March 2020 - tor-commits - lists.torproject.org

[tor/maint-0.4.1] When parsing, reject >1024-bit RSA private keys sooner.
by nickm＠torproject.org 18 Mar '20

18 Mar '20

commit 9e1085c924133d7b73c7b0a42282fb13b34f28b8 Author: Nick Mathewson <nickm(a)torproject.org> Date: Wed Feb 5 11:11:35 2020 -0500 When parsing, reject >1024-bit RSA private keys sooner. Private-key validation is fairly expensive for long keys in openssl, so we need to avoid it sooner. --- src/feature/dirparse/parsecommon.c | 3 ++- src/lib/crypt_ops/crypto_rsa.c | 27 +++++++++++++++++++++------ src/lib/crypt_ops/crypto_rsa.h | 5 ++++- src/lib/crypt_ops/crypto_rsa_nss.c | 14 +++++++++++++- src/lib/crypt_ops/crypto_rsa_openssl.c | 11 +++++++++-- 5 files changed, 49 insertions(+), 11 deletions(-) diff --git a/src/feature/dirparse/parsecommon.c b/src/feature/dirparse/parsecommon.c index 632f5adff..5b753f0f2 100644 --- a/src/feature/dirparse/parsecommon.c +++ b/src/feature/dirparse/parsecommon.c @@ -389,7 +389,8 @@ get_next_token(memarea_t *area, RET_ERR("Couldn't parse public key."); } else if (!strcmp(tok->object_type, "RSA PRIVATE KEY")) { /* private key */ tok->key = crypto_pk_new(); - if (crypto_pk_read_private_key_from_string(tok->key, obstart, eol-obstart)) + if (crypto_pk_read_private_key1024_from_string(tok->key, + obstart, eol-obstart)) RET_ERR("Couldn't parse private key."); } else { /* If it's something else, try to base64-decode it */ int r; diff --git a/src/lib/crypt_ops/crypto_rsa.c b/src/lib/crypt_ops/crypto_rsa.c index c9189b0df..8fd8a8aa7 100644 --- a/src/lib/crypt_ops/crypto_rsa.c +++ b/src/lib/crypt_ops/crypto_rsa.c @@ -490,7 +490,7 @@ crypto_pk_write_private_key_to_string(crypto_pk_t *env, static int crypto_pk_read_from_string_generic(crypto_pk_t *env, const char *src, size_t len, int severity, - bool private_key) + bool private_key, int max_bits) { if (len == (size_t)-1) // "-1" indicates "use the length of the string." len = strlen(src); @@ -510,7 +510,7 @@ crypto_pk_read_from_string_generic(crypto_pk_t *env, const char *src, } crypto_pk_t *pk = private_key - ? crypto_pk_asn1_decode_private((const char*)buf, n) + ? crypto_pk_asn1_decode_private((const char*)buf, n, max_bits) : crypto_pk_asn1_decode((const char*)buf, n); if (! pk) { log_fn(severity, LD_CRYPTO, @@ -539,7 +539,8 @@ int crypto_pk_read_public_key_from_string(crypto_pk_t *env, const char *src, size_t len) { - return crypto_pk_read_from_string_generic(env, src, len, LOG_INFO, false); + return crypto_pk_read_from_string_generic(env, src, len, LOG_INFO, false, + -1); } /** Read a PEM-encoded private key from the len-byte string src @@ -550,7 +551,21 @@ int crypto_pk_read_private_key_from_string(crypto_pk_t *env, const char *src, ssize_t len) { - return crypto_pk_read_from_string_generic(env, src, len, LOG_INFO, true); + return crypto_pk_read_from_string_generic(env, src, len, LOG_INFO, true, + -1); +} + +/** + * As crypto_pk_read_private_key_from_string(), but reject any key + * with a modulus longer than 1024 bits before doing any expensive + * validation on it. + */ +int +crypto_pk_read_private_key1024_from_string(crypto_pk_t *env, + const char *src, ssize_t len) +{ + return crypto_pk_read_from_string_generic(env, src, len, LOG_INFO, true, + 1024); } /** If a file is longer than this, we won't try to decode its private key */ @@ -578,7 +593,7 @@ crypto_pk_read_private_key_from_filename(crypto_pk_t *env, } int rv = crypto_pk_read_from_string_generic(env, buf, (ssize_t)st.st_size, - LOG_WARN, true); + LOG_WARN, true, -1); if (rv < 0) { log_warn(LD_CRYPTO, "Unable to decode private key from file %s", escaped(keyfile)); @@ -662,7 +677,7 @@ crypto_pk_base64_decode_private(const char *str, size_t len) goto out; } - pk = crypto_pk_asn1_decode_private(der, der_len); + pk = crypto_pk_asn1_decode_private(der, der_len, -1); out: memwipe(der, 0, len+1); diff --git a/src/lib/crypt_ops/crypto_rsa.h b/src/lib/crypt_ops/crypto_rsa.h index c1ea767f8..6d9cc8d30 100644 --- a/src/lib/crypt_ops/crypto_rsa.h +++ b/src/lib/crypt_ops/crypto_rsa.h @@ -61,6 +61,8 @@ int crypto_pk_read_public_key_from_string(crypto_pk_t *env, const char *src, size_t len); int crypto_pk_read_private_key_from_string(crypto_pk_t *env, const char *s, ssize_t len); +int crypto_pk_read_private_key1024_from_string(crypto_pk_t *env, + const char *src, ssize_t len); int crypto_pk_write_private_key_to_filename(crypto_pk_t *env, const char *fname); @@ -95,7 +97,8 @@ int crypto_pk_asn1_encode(const crypto_pk_t *pk, char *dest, size_t dest_len); crypto_pk_t *crypto_pk_asn1_decode(const char *str, size_t len); int crypto_pk_asn1_encode_private(const crypto_pk_t *pk, char *dest, size_t dest_len); -crypto_pk_t *crypto_pk_asn1_decode_private(const char *str, size_t len); +crypto_pk_t *crypto_pk_asn1_decode_private(const char *str, size_t len, + int max_bits); int crypto_pk_get_fingerprint(crypto_pk_t *pk, char *fp_out,int add_space); int crypto_pk_get_hashed_fingerprint(crypto_pk_t *pk, char *fp_out); void crypto_add_spaces_to_fp(char *out, size_t outlen, const char *in); diff --git a/src/lib/crypt_ops/crypto_rsa_nss.c b/src/lib/crypt_ops/crypto_rsa_nss.c index ad2ad38b6..4cf699067 100644 --- a/src/lib/crypt_ops/crypto_rsa_nss.c +++ b/src/lib/crypt_ops/crypto_rsa_nss.c @@ -679,9 +679,12 @@ crypto_pk_asn1_encode_private(const crypto_pk_t *pk, /** Given a buffer containing the DER representation of the * private key str, decode and return the result on success, or NULL * on failure. + * + * If max_bits is nonnegative, reject any key longer than max_bits + * without performing any expensive validation on it. */ crypto_pk_t * -crypto_pk_asn1_decode_private(const char *str, size_t len) +crypto_pk_asn1_decode_private(const char *str, size_t len, int max_bits) { tor_assert(str); tor_assert(len < INT_MAX); @@ -731,6 +734,15 @@ crypto_pk_asn1_decode_private(const char *str, size_t len) output = NULL; } + if (output) { + const int bits = SECKEY_PublicKeyStrengthInBits(output->pubkey); + if (max_bits > 0 && bits > max_bits) { + log_info(LD_CRYPTO, "Private key longer than expected."); + crypto_pk_free(output); + output = NULL; + } + } + if (slot) PK11_FreeSlot(slot); diff --git a/src/lib/crypt_ops/crypto_rsa_openssl.c b/src/lib/crypt_ops/crypto_rsa_openssl.c index fbdc76ccd..022a0dc09 100644 --- a/src/lib/crypt_ops/crypto_rsa_openssl.c +++ b/src/lib/crypt_ops/crypto_rsa_openssl.c @@ -566,9 +566,12 @@ crypto_pk_asn1_encode_private(const crypto_pk_t *pk, char *dest, /** Decode an ASN.1-encoded private key from str; return the result on * success and NULL on failure. + * + * If max_bits is nonnegative, reject any key longer than max_bits + * without performing any expensive validation on it. */ crypto_pk_t * -crypto_pk_asn1_decode_private(const char *str, size_t len) +crypto_pk_asn1_decode_private(const char *str, size_t len, int max_bits) { RSA *rsa; unsigned char *buf; @@ -578,7 +581,11 @@ crypto_pk_asn1_decode_private(const char *str, size_t len) rsa = d2i_RSAPrivateKey(NULL, &cp, len); tor_free(buf); if (!rsa) { - crypto_openssl_log_errors(LOG_WARN,"decoding public key"); + crypto_openssl_log_errors(LOG_WARN,"decoding private key"); + return NULL; + } + if (max_bits >= 0 && RSA_bits(rsa) > max_bits) { + log_info(LD_CRYPTO, "Private key longer than expected."); return NULL; } crypto_pk_t *result = crypto_new_pk_from_openssl_rsa_(rsa);

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[tor/maint-0.3.5] Port rsa_private_key_too_long() to work on OpenSSL 1.1.0.
by nickm＠torproject.org 18 Mar '20

18 Mar '20

commit 0526801ed4caba4393942e62def2cb35f0f298b3 Author: Nick Mathewson <nickm(a)torproject.org> Date: Wed Mar 18 08:19:48 2020 -0400 Port rsa_private_key_too_long() to work on OpenSSL 1.1.0. --- src/lib/crypt_ops/crypto_rsa_openssl.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/src/lib/crypt_ops/crypto_rsa_openssl.c b/src/lib/crypt_ops/crypto_rsa_openssl.c index 6f3ac6fde..17eae24cc 100644 --- a/src/lib/crypt_ops/crypto_rsa_openssl.c +++ b/src/lib/crypt_ops/crypto_rsa_openssl.c @@ -573,6 +573,8 @@ rsa_private_key_too_long(RSA *rsa, int max_bits) { const BIGNUM *n, *e, *p, *q, *d, *dmp1, *dmq1, *iqmp; #ifdef OPENSSL_1_1_API + +#if OPENSSL_VERSION_NUMBER >= OPENSSL_V_SERIES(1,1,1) n = RSA_get0_n(rsa); e = RSA_get0_e(rsa); p = RSA_get0_p(rsa); @@ -581,6 +583,11 @@ rsa_private_key_too_long(RSA *rsa, int max_bits) dmp1 = RSA_get0_dmp1(rsa); dmq1 = RSA_get0_dmq1(rsa); iqmp = RSA_get0_iqmp(rsa); +#else + /* The accessors above did not exist in openssl 1.1.0. */ + p = q = dmp1 = dmq1 = iqmp = NULL; + RSA_get0_key(rsa, &n, &e, &d); +#endif if (RSA_bits(rsa) > max_bits) return true;

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[tor/maint-0.4.1] changes file for 33119 aka TROVE-2020-002
by nickm＠torproject.org 18 Mar '20

18 Mar '20

commit d0bce65ce2426793a975e691204c3fb2ac667f66 Author: Nick Mathewson <nickm(a)torproject.org> Date: Wed Feb 5 12:02:32 2020 -0500 changes file for 33119 aka TROVE-2020-002 --- changes/ticket33119 | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/changes/ticket33119 b/changes/ticket33119 new file mode 100644 index 000000000..11c20bc7a --- /dev/null +++ b/changes/ticket33119 @@ -0,0 +1,8 @@ + o Major bugfixes (security, denial-of-service): + - Fix a denial-of-service bug that could be used by anyone to consume a + bunch of CPU on any Tor relay or authority, or by directories to + consume a bunch of CPU on clients or hidden services. Because + of the potential for CPU consumption to introduce observable + timing patterns, we are treating this as a high-severity security + issue. Fixes bug 33119; bugfix on 0.2.1.5-alpha. We are also tracking + this issue as TROVE-2020-002.

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[tor/maint-0.4.1] Revise TROVE-2020-002 fix to work on older OpenSSL versions.
by nickm＠torproject.org 18 Mar '20

18 Mar '20

commit be064f77b93bda370e4165e6ad6da17324835c9e Author: Nick Mathewson <nickm(a)torproject.org> Date: Sat Mar 14 13:38:53 2020 -0400 Revise TROVE-2020-002 fix to work on older OpenSSL versions. Although OpenSSL before 1.1.1 is no longer supported, it's possible that somebody is still using it with 0.3.5, so we probably shouldn't break it with this fix. --- src/lib/crypt_ops/crypto_rsa_openssl.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/src/lib/crypt_ops/crypto_rsa_openssl.c b/src/lib/crypt_ops/crypto_rsa_openssl.c index 022a0dc09..39b7aaf0c 100644 --- a/src/lib/crypt_ops/crypto_rsa_openssl.c +++ b/src/lib/crypt_ops/crypto_rsa_openssl.c @@ -584,7 +584,11 @@ crypto_pk_asn1_decode_private(const char *str, size_t len, int max_bits) crypto_openssl_log_errors(LOG_WARN,"decoding private key"); return NULL; } +#ifdef OPENSSL_1_1_API if (max_bits >= 0 && RSA_bits(rsa) > max_bits) { +#else + if (max_bits >= 0 && rsa->n && BN_num_bits(rsa->n) > max_bits) { +#endif log_info(LD_CRYPTO, "Private key longer than expected."); return NULL; }

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[tor/maint-0.4.1] Add a test for crypto_pk_asn1_decode_private maxbits.
by nickm＠torproject.org 18 Mar '20

18 Mar '20

commit ab2e66ccdc4406a195d77b202bae21c17c634cb5 Author: Nick Mathewson <nickm(a)torproject.org> Date: Sat Mar 14 13:50:38 2020 -0400 Add a test for crypto_pk_asn1_decode_private maxbits. --- src/test/test_crypto.c | 24 ++++++++++++++++++++++++ 1 file changed, 24 insertions(+) diff --git a/src/test/test_crypto.c b/src/test/test_crypto.c index fa79f4cc4..2373e5bf8 100644 --- a/src/test/test_crypto.c +++ b/src/test/test_crypto.c @@ -1492,6 +1492,29 @@ test_crypto_pk_pem_encrypted(void *arg) } static void +test_crypto_pk_bad_size(void *arg) +{ + (void)arg; + crypto_pk_t *pk1 = pk_generate(0); + crypto_pk_t *pk2 = NULL; + char buf[2048]; + int n = crypto_pk_asn1_encode_private(pk1, buf, sizeof(buf)); + tt_int_op(n, OP_GT, 0); + + /* Set the max bit count smaller: we should refuse to decode the key.*/ + pk2 = crypto_pk_asn1_decode_private(buf, n, 1020); + tt_assert(! pk2); + + /* Set the max bit count larger: it should decode fine. */ + pk2 = crypto_pk_asn1_decode_private(buf, n, 2048); + tt_assert(pk2); + + done: + crypto_pk_free(pk1); + crypto_pk_free(pk2); +} + +static void test_crypto_pk_invalid_private_key(void *arg) { (void)arg; @@ -3163,6 +3186,7 @@ struct testcase_t crypto_tests[] = { { "pk_fingerprints", test_crypto_pk_fingerprints, TT_FORK, NULL, NULL }, { "pk_base64", test_crypto_pk_base64, TT_FORK, NULL, NULL }, { "pk_pem_encrypted", test_crypto_pk_pem_encrypted, TT_FORK, NULL, NULL }, + { "pk_bad_size", test_crypto_pk_bad_size, 0, NULL, NULL }, { "pk_invalid_private_key", test_crypto_pk_invalid_private_key, 0, NULL, NULL }, CRYPTO_LEGACY(digests),

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[tor/maint-0.4.1] Fix memory leak in crypto_pk_asn1_decode_private.
by nickm＠torproject.org 18 Mar '20

18 Mar '20

commit 29c9675bdeb5a63564e9a76dcd7162bef884b240 Author: Nick Mathewson <nickm(a)torproject.org> Date: Sat Mar 14 14:17:33 2020 -0400 Fix memory leak in crypto_pk_asn1_decode_private. (Deep, deep thanks to Taylor for reminding me to test this!) --- src/lib/crypt_ops/crypto_rsa_openssl.c | 1 + 1 file changed, 1 insertion(+) diff --git a/src/lib/crypt_ops/crypto_rsa_openssl.c b/src/lib/crypt_ops/crypto_rsa_openssl.c index 39b7aaf0c..0db25f347 100644 --- a/src/lib/crypt_ops/crypto_rsa_openssl.c +++ b/src/lib/crypt_ops/crypto_rsa_openssl.c @@ -590,6 +590,7 @@ crypto_pk_asn1_decode_private(const char *str, size_t len, int max_bits) if (max_bits >= 0 && rsa->n && BN_num_bits(rsa->n) > max_bits) { #endif log_info(LD_CRYPTO, "Private key longer than expected."); + RSA_free(rsa); return NULL; } crypto_pk_t *result = crypto_new_pk_from_openssl_rsa_(rsa);

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[tor/maint-0.4.1] Merge branch 'trove_2020_002_035' into trove_2020_002_041
by nickm＠torproject.org 18 Mar '20

18 Mar '20

commit dd6e2277e0d336f3d519f88d792b832d04e2c323 Merge: 1a375c3b1 29c9675bd Author: Nick Mathewson <nickm(a)torproject.org> Date: Sat Mar 14 14:20:51 2020 -0400 Merge branch 'trove_2020_002_035' into trove_2020_002_041 src/lib/crypt_ops/crypto_rsa_openssl.c | 5 +++++ src/test/test_crypto.c | 24 ++++++++++++++++++++++++ 2 files changed, 29 insertions(+)

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[tor/maint-0.4.1] Add off-by-one checks for key length.
by nickm＠torproject.org 18 Mar '20

18 Mar '20

commit 2328c79a5fbc2f1995390dd08002244bc952246d Author: Nick Mathewson <nickm(a)torproject.org> Date: Tue Mar 17 10:07:54 2020 -0400 Add off-by-one checks for key length. --- src/test/test_crypto.c | 15 +++++++++++++++ 1 file changed, 15 insertions(+) diff --git a/src/test/test_crypto.c b/src/test/test_crypto.c index 2373e5bf8..5af0cce13 100644 --- a/src/test/test_crypto.c +++ b/src/test/test_crypto.c @@ -1505,6 +1505,21 @@ test_crypto_pk_bad_size(void *arg) pk2 = crypto_pk_asn1_decode_private(buf, n, 1020); tt_assert(! pk2); + /* Set the max bit count one bit smaller: we should refuse to decode the + key.*/ + pk2 = crypto_pk_asn1_decode_private(buf, n, 1023); + tt_assert(! pk2); + + /* Correct size: should work. */ + pk2 = crypto_pk_asn1_decode_private(buf, n, 1024); + tt_assert(pk2); + crypto_pk_free(pk2); + + /* One bit larger: should work. */ + pk2 = crypto_pk_asn1_decode_private(buf, n, 1025); + tt_assert(pk2); + crypto_pk_free(pk2); + /* Set the max bit count larger: it should decode fine. */ pk2 = crypto_pk_asn1_decode_private(buf, n, 2048); tt_assert(pk2);

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[tor/maint-0.4.1] Merge branch 'trove_2020_002_035' into trove_2020_002_041
by nickm＠torproject.org 18 Mar '20

18 Mar '20

commit 9163781039b96e859fc102f003a274e9716cc02d Merge: dd6e2277e f958b537a Author: Nick Mathewson <nickm(a)torproject.org> Date: Tue Mar 17 10:45:03 2020 -0400 Merge branch 'trove_2020_002_035' into trove_2020_002_041 src/lib/crypt_ops/crypto_rsa_nss.c | 2 +- src/lib/crypt_ops/crypto_rsa_openssl.c | 57 +++++++++++++++++++++++++++++++--- src/test/test_crypto.c | 15 +++++++++ 3 files changed, 68 insertions(+), 6 deletions(-)

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[tor/maint-0.4.1] Extract key length check into a new function, and check more fields.
by nickm＠torproject.org 18 Mar '20

18 Mar '20

commit 8abdb394893a1704f885278f5f5d7913cdf516c9 Author: Nick Mathewson <nickm(a)torproject.org> Date: Tue Mar 17 10:04:38 2020 -0400 Extract key length check into a new function, and check more fields. In the openssl that I have, it should be safe to only check the size of n. But if I'm wrong, or if other openssls work differently, we should check whether any of the fields are too large. Issue spotted by Teor. --- src/lib/crypt_ops/crypto_rsa_openssl.c | 57 +++++++++++++++++++++++++++++++--- 1 file changed, 52 insertions(+), 5 deletions(-) diff --git a/src/lib/crypt_ops/crypto_rsa_openssl.c b/src/lib/crypt_ops/crypto_rsa_openssl.c index 0db25f347..6f3ac6fde 100644 --- a/src/lib/crypt_ops/crypto_rsa_openssl.c +++ b/src/lib/crypt_ops/crypto_rsa_openssl.c @@ -33,6 +33,7 @@ ENABLE_GCC_WARNING(redundant-decls) #include "lib/encoding/binascii.h" #include <string.h> +#include <stdbool.h> /** Declaration for crypto_pk_t structure. */ struct crypto_pk_t @@ -564,6 +565,56 @@ crypto_pk_asn1_encode_private(const crypto_pk_t *pk, char *dest, return len; } +/** Check whether any component of a private key is too large in a way that + * seems likely to make verification too expensive. Return true if it's too + * long, and false otherwise. */ +static bool +rsa_private_key_too_long(RSA *rsa, int max_bits) +{ + const BIGNUM *n, *e, *p, *q, *d, *dmp1, *dmq1, *iqmp; +#ifdef OPENSSL_1_1_API + n = RSA_get0_n(rsa); + e = RSA_get0_e(rsa); + p = RSA_get0_p(rsa); + q = RSA_get0_q(rsa); + d = RSA_get0_d(rsa); + dmp1 = RSA_get0_dmp1(rsa); + dmq1 = RSA_get0_dmq1(rsa); + iqmp = RSA_get0_iqmp(rsa); + + if (RSA_bits(rsa) > max_bits) + return true; +#else + n = rsa->n; + e = rsa->e; + p = rsa->p; + q = rsa->q; + d = rsa->d; + dmp1 = rsa->dmp1; + dmq1 = rsa->dmq1; + iqmp = rsa->iqmp; +#endif + + if (n && BN_num_bits(n) > max_bits) + return true; + if (e && BN_num_bits(e) > max_bits) + return true; + if (p && BN_num_bits(p) > max_bits) + return true; + if (q && BN_num_bits(q) > max_bits) + return true; + if (d && BN_num_bits(d) > max_bits) + return true; + if (dmp1 && BN_num_bits(dmp1) > max_bits) + return true; + if (dmq1 && BN_num_bits(dmq1) > max_bits) + return true; + if (iqmp && BN_num_bits(iqmp) > max_bits) + return true; + + return false; +} + /** Decode an ASN.1-encoded private key from str; return the result on * success and NULL on failure. * @@ -584,11 +635,7 @@ crypto_pk_asn1_decode_private(const char *str, size_t len, int max_bits) crypto_openssl_log_errors(LOG_WARN,"decoding private key"); return NULL; } -#ifdef OPENSSL_1_1_API - if (max_bits >= 0 && RSA_bits(rsa) > max_bits) { -#else - if (max_bits >= 0 && rsa->n && BN_num_bits(rsa->n) > max_bits) { -#endif + if (max_bits >= 0 && rsa_private_key_too_long(rsa, max_bits)) { log_info(LD_CRYPTO, "Private key longer than expected."); RSA_free(rsa); return NULL;

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