commit 9e1085c924133d7b73c7b0a42282fb13b34f28b8 Author: Nick Mathewson nickm@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 <b>len</b>-byte string <b>src</b> @@ -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 <b>str</b>, decode and return the result on success, or NULL * on failure. + * + * If <b>max_bits</b> 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 <b>str</b>; return the result on * success and NULL on failure. + * + * If <b>max_bits</b> 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);