From a71739cc64d1c15ac8fbca803a5ae75afa45a1aa Mon Sep 17 00:00:00 2001 From: Ralph Boehme Date: Tue, 17 May 2016 12:30:46 +0200 Subject: [PATCH 01/12] librpc/ndr: add flag LIBNDR_FLAG_NO_COMPRESSION This flag can be used to change marshalling behaviour with regard to compression. Example: DNS packets make use of so called DNS name compression which means that for identical strings in a DNS packet, the second string is replaced with a reference (an offset) to the first. Setting this flag requests to turns off the marshalling compression. This will be used in the next commit to prevent name compression in DNS TSIG records. Bug: https://bugzilla.samba.org/show_bug.cgi?id=11520 Signed-off-by: Ralph Boehme Reviewed-by: Garming Sam (cherry picked from commit df079962ef708de96e54ded13da04b6e12ac00d0) --- librpc/idl/idl_types.h | 1 + librpc/ndr/libndr.h | 3 +++ librpc/ndr/ndr_dns.c | 50 +++++++++++++++++++++++++++----------------------- 3 files changed, 31 insertions(+), 23 deletions(-) diff --git a/librpc/idl/idl_types.h b/librpc/idl/idl_types.h index 838c219..72a5d85 100644 --- a/librpc/idl/idl_types.h +++ b/librpc/idl/idl_types.h @@ -40,6 +40,7 @@ #define NDR_ALIGN2 LIBNDR_FLAG_ALIGN2 #define NDR_ALIGN4 LIBNDR_FLAG_ALIGN4 #define NDR_ALIGN8 LIBNDR_FLAG_ALIGN8 +#define NDR_NO_COMP LIBNDR_FLAG_NO_COMPRESSION /* this flag is used to force a section of IDL as little endian. It is needed for the epmapper IDL, which is defined as always being LE */ diff --git a/librpc/ndr/libndr.h b/librpc/ndr/libndr.h index c6116ed..2275f16 100644 --- a/librpc/ndr/libndr.h +++ b/librpc/ndr/libndr.h @@ -125,6 +125,9 @@ struct ndr_print { #define LIBNDR_FLAG_STR_RAW8 (1<<13) #define LIBNDR_STRING_FLAGS (0x7FFC) +/* Disable string token compression */ +#define LIBNDR_FLAG_NO_COMPRESSION (1<<15) + /* * don't debug NDR_ERR_BUFSIZE failures, * as the available buffer might be incomplete. diff --git a/librpc/ndr/ndr_dns.c b/librpc/ndr/ndr_dns.c index ab0c83a..fcc1315 100644 --- a/librpc/ndr/ndr_dns.c +++ b/librpc/ndr/ndr_dns.c @@ -169,28 +169,30 @@ _PUBLIC_ enum ndr_err_code ndr_push_dns_string(struct ndr_push *ndr, size_t complen; uint32_t offset; - /* see if we have pushed the remaining string already, - * if so we use a label pointer to this string - */ - ndr_err = ndr_token_retrieve_cmp_fn(&ndr->dns_string_list, s, - &offset, - (comparison_fn_t)strcmp, - false); - if (NDR_ERR_CODE_IS_SUCCESS(ndr_err)) { - uint8_t b[2]; - - if (offset > 0x3FFF) { - return ndr_push_error(ndr, NDR_ERR_STRING, - "offset for dns string " \ - "label pointer " \ - "%u[%08X] > 0x00003FFF", - offset, offset); + if (!(ndr->flags & LIBNDR_FLAG_NO_COMPRESSION)) { + /* see if we have pushed the remaining string already, + * if so we use a label pointer to this string + */ + ndr_err = ndr_token_retrieve_cmp_fn(&ndr->dns_string_list, s, + &offset, + (comparison_fn_t)strcmp, + false); + if (NDR_ERR_CODE_IS_SUCCESS(ndr_err)) { + uint8_t b[2]; + + if (offset > 0x3FFF) { + return ndr_push_error(ndr, NDR_ERR_STRING, + "offset for dns string " \ + "label pointer " \ + "%u[%08X] > 0x00003FFF", + offset, offset); + } + + b[0] = 0xC0 | (offset>>8); + b[1] = (offset & 0xFF); + + return ndr_push_bytes(ndr, b, 2); } - - b[0] = 0xC0 | (offset>>8); - b[1] = (offset & 0xFF); - - return ndr_push_bytes(ndr, b, 2); } complen = strcspn(s, "."); @@ -213,8 +215,10 @@ _PUBLIC_ enum ndr_err_code ndr_push_dns_string(struct ndr_push *ndr, /* remember the current componemt + the rest of the string * so it can be reused later */ - NDR_CHECK(ndr_token_store(ndr, &ndr->dns_string_list, s, - ndr->offset)); + if (!(ndr->flags & LIBNDR_FLAG_NO_COMPRESSION)) { + NDR_CHECK(ndr_token_store(ndr, &ndr->dns_string_list, s, + ndr->offset)); + } /* push just this component into the blob */ NDR_CHECK(ndr_push_bytes(ndr, (const uint8_t *)compname, -- 2.5.0 From 12e951683c7216d824761132e24049fe9f7e53f8 Mon Sep 17 00:00:00 2001 From: Ralph Boehme Date: Tue, 17 May 2016 14:34:52 +0200 Subject: [PATCH 02/12] librpc/dns: don't compress strings in TKEY and TSIG responses Certain DNS clients fail TSIG record MAC validation if the TSIG record contains compressed strings. Windows DNS server behaviour seems to be to not send compressed names in TKEY and TSIG records. This patch ensures we conform to this behaviour. Bug: https://bugzilla.samba.org/show_bug.cgi?id=11520 Signed-off-by: Ralph Boehme Reviewed-by: Garming Sam (cherry picked from commit a51f9989564c28aeece50b56a59e9bb60d41340b) --- librpc/idl/dns.idl | 6 +++--- librpc/ndr/ndr_dns.c | 13 +++++++++++++ 2 files changed, 16 insertions(+), 3 deletions(-) diff --git a/librpc/idl/dns.idl b/librpc/idl/dns.idl index 5435fcf..13dd53b 100644 --- a/librpc/idl/dns.idl +++ b/librpc/idl/dns.idl @@ -179,7 +179,7 @@ interface dns uint8 option_data[option_length]; } dns_opt_record; - typedef [public] struct { + typedef [flag(NDR_NO_COMP),public] struct { dns_string algorithm; uint32 inception; uint32 expiration; @@ -191,7 +191,7 @@ interface dns uint8 other_data[other_size]; } dns_tkey_record; - typedef [public] struct { + typedef [flag(NDR_NO_COMP),public] struct { dns_string algorithm_name; uint16 time_prefix; /* 0 until February 2106*/ uint32 time; @@ -204,7 +204,7 @@ interface dns uint8 other_data[other_size]; } dns_tsig_record; - typedef [flag(NDR_NOALIGN|NDR_BIG_ENDIAN|NDR_PAHEX),public] struct { + typedef [flag(NDR_NO_COMP|NDR_NOALIGN|NDR_BIG_ENDIAN|NDR_PAHEX),public] struct { dns_string name; dns_qclass rr_class; uint32 ttl; diff --git a/librpc/ndr/ndr_dns.c b/librpc/ndr/ndr_dns.c index fcc1315..7e6286a 100644 --- a/librpc/ndr/ndr_dns.c +++ b/librpc/ndr/ndr_dns.c @@ -268,8 +268,21 @@ _PUBLIC_ enum ndr_err_code ndr_push_dns_res_rec(struct ndr_push *ndr, ndr_set_flags(&ndr->flags, LIBNDR_PRINT_ARRAY_HEX | LIBNDR_FLAG_NOALIGN); if (ndr_flags & NDR_SCALARS) { + uint32_t _flags_save_name = ndr->flags; + NDR_CHECK(ndr_push_align(ndr, 4)); + + switch (r->rr_type) { + case DNS_QTYPE_TKEY: + case DNS_QTYPE_TSIG: + ndr_set_flags(&ndr->flags, LIBNDR_FLAG_NO_COMPRESSION); + break; + default: + break; + } NDR_CHECK(ndr_push_dns_string(ndr, NDR_SCALARS, r->name)); + ndr->flags = _flags_save_name; + NDR_CHECK(ndr_push_dns_qtype(ndr, NDR_SCALARS, r->rr_type)); NDR_CHECK(ndr_push_dns_qclass(ndr, NDR_SCALARS, r->rr_class)); NDR_CHECK(ndr_push_uint32(ndr, NDR_SCALARS, r->ttl)); -- 2.5.0 From a4c1b732017751d6c9805e4dbed4be393480a108 Mon Sep 17 00:00:00 2001 From: Ralph Boehme Date: Sat, 14 May 2016 19:08:51 +0200 Subject: [PATCH 03/12] librpc/dns: remove original_id from dns_fake_tsig_rec Cf RFC2845, 3.4.2. "TSIG Variables", the request id (original_id) is not used in the MAC calculation. This also explains the mysterious 2 bytes padding. Bug: https://bugzilla.samba.org/show_bug.cgi?id=11520 Signed-off-by: Ralph Boehme Reviewed-by: Garming Sam (cherry picked from commit bea4aec521576576b8dc55065f11c6c5025d9c4f) --- librpc/idl/dns.idl | 1 - source4/dns_server/dns_crypto.c | 3 --- 2 files changed, 4 deletions(-) diff --git a/librpc/idl/dns.idl b/librpc/idl/dns.idl index 13dd53b..aebb106 100644 --- a/librpc/idl/dns.idl +++ b/librpc/idl/dns.idl @@ -212,7 +212,6 @@ interface dns uint16 time_prefix; /* 0 until February 2106*/ uint32 time; uint16 fudge; - uint16 original_id; uint16 error; uint16 other_size; uint8 other_data[other_size]; diff --git a/source4/dns_server/dns_crypto.c b/source4/dns_server/dns_crypto.c index 3f199de..502887f 100644 --- a/source4/dns_server/dns_crypto.c +++ b/source4/dns_server/dns_crypto.c @@ -207,9 +207,6 @@ WERROR dns_verify_tsig(struct dns_server *dns, return WERR_NOMEM; } - /*FIXME: Why is there too much padding? */ - buffer_len -= 2; - /* Now we also need to count down the additional record counter */ arcount = RSVAL(buffer, 10); RSSVAL(buffer, 10, arcount-1); -- 2.5.0 From 21627b833635f7233317ca1c721e5dfbaf4685f1 Mon Sep 17 00:00:00 2001 From: Ralph Boehme Date: Mon, 23 May 2016 19:09:05 +0200 Subject: [PATCH 04/12] s4/dns_server: include request MAC in TSIG response MAC calculation According to RFC 2845 "4.2 TSIG on Answers", when the request is signed, the request MAC must be included in the response MAC calculation. Bug: https://bugzilla.samba.org/show_bug.cgi?id=11520 Signed-off-by: Ralph Boehme Reviewed-by: Garming Sam (cherry picked from commit 8ed125e8bb13904638f8506e860c169f788e8ee9) --- source4/dns_server/dns_crypto.c | 37 ++++++++++++++++++++++++++++++++++--- 1 file changed, 34 insertions(+), 3 deletions(-) diff --git a/source4/dns_server/dns_crypto.c b/source4/dns_server/dns_crypto.c index 502887f..a8d76a4 100644 --- a/source4/dns_server/dns_crypto.c +++ b/source4/dns_server/dns_crypto.c @@ -243,12 +243,14 @@ WERROR dns_sign_tsig(struct dns_server *dns, time_t current_time = time(NULL); DATA_BLOB packet_blob, tsig_blob, sig; uint8_t *buffer = NULL; + uint8_t *p = NULL; size_t buffer_len = 0; struct dns_server_tkey * tkey = NULL; struct dns_res_rec *tsig = talloc_zero(mem_ctx, struct dns_res_rec); struct dns_fake_tsig_rec *check_rec = talloc_zero(mem_ctx, struct dns_fake_tsig_rec); + size_t mac_size = 0; if (tsig == NULL) { return WERR_NOMEM; @@ -298,15 +300,44 @@ WERROR dns_sign_tsig(struct dns_server *dns, return DNS_ERR(SERVER_FAILURE); } - buffer_len = packet_blob.length + tsig_blob.length; + if (state->tsig != NULL) { + mac_size = state->tsig->rdata.tsig_record.mac_size; + } + + buffer_len = mac_size; + + buffer_len += packet_blob.length; + if (buffer_len < packet_blob.length) { + return WERR_INVALID_PARAM; + } + buffer_len += tsig_blob.length; + if (buffer_len < tsig_blob.length) { + return WERR_INVALID_PARAM; + } + buffer = talloc_zero_array(mem_ctx, uint8_t, buffer_len); if (buffer == NULL) { return WERR_NOMEM; } - memcpy(buffer, packet_blob.data, packet_blob.length); - memcpy(buffer+packet_blob.length, tsig_blob.data, tsig_blob.length); + p = buffer; + + /* + * RFC 2845 "4.2 TSIG on Answers", how to lay out the buffer + * that we're going to sign: + * 1. MAC of request (if present) + * 2. Outgoing packet + * 3. TSIG record + */ + if (mac_size > 0) { + memcpy(p, state->tsig->rdata.tsig_record.mac, mac_size); + p += mac_size; + } + + memcpy(p, packet_blob.data, packet_blob.length); + p += packet_blob.length; + memcpy(p, tsig_blob.data, tsig_blob.length); status = gensec_sign_packet(tkey->gensec, mem_ctx, buffer, buffer_len, buffer, buffer_len, &sig); -- 2.5.0 From 7e1ba3a6fe5acb65d729ea4901cbeecf4cc06843 Mon Sep 17 00:00:00 2001 From: Ralph Boehme Date: Mon, 30 May 2016 16:03:33 +0200 Subject: [PATCH 05/12] s4/dns_server: split out function that does the MAC computation Split out function that does the MAC computation from the TSIG record creating function. This will later simplify the code when creating error responsed to TSIG requests with bad MACs where we have to add the TSIG record with an empty MAC. No functional behaviour change besides hard coding "gss-tsig" algorithm name: later when sending a TSIG error response for a TKEY request with a bad keyname, we won't have a tkey to fetch the algorithm name from. Bug: https://bugzilla.samba.org/show_bug.cgi?id=11520 Signed-off-by: Ralph Boehme Reviewed-by: Garming Sam (cherry picked from commit 830316ce84c6f4994841a1c68e60d90225a2963d) --- source4/dns_server/dns_crypto.c | 75 ++++++++++++++++++++++++++--------------- 1 file changed, 48 insertions(+), 27 deletions(-) diff --git a/source4/dns_server/dns_crypto.c b/source4/dns_server/dns_crypto.c index a8d76a4..a49b23c 100644 --- a/source4/dns_server/dns_crypto.c +++ b/source4/dns_server/dns_crypto.c @@ -231,41 +231,27 @@ WERROR dns_verify_tsig(struct dns_server *dns, return WERR_OK; } -WERROR dns_sign_tsig(struct dns_server *dns, - TALLOC_CTX *mem_ctx, - struct dns_request_state *state, - struct dns_name_packet *packet, - uint16_t error) +static WERROR dns_tsig_compute_mac(TALLOC_CTX *mem_ctx, + struct dns_request_state *state, + struct dns_name_packet *packet, + struct dns_server_tkey *tkey, + time_t current_time, + DATA_BLOB *_psig) { - WERROR werror; NTSTATUS status; enum ndr_err_code ndr_err; - time_t current_time = time(NULL); DATA_BLOB packet_blob, tsig_blob, sig; uint8_t *buffer = NULL; uint8_t *p = NULL; size_t buffer_len = 0; - struct dns_server_tkey * tkey = NULL; - struct dns_res_rec *tsig = talloc_zero(mem_ctx, struct dns_res_rec); - struct dns_fake_tsig_rec *check_rec = talloc_zero(mem_ctx, struct dns_fake_tsig_rec); size_t mac_size = 0; - if (tsig == NULL) { - return WERR_NOMEM; - } - if (check_rec == NULL) { return WERR_NOMEM; } - tkey = dns_find_tkey(dns->tkeys, state->key_name); - if (tkey == NULL) { - /* FIXME: read up on what to do when we can't find a key */ - return WERR_OK; - } - /* first build and verify check packet */ check_rec->name = talloc_strdup(check_rec, tkey->name); if (check_rec->name == NULL) { @@ -345,19 +331,54 @@ WERROR dns_sign_tsig(struct dns_server *dns, return ntstatus_to_werror(status); } - tsig->name = talloc_strdup(tsig, check_rec->name); + *_psig = sig; + return WERR_OK; +} + +WERROR dns_sign_tsig(struct dns_server *dns, + TALLOC_CTX *mem_ctx, + struct dns_request_state *state, + struct dns_name_packet *packet, + uint16_t error) +{ + WERROR werror; + time_t current_time = time(NULL); + struct dns_server_tkey *tkey = NULL; + struct dns_res_rec *tsig = NULL; + DATA_BLOB sig = (DATA_BLOB) { + .data = NULL, + .length = 0 + }; + + tsig = talloc_zero(mem_ctx, struct dns_res_rec); + if (tsig == NULL) { + return WERR_NOMEM; + } + + tkey = dns_find_tkey(dns->tkeys, state->key_name); + if (tkey == NULL) { + /* FIXME: read up on what to do when we can't find a key */ + return WERR_OK; + } + + werror = dns_tsig_compute_mac(mem_ctx, state, packet, + tkey, current_time, &sig); + if (!W_ERROR_IS_OK(werror)) { + return werror; + } + + tsig->name = talloc_strdup(tsig, state->key_name); if (tsig->name == NULL) { return WERR_NOMEM; } - tsig->rr_class = check_rec->rr_class; + tsig->rr_class = DNS_QCLASS_ANY; tsig->rr_type = DNS_QTYPE_TSIG; tsig->ttl = 0; tsig->length = UINT16_MAX; - tsig->rdata.tsig_record.algorithm_name = talloc_strdup(tsig, - check_rec->algorithm_name); - tsig->rdata.tsig_record.time_prefix = check_rec->time_prefix; - tsig->rdata.tsig_record.time = check_rec->time; - tsig->rdata.tsig_record.fudge = check_rec->fudge; + tsig->rdata.tsig_record.algorithm_name = talloc_strdup(tsig, "gss-tsig"); + tsig->rdata.tsig_record.time_prefix = 0; + tsig->rdata.tsig_record.time = current_time; + tsig->rdata.tsig_record.fudge = 300; tsig->rdata.tsig_record.error = state->tsig_error; tsig->rdata.tsig_record.original_id = packet->id; tsig->rdata.tsig_record.other_size = 0; -- 2.5.0 From e984a3ea9fc5fb20cfa725b8964c7cba91f71e03 Mon Sep 17 00:00:00 2001 From: Ralph Boehme Date: Mon, 30 May 2016 16:56:21 +0200 Subject: [PATCH 06/12] s4/dns_server: not finding the key here is a fatal error Bug: https://bugzilla.samba.org/show_bug.cgi?id=11520 Signed-off-by: Ralph Boehme Reviewed-by: Garming Sam (cherry picked from commit c1fca8fa398461fb0a67dbb0e181c71b83a32b62) --- source4/dns_server/dns_crypto.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/source4/dns_server/dns_crypto.c b/source4/dns_server/dns_crypto.c index a49b23c..1590814 100644 --- a/source4/dns_server/dns_crypto.c +++ b/source4/dns_server/dns_crypto.c @@ -357,8 +357,7 @@ WERROR dns_sign_tsig(struct dns_server *dns, tkey = dns_find_tkey(dns->tkeys, state->key_name); if (tkey == NULL) { - /* FIXME: read up on what to do when we can't find a key */ - return WERR_OK; + return DNS_ERR(SERVER_FAILURE); } werror = dns_tsig_compute_mac(mem_ctx, state, packet, -- 2.5.0 From 5b3ac99b7ddf7983de40ee9399168b0233173ba4 Mon Sep 17 00:00:00 2001 From: Ralph Boehme Date: Mon, 30 May 2016 16:37:32 +0200 Subject: [PATCH 07/12] s4/dns_server: ensure we store the key name in error code paths We need the TKEY name when adding TSIG records to error responses. Bug: https://bugzilla.samba.org/show_bug.cgi?id=11520 Signed-off-by: Ralph Boehme Reviewed-by: Garming Sam (cherry picked from commit 77c5bfdce417a36b523e9901668fbff0d42f1ed2) --- source4/dns_server/dns_crypto.c | 21 +++++++++++++++++---- 1 file changed, 17 insertions(+), 4 deletions(-) diff --git a/source4/dns_server/dns_crypto.c b/source4/dns_server/dns_crypto.c index 1590814..47b75fc 100644 --- a/source4/dns_server/dns_crypto.c +++ b/source4/dns_server/dns_crypto.c @@ -146,10 +146,27 @@ WERROR dns_verify_tsig(struct dns_server *dns, tkey = dns_find_tkey(dns->tkeys, state->tsig->name); if (tkey == NULL) { + /* + * We must save the name for use in the TSIG error + * response and have no choice here but to save the + * keyname from the TSIG request. + */ + state->key_name = talloc_strdup(state->mem_ctx, + state->tsig->name); state->tsig_error = DNS_RCODE_BADKEY; return DNS_ERR(NOTAUTH); } + /* + * Remember the keyname that found an existing tkey, used + * later to fetch the key with dns_find_tkey() when signing + * and adding a TSIG record with MAC. + */ + state->key_name = talloc_strdup(state->mem_ctx, tkey->name); + if (state->key_name == NULL) { + return WERR_NOMEM; + } + /* FIXME: check TSIG here */ if (check_rec == NULL) { return WERR_NOMEM; @@ -223,10 +240,6 @@ WERROR dns_verify_tsig(struct dns_server *dns, } state->authenticated = true; - state->key_name = talloc_strdup(state->mem_ctx, tkey->name); - if (state->key_name == NULL) { - return WERR_NOMEM; - } return WERR_OK; } -- 2.5.0 From f53ac729d4734f01768ffbac03f36aa53ebdc95f Mon Sep 17 00:00:00 2001 From: Ralph Boehme Date: Mon, 30 May 2016 16:40:45 +0200 Subject: [PATCH 08/12] s4/dns_server: error codes for failing MAC verification in TSIG requests According to RFC 2845 "4.5.3. MAC check and error handling" we must return NOTAUTH and DNS_RCODE_BADSIG when MAC verification fails. Bug: https://bugzilla.samba.org/show_bug.cgi?id=11520 Signed-off-by: Ralph Boehme Reviewed-by: Garming Sam (cherry picked from commit 8b4a2dcf38e9f38bb99bd1daa5e0d5da176a1e15) --- source4/dns_server/dns_crypto.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/source4/dns_server/dns_crypto.c b/source4/dns_server/dns_crypto.c index 47b75fc..21d30d7 100644 --- a/source4/dns_server/dns_crypto.c +++ b/source4/dns_server/dns_crypto.c @@ -231,7 +231,8 @@ WERROR dns_verify_tsig(struct dns_server *dns, status = gensec_check_packet(tkey->gensec, buffer, buffer_len, buffer, buffer_len, &sig); if (NT_STATUS_EQUAL(NT_STATUS_ACCESS_DENIED, status)) { - return DNS_ERR(BADKEY); + state->tsig_error = DNS_RCODE_BADSIG; + return DNS_ERR(NOTAUTH); } if (!NT_STATUS_IS_OK(status)) { -- 2.5.0 From a6f86e88832a2f27630178b484433a43534eb0d3 Mon Sep 17 00:00:00 2001 From: Ralph Boehme Date: Mon, 30 May 2016 17:25:56 +0200 Subject: [PATCH 09/12] s4/dns_server: don't compute TSIG MAC in TSIG error records See RFC 2845 "4.3. TSIG on TSIG Error returns". Bug: https://bugzilla.samba.org/show_bug.cgi?id=11520 Signed-off-by: Ralph Boehme Reviewed-by: Garming Sam (cherry picked from commit 8f46bf2102a91c5f2d5beee530ece0387fdfbb0c) --- source4/dns_server/dns_crypto.c | 27 +++++++++++++++------------ 1 file changed, 15 insertions(+), 12 deletions(-) diff --git a/source4/dns_server/dns_crypto.c b/source4/dns_server/dns_crypto.c index 21d30d7..6079357 100644 --- a/source4/dns_server/dns_crypto.c +++ b/source4/dns_server/dns_crypto.c @@ -357,7 +357,6 @@ WERROR dns_sign_tsig(struct dns_server *dns, { WERROR werror; time_t current_time = time(NULL); - struct dns_server_tkey *tkey = NULL; struct dns_res_rec *tsig = NULL; DATA_BLOB sig = (DATA_BLOB) { .data = NULL, @@ -369,15 +368,18 @@ WERROR dns_sign_tsig(struct dns_server *dns, return WERR_NOMEM; } - tkey = dns_find_tkey(dns->tkeys, state->key_name); - if (tkey == NULL) { - return DNS_ERR(SERVER_FAILURE); - } + if (state->tsig_error == DNS_RCODE_OK) { + struct dns_server_tkey *tkey = dns_find_tkey( + dns->tkeys, state->key_name); + if (tkey == NULL) { + return DNS_ERR(SERVER_FAILURE); + } - werror = dns_tsig_compute_mac(mem_ctx, state, packet, - tkey, current_time, &sig); - if (!W_ERROR_IS_OK(werror)) { - return werror; + werror = dns_tsig_compute_mac(mem_ctx, state, packet, + tkey, current_time, &sig); + if (!W_ERROR_IS_OK(werror)) { + return werror; + } } tsig->name = talloc_strdup(tsig, state->key_name); @@ -396,9 +398,10 @@ WERROR dns_sign_tsig(struct dns_server *dns, tsig->rdata.tsig_record.original_id = packet->id; tsig->rdata.tsig_record.other_size = 0; tsig->rdata.tsig_record.other_data = NULL; - tsig->rdata.tsig_record.mac_size = sig.length; - tsig->rdata.tsig_record.mac = talloc_memdup(tsig, sig.data, sig.length); - + if (sig.length > 0) { + tsig->rdata.tsig_record.mac_size = sig.length; + tsig->rdata.tsig_record.mac = talloc_memdup(tsig, sig.data, sig.length); + } if (packet->arcount == 0) { packet->additional = talloc_zero(mem_ctx, struct dns_res_rec); -- 2.5.0 From d4127547320faeb5af26cd01b89f9c2cd04c323a Mon Sep 17 00:00:00 2001 From: Ralph Boehme Date: Mon, 30 May 2016 16:42:14 +0200 Subject: [PATCH 10/12] s4/dns_server: prepare sending correct error responses for dns_verify_tsig() errors Call dns_verify_tsig() after updating state.flags and assign and use out_packet for dns_verify_tsig(). We will need the updated flags when sending TSIG error responses when TSIG request MAC verification fails and dns_verify_tsig() uses the passed in packet as response, so we have to make sure we copy in_packet to out_packet before calling out and pass out_packet. Bug: https://bugzilla.samba.org/show_bug.cgi?id=11520 Signed-off-by: Ralph Boehme Reviewed-by: Garming Sam (cherry picked from commit ba683d459e1b1550d0a4de3a0f576c857ee595c8) --- source4/dns_server/dns_server.c | 15 +++++++-------- 1 file changed, 7 insertions(+), 8 deletions(-) diff --git a/source4/dns_server/dns_server.c b/source4/dns_server/dns_server.c index a2dc151..2bc2174 100644 --- a/source4/dns_server/dns_server.c +++ b/source4/dns_server/dns_server.c @@ -152,14 +152,6 @@ static struct tevent_req *dns_process_send(TALLOC_CTX *mem_ctx, NDR_PRINT_DEBUGC(DBGC_DNS, dns_name_packet, &state->in_packet); } - ret = dns_verify_tsig(dns, state, &state->state, &state->in_packet, in); - if (!W_ERROR_IS_OK(ret)) { - DEBUG(1, ("Failed to verify TSIG!\n")); - state->dns_err = werr_to_dns_err(ret); - tevent_req_done(req); - return tevent_req_post(req, ev); - } - if (state->in_packet.operation & DNS_FLAG_REPLY) { DEBUG(1, ("Won't reply to replies.\n")); tevent_req_werror(req, WERR_INVALID_PARAM); @@ -176,6 +168,13 @@ static struct tevent_req *dns_process_send(TALLOC_CTX *mem_ctx, state->out_packet = state->in_packet; + ret = dns_verify_tsig(dns, state, &state->state, &state->out_packet, in); + if (!W_ERROR_IS_OK(ret)) { + state->dns_err = werr_to_dns_err(ret); + tevent_req_done(req); + return tevent_req_post(req, ev); + } + switch (state->in_packet.operation & DNS_OPCODE) { case DNS_OPCODE_QUERY: subreq = dns_server_process_query_send( -- 2.5.0 From a6795bee234ab70708f194436094470708fec2f3 Mon Sep 17 00:00:00 2001 From: Ralph Boehme Date: Mon, 30 May 2016 16:44:00 +0200 Subject: [PATCH 11/12] s4/dns_server: enable sending of TSIG error records This final patch enables sending TSIG error records by adding DNS_RCODE_NOTAUTH to the set of error conditions that are allowed to trigger sending a full generated response. See RFC 2845 "4.5.1. KEY check and error handling" and "4.5.3. MAC check and error handling". Bug: https://bugzilla.samba.org/show_bug.cgi?id=11520 Signed-off-by: Ralph Boehme Reviewed-by: Garming Sam (cherry picked from commit 88700e7d890c017e2d360fe4385e196f4016db4a) --- source4/dns_server/dns_server.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/source4/dns_server/dns_server.c b/source4/dns_server/dns_server.c index 2bc2174..ba7df87 100644 --- a/source4/dns_server/dns_server.c +++ b/source4/dns_server/dns_server.c @@ -235,7 +235,9 @@ static WERROR dns_process_recv(struct tevent_req *req, TALLOC_CTX *mem_ctx, return ret; } if ((state->dns_err != DNS_RCODE_OK) && - (state->dns_err != DNS_RCODE_NXDOMAIN)) { + (state->dns_err != DNS_RCODE_NXDOMAIN) && + (state->dns_err != DNS_RCODE_NOTAUTH)) + { goto drop; } if (state->dns_err != DNS_RCODE_OK) { -- 2.5.0 From 9240ca84e9417faa2b79f7f2243ebc92c94d7808 Mon Sep 17 00:00:00 2001 From: Ralph Boehme Date: Wed, 4 May 2016 14:26:16 +0200 Subject: [PATCH 12/12] selftest: add test for DNS updates with TKEY/TSIG Bug: https://bugzilla.samba.org/show_bug.cgi?id=11520 Signed-off-by: Ralph Boehme Reviewed-by: Garming Sam Autobuild-User(master): Garming Sam Autobuild-Date(master): Thu Jun 16 04:07:41 CEST 2016 on sn-devel-144 (backported from commit 721b21bb801735fe9179502ff34e7a707176dbd8) --- python/samba/tests/dns_tkey.py | 487 +++++++++++++++++++++++++++++++++++++++++ source4/selftest/tests.py | 2 + 2 files changed, 489 insertions(+) create mode 100644 python/samba/tests/dns_tkey.py diff --git a/python/samba/tests/dns_tkey.py b/python/samba/tests/dns_tkey.py new file mode 100644 index 0000000..e47a647 --- /dev/null +++ b/python/samba/tests/dns_tkey.py @@ -0,0 +1,487 @@ +# Unix SMB/CIFS implementation. +# Copyright (C) Kai Blin 2011 +# Copyright (C) Ralph Boehme 2016 +# +# This program is free software; you can redistribute it and/or modify +# it under the terms of the GNU General Public License as published by +# the Free Software Foundation; either version 3 of the License, or +# (at your option) any later version. +# +# This program 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 . +# + +import sys +import struct +import random +import socket +import optparse +import uuid +import time +import samba.ndr as ndr +import samba.getopt as options +from samba import credentials +from samba.dcerpc import dns, dnsp +from samba.tests.subunitrun import SubunitOptions, TestProgram +from samba import gensec, tests + +parser = optparse.OptionParser("dns.py [options]") +sambaopts = options.SambaOptions(parser) +parser.add_option_group(sambaopts) + +# This timeout only has relevance when testing against Windows +# Format errors tend to return patchy responses, so a timeout is needed. +parser.add_option("--timeout", type="int", dest="timeout", + help="Specify timeout for DNS requests") + +# use command line creds if available +credopts = options.CredentialsOptions(parser) +parser.add_option_group(credopts) +subunitopts = SubunitOptions(parser) +parser.add_option_group(subunitopts) + +opts, args = parser.parse_args() +timeout = opts.timeout + +if len(args) < 2: + parser.print_usage() + sys.exit(1) + +server_name = args[0] +server_ip = args[1] + + +class DNSTest(tests.TestCase): + def setUp(self): + super(DNSTest, self).setUp() + self.server = server_name + self.server_ip = server_ip + self.settings = {} + self.settings["lp_ctx"] = self.lp_ctx = tests.env_loadparm() + self.settings["target_hostname"] = self.server + + self.creds = credentials.Credentials() + self.creds.guess(self.lp_ctx) + self.creds.set_username(tests.env_get_var_value('USERNAME')) + self.creds.set_password(tests.env_get_var_value('PASSWORD')) + self.creds.set_kerberos_state(credentials.MUST_USE_KERBEROS) + self.newrecname = "tkeytsig.%s" % self.get_dns_domain() + + def errstr(self, errcode): + "Return a readable error code" + string_codes = [ + "OK", + "FORMERR", + "SERVFAIL", + "NXDOMAIN", + "NOTIMP", + "REFUSED", + "YXDOMAIN", + "YXRRSET", + "NXRRSET", + "NOTAUTH", + "NOTZONE", + "0x0B", + "0x0C", + "0x0D", + "0x0E", + "0x0F", + "BADSIG", + "BADKEY" + ] + + return string_codes[errcode] + + def assert_rcode_equals(self, rcode, expected): + "Helper function to check return code" + self.assertEquals(rcode, expected, "Expected RCODE %s, got %s" % + (self.errstr(expected), self.errstr(rcode))) + + def assert_dns_rcode_equals(self, packet, rcode): + "Helper function to check return code" + p_errcode = packet.operation & 0x000F + self.assertEquals(p_errcode, rcode, "Expected RCODE %s, got %s" % + (self.errstr(rcode), self.errstr(p_errcode))) + + def assert_dns_opcode_equals(self, packet, opcode): + "Helper function to check opcode" + p_opcode = packet.operation & 0x7800 + self.assertEquals(p_opcode, opcode, "Expected OPCODE %s, got %s" % + (opcode, p_opcode)) + + def make_name_packet(self, opcode, qid=None): + "Helper creating a dns.name_packet" + p = dns.name_packet() + if qid is None: + p.id = random.randint(0x0, 0xff00) + p.operation = opcode + p.questions = [] + p.additional = [] + return p + + def finish_name_packet(self, packet, questions): + "Helper to finalize a dns.name_packet" + packet.qdcount = len(questions) + packet.questions = questions + + def make_name_question(self, name, qtype, qclass): + "Helper creating a dns.name_question" + q = dns.name_question() + q.name = name + q.question_type = qtype + q.question_class = qclass + return q + + def make_txt_record(self, records): + rdata_txt = dns.txt_record() + s_list = dnsp.string_list() + s_list.count = len(records) + s_list.str = records + rdata_txt.txt = s_list + return rdata_txt + + def get_dns_domain(self): + "Helper to get dns domain" + return self.creds.get_realm().lower() + + def dns_transaction_udp(self, packet, host, + dump=False, timeout=timeout): + "send a DNS query and read the reply" + s = None + try: + send_packet = ndr.ndr_pack(packet) + if dump: + print self.hexdump(send_packet) + s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM, 0) + s.settimeout(timeout) + s.connect((host, 53)) + s.sendall(send_packet, 0) + recv_packet = s.recv(2048, 0) + if dump: + print self.hexdump(recv_packet) + response = ndr.ndr_unpack(dns.name_packet, recv_packet) + return (response, recv_packet) + finally: + if s is not None: + s.close() + + def dns_transaction_tcp(self, packet, host, + dump=False, timeout=timeout): + "send a DNS query and read the reply, also return the raw packet" + s = None + try: + send_packet = ndr.ndr_pack(packet) + if dump: + print self.hexdump(send_packet) + s = socket.socket(socket.AF_INET, socket.SOCK_STREAM, 0) + s.settimeout(timeout) + s.connect((host, 53)) + tcp_packet = struct.pack('!H', len(send_packet)) + tcp_packet += send_packet + s.sendall(tcp_packet) + + recv_packet = s.recv(0xffff + 2, 0) + if dump: + print self.hexdump(recv_packet) + response = ndr.ndr_unpack(dns.name_packet, recv_packet[2:]) + + finally: + if s is not None: + s.close() + + # unpacking and packing again should produce same bytestream + my_packet = ndr.ndr_pack(response) + self.assertEquals(my_packet, recv_packet[2:]) + + return (response, recv_packet[2:]) + + def tkey_trans(self): + "Do a TKEY transaction and establish a gensec context" + + self.key_name = "%s.%s" % (uuid.uuid4(), self.get_dns_domain()) + + p = self.make_name_packet(dns.DNS_OPCODE_QUERY) + q = self.make_name_question(self.key_name, + dns.DNS_QTYPE_TKEY, + dns.DNS_QCLASS_IN) + questions = [] + questions.append(q) + self.finish_name_packet(p, questions) + + r = dns.res_rec() + r.name = self.key_name + r.rr_type = dns.DNS_QTYPE_TKEY + r.rr_class = dns.DNS_QCLASS_IN + r.ttl = 0 + r.length = 0xffff + rdata = dns.tkey_record() + rdata.algorithm = "gss-tsig" + rdata.inception = int(time.time()) + rdata.expiration = int(time.time()) + 60*60 + rdata.mode = dns.DNS_TKEY_MODE_GSSAPI + rdata.error = 0 + rdata.other_size = 0 + + self.g = gensec.Security.start_client(self.settings) + self.g.set_credentials(self.creds) + self.g.set_target_service("dns") + self.g.set_target_hostname(self.server) + self.g.want_feature(gensec.FEATURE_SIGN) + self.g.start_mech_by_name("spnego") + + finished = False + client_to_server = "" + + (finished, server_to_client) = self.g.update(client_to_server) + self.assertFalse(finished) + + data = [ord(x) for x in list(server_to_client)] + rdata.key_data = data + rdata.key_size = len(data) + r.rdata = rdata + + additional = [r] + p.arcount = 1 + p.additional = additional + + (response, response_packet) = self.dns_transaction_tcp(p, self.server_ip) + self.assert_dns_rcode_equals(response, dns.DNS_RCODE_OK) + + tkey_record = response.answers[0].rdata + data = [chr(x) for x in tkey_record.key_data] + server_to_client = ''.join(data) + (finished, client_to_server) = self.g.update(server_to_client) + self.assertTrue(finished) + + self.verify_packet(response, response_packet) + + def verify_packet(self, response, response_packet, request_mac=""): + self.assertEqual(response.additional[0].rr_type, dns.DNS_QTYPE_TSIG) + + tsig_record = response.additional[0].rdata + mac = ''.join([chr(x) for x in tsig_record.mac]) + + # Cut off tsig record from dns response packet for MAC verification + # and reset additional record count. + key_name_len = len(self.key_name) + 2 + tsig_record_len = len(ndr.ndr_pack(tsig_record)) + key_name_len + 10 + + response_packet_list = list(response_packet) + del response_packet_list[-tsig_record_len:] + response_packet_list[11] = chr(0) + response_packet_wo_tsig = ''.join(response_packet_list) + + fake_tsig = dns.fake_tsig_rec() + fake_tsig.name = self.key_name + fake_tsig.rr_class = dns.DNS_QCLASS_ANY + fake_tsig.ttl = 0 + fake_tsig.time_prefix = tsig_record.time_prefix + fake_tsig.time = tsig_record.time + fake_tsig.algorithm_name = tsig_record.algorithm_name + fake_tsig.fudge = tsig_record.fudge + fake_tsig.error = 0 + fake_tsig.other_size = 0 + fake_tsig_packet = ndr.ndr_pack(fake_tsig) + + data = request_mac + response_packet_wo_tsig + fake_tsig_packet + self.g.check_packet(data, data, mac) + + def sign_packet(self, packet, key_name): + "Sign a packet, calculate a MAC and add TSIG record" + packet_data = ndr.ndr_pack(packet) + + fake_tsig = dns.fake_tsig_rec() + fake_tsig.name = key_name + fake_tsig.rr_class = dns.DNS_QCLASS_ANY + fake_tsig.ttl = 0 + fake_tsig.time_prefix = 0 + fake_tsig.time = int(time.time()) + fake_tsig.algorithm_name = "gss-tsig" + fake_tsig.fudge = 300 + fake_tsig.error = 0 + fake_tsig.other_size = 0 + fake_tsig_packet = ndr.ndr_pack(fake_tsig) + + data = packet_data + fake_tsig_packet + mac = self.g.sign_packet(data, data) + mac_list = [ord(x) for x in list(mac)] + + rdata = dns.tsig_record() + rdata.algorithm_name = "gss-tsig" + rdata.time_prefix = 0 + rdata.time = fake_tsig.time + rdata.fudge = 300 + rdata.original_id = packet.id + rdata.error = 0 + rdata.other_size = 0 + rdata.mac = mac_list + rdata.mac_size = len(mac_list) + + r = dns.res_rec() + r.name = key_name + r.rr_type = dns.DNS_QTYPE_TSIG + r.rr_class = dns.DNS_QCLASS_ANY + r.ttl = 0 + r.length = 0xffff + r.rdata = rdata + + additional = [r] + packet.additional = additional + packet.arcount = 1 + + return mac + + def bad_sign_packet(self, packet, key_name): + '''Add bad signature for a packet by bitflipping + the final byte in the MAC''' + + mac_list = [ord(x) for x in list("badmac")] + + rdata = dns.tsig_record() + rdata.algorithm_name = "gss-tsig" + rdata.time_prefix = 0 + rdata.time = int(time.time()) + rdata.fudge = 300 + rdata.original_id = packet.id + rdata.error = 0 + rdata.other_size = 0 + rdata.mac = mac_list + rdata.mac_size = len(mac_list) + + r = dns.res_rec() + r.name = key_name + r.rr_type = dns.DNS_QTYPE_TSIG + r.rr_class = dns.DNS_QCLASS_ANY + r.ttl = 0 + r.length = 0xffff + r.rdata = rdata + + additional = [r] + packet.additional = additional + packet.arcount = 1 + + def search_record(self, name): + p = self.make_name_packet(dns.DNS_OPCODE_QUERY) + questions = [] + + q = self.make_name_question(name, dns.DNS_QTYPE_TXT, dns.DNS_QCLASS_IN) + questions.append(q) + + self.finish_name_packet(p, questions) + (response, response_packet) = self.dns_transaction_udp(p, self.server_ip) + return response.operation & 0x000F + + def make_update_request(self, delete=False): + "Create a DNS update request" + + rr_class = dns.DNS_QCLASS_IN + ttl = 900 + + if delete: + rr_class = dns.DNS_QCLASS_NONE + ttl = 0 + + p = self.make_name_packet(dns.DNS_OPCODE_UPDATE) + q = self.make_name_question(self.get_dns_domain(), + dns.DNS_QTYPE_SOA, + dns.DNS_QCLASS_IN) + questions = [] + questions.append(q) + self.finish_name_packet(p, questions) + + updates = [] + r = dns.res_rec() + r.name = self.newrecname + r.rr_type = dns.DNS_QTYPE_TXT + r.rr_class = rr_class + r.ttl = ttl + r.length = 0xffff + rdata = self.make_txt_record(['"This is a test"']) + r.rdata = rdata + updates.append(r) + p.nscount = len(updates) + p.nsrecs = updates + + return p + + +class TestDNSUpdates(DNSTest): + def test_tkey(self): + "test DNS TKEY handshake" + + self.tkey_trans() + + def test_update_wo_tsig(self): + "test DNS update without TSIG record" + + p = self.make_update_request() + (response, response_p) = self.dns_transaction_udp(p, self.server_ip) + self.assert_dns_rcode_equals(response, dns.DNS_RCODE_REFUSED) + + rcode = self.search_record(self.newrecname) + self.assert_rcode_equals(rcode, dns.DNS_RCODE_NXDOMAIN) + + def test_update_tsig_bad_keyname(self): + "test DNS update with a TSIG record with a bad keyname" + + self.tkey_trans() + + p = self.make_update_request() + self.sign_packet(p, "badkey") + (response, response_p) = self.dns_transaction_udp(p, self.server_ip) + self.assert_dns_rcode_equals(response, dns.DNS_RCODE_NOTAUTH) + tsig_record = response.additional[0].rdata + self.assertEquals(tsig_record.error, dns.DNS_RCODE_BADKEY) + self.assertEquals(tsig_record.mac_size, 0) + + rcode = self.search_record(self.newrecname) + self.assert_rcode_equals(rcode, dns.DNS_RCODE_NXDOMAIN) + + def test_update_tsig_bad_mac(self): + "test DNS update with a TSIG record with a bad MAC" + + self.tkey_trans() + + p = self.make_update_request() + self.bad_sign_packet(p, self.key_name) + (response, response_p) = self.dns_transaction_udp(p, self.server_ip) + self.assert_dns_rcode_equals(response, dns.DNS_RCODE_NOTAUTH) + tsig_record = response.additional[0].rdata + self.assertEquals(tsig_record.error, dns.DNS_RCODE_BADSIG) + self.assertEquals(tsig_record.mac_size, 0) + + rcode = self.search_record(self.newrecname) + self.assert_rcode_equals(rcode, dns.DNS_RCODE_NXDOMAIN) + + def test_update_tsig(self): + "test DNS update with correct TSIG record" + + self.tkey_trans() + + p = self.make_update_request() + mac = self.sign_packet(p, self.key_name) + (response, response_p) = self.dns_transaction_udp(p, self.server_ip) + self.assert_dns_rcode_equals(response, dns.DNS_RCODE_OK) + self.verify_packet(response, response_p, mac) + + # Check the record is around + rcode = self.search_record(self.newrecname) + self.assert_rcode_equals(rcode, dns.DNS_RCODE_OK) + + # Now delete the record + p = self.make_update_request(delete=True) + mac = self.sign_packet(p, self.key_name) + (response, response_p) = self.dns_transaction_udp(p, self.server_ip) + self.assert_dns_rcode_equals(response, dns.DNS_RCODE_OK) + self.verify_packet(response, response_p, mac) + + # check it's gone + rcode = self.search_record(self.newrecname) + self.assert_rcode_equals(rcode, dns.DNS_RCODE_NXDOMAIN) + +TestProgram(module=__name__, opts=subunitopts) diff --git a/source4/selftest/tests.py b/source4/selftest/tests.py index c829608..9c0a0ef 100755 --- a/source4/selftest/tests.py +++ b/source4/selftest/tests.py @@ -358,6 +358,8 @@ for f in sorted(os.listdir(os.path.join(samba4srcdir, "../pidl/tests"))): # DNS tests plantestsuite_loadlist("samba.tests.dns", "fl2003dc:local", [python, os.path.join(srcdir(), "python/samba/tests/dns.py"), '$SERVER', '$SERVER_IP', '--machine-pass', '-U"$USERNAME%$PASSWORD"', '--workgroup=$DOMAIN', '$LOADLIST', '$LISTOPT']) +plantestsuite_loadlist("samba.tests.dns_tkey", "fl2008r2dc", [python, os.path.join(srcdir(), "python/samba/tests/dns_tkey.py"), '$SERVER', '$SERVER_IP', '--machine-pass', '-U"$USERNAME%$PASSWORD"', '--workgroup=$DOMAIN', '$LOADLIST', '$LISTOPT']) + for t in smbtorture4_testsuites("dns_internal."): plansmbtorture4testsuite(t, "ad_dc_ntvfs:local", '//$SERVER/whavever') -- 2.5.0