talons

commit 5805ff8180e298a04a4c99ab57374cf87e273c11
parent dc1debf5645c552a1cd9c6be5313e0ed8b797d28
Author: Andrej Kacian <ticho@claws-mail.org>
Date:   Thu, 14 Dec 2017 23:18:50 +0100

Fix buffer length handling in GnuTLS password encryption and decryption.

Also zero out one forgotten copy of plaintext password
before freeing it. Oops!

Diffstat:
M
src/password.c
 | 
18
+++++++++++++-----

1 file changed, 13 insertions(+), 5 deletions(-)
diff --git a/src/password.c b/src/password.c
@@ -356,7 +356,7 @@ gchar *password_encrypt_gnutls(const gchar *password,
 	/* Fill buf with one block of random data, our password, pad the
 	 * rest with zero bytes. */
 	buf = malloc(BUFSIZE + blocklen);
-	memset(buf, 0, BUFSIZE);
+	memset(buf, 0, BUFSIZE + blocklen);
 	if (!get_random_bytes(buf, blocklen)) {
 		g_free(buf);
 		g_free(key.data);
@@ -389,7 +389,7 @@ gchar *password_encrypt_gnutls(const gchar *password,
 
 	/* And finally prepare the resulting string:
 	 * "{algorithm,rounds}base64encodedciphertext" */
-	base = g_base64_encode(encbuf, BUFSIZE);
+	base = g_base64_encode(encbuf, BUFSIZE + blocklen);
 	g_free(encbuf);
 	output = g_strdup_printf("{%s,%d}%s",
 			gnutls_cipher_get_name(algo), rounds, base);
@@ -479,6 +479,7 @@ gchar *password_decrypt_gnutls(const gchar *password,
 			g_free(tmp);
 		return NULL;
 	}
+	debug_print("Encrypted password string length: %lu\n", len);
 
 	/* Initialize the decryption */
 	ret = gnutls_cipher_init(&handle, algo, &key, &iv);
@@ -490,10 +491,13 @@ gchar *password_decrypt_gnutls(const gchar *password,
 		return NULL;
 	}
 
-	buf = malloc(len + blocklen);
-	memset(buf, 0, len + blocklen);
+	/* Allocate the buffer to store decrypted plaintext in. */
+	buf = malloc(len);
+	memset(buf, 0, len);
+
+	/* Decrypt! */
 	ret = gnutls_cipher_decrypt2(handle, tmp, len,
-			buf, len + blocklen);
+			buf, len);
 	g_free(tmp);
 	if (ret < 0) {
 		debug_print("Decryption failed: %s\n", gnutls_strerror(ret));
@@ -509,8 +513,12 @@ gchar *password_decrypt_gnutls(const gchar *password,
 	g_free(key.data);
 	g_free(iv.data);
 
+	/* 'buf+blocklen' should now be pointing to the plaintext
+	 * password string. The first block contains random data from the IV. */
 	tmp = g_strndup(buf + blocklen, MIN(strlen(buf + blocklen), BUFSIZE));
+	memset(buf, 0, len);
 	g_free(buf);
+
 	return tmp;
 }