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Fix crypto_free zeroing of encryption keys

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The zeroing MUST use the correct cipher length as keys can be both
longer or shorter than the digest. In one case only some part of the key
may end up being zeroed, in the other memory corruption may happen as
we zero memory we do not own.

Signed-off-by: Simo Sorce <simo@redhat.com>
Reviewed-by: Anderson Toshiyuki Sasaki <ansasaki@redhat.com>
Reviewed-by: Andreas Schneider <asn@cryptomilk.org>
This commit is contained in:
Simo Sorce
2018-10-03 09:14:45 -04:00
committed by Andreas Schneider
parent 7c444c09d7
commit 449954d99a
1 changed files with 5 additions and 5 deletions
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10
src/wrapper.c
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@@ -168,9 +168,6 @@ void crypto_free(struct ssh_crypto_struct *crypto)
ssh_key_free(crypto->server_pubkey); ssh_key_free(crypto->server_pubkey);
cipher_free(crypto->in_cipher);
cipher_free(crypto->out_cipher);
ssh_dh_cleanup(crypto); ssh_dh_cleanup(crypto);
bignum_safe_free(crypto->k); bignum_safe_free(crypto->k);
#ifdef HAVE_ECDH #ifdef HAVE_ECDH
@@ -211,14 +208,17 @@ void crypto_free(struct ssh_crypto_struct *crypto)
SAFE_FREE(crypto->encryptMAC); SAFE_FREE(crypto->encryptMAC);
SAFE_FREE(crypto->decryptMAC); SAFE_FREE(crypto->decryptMAC);
if (crypto->encryptkey != NULL) { if (crypto->encryptkey != NULL) {
explicit_bzero(crypto->encryptkey, crypto->digest_len); explicit_bzero(crypto->encryptkey, crypto->out_cipher->keysize / 8);
SAFE_FREE(crypto->encryptkey); SAFE_FREE(crypto->encryptkey);
} }
if (crypto->decryptkey != NULL) { if (crypto->decryptkey != NULL) {
explicit_bzero(crypto->decryptkey, crypto->digest_len); explicit_bzero(crypto->decryptkey, crypto->in_cipher->keysize / 8);
SAFE_FREE(crypto->decryptkey); SAFE_FREE(crypto->decryptkey);
} }
cipher_free(crypto->in_cipher);
cipher_free(crypto->out_cipher);
for (i = 0; i < SSH_KEX_METHODS; i++) { for (i = 0; i < SSH_KEX_METHODS; i++) {
SAFE_FREE(crypto->client_kex.methods[i]); SAFE_FREE(crypto->client_kex.methods[i]);
SAFE_FREE(crypto->server_kex.methods[i]); SAFE_FREE(crypto->server_kex.methods[i]);