commit 1880a6a88e240556a8e6b169f1160aa8220ab0ec Author: Nick Mathewson nickm@torproject.org Date: Sat Nov 11 14:21:37 2017 -0500

Avoid asking for passphrase on junky PEM input

Fixes bug 24246 and TROVE-2017-011.

This bug is so old, it's in Matej's code. Seems to have been introduced with e01522bbed6eea. --- changes/trove-2017-011 | 8 ++++++++ src/common/crypto.c | 16 +++++++++++++--- 2 files changed, 21 insertions(+), 3 deletions(-)

diff --git a/changes/trove-2017-011 b/changes/trove-2017-011 new file mode 100644 index 000000000..82d20d9e7 --- /dev/null +++ b/changes/trove-2017-011 @@ -0,0 +1,8 @@ + o Major bugfixes (security): + - Fix a denial of service bug where an attacker could use a malformed + directory object to cause a Tor instance to pause while OpenSSL would + try to read a passphrase from the terminal. (If the terminal was not + available, tor would continue running.) Fixes bug 24246; bugfix on + every version of Tor. Also tracked as TROVE-2017-011 and + CVE-2017-8821. Found by OSS-Fuzz as testcase 6360145429790720. + diff --git a/src/common/crypto.c b/src/common/crypto.c index f7362765d..8d816652d 100644 --- a/src/common/crypto.c +++ b/src/common/crypto.c @@ -592,11 +592,21 @@ crypto_pk_generate_key_with_bits(crypto_pk_t *env, int bits) return 0; }

+/** A PEM callback that always reports a failure to get a password */ +static int +pem_no_password_cb(char *buf, int size, int rwflag, void *u) +{ + (void)buf; + (void)size; + (void)rwflag; + (void)u; + return 0; +} + /** Read a PEM-encoded private key from the <b>len</b>-byte string <b>s</b> * into <b>env</b>. Return 0 on success, -1 on failure. If len is -1, * the string is nul-terminated. */ -/* Used here, and used for testing. */ int crypto_pk_read_private_key_from_string(crypto_pk_t *env, const char *s, ssize_t len) @@ -615,7 +625,7 @@ crypto_pk_read_private_key_from_string(crypto_pk_t *env, if (env->key) RSA_free(env->key);

- env->key = PEM_read_bio_RSAPrivateKey(b,NULL,NULL,NULL); + env->key = PEM_read_bio_RSAPrivateKey(b,NULL,pem_no_password_cb,NULL);

BIO_free(b);

@@ -747,7 +757,7 @@ crypto_pk_read_public_key_from_string(crypto_pk_t *env, const char *src,

if (env->key) RSA_free(env->key); - env->key = PEM_read_bio_RSAPublicKey(b, NULL, NULL, NULL); + env->key = PEM_read_bio_RSAPublicKey(b, NULL, pem_no_password_cb, NULL); BIO_free(b); if (!env->key) { crypto_log_errors(LOG_WARN, "reading public key from string");