tor-commits August 2017

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[tor/release-0.2.9] Merge branch 'maint-0.2.9' into release-0.2.9
by nickm＠torproject.org 01 Aug '17

01 Aug '17

commit ad54a025d6cfbb74c7b1263c58d7729fe182d6ec Merge: 919106989 58e1c6dd8 Author: Nick Mathewson <nickm(a)torproject.org> Date: Tue Aug 1 11:30:33 2017 -0400 Merge branch 'maint-0.2.9' into release-0.2.9 changes/bug19025 | 4 ++++ changes/ticket19769 | 7 +++++++ src/or/dns.c | 33 ++++++++++++--------------------- src/or/dns.h | 14 ++++++++++++-- src/or/or.h | 12 ------------ src/test/test_cell_formats.c | 6 +++--- src/test/test_dns.c | 28 ++++------------------------ 7 files changed, 42 insertions(+), 62 deletions(-)

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[tor/master] Merge branch 'maint-0.2.9' into maint-0.3.0
by nickm＠torproject.org 01 Aug '17

01 Aug '17

commit 4d262035280101fcf54ab770ad3341215c261bd8 Merge: f69797b67 58e1c6dd8 Author: Nick Mathewson <nickm(a)torproject.org> Date: Tue Aug 1 11:30:33 2017 -0400 Merge branch 'maint-0.2.9' into maint-0.3.0

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[tor/master] Merge branch 'maint-0.3.0' into maint-0.3.1
by nickm＠torproject.org 01 Aug '17

01 Aug '17

commit b2d528d3be456c12c5c922935d68acceb516824b Merge: 751c71827 4d2620352 Author: Nick Mathewson <nickm(a)torproject.org> Date: Tue Aug 1 11:30:33 2017 -0400 Merge branch 'maint-0.3.0' into maint-0.3.1

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[tor/release-0.2.9] Changes file for 19025.
by nickm＠torproject.org 01 Aug '17

01 Aug '17

commit 0151e1d1586b2e96dffb667cf2825e4fe993b62e Author: Nick Mathewson <nickm(a)torproject.org> Date: Wed Jan 18 09:01:26 2017 -0500 Changes file for 19025. --- changes/bug19025 | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/changes/bug19025 b/changes/bug19025 new file mode 100644 index 000000000..0f365f52b --- /dev/null +++ b/changes/bug19025 @@ -0,0 +1,4 @@ + o Major bugfixes (DNS): + - Fix a bug that prevented exit nodes from caching DNS records for more + than 60 seconds. + Fixes bug 19025; bugfix on 0.2.4.7-alpha.

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[tor/release-0.2.9] DefecTor countermeasure: change server- and client-side DNS TTL clipping
by nickm＠torproject.org 01 Aug '17

01 Aug '17

commit 609065f165a8e145f404e55e01e8f5ac5c013bc3 Author: Nick Mathewson <nickm(a)torproject.org> Date: Mon Jan 2 14:55:39 2017 -0500 DefecTor countermeasure: change server- and client-side DNS TTL clipping The server-side clipping now clamps to one of two values, both for what to report, and how long to cache. Additionally, we move some defines to dns.h, and give them better names. --- changes/ticket19769 | 7 +++++++ src/or/dns.c | 30 ++++++++++-------------------- src/or/dns.h | 14 ++++++++++++-- src/or/or.h | 12 ------------ src/test/test_dns.c | 28 ++++------------------------ 5 files changed, 33 insertions(+), 58 deletions(-) diff --git a/changes/ticket19769 b/changes/ticket19769 new file mode 100644 index 000000000..9fc05c3e9 --- /dev/null +++ b/changes/ticket19769 @@ -0,0 +1,7 @@ + o Major features (security): + - Change the algorithm used to decide DNS TTLs on client and server side, + to better resist DNS-based correlation attacks like the DefecTor attack + of Greschbach, Pulls, Roberts, Winter, and Feamster). Now + relays only return one of two possible DNS TTL values, and clients + are willing to believe DNS TTL values up to 3 hours long. + Closes ticket 19769. diff --git a/src/or/dns.c b/src/or/dns.c index 5f9813b91..41a6dfd0a 100644 --- a/src/or/dns.c +++ b/src/or/dns.c @@ -243,29 +243,19 @@ has_dns_init_failed(void) } /** Helper: Given a TTL from a DNS response, determine what TTL to give the - * OP that asked us to resolve it. */ + * OP that asked us to resolve it, and how long to cache that record + * ourselves. */ uint32_t dns_clip_ttl(uint32_t ttl) { - if (ttl < MIN_DNS_TTL) - return MIN_DNS_TTL; - else if (ttl > MAX_DNS_TTL) - return MAX_DNS_TTL; - else - return ttl; -} - -/** Helper: Given a TTL from a DNS response, determine how long to hold it in - * our cache. */ -STATIC uint32_t -dns_get_expiry_ttl(uint32_t ttl) -{ - if (ttl < MIN_DNS_TTL) - return MIN_DNS_TTL; - else if (ttl > MAX_DNS_ENTRY_AGE) - return MAX_DNS_ENTRY_AGE; + /* This logic is a defense against "DefectTor" DNS-based traffic + * confirmation attacks, as in https://nymity.ch/tor-dns/tor-dns.pdf . + * We only give two values: a "low" value and a "high" value. + */ + if (ttl < MIN_DNS_TTL_AT_EXIT) + return MIN_DNS_TTL_AT_EXIT; else - return ttl; + return MAX_DNS_TTL_AT_EXIT; } /** Helper: free storage held by an entry in the DNS cache. */ @@ -1317,7 +1307,7 @@ make_pending_resolve_cached(cached_resolve_t *resolve) resolve->ttl_hostname < ttl) ttl = resolve->ttl_hostname; - set_expiry(new_resolve, time(NULL) + dns_get_expiry_ttl(ttl)); + set_expiry(new_resolve, time(NULL) + dns_clip_ttl(ttl)); } assert_cache_ok(); diff --git a/src/or/dns.h b/src/or/dns.h index b14f7dd29..951a2a346 100644 --- a/src/or/dns.h +++ b/src/or/dns.h @@ -12,6 +12,18 @@ #ifndef TOR_DNS_H #define TOR_DNS_H +/** Lowest value for DNS ttl that a server will give. */ +#define MIN_DNS_TTL_AT_EXIT (5*60) +/** Highest value for DNS ttl that a server will give. */ +#define MAX_DNS_TTL_AT_EXIT (60*60) + +/** How long do we keep DNS cache entries before purging them (regardless of + * their TTL)? */ +#define MAX_DNS_ENTRY_AGE (3*60*60) +/** How long do we cache/tell clients to cache DNS records when no TTL is + * known? */ +#define DEFAULT_DNS_TTL (30*60) + int dns_init(void); int has_dns_init_failed(void); void dns_free_all(void); @@ -31,8 +43,6 @@ void dump_dns_mem_usage(int severity); #ifdef DNS_PRIVATE #include "dns_structs.h" -STATIC uint32_t dns_get_expiry_ttl(uint32_t ttl); - MOCK_DECL(STATIC int,dns_resolve_impl,(edge_connection_t *exitconn, int is_resolve,or_circuit_t *oncirc, char **hostname_out, int *made_connection_pending_out, cached_resolve_t **resolve_out)); diff --git a/src/or/or.h b/src/or/or.h index 66717792b..e48cd92f0 100644 --- a/src/or/or.h +++ b/src/or/or.h @@ -143,18 +143,6 @@ /** Maximum size of a single extrainfo document, as above. */ #define MAX_EXTRAINFO_UPLOAD_SIZE 50000 -/** How long do we keep DNS cache entries before purging them (regardless of - * their TTL)? */ -#define MAX_DNS_ENTRY_AGE (30*60) -/** How long do we cache/tell clients to cache DNS records when no TTL is - * known? */ -#define DEFAULT_DNS_TTL (30*60) -/** How long can a TTL be before we stop believing it? */ -#define MAX_DNS_TTL (3*60*60) -/** How small can a TTL be before we stop believing it? Provides rudimentary - * pinning. */ -#define MIN_DNS_TTL 60 - /** How often do we rotate onion keys? */ #define MIN_ONION_KEY_LIFETIME (7*24*60*60) /** How often do we rotate TLS contexts? */ diff --git a/src/test/test_dns.c b/src/test/test_dns.c index 8346c0a33..6a8e92cb4 100644 --- a/src/test/test_dns.c +++ b/src/test/test_dns.c @@ -16,30 +16,11 @@ NS(test_main)(void *arg) { (void)arg; - uint32_t ttl_mid = MIN_DNS_TTL / 2 + MAX_DNS_TTL / 2; + uint32_t ttl_mid = MIN_DNS_TTL_AT_EXIT / 2 + MAX_DNS_TTL_AT_EXIT / 2; - tt_int_op(dns_clip_ttl(MIN_DNS_TTL - 1),==,MIN_DNS_TTL); - tt_int_op(dns_clip_ttl(ttl_mid),==,ttl_mid); - tt_int_op(dns_clip_ttl(MAX_DNS_TTL + 1),==,MAX_DNS_TTL); - - done: - return; -} - -#undef NS_SUBMODULE - -#define NS_SUBMODULE expiry_ttl - -static void -NS(test_main)(void *arg) -{ - (void)arg; - - uint32_t ttl_mid = MIN_DNS_TTL / 2 + MAX_DNS_ENTRY_AGE / 2; - - tt_int_op(dns_get_expiry_ttl(MIN_DNS_TTL - 1),==,MIN_DNS_TTL); - tt_int_op(dns_get_expiry_ttl(ttl_mid),==,ttl_mid); - tt_int_op(dns_get_expiry_ttl(MAX_DNS_ENTRY_AGE + 1),==,MAX_DNS_ENTRY_AGE); + tt_int_op(dns_clip_ttl(MIN_DNS_TTL_AT_EXIT - 1),==,MIN_DNS_TTL_AT_EXIT); + tt_int_op(dns_clip_ttl(ttl_mid),==,MAX_DNS_TTL_AT_EXIT); + tt_int_op(dns_clip_ttl(MAX_DNS_TTL_AT_EXIT + 1),==,MAX_DNS_TTL_AT_EXIT); done: return; @@ -749,7 +730,6 @@ NS(test_main)(void *arg) struct testcase_t dns_tests[] = { TEST_CASE(clip_ttl), - TEST_CASE(expiry_ttl), TEST_CASE(resolve), TEST_CASE_ASPECT(resolve_impl, addr_is_ip_no_need_to_resolve), TEST_CASE_ASPECT(resolve_impl, non_exit),

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[tor/master] Merge branch 'maint-0.3.1'
by nickm＠torproject.org 01 Aug '17

01 Aug '17

commit 39ade001a70178adcd63c12a7246a23ab4d07534 Merge: ba7d6a1e1 b2d528d3b Author: Nick Mathewson <nickm(a)torproject.org> Date: Tue Aug 1 11:30:33 2017 -0400 Merge branch 'maint-0.3.1'

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[tor/release-0.3.1] Merge branch 'maint-0.2.9' into maint-0.3.0
by nickm＠torproject.org 01 Aug '17

01 Aug '17

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[tor/release-0.3.1] Merge remote-tracking branch 'public/bug19769_19025_029' into maint-0.2.9
by nickm＠torproject.org 01 Aug '17

01 Aug '17

commit 58e1c6dd868704520fcbd7d8d8bdd7f8dd6f5c58 Merge: 8500f0e4e 0151e1d15 Author: Nick Mathewson <nickm(a)torproject.org> Date: Tue Aug 1 11:30:29 2017 -0400 Merge remote-tracking branch 'public/bug19769_19025_029' into maint-0.2.9 changes/bug19025 | 4 ++++ changes/ticket19769 | 7 +++++++ src/or/dns.c | 33 ++++++++++++--------------------- src/or/dns.h | 14 ++++++++++++-- src/or/or.h | 12 ------------ src/test/test_cell_formats.c | 6 +++--- src/test/test_dns.c | 28 ++++------------------------ 7 files changed, 42 insertions(+), 62 deletions(-)

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[tor/release-0.3.1] Merge branch 'maint-0.3.1' into release-0.3.1
by nickm＠torproject.org 01 Aug '17

01 Aug '17

commit c1b411109e857ba493a34a5ba8f8bad196ca0f26 Merge: 6ddc4d5e2 b2d528d3b Author: Nick Mathewson <nickm(a)torproject.org> Date: Tue Aug 1 11:30:33 2017 -0400 Merge branch 'maint-0.3.1' into release-0.3.1

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[tor/release-0.3.0] Merge branch 'maint-0.2.9' into maint-0.3.0
by nickm＠torproject.org 01 Aug '17

01 Aug '17

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tor-commits August 2017