[Pkg-voip-commits] [bctoolbox] 24/60: backport of Fix DHM secret extraction to polarssl1.3 4bebece81ba624ba254ac348032c2b5cac99639f

[Bernhard Schmidt]

This is an automated email from the git hooks/post-receive script.

berni pushed a commit to branch debian/sid
in repository bctoolbox.

commit da0816a3ca74b164b45c54fe5caaa1db8789c356
Author: Johan Pascal <johan.pascal at belledonne-communications.com>
Date:   Fri Apr 7 11:53:39 2017 +0700

    backport of Fix DHM secret extraction to polarssl1.3
    4bebece81ba624ba254ac348032c2b5cac99639f
---
 src/crypto/polarssl.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/src/crypto/polarssl.c b/src/crypto/polarssl.c
index a998575..6c38333 100644
--- a/src/crypto/polarssl.c
+++ b/src/crypto/polarssl.c
@@ -628,14 +628,20 @@ void bctbx_DHMCreatePublic(bctbx_DHMContext_t *context, int (*rngFunction)(void
 /* compute secret - the ->peer field of context must have been set before calling this function */
 void bctbx_DHMComputeSecret(bctbx_DHMContext_t *context, int (*rngFunction)(void *, uint8_t *, size_t), void *rngContext) {
 	size_t keyLength;
+	uint8_t sharedSecretBuffer[384]; /* longest shared secret available in these mode */
 
 	/* import the peer public value G^Y mod P in the polar ssl context */
 	dhm_read_public((dhm_context *)(context->cryptoModuleData), context->peer, context->primeLength);
 
 	/* compute the secret key */
 	keyLength = context->primeLength; /* undocumented but this value seems to be in/out, so we must set it to the expected key length */
-	context->key = (uint8_t *)malloc(keyLength*sizeof(uint8_t)); /* allocate key buffer */
-	dhm_calc_secret((dhm_context *)(context->cryptoModuleData), context->key, &keyLength, (int (*)(void *, unsigned char *, size_t))rngFunction, rngContext);
+	context->key = (uint8_t *)malloc(keyLength*sizeof(uint8_t)); /* allocate and reset the key buffer */
+	memset(context->key,0, keyLength);
+
+	dhm_calc_secret((dhm_context *)(context->cryptoModuleData), sharedSecretBuffer, &keyLength, (int (*)(void *, unsigned char *, size_t))rngFunction, rngContext);
+	/* now copy the resulting secret in the correct place in buffer(result may actually miss some front zero bytes, real length of output is now in keyLength but we want primeLength bytes) */
+	memcpy(context->key+(context->primeLength-keyLength), sharedSecretBuffer, keyLength);
+	memset(sharedSecretBuffer, 0, 384); /* purge secret from temporary buffer */
 }
 
 /* clean DHM context */

-- 
Alioth's /usr/local/bin/git-commit-notice on /srv/git.debian.org/git/pkg-voip/bctoolbox.git