diff options
| -rw-r--r-- | ChangeLog | 11 | ||||
| -rw-r--r-- | NEWS | 4 | ||||
| -rw-r--r-- | resolv/Makefile | 4 | ||||
| -rw-r--r-- | resolv/res_send.c | 100 | ||||
| -rw-r--r-- | resolv/tst-resolv-rotate.c | 263 |
5 files changed, 354 insertions, 28 deletions
@@ -1,3 +1,14 @@ +2017-06-30 Florian Weimer <fweimer@redhat.com> + + [BZ #19570] + * resolv/res_send.c (nameserver_offset): New function. + (__libc_res_nsend): Use it to implement RES_ROTATE. + (get_nsaddr): Add assert with name server + range check. + * resolv/Makefile (xtests): Add tst-resolv-rotate. + (tst-resolv-rotate): Link against libpthread. + * resolv/tst-resolv-rotate.c: New file. + 2017-06-29 Joseph Myers <joseph@codesourcery.com> [BZ #21457] @@ -230,6 +230,10 @@ Version 2.26 - Exponential and Logarithmic Function: clog10f128. +* When the “rotate” (RES_ROTATE) DNS stub resolver option is active, glibc + will now randomly pick a name server from the configuration as a starting + point. (Previously, the second name server was always used.) + Security related changes: * The DNS stub resolver limits the advertised UDP buffer size to 1200 bytes, diff --git a/resolv/Makefile b/resolv/Makefile index 8294d9481c..bab1ac24a6 100644 --- a/resolv/Makefile +++ b/resolv/Makefile @@ -69,6 +69,9 @@ tests-internal += tst-inet_pton # This test sends millions of packets and is rather slow. xtests += tst-resolv-qtypes + +# This test has dropped packet tests and runs for a long time. +xtests += tst-resolv-rotate endif extra-libs-others = $(extra-libs) libresolv-routines := res_comp res_debug \ @@ -148,6 +151,7 @@ $(objpfx)tst-resolv-res_init: $(libdl) $(objpfx)libresolv.so $(objpfx)tst-resolv-res_init-thread: $(libdl) $(objpfx)libresolv.so \ $(shared-thread-library) $(objpfx)tst-resolv-qtypes: $(objpfx)libresolv.so $(shared-thread-library) +$(objpfx)tst-resolv-rotate: $(objpfx)libresolv.so $(shared-thread-library) $(objpfx)tst-resolv-search: $(objpfx)libresolv.so $(shared-thread-library) $(objpfx)tst-resolv-canonname: \ $(libdl) $(objpfx)libresolv.so $(shared-thread-library) diff --git a/resolv/res_send.c b/resolv/res_send.c index b7b8ecdfc4..a1104b3131 100644 --- a/resolv/res_send.c +++ b/resolv/res_send.c @@ -109,6 +109,7 @@ #include <unistd.h> #include <kernel-features.h> #include <libc-diag.h> +#include <hp-timing.h> #if PACKETSZ > 65536 #define MAXPACKET PACKETSZ @@ -188,7 +189,7 @@ evNowTime(struct timespec *res) { /* Forward. */ -static struct sockaddr *get_nsaddr (res_state, int); +static struct sockaddr *get_nsaddr (res_state, unsigned int); static int send_vc(res_state, const u_char *, int, const u_char *, int, u_char **, int *, int *, int, u_char **, @@ -291,6 +292,62 @@ res_nameinquery(const char *name, int type, int class, } libresolv_hidden_def (res_nameinquery) +/* Returns a shift value for the name server index. Used to implement + RES_ROTATE. */ +static unsigned int +nameserver_offset (struct __res_state *statp) +{ + /* If we only have one name server or rotation is disabled, return + offset 0 (no rotation). */ + unsigned int nscount = statp->nscount; + if (nscount <= 1 || !(statp->options & RES_ROTATE)) + return 0; + + /* Global offset. The lowest bit indicates whether the offset has + been initialized with a random value. Use relaxed MO to access + global_offset because all we need is a sequence of roughly + sequential value. */ + static unsigned int global_offset; + unsigned int offset = atomic_fetch_add_relaxed (&global_offset, 2); + if ((offset & 1) == 0) + { + /* Initialization is required. */ +#if HP_TIMING_AVAIL + uint64_t ticks; + HP_TIMING_NOW (ticks); + offset = ticks; +#else + struct timeval tv; + __gettimeofday (&tv, NULL); + offset = ((tv.tv_sec << 8) ^ tv.tv_usec); +#endif + /* The lowest bit is the most random. Preserve it. */ + offset <<= 1; + + /* Store the new starting value. atomic_fetch_add_relaxed + returns the old value, so emulate that by storing the new + (incremented) value. Concurrent initialization with + different random values is harmless. */ + atomic_store_relaxed (&global_offset, (offset | 1) + 2); + } + + /* Remove the initialization bit. */ + offset >>= 1; + + /* Avoid the division in the most common cases. */ + switch (nscount) + { + case 2: + return offset & 1; + case 3: + return offset % 3; + case 4: + return offset & 3; + default: + return offset % nscount; + } +} + /* int * res_queriesmatch(buf1, eom1, buf2, eom2) * is there a 1:1 mapping of (name,type,class) @@ -352,7 +409,7 @@ __libc_res_nsend(res_state statp, const u_char *buf, int buflen, u_char *ans, int anssiz, u_char **ansp, u_char **ansp2, int *nansp2, int *resplen2, int *ansp2_malloced) { - int gotsomewhere, terrno, try, v_circuit, resplen, ns, n; + int gotsomewhere, terrno, try, v_circuit, resplen, n; if (statp->nscount == 0) { __set_errno (ESRCH); @@ -382,7 +439,7 @@ __libc_res_nsend(res_state statp, const u_char *buf, int buflen, if (EXT(statp).nscount != statp->nscount) needclose++; else - for (ns = 0; ns < statp->nscount; ns++) { + for (unsigned int ns = 0; ns < statp->nscount; ns++) { if (statp->nsaddr_list[ns].sin_family != 0 && !sock_eq((struct sockaddr_in6 *) &statp->nsaddr_list[ns], @@ -402,7 +459,7 @@ __libc_res_nsend(res_state statp, const u_char *buf, int buflen, * Maybe initialize our private copy of the ns_addr_list. */ if (EXT(statp).nscount == 0) { - for (ns = 0; ns < statp->nscount; ns++) { + for (unsigned int ns = 0; ns < statp->nscount; ns++) { EXT(statp).nssocks[ns] = -1; if (statp->nsaddr_list[ns].sin_family == 0) continue; @@ -420,35 +477,21 @@ __libc_res_nsend(res_state statp, const u_char *buf, int buflen, EXT(statp).nscount = statp->nscount; } - /* - * Some resolvers want to even out the load on their nameservers. - * Note that RES_BLAST overrides RES_ROTATE. - */ - if (__glibc_unlikely ((statp->options & RES_ROTATE) != 0)) { - struct sockaddr_in ina; - struct sockaddr_in6 *inp; - int lastns = statp->nscount - 1; - int fd; - - inp = EXT(statp).nsaddrs[0]; - ina = statp->nsaddr_list[0]; - fd = EXT(statp).nssocks[0]; - for (ns = 0; ns < lastns; ns++) { - EXT(statp).nsaddrs[ns] = EXT(statp).nsaddrs[ns + 1]; - statp->nsaddr_list[ns] = statp->nsaddr_list[ns + 1]; - EXT(statp).nssocks[ns] = EXT(statp).nssocks[ns + 1]; - } - EXT(statp).nsaddrs[lastns] = inp; - statp->nsaddr_list[lastns] = ina; - EXT(statp).nssocks[lastns] = fd; - } + /* Name server index offset. Used to implement + RES_ROTATE. */ + unsigned int ns_offset = nameserver_offset (statp); /* * Send request, RETRY times, or until successful. */ for (try = 0; try < statp->retry; try++) { - for (ns = 0; ns < statp->nscount; ns++) + for (unsigned ns_shift = 0; ns_shift < statp->nscount; ns_shift++) { + /* The actual name server index. This implements + RES_ROTATE. */ + unsigned int ns = ns_shift + ns_offset; + if (ns >= statp->nscount) + ns -= statp->nscount; #ifdef DEBUG char tmpbuf[40]; struct sockaddr *nsap = get_nsaddr (statp, ns); @@ -544,8 +587,9 @@ libresolv_hidden_def (res_nsend) /* Private */ static struct sockaddr * -get_nsaddr (res_state statp, int n) +get_nsaddr (res_state statp, unsigned int n) { + assert (n < statp->nscount); if (statp->nsaddr_list[n].sin_family == 0 && EXT(statp).nsaddrs[n] != NULL) /* EXT(statp).nsaddrs[n] holds an address that is larger than diff --git a/resolv/tst-resolv-rotate.c b/resolv/tst-resolv-rotate.c new file mode 100644 index 0000000000..d01b85b2fe --- /dev/null +++ b/resolv/tst-resolv-rotate.c @@ -0,0 +1,263 @@ +/* Check that RES_ROTATE works with few nameserver entries (bug 13028). + Copyright (C) 2017 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 + <http://www.gnu.org/licenses/>. */ + +#include <netdb.h> +#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/test-driver.h> + +static volatile int drop_server = -1; +static volatile unsigned int query_counts[resolv_max_test_servers]; + +static const char address_ipv4[4] = {192, 0, 2, 1}; +static const char address_ipv6[16] + = {0x20, 0x01, 0xd, 0xb8, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1}; + +static void +response (const struct resolv_response_context *ctx, + struct resolv_response_builder *b, + const char *qname, uint16_t qclass, uint16_t qtype) +{ + if (ctx->server_index == drop_server) + { + resolv_response_drop (b); + resolv_response_close (b); + return; + } + + bool force_tcp = strncmp (qname, "2.", 2) == 0; + struct resolv_response_flags flags = {.tc = force_tcp && !ctx->tcp}; + resolv_response_init (b, flags); + resolv_response_add_question (b, qname, qclass, qtype); + if (flags.tc) + return; + + TEST_VERIFY_EXIT (ctx->server_index < resolv_max_test_servers); + ++query_counts[ctx->server_index]; + + resolv_response_section (b, ns_s_an); + resolv_response_open_record (b, qname, qclass, qtype, 0); + switch (qtype) + { + case T_A: + { + char addr[sizeof (address_ipv4)]; + memcpy (addr, address_ipv4, sizeof (address_ipv4)); + addr[3] = 1 + ctx->tcp; + resolv_response_add_data (b, addr, sizeof (addr)); + } + break; + case T_AAAA: + { + char addr[sizeof (address_ipv6)]; + memcpy (addr, address_ipv6, sizeof (address_ipv6)); + addr[15] = 1 + ctx->tcp; + resolv_response_add_data (b, addr, sizeof (addr)); + } + break; + case T_PTR: + if (force_tcp) + resolv_response_add_name (b, "2.host.example"); + else + resolv_response_add_name (b, "host.example"); + break; + default: + FAIL_EXIT1 ("unexpected QTYPE: %s/%u/%u", qname, qclass, qtype); + } + resolv_response_close_record (b); +} + +static void +check_forward_1 (const char *name, int family) +{ + unsigned char lsb; + if (strncmp (name, "2.", 2) == 0) + lsb = 2; + else + lsb = 1; + + char expected_hostent_v4[200]; + snprintf (expected_hostent_v4, sizeof (expected_hostent_v4), + "name: %s\naddress: 192.0.2.%d\n", name, lsb); + char expected_hostent_v6[200]; + snprintf (expected_hostent_v6, sizeof (expected_hostent_v6), + "name: %s\naddress: 2001:db8::%d\n", name, lsb); + char expected_ai[200]; + + unsigned char address[16]; + size_t address_length; + + char *expected_hostent; + switch (family) + { + case AF_INET: + expected_hostent = expected_hostent_v4; + snprintf (expected_ai, sizeof (expected_ai), + "address: STREAM/TCP 192.0.2.%d 80\n", lsb); + TEST_VERIFY_EXIT (sizeof (address_ipv4) == sizeof (struct in_addr)); + memcpy (address, address_ipv4, sizeof (address_ipv4)); + address_length = sizeof (address_ipv4); + break; + case AF_INET6: + expected_hostent = expected_hostent_v6; + snprintf (expected_ai, sizeof (expected_ai), + "address: STREAM/TCP 2001:db8::%d 80\n", lsb); + TEST_VERIFY_EXIT (sizeof (address_ipv6) == sizeof (struct in6_addr)); + memcpy (address, address_ipv6, sizeof (address_ipv6)); + address_length = sizeof (address_ipv6); + break; + case AF_UNSPEC: + expected_hostent = NULL; + snprintf (expected_ai, sizeof (expected_ai), + "address: STREAM/TCP 192.0.2.%d 80\n" + "address: STREAM/TCP 2001:db8::%d 80\n", + lsb, lsb); + address_length = 0; + break; + default: + FAIL_EXIT1 ("unknown address family %d", family); + } + + + if (family == AF_INET) + { + struct hostent *e = gethostbyname (name); + check_hostent (name, e, expected_hostent_v4); + } + + if (family != AF_UNSPEC) + { + struct hostent *e = gethostbyname2 (name, family); + check_hostent (name, e, expected_hostent); + } + + if (address_length > 0) + { + address[address_length - 1] = lsb; + struct hostent *e = gethostbyaddr (address, address_length, family); + check_hostent (name, e, expected_hostent); + } + + struct addrinfo hints = + { + .ai_family = family, + .ai_socktype = SOCK_STREAM, + .ai_protocol = IPPROTO_TCP, + }; + struct addrinfo *ai; + int ret = getaddrinfo (name, "80", &hints, &ai); + check_addrinfo (name, ai, ret, expected_ai); + if (ret == 0) + { + for (struct addrinfo *p = ai; p != NULL; p = p->ai_next) + { + char host[200]; + ret = getnameinfo (p->ai_addr, p->ai_addrlen, + host, sizeof (host), + NULL, 0, /* service */ + 0); + if (ret != 0) + { + support_record_failure (); + printf ("error: getnameinfo: %d\n", ret); + } + else + { + if (lsb == 1) + TEST_VERIFY (strcmp (host, "host.example") == 0); + else + TEST_VERIFY (strcmp (host, "2.host.example") == 0); + } + } + freeaddrinfo (ai); + } +} + +static void +check_forward (int family) +{ + check_forward_1 ("host.example", family); + check_forward_1 ("2.host.example", family); +} + +static int +do_test (void) +{ + for (int force_tcp = 0; force_tcp < 2; ++force_tcp) + for (int nscount = 1; nscount <= 3; ++nscount) + for (int disable_server = -1; disable_server < nscount; ++disable_server) + for (drop_server = -1; drop_server < nscount; ++drop_server) + { + /* A disabled server will never receive queries and + therefore cannot drop them. */ + if (drop_server >= 0 && drop_server == disable_server) + continue; + /* No servers remaining to query, all queries are expected + to fail. */ + int broken_servers = (disable_server >= 0) + (drop_server >= 0); + if (nscount <= broken_servers) + continue; + + if (test_verbose > 0) + printf ("info: tcp=%d nscount=%d disable=%d drop=%d\n", + force_tcp, nscount, disable_server, drop_server); + struct resolv_redirect_config config = + { + .response_callback = response, + .nscount = nscount + }; + if (disable_server >= 0) + { + config.servers[disable_server].disable_udp = true; + config.servers[disable_server].disable_tcp = true; + } + + struct resolv_test *aux = resolv_test_start (config); + _res.options |= RES_ROTATE; + + /* Run a few queries to make sure that all of them + succeed. We always perform more than nscount queries, + so we cover all active servers due to RES_ROTATE. */ + for (size_t i = 0; i < resolv_max_test_servers; ++i) + query_counts[i] = 0; + check_forward (AF_INET); + check_forward (AF_INET6); + check_forward (AF_UNSPEC); + + for (int i = 0; i < nscount; ++i) + { + if (i != disable_server && i != drop_server + && query_counts[i] == 0) + { + support_record_failure (); + printf ("error: nscount=%d, but no query to server %d\n", + nscount, i); + } + } + + resolv_test_end (aux); + } + return 0; +} + +#define TIMEOUT 300 +#include <support/test-driver.c> |