tequilaOS/platform_system_vold
2
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity

cryptfs: Make decrypted key buffers large enough

Browse source 
Looking at the EVP_DecryptUpdate() documentation, we need a
buffer which isn't just the keysize, but also provides the
cipher block length minus one byte extra.  For EVP_aes_128_cbc(),
that block length is 16, but we use the maximum block length to
be safe for any future cipher change.

For two of our decrypted_master_key usages, the buffer was
already sufficiently sized.  But for one of our instances,
in cryptfs_enable_internal(), the buffer was previously
smaller than this.  So this CL represents a possible behavior
change if we were ever overrunning that buffer.

Bug: 73079191, 73176599
Test: Flashed an encrypted sailfish and it booted.

Change-Id: Ic5043340910dc7d625e6e5baedbca5bd4b2bfb03
This commit is contained in:
Greg Kaiser 2018-02-09 17:01:06 -08:00
parent 1452b27d4e
commit 4a35ef0a53
1 changed files with 8 additions and 5 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

13
cryptfs.cpp
View file

@ -98,6 +98,11 @@ extern "C" {
#define CREATE_CRYPTO_BLK_DEV_FLAGS_ALLOW_ENCRYPT_OVERRIDE (1)
// EVP_DecryptUpdate() requires not just our key length, but up to
// block length - 1 additional bytes for its work. We provide a buffer
// size that will work for all possible ciphers.
#define DECRYPTED_MASTER_KEY_BUF_SIZE (KEY_LEN_BYTES + EVP_MAX_BLOCK_LENGTH - 1)
static int put_crypt_ftr_and_key(struct crypt_mnt_ftr* crypt_ftr);
static unsigned char saved_master_key[KEY_LEN_BYTES];
@ -1595,8 +1600,7 @@ static int do_crypto_complete(const char *mount_point)
static int test_mount_encrypted_fs(struct crypt_mnt_ftr* crypt_ftr,
const char *passwd, const char *mount_point, const char *label)
{
/* Allocate enough space for a 256 bit key, but we may use less */
unsigned char decrypted_master_key[32];
unsigned char decrypted_master_key[DECRYPTED_MASTER_KEY_BUF_SIZE];
char crypto_blkdev[MAXPATHLEN];
char real_blkdev[MAXPATHLEN];
char tmp_mount_point[64];
@ -1853,8 +1857,7 @@ int cryptfs_check_passwd(const char *passwd)
int cryptfs_verify_passwd(const char *passwd)
{
struct crypt_mnt_ftr crypt_ftr;
/* Allocate enough space for a 256 bit key, but we may use less */
unsigned char decrypted_master_key[32];
unsigned char decrypted_master_key[DECRYPTED_MASTER_KEY_BUF_SIZE];
char encrypted_state[PROPERTY_VALUE_MAX];
int rc;
@ -2004,7 +2007,7 @@ static int vold_unmountAll(void) {
int cryptfs_enable_internal(int crypt_type, const char* passwd, int no_ui) {
char crypto_blkdev[MAXPATHLEN], real_blkdev[MAXPATHLEN];
unsigned char decrypted_master_key[KEY_LEN_BYTES];
unsigned char decrypted_master_key[DECRYPTED_MASTER_KEY_BUF_SIZE];
int rc=-1, i;
struct crypt_mnt_ftr crypt_ftr;
struct crypt_persist_data *pdata;