diff options
| -rw-r--r-- | NEWS | 9 | ||||
| -rw-r--r-- | resolv/Makefile | 2 | ||||
| -rw-r--r-- | resolv/res_debug.c | 1 | ||||
| -rw-r--r-- | resolv/res_init.c | 3 | ||||
| -rw-r--r-- | resolv/res_mkquery.c | 2 | ||||
| -rw-r--r-- | resolv/res_send.c | 21 | ||||
| -rw-r--r-- | resolv/resolv.h | 1 | ||||
| -rw-r--r-- | resolv/tst-resolv-res_init-skeleton.c | 10 | ||||
| -rw-r--r-- | resolv/tst-resolv-trustad.c | 200 | ||||
| -rw-r--r-- | support/resolv_test.c | 2 | ||||
| -rw-r--r-- | support/resolv_test.h | 3 |
11 files changed, 253 insertions, 1 deletions
diff --git a/NEWS b/NEWS index 4e28dc473c..12b239c1fb 100644 --- a/NEWS +++ b/NEWS @@ -40,6 +40,15 @@ Major new features: * New locale added: mnw_MM (Mon language spoken in Myanmar). +* The DNS stub resolver will optionally send the AD (authenticated data) bit + in queries if the trust-ad option is set via the options directive in + /etc/resolv.conf (or if RES_TRUSTAD is set in _res.options). In this + mode, the AD bit, as provided by the name server, is available to + applications which call res_search and related functions. In the default + mode, the AD bit is not set in queries, and it is automatically cleared in + responses, indicating a lack of DNSSEC validation. (Therefore, the name + servers and the network path to them are treated as untrusted.) + Deprecated and removed features, and other changes affecting compatibility: * The totalorder and totalordermag functions, and the corresponding diff --git a/resolv/Makefile b/resolv/Makefile index 3cb64e65f5..cd097bd315 100644 --- a/resolv/Makefile +++ b/resolv/Makefile @@ -68,6 +68,7 @@ tests += \ tst-resolv-ai_idn-latin1 \ tst-resolv-ai_idn-nolibidn2 \ tst-resolv-canonname \ + tst-resolv-trustad \ # Needs resolv_context. tests-internal += \ @@ -199,6 +200,7 @@ $(objpfx)tst-resolv-threads: \ $(libdl) $(objpfx)libresolv.so $(shared-thread-library) $(objpfx)tst-resolv-canonname: \ $(libdl) $(objpfx)libresolv.so $(shared-thread-library) +$(objpfx)tst-resolv-trustad: $(objpfx)libresolv.so $(shared-thread-library) $(objpfx)tst-ns_name: $(objpfx)libresolv.so $(objpfx)tst-ns_name.out: tst-ns_name.data diff --git a/resolv/res_debug.c b/resolv/res_debug.c index 4dac71f3c9..844269cffa 100644 --- a/resolv/res_debug.c +++ b/resolv/res_debug.c @@ -612,6 +612,7 @@ p_option(u_long option) { case RES_USE_DNSSEC: return "dnssec"; case RES_NOTLDQUERY: return "no-tld-query"; case RES_NORELOAD: return "no-reload"; + case RES_TRUSTAD: return "trust-ad"; /* XXX nonreentrant */ default: sprintf(nbuf, "?0x%lx?", (u_long)option); return (nbuf); diff --git a/resolv/res_init.c b/resolv/res_init.c index 1b8e062732..c2f2c7b7e7 100644 --- a/resolv/res_init.c +++ b/resolv/res_init.c @@ -679,7 +679,8 @@ res_setoptions (struct resolv_conf_parser *parser, const char *options) { STRnLEN ("no_tld_query"), 0, RES_NOTLDQUERY }, { STRnLEN ("no-tld-query"), 0, RES_NOTLDQUERY }, { STRnLEN ("no-reload"), 0, RES_NORELOAD }, - { STRnLEN ("use-vc"), 0, RES_USEVC } + { STRnLEN ("use-vc"), 0, RES_USEVC }, + { STRnLEN ("trust-ad"), 0, RES_TRUSTAD }, }; #define noptions (sizeof (options) / sizeof (options[0])) for (int i = 0; i < noptions; ++i) diff --git a/resolv/res_mkquery.c b/resolv/res_mkquery.c index cf0c9e229c..0d39353b41 100644 --- a/resolv/res_mkquery.c +++ b/resolv/res_mkquery.c @@ -118,6 +118,8 @@ __res_context_mkquery (struct resolv_context *ctx, int op, const char *dname, the application does multiple requests. */ hp->id = random_bits (); hp->opcode = op; + if (ctx->resp->options & RES_TRUSTAD) + hp->ad = 1; hp->rd = (ctx->resp->options & RES_RECURSE) != 0; hp->rcode = NOERROR; cp = buf + HFIXEDSZ; diff --git a/resolv/res_send.c b/resolv/res_send.c index 47bfba6747..fce810031f 100644 --- a/resolv/res_send.c +++ b/resolv/res_send.c @@ -332,6 +332,15 @@ nameserver_offset (struct __res_state *statp) } } +/* Clear the AD bit unless the trust-ad option was specified in the + resolver configuration. */ +static void +mask_ad_bit (struct resolv_context *ctx, void *buf) +{ + if (!(ctx->resp->options & RES_TRUSTAD)) + ((HEADER *) buf)->ad = 0; +} + /* int * res_queriesmatch(buf1, eom1, buf2, eom2) * is there a 1:1 mapping of (name,type,class) @@ -525,6 +534,18 @@ __res_context_send (struct resolv_context *ctx, resplen = n; + /* Mask the AD bit in both responses unless it is + marked trusted. */ + if (resplen > HFIXEDSZ) + { + if (ansp != NULL) + mask_ad_bit (ctx, *ansp); + else + mask_ad_bit (ctx, ans); + } + if (resplen2 != NULL && *resplen2 > HFIXEDSZ) + mask_ad_bit (ctx, *ansp2); + /* * If we have temporarily opened a virtual circuit, * or if we haven't been asked to keep a socket open, diff --git a/resolv/resolv.h b/resolv/resolv.h index 7a8023ae9d..a039a9e636 100644 --- a/resolv/resolv.h +++ b/resolv/resolv.h @@ -131,6 +131,7 @@ struct res_sym { #define RES_NOTLDQUERY 0x01000000 /* Do not look up unqualified name as a TLD. */ #define RES_NORELOAD 0x02000000 /* No automatic configuration reload. */ +#define RES_TRUSTAD 0x04000000 /* Request AD bit, keep it in responses. */ #define RES_DEFAULT (RES_RECURSE|RES_DEFNAMES|RES_DNSRCH) diff --git a/resolv/tst-resolv-res_init-skeleton.c b/resolv/tst-resolv-res_init-skeleton.c index d4da8b64d4..9934d2396b 100644 --- a/resolv/tst-resolv-res_init-skeleton.c +++ b/resolv/tst-resolv-res_init-skeleton.c @@ -127,6 +127,7 @@ print_resp (FILE *fp, res_state resp) "single-request-reopen"); print_option_flag (fp, &options, RES_NOTLDQUERY, "no-tld-query"); print_option_flag (fp, &options, RES_NORELOAD, "no-reload"); + print_option_flag (fp, &options, RES_TRUSTAD, "trust-ad"); fputc ('\n', fp); if (options != 0) fprintf (fp, "; error: unresolved option bits: 0x%x\n", options); @@ -711,6 +712,15 @@ struct test_case test_cases[] = "nameserver 192.0.2.1\n" "; nameserver[0]: [192.0.2.1]:53\n" }, + {.name = "trust-ad flag", + .conf = "options trust-ad\n" + "nameserver 192.0.2.1\n", + .expected = "options trust-ad\n" + "search example.com\n" + "; search[0]: example.com\n" + "nameserver 192.0.2.1\n" + "; nameserver[0]: [192.0.2.1]:53\n" + }, { NULL } }; diff --git a/resolv/tst-resolv-trustad.c b/resolv/tst-resolv-trustad.c new file mode 100644 index 0000000000..fc9ae540a2 --- /dev/null +++ b/resolv/tst-resolv-trustad.c @@ -0,0 +1,200 @@ +/* Test the behavior of the trust-ad option. + Copyright (C) 2019 Free Software Foundation, Inc. + This file is part of the GNU C Library. + + The GNU C Library is free software; you can redistribute it and/or + modify it under the terms of the GNU Lesser General Public + License as published by the Free Software Foundation; either + version 2.1 of the License, or (at your option) any later version. + + The GNU C Library 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 + Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General Public + License along with the GNU C Library; if not, see + <https://www.gnu.org/licenses/>. */ + +#include <resolv.h> +#include <stdlib.h> +#include <string.h> +#include <support/check.h> +#include <support/check_nss.h> +#include <support/resolv_test.h> +#include <support/support.h> + +/* This controls properties of the response. volatile because + __res_send is incorrectly declared as __THROW. */ +static volatile unsigned char response_number; +static volatile bool response_ad_bit; +static volatile bool query_ad_bit; + +static void +response (const struct resolv_response_context *ctx, + struct resolv_response_builder *b, + const char *qname, uint16_t qclass, uint16_t qtype) +{ + TEST_COMPARE (qclass, C_IN); + TEST_COMPARE (qtype, T_A); + TEST_COMPARE_STRING (qname, "www.example"); + + HEADER header; + memcpy (&header, ctx->query_buffer, sizeof (header)); + TEST_COMPARE (header.ad, query_ad_bit); + + struct resolv_response_flags flags = { .ad = response_ad_bit, }; + resolv_response_init (b, flags); + resolv_response_add_question (b, qname, qclass, qtype); + resolv_response_section (b, ns_s_an); + resolv_response_open_record (b, qname, qclass, T_A, 0x12345678); + char addr[4] = { 192, 0, 2, response_number }; + resolv_response_add_data (b, addr, sizeof (addr)); + resolv_response_close_record (b); +} + +static void +check_answer (const unsigned char *buffer, size_t buffer_length, + bool expected_ad) +{ + HEADER header; + TEST_VERIFY (buffer_length > sizeof (header)); + memcpy (&header, buffer, sizeof (header)); + TEST_COMPARE (0, header.aa); + TEST_COMPARE (expected_ad, header.ad); + TEST_COMPARE (0, header.opcode); + TEST_COMPARE (1, header.qr); + TEST_COMPARE (0, header.rcode); + TEST_COMPARE (1, header.rd); + TEST_COMPARE (0, header.tc); + TEST_COMPARE (1, ntohs (header.qdcount)); + TEST_COMPARE (1, ntohs (header.ancount)); + TEST_COMPARE (0, ntohs (header.nscount)); + TEST_COMPARE (0, ntohs (header.arcount)); + + char *description = xasprintf ("response=%d ad=%d", + response_number, expected_ad); + char *expected = xasprintf ("name: www.example\n" + "address: 192.0.2.%d\n", response_number); + check_dns_packet (description, buffer, buffer_length, expected); + free (expected); + free (description); +} + +static int +do_test (void) +{ + struct resolv_test *aux = resolv_test_start + ((struct resolv_redirect_config) + { + .response_callback = response, + }); + + /* By default, the resolver is not trusted, and the AD bit is + cleared. */ + + static const unsigned char hand_crafted_query[] = + { + 10, 11, /* Transaction ID. */ + 1, 0x20, /* Query with RD, AD flags. */ + 0, 1, /* One question. */ + 0, 0, 0, 0, 0, 0, /* The other sections are empty. */ + 3, 'w', 'w', 'w', 7, 'e', 'x', 'a', 'm', 'p', 'l', 'e', 0, + 0, T_A, /* A query. */ + 0, 1, /* Class IN. */ + }; + + ++response_number; + response_ad_bit = false; + + unsigned char buffer[512]; + memset (buffer, 255, sizeof (buffer)); + query_ad_bit = true; + int ret = res_send (hand_crafted_query, sizeof (hand_crafted_query), + buffer, sizeof (buffer)); + TEST_VERIFY (ret > 0); + check_answer (buffer, ret, false); + + ++response_number; + memset (buffer, 255, sizeof (buffer)); + query_ad_bit = false; + ret = res_query ("www.example", C_IN, T_A, buffer, sizeof (buffer)); + TEST_VERIFY (ret > 0); + check_answer (buffer, ret, false); + response_ad_bit = true; + + response_ad_bit = true; + + ++response_number; + query_ad_bit = true; + ret = res_send (hand_crafted_query, sizeof (hand_crafted_query), + buffer, sizeof (buffer)); + TEST_VERIFY (ret > 0); + check_answer (buffer, ret, false); + + ++response_number; + memset (buffer, 255, sizeof (buffer)); + query_ad_bit = false; + ret = res_query ("www.example", C_IN, T_A, buffer, sizeof (buffer)); + TEST_VERIFY (ret > 0); + check_answer (buffer, ret, false); + + /* No AD bit set in generated queries. */ + memset (buffer, 255, sizeof (buffer)); + ret = res_mkquery (QUERY, "www.example", C_IN, T_A, + (const unsigned char *) "", 0, NULL, + buffer, sizeof (buffer)); + HEADER header; + memcpy (&header, buffer, sizeof (header)); + TEST_VERIFY (!header.ad); + + /* With RES_TRUSTAD, the AD bit is passed through if it set in the + response. It is also included in queries. */ + + _res.options |= RES_TRUSTAD; + query_ad_bit = true; + + response_ad_bit = false; + + ++response_number; + memset (buffer, 255, sizeof (buffer)); + ret = res_send (hand_crafted_query, sizeof (hand_crafted_query), + buffer, sizeof (buffer)); + TEST_VERIFY (ret > 0); + check_answer (buffer, ret, false); + + ++response_number; + memset (buffer, 255, sizeof (buffer)); + ret = res_query ("www.example", C_IN, T_A, buffer, sizeof (buffer)); + TEST_VERIFY (ret > 0); + check_answer (buffer, ret, false); + + response_ad_bit = true; + + ++response_number; + memset (buffer, 0, sizeof (buffer)); + ret = res_send (hand_crafted_query, sizeof (hand_crafted_query), + buffer, sizeof (buffer)); + TEST_VERIFY (ret > 0); + check_answer (buffer, ret, true); + + ++response_number; + memset (buffer, 0, sizeof (buffer)); + ret = res_query ("www.example", C_IN, T_A, buffer, sizeof (buffer)); + TEST_VERIFY (ret > 0); + check_answer (buffer, ret, true); + + /* AD bit set in generated queries. */ + memset (buffer, 0, sizeof (buffer)); + ret = res_mkquery (QUERY, "www.example", C_IN, T_A, + (const unsigned char *) "", 0, NULL, + buffer, sizeof (buffer)); + memcpy (&header, buffer, sizeof (header)); + TEST_VERIFY (header.ad); + + resolv_test_end (aux); + + return 0; +} + +#include <support/test-driver.c> diff --git a/support/resolv_test.c b/support/resolv_test.c index aeca519ee3..b1c745dc8c 100644 --- a/support/resolv_test.c +++ b/support/resolv_test.c @@ -182,6 +182,8 @@ resolv_response_init (struct resolv_response_builder *b, if (flags.tc) b->buffer[2] |= 0x02; b->buffer[3] = 0x80 | flags.rcode; /* Always set RA. */ + if (flags.ad) + b->buffer[3] |= 0x20; /* Fill in the initial section count values. */ b->buffer[4] = flags.qdcount >> 8; diff --git a/support/resolv_test.h b/support/resolv_test.h index e36e3e3ae0..02a11bd712 100644 --- a/support/resolv_test.h +++ b/support/resolv_test.h @@ -134,6 +134,9 @@ struct resolv_response_flags /* If true, the TC (truncation) flag will be set. */ bool tc; + /* If true, the AD (authenticated data) flag will be set. */ + bool ad; + /* Initial section count values. Can be used to artificially increase the counts, for malformed packet testing.*/ unsigned short qdcount; |