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vold: cryptfs: Don't update KDF without validating pwd/key.

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Prior to this, the Key derivation function would get
 blindly updated even if the user entered the wrong password.
Now, we only attempt to upgrade the KDF if the pwd/key have
been verified (i.e. after a successful mount).

Bug: 11460197
Change-Id: I0469228cc9b87c47754e8ca3c7146651da177da5
This commit is contained in:
JP Abgrall 2013-11-15 13:42:56 -08:00
parent 6bcd362edd
commit 7bdfa52d93
1 changed files with 25 additions and 17 deletions
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42
cryptfs.c
View file

@ -351,6 +351,9 @@ static void upgrade_crypt_ftr(int fd, struct crypt_mnt_ftr *crypt_ftr, off64_t o
if ((crypt_ftr->major_version == 1) && (crypt_ftr->minor_version)) {
SLOGW("upgrading crypto footer to 1.2");
/* But keep the old kdf_type.
* It will get updated later to KDF_SCRYPT after the password has been verified.
*/
crypt_ftr->kdf_type = KDF_PBKDF2;
get_device_scrypt_params(crypt_ftr);
crypt_ftr->minor_version = 2;
@ -922,7 +925,7 @@ static int encrypt_master_key(char *passwd, unsigned char *salt,
}
}
static int decrypt_master_key(char *passwd, unsigned char *salt,
static int decrypt_master_key_aux(char *passwd, unsigned char *salt,
unsigned char *encrypted_master_key,
unsigned char *decrypted_master_key,
kdf_func kdf, void *kdf_params)
@ -966,7 +969,7 @@ static void get_kdf_func(struct crypt_mnt_ftr *ftr, kdf_func *kdf, void** kdf_pa
}
}
static int decrypt_master_key_and_upgrade(char *passwd, unsigned char *decrypted_master_key,
static int decrypt_master_key(char *passwd, unsigned char *decrypted_master_key,
struct crypt_mnt_ftr *crypt_ftr)
{
kdf_func kdf;
@ -974,21 +977,10 @@ static int decrypt_master_key_and_upgrade(char *passwd, unsigned char *decrypted
int ret;
get_kdf_func(crypt_ftr, &kdf, &kdf_params);
ret = decrypt_master_key(passwd, crypt_ftr->salt, crypt_ftr->master_key, decrypted_master_key, kdf,
ret = decrypt_master_key_aux(passwd, crypt_ftr->salt, crypt_ftr->master_key, decrypted_master_key, kdf,
kdf_params);
if (ret != 0) {
SLOGW("failure decrypting master key");
return ret;
}
/*
* Upgrade if we're not using the latest KDF.
*/
if (crypt_ftr->kdf_type != KDF_SCRYPT) {
crypt_ftr->kdf_type = KDF_SCRYPT;
encrypt_master_key(passwd, crypt_ftr->salt, decrypted_master_key, crypt_ftr->master_key,
crypt_ftr);
put_crypt_ftr_and_key(crypt_ftr);
}
return ret;
@ -1230,7 +1222,10 @@ static int test_mount_encrypted_fs(char *passwd, char *mount_point, char *label)
orig_failed_decrypt_count = crypt_ftr.failed_decrypt_count;
if (! (crypt_ftr.flags & CRYPT_MNT_KEY_UNENCRYPTED) ) {
decrypt_master_key_and_upgrade(passwd, decrypted_master_key, &crypt_ftr);
if (decrypt_master_key(passwd, decrypted_master_key, &crypt_ftr)) {
SLOGE("Failed to decrypt master key\n");
return -1;
}
}
if (create_crypto_blk_dev(&crypt_ftr, decrypted_master_key,
@ -1280,7 +1275,20 @@ static int test_mount_encrypted_fs(char *passwd, char *mount_point, char *label)
memcpy(saved_master_key, decrypted_master_key, KEY_LEN_BYTES);
saved_mount_point = strdup(mount_point);
master_key_saved = 1;
SLOGD("%s(): Master key saved\n", __FUNCTION__);
rc = 0;
/*
* Upgrade if we're not using the latest KDF.
*/
if (crypt_ftr.kdf_type != KDF_SCRYPT) {
crypt_ftr.kdf_type = KDF_SCRYPT;
rc = encrypt_master_key(passwd, crypt_ftr.salt, saved_master_key, crypt_ftr.master_key,
&crypt_ftr);
if (!rc) {
rc = put_crypt_ftr_and_key(&crypt_ftr);
}
SLOGD("Key Derivation Function upgrade: rc=%d\n", rc);
}
}
return rc;
@ -1383,7 +1391,7 @@ int cryptfs_verify_passwd(char *passwd)
/* If the device has no password, then just say the password is valid */
rc = 0;
} else {
decrypt_master_key_and_upgrade(passwd, decrypted_master_key, &crypt_ftr);
decrypt_master_key(passwd, decrypted_master_key, &crypt_ftr);
if (!memcmp(decrypted_master_key, saved_master_key, crypt_ftr.keysize)) {
/* They match, the password is correct */
rc = 0;
@ -1777,7 +1785,7 @@ int cryptfs_enable(char *howarg, char *passwd)
save_persistent_data();
}
decrypt_master_key_and_upgrade(passwd, decrypted_master_key, &crypt_ftr);
decrypt_master_key(passwd, decrypted_master_key, &crypt_ftr);
create_crypto_blk_dev(&crypt_ftr, decrypted_master_key, real_blkdev, crypto_blkdev,
"userdata");