temp, DNS_NAME_LEN);
+ query_name = (len < 0 ? "*unparsable*" : temp);
+ msg_warn("%s in %s of %s record for %s: %.100s",
+ gripe, location, dns_strtype(type), query_name, name);
+ }
+ return (result);
+}
+
+/* dns_get_rr - extract resource record from name server reply */
+
+static int dns_get_rr(DNS_RR **list, const char *orig_name, DNS_REPLY *reply,
+ unsigned char *pos, char *rr_name,
+ DNS_FIXED *fixed)
+{
+ char temp[DNS_NAME_LEN];
+ char *tempbuf = temp;
+ UINT32_TYPE soa_buf[5];
+ int comp_len;
+ ssize_t data_len;
+ unsigned pref = 0;
+ unsigned char *src;
+ unsigned char *dst;
+ int ch;
+
+#define MIN2(a, b) ((unsigned)(a) < (unsigned)(b) ? (a) : (b))
+
+ *list = 0;
+
+ switch (fixed->type) {
+ default:
+ msg_panic("dns_get_rr: don't know how to extract resource type %s",
+ dns_strtype(fixed->type));
+ case T_CNAME:
+ case T_DNAME:
+ case T_MB:
+ case T_MG:
+ case T_MR:
+ case T_NS:
+ case T_PTR:
+ if (dn_expand(reply->buf, reply->end, pos, temp, sizeof(temp)) < 0)
+ return (DNS_RETRY);
+ if (!valid_rr_name(temp, "resource data", fixed->type, reply))
+ return (DNS_INVAL);
+ data_len = strlen(temp) + 1;
+ break;
+ case T_MX:
+ GETSHORT(pref, pos);
+ if (dn_expand(reply->buf, reply->end, pos, temp, sizeof(temp)) < 0)
+ return (DNS_RETRY);
+ /* Don't even think of returning an invalid hostname to the caller. */
+ if (*temp == 0)
+ return (DNS_NULLMX); /* TODO: descriptive text */
+ if (!valid_rr_name(temp, "resource data", fixed->type, reply))
+ return (DNS_INVAL);
+ data_len = strlen(temp) + 1;
+ break;
+ case T_A:
+ if (fixed->length != INET_ADDR_LEN) {
+ msg_warn("extract_answer: bad address length: %d", fixed->length);
+ return (DNS_RETRY);
+ }
+ if (fixed->length > sizeof(temp))
+ msg_panic("dns_get_rr: length %d > DNS_NAME_LEN",
+ fixed->length);
+ memcpy(temp, pos, fixed->length);
+ data_len = fixed->length;
+ break;
+#ifdef T_AAAA
+ case T_AAAA:
+ if (fixed->length != INET6_ADDR_LEN) {
+ msg_warn("extract_answer: bad address length: %d", fixed->length);
+ return (DNS_RETRY);
+ }
+ if (fixed->length > sizeof(temp))
+ msg_panic("dns_get_rr: length %d > DNS_NAME_LEN",
+ fixed->length);
+ memcpy(temp, pos, fixed->length);
+ data_len = fixed->length;
+ break;
+#endif
+
+ /*
+ * We impose the same length limit here as for DNS names. However,
+ * see T_TLSA discussion below.
+ */
+ case T_TXT:
+ data_len = MIN2(pos[0] + 1, MIN2(fixed->length + 1, sizeof(temp)));
+ for (src = pos + 1, dst = (unsigned char *) (temp);
+ dst < (unsigned char *) (temp) + data_len - 1; /* */ ) {
+ ch = *src++;
+ *dst++ = (ISPRINT(ch) ? ch : ' ');
+ }
+ *dst = 0;
+ break;
+
+ /*
+ * For a full certificate, fixed->length may be longer than
+ * sizeof(tmpbuf) == DNS_NAME_LEN. Since we don't need a decode
+ * buffer, just copy the raw data into the rr.
+ *
+ * XXX Reject replies with bogus length < 3.
+ *
+ * XXX What about enforcing a sane upper bound? The RFC 1035 hard
+ * protocol limit is the RRDATA length limit of 65535.
+ */
+ case T_TLSA:
+ data_len = fixed->length;
+ tempbuf = (char *) pos;
+ break;
+
+ /*
+ * We use the SOA record TTL to determine the negative reply TTL. We
+ * save the time fields in the SOA record for debugging, but for now
+ * we don't bother saving the source host and mailbox information, as
+ * that would require changes to the DNS_RR structure and APIs. See
+ * also code in dns_strrecord().
+ */
+ case T_SOA:
+ comp_len = dn_skipname(pos, reply->end);
+ if (comp_len < 0)
+ return (DNS_RETRY);
+ pos += comp_len;
+ comp_len = dn_skipname(pos, reply->end);
+ if (comp_len < 0)
+ return (DNS_RETRY);
+ pos += comp_len;
+ if (reply->end - pos < sizeof(soa_buf)) {
+ msg_warn("extract_answer: bad SOA length: %d", fixed->length);
+ return (DNS_RETRY);
+ }
+ GETLONG(soa_buf[0], pos); /* Serial */
+ GETLONG(soa_buf[1], pos); /* Refresh */
+ GETLONG(soa_buf[2], pos); /* Retry */
+ GETLONG(soa_buf[3], pos); /* Expire */
+ GETLONG(soa_buf[4], pos); /* Ncache TTL */
+ tempbuf = (char *) soa_buf;
+ data_len = sizeof(soa_buf);
+ break;
+ }
+ *list = dns_rr_create(orig_name, rr_name, fixed->type, fixed->class,
+ fixed->ttl, pref, tempbuf, data_len);
+ return (DNS_OK);
+}
+
+/* dns_get_alias - extract CNAME from name server reply */
+
+static int dns_get_alias(DNS_REPLY *reply, unsigned char *pos,
+ DNS_FIXED *fixed, char *cname, int c_len)
+{
+ if (fixed->type != T_CNAME)
+ msg_panic("dns_get_alias: bad type %s", dns_strtype(fixed->type));
+ if (dn_expand(reply->buf, reply->end, pos, cname, c_len) < 0)
+ return (DNS_RETRY);
+ if (!valid_rr_name(cname, "resource data", fixed->type, reply))
+ return (DNS_INVAL);
+ return (DNS_OK);
+}
+
+/* dns_get_answer - extract answers from name server reply */
+
+static int dns_get_answer(const char *orig_name, DNS_REPLY *reply, int type,
+ DNS_RR **rrlist, VSTRING *fqdn, char *cname, int c_len,
+ int *maybe_secure)
+{
+ char rr_name[DNS_NAME_LEN];
+ unsigned char *pos;
+ int answer_count = reply->answer_count;
+ int len;
+ DNS_FIXED fixed;
+ DNS_RR *rr;
+ int resource_found = 0;
+ int cname_found = 0;
+ int not_found_status = DNS_NOTFOUND; /* can't happen */
+ int status;
+
+ /*
+ * Initialize. Skip over the name server query if we haven't yet.
+ */
+ if (reply->answer_start == 0)
+ if ((status = dns_skip_query(reply)) < 0)
+ return (status);
+ pos = reply->answer_start;
+
+ /*
+ * Either this, or use a GOTO for emergency exits. The purpose is to
+ * prevent incomplete answers from being passed back to the caller.
+ */
+#define CORRUPT(status) { \
+ if (rrlist && *rrlist) { \
+ dns_rr_free(*rrlist); \
+ *rrlist = 0; \
+ } \
+ return (status); \
+ }
+
+ /*
+ * Iterate over all answers.
+ */
+ while (answer_count-- > 0) {
+
+ /*
+ * Optionally extract the fully-qualified domain name.
+ */
+ if (pos >= reply->end)
+ CORRUPT(DNS_RETRY);
+ len = dn_expand(reply->buf, reply->end, pos, rr_name, DNS_NAME_LEN);
+ if (len < 0)
+ CORRUPT(DNS_RETRY);
+ pos += len;
+
+ /*
+ * Extract the fixed reply data: type, class, ttl, length.
+ */
+ if (pos + RRFIXEDSZ > reply->end)
+ CORRUPT(DNS_RETRY);
+ if ((status = dns_get_fixed(pos, &fixed)) != DNS_OK)
+ CORRUPT(status);
+ if (strcmp(orig_name, ".") == 0 && *rr_name == 0)
+ /* Allow empty response name for root queries. */ ;
+ else if (!valid_rr_name(rr_name, "resource name", fixed.type, reply))
+ CORRUPT(DNS_INVAL);
+ if (fqdn)
+ vstring_strcpy(fqdn, rr_name);
+ if (msg_verbose)
+ msg_info("dns_get_answer: type %s for %s",
+ dns_strtype(fixed.type), rr_name);
+ pos += RRFIXEDSZ;
+
+ /*
+ * Optionally extract the requested resource or CNAME data.
+ */
+ if (pos + fixed.length > reply->end)
+ CORRUPT(DNS_RETRY);
+ if (type == fixed.type || type == T_ANY) { /* requested type */
+ if (rrlist) {
+ if ((status = dns_get_rr(&rr, orig_name, reply, pos, rr_name,
+ &fixed)) == DNS_OK) {
+ resource_found++;
+ rr->dnssec_valid = *maybe_secure ? reply->dnssec_ad : 0;
+ *rrlist = dns_rr_append(*rrlist, rr);
+ } else if (status == DNS_NULLMX) {
+ CORRUPT(status); /* TODO: use better name */
+ } else if (not_found_status != DNS_RETRY)
+ not_found_status = status;
+ } else
+ resource_found++;
+ } else if (fixed.type == T_CNAME) { /* cname resource */
+ cname_found++;
+ if (cname && c_len > 0)
+ if ((status = dns_get_alias(reply, pos, &fixed, cname, c_len)) != DNS_OK)
+ CORRUPT(status);
+ if (!reply->dnssec_ad)
+ *maybe_secure = 0;
+ }
+ pos += fixed.length;
+ }
+
+ /*
+ * See what answer we came up with. Report success when the requested
+ * information was found. Otherwise, when a CNAME was found, report that
+ * more recursion is needed. Otherwise report failure.
+ */
+ if (resource_found)
+ return (DNS_OK);
+ if (cname_found)
+ return (DNS_RECURSE);
+ return (not_found_status);
+}
+
+/* dns_lookup_x - DNS lookup user interface */
+
+int dns_lookup_x(const char *name, unsigned type, unsigned flags,
+ DNS_RR **rrlist, VSTRING *fqdn, VSTRING *why,
+ int *rcode, unsigned lflags)
+{
+ char cname[DNS_NAME_LEN];
+ int c_len = sizeof(cname);
+ static DNS_REPLY reply;
+ int count;
+ int status;
+ int maybe_secure = 1; /* Query name presumed secure */
+ const char *orig_name = name;
+
+ /*
+ * Reset results early. DNS_OK is not the only status that returns
+ * resource records; DNS_NOTFOUND will do that too, if requested.
+ */
+ if (rrlist)
+ *rrlist = 0;
+
+ /*
+ * DJBDNS produces a bogus A record when given a numerical hostname.
+ */
+ if (valid_hostaddr(name, DONT_GRIPE)) {
+ if (why)
+ vstring_sprintf(why,
+ "Name service error for %s: invalid host or domain name",
+ name);
+ if (rcode)
+ *rcode = NXDOMAIN;
+ SET_H_ERRNO(HOST_NOT_FOUND);
+ return (DNS_NOTFOUND);
+ }
+
+ /*
+ * The Linux resolver misbehaves when given an invalid domain name.
+ */
+ if (strcmp(name, ".") && !valid_hostname(name, DONT_GRIPE | DO_WILDCARD)) {
+ if (why)
+ vstring_sprintf(why,
+ "Name service error for %s: invalid host or domain name",
+ name);
+ if (rcode)
+ *rcode = NXDOMAIN;
+ SET_H_ERRNO(HOST_NOT_FOUND);
+ return (DNS_NOTFOUND);
+ }
+
+ /*
+ * Perform the lookup. Follow CNAME chains, but only up to a
+ * pre-determined maximum.
+ */
+ for (count = 0; count < 10; count++) {
+
+ /*
+ * Perform the DNS lookup, and pre-parse the name server reply.
+ */
+ status = dns_query(name, type, flags, &reply, why, lflags);
+ if (rcode)
+ *rcode = reply.rcode;
+ if (status != DNS_OK) {
+
+ /*
+ * If the record does not exist, and we have a copy of the server
+ * response, try to extract the negative caching TTL for the SOA
+ * record in the authority section. DO NOT return an error if an
+ * SOA record is malformed.
+ */
+ if (status == DNS_NOTFOUND && TEST_HAVE_DNS_REPLY_PACKET(&reply)
+ && reply.auth_count > 0) {
+ reply.answer_count = reply.auth_count; /* XXX TODO: Fix API */
+ (void) dns_get_answer(orig_name, &reply, T_SOA, rrlist, fqdn,
+ cname, c_len, &maybe_secure);
+ }
+ if (DNS_WANT_DNSSEC_VALIDATION(flags)
+ && !DNS_SEC_STATS_TEST(DNS_SEC_FLAG_AVAILABLE | \
+ DNS_SEC_FLAG_DONT_PROBE))
+ dns_sec_probe(flags); /* XXX Clobbers 'reply' */
+ return (status);
+ }
+
+ /*
+ * Extract resource records of the requested type. Pick up CNAME
+ * information just in case the requested data is not found.
+ */
+ status = dns_get_answer(orig_name, &reply, type, rrlist, fqdn,
+ cname, c_len, &maybe_secure);
+ if (DNS_WANT_DNSSEC_VALIDATION(flags)
+ && !DNS_SEC_STATS_TEST(DNS_SEC_FLAG_AVAILABLE | \
+ DNS_SEC_FLAG_DONT_PROBE))
+ dns_sec_probe(flags); /* XXX Clobbers 'reply' */
+ switch (status) {
+ default:
+ if (why)
+ vstring_sprintf(why, "Name service error for name=%s type=%s: "
+ "Malformed or unexpected name server reply",
+ name, dns_strtype(type));
+ return (status);
+ case DNS_NULLMX:
+ if (why)
+ vstring_sprintf(why, "Domain %s does not accept mail (nullMX)",
+ name);
+ SET_H_ERRNO(NO_DATA);
+ return (status);
+ case DNS_OK:
+ if (rrlist && dns_rr_filter_maps) {
+ if (dns_rr_filter_execute(rrlist) < 0) {
+ if (why)
+ vstring_sprintf(why,
+ "Error looking up name=%s type=%s: "
+ "Invalid DNS reply filter syntax",
+ name, dns_strtype(type));
+ dns_rr_free(*rrlist);
+ *rrlist = 0;
+ status = DNS_RETRY;
+ } else if (*rrlist == 0) {
+ if (why)
+ vstring_sprintf(why,
+ "Error looking up name=%s type=%s: "
+ "DNS reply filter drops all results",
+ name, dns_strtype(type));
+ status = DNS_POLICY;
+ }
+ }
+ return (status);
+ case DNS_RECURSE:
+ if (msg_verbose)
+ msg_info("dns_lookup: %s aliased to %s", name, cname);
+#if RES_USE_DNSSEC
+
+ /*
+ * Once an intermediate CNAME reply is not validated, all
+ * consequent RRs are deemed not validated, so we don't ask for
+ * further DNSSEC replies.
+ */
+ if (maybe_secure == 0)
+ flags &= ~RES_USE_DNSSEC;
+#endif
+ name = cname;
+ }
+ }
+ if (why)
+ vstring_sprintf(why, "Name server loop for %s", name);
+ msg_warn("dns_lookup: Name server loop for %s", name);
+ return (DNS_NOTFOUND);
+}
+
+/* dns_lookup_rl - DNS lookup interface with types list */
+
+int dns_lookup_rl(const char *name, unsigned flags, DNS_RR **rrlist,
+ VSTRING *fqdn, VSTRING *why, int *rcode,
+ int lflags,...)
+{
+ va_list ap;
+ unsigned type, next;
+ int status = DNS_NOTFOUND;
+ int hpref_status = INT_MIN;
+ VSTRING *hpref_rtext = 0;
+ int hpref_rcode;
+ int hpref_h_errno;
+ DNS_RR *rr;
+
+ /* Save intermediate highest-priority result. */
+#define SAVE_HPREF_STATUS() do { \
+ hpref_status = status; \
+ if (rcode) \
+ hpref_rcode = *rcode; \
+ if (why && status != DNS_OK) \
+ vstring_strcpy(hpref_rtext ? hpref_rtext : \
+ (hpref_rtext = vstring_alloc(VSTRING_LEN(why))), \
+ vstring_str(why)); \
+ hpref_h_errno = h_errno; \
+ } while (0)
+
+ /* Restore intermediate highest-priority result. */
+#define RESTORE_HPREF_STATUS() do { \
+ status = hpref_status; \
+ if (rcode) \
+ *rcode = hpref_rcode; \
+ if (why && status != DNS_OK) \
+ vstring_strcpy(why, vstring_str(hpref_rtext)); \
+ SET_H_ERRNO(hpref_h_errno); \
+ } while (0)
+
+ if (rrlist)
+ *rrlist = 0;
+ va_start(ap, lflags);
+ for (type = va_arg(ap, unsigned); type != 0; type = next) {
+ next = va_arg(ap, unsigned);
+ if (msg_verbose)
+ msg_info("lookup %s type %s flags %s",
+ name, dns_strtype(type), dns_str_resflags(flags));
+ status = dns_lookup_x(name, type, flags, rrlist ? &rr : (DNS_RR **) 0,
+ fqdn, why, rcode, lflags);
+ if (rrlist && rr)
+ *rrlist = dns_rr_append(*rrlist, rr);
+ if (status == DNS_OK) {
+ if (lflags & DNS_REQ_FLAG_STOP_OK)
+ break;
+ } else if (status == DNS_INVAL) {
+ if (lflags & DNS_REQ_FLAG_STOP_INVAL)
+ break;
+ } else if (status == DNS_POLICY) {
+ if (type == T_MX && (lflags & DNS_REQ_FLAG_STOP_MX_POLICY))
+ break;
+ } else if (status == DNS_NULLMX) {
+ if (lflags & DNS_REQ_FLAG_STOP_NULLMX)
+ break;
+ }
+ /* XXX Stop after NXDOMAIN error. */
+ if (next == 0)
+ break;
+ if (status >= hpref_status)
+ SAVE_HPREF_STATUS(); /* save last info */
+ }
+ va_end(ap);
+ if (status < hpref_status)
+ RESTORE_HPREF_STATUS(); /* else report last info */
+ if (hpref_rtext)
+ vstring_free(hpref_rtext);
+ return (status);
+}
+
+/* dns_lookup_rv - DNS lookup interface with types vector */
+
+int dns_lookup_rv(const char *name, unsigned flags, DNS_RR **rrlist,
+ VSTRING *fqdn, VSTRING *why, int *rcode,
+ int lflags, unsigned *types)
+{
+ unsigned type, next;
+ int status = DNS_NOTFOUND;
+ int hpref_status = INT_MIN;
+ VSTRING *hpref_rtext = 0;
+ int hpref_rcode;
+ int hpref_h_errno;
+ DNS_RR *rr;
+
+ if (rrlist)
+ *rrlist = 0;
+ for (type = *types++; type != 0; type = next) {
+ next = *types++;
+ if (msg_verbose)
+ msg_info("lookup %s type %s flags %s",
+ name, dns_strtype(type), dns_str_resflags(flags));
+ status = dns_lookup_x(name, type, flags, rrlist ? &rr : (DNS_RR **) 0,
+ fqdn, why, rcode, lflags);
+ if (rrlist && rr)
+ *rrlist = dns_rr_append(*rrlist, rr);
+ if (status == DNS_OK) {
+ if (lflags & DNS_REQ_FLAG_STOP_OK)
+ break;
+ } else if (status == DNS_INVAL) {
+ if (lflags & DNS_REQ_FLAG_STOP_INVAL)
+ break;
+ } else if (status == DNS_POLICY) {
+ if (type == T_MX && (lflags & DNS_REQ_FLAG_STOP_MX_POLICY))
+ break;
+ } else if (status == DNS_NULLMX) {
+ if (lflags & DNS_REQ_FLAG_STOP_NULLMX)
+ break;
+ }
+ /* XXX Stop after NXDOMAIN error. */
+ if (next == 0)
+ break;
+ if (status >= hpref_status)
+ SAVE_HPREF_STATUS(); /* save last info */
+ }
+ if (status < hpref_status)
+ RESTORE_HPREF_STATUS(); /* else report last info */
+ if (hpref_rtext)
+ vstring_free(hpref_rtext);
+ return (status);
+}