ext4crypt: support synthetic keys v3 on May update
Re-implemented SP800Derive in C++, which is added as the new key
derivation function in Android 9.0 May update. From file
services/core/java/com/android/server/locksettings/SP800Derive.java in
frameworks/base.
This is required to get TWRP working on any Android device that has a
screen lock set up after the May update.
Change-Id: I5c1a51b110033f2b0b75d5e36fd8098c05e95179
diff --git a/crypto/ext4crypt/Decrypt.cpp b/crypto/ext4crypt/Decrypt.cpp
index e69b647..d8542dc 100644
--- a/crypto/ext4crypt/Decrypt.cpp
+++ b/crypto/ext4crypt/Decrypt.cpp
@@ -244,13 +244,6 @@
return false;
}
-// The password data is stored in big endian and has to be swapped on little endian ARM
-template <class T>
-void endianswap(T *objp) {
- unsigned char *memp = reinterpret_cast<unsigned char*>(objp);
- std::reverse(memp, memp + sizeof(T));
-}
-
/* This is the structure of the data in the password data (*.pwd) file which the structure can be found
* https://android.googlesource.com/platform/frameworks/base/+/android-8.0.0_r23/services/core/java/com/android/server/locksettings/SyntheticPasswordManager.java#187 */
struct password_data_struct {
@@ -442,7 +435,8 @@
namespace keystore {
#define SYNTHETIC_PASSWORD_VERSION_V1 1
-#define SYNTHETIC_PASSWORD_VERSION 2
+#define SYNTHETIC_PASSWORD_VERSION_V2 2
+#define SYNTHETIC_PASSWORD_VERSION_V3 3
#define SYNTHETIC_PASSWORD_PASSWORD_BASED 0
#define SYNTHETIC_PASSWORD_KEY_PREFIX "USRSKEY_synthetic_password_"
#define USR_PRIVATE_KEY_PREFIX "USRPKEY_synthetic_password_"
@@ -579,7 +573,8 @@
return disk_decryption_secret_key;
}
unsigned char* byteptr = (unsigned char*)spblob_data.data();
- if (*byteptr != SYNTHETIC_PASSWORD_VERSION && *byteptr != SYNTHETIC_PASSWORD_VERSION_V1) {
+ if (*byteptr != SYNTHETIC_PASSWORD_VERSION_V2 && *byteptr != SYNTHETIC_PASSWORD_VERSION_V1
+ && *byteptr != SYNTHETIC_PASSWORD_VERSION_V3) {
printf("Unsupported synthetic password version %i\n", *byteptr);
return disk_decryption_secret_key;
}
@@ -772,9 +767,10 @@
}
stop_keystore();
return disk_decryption_secret_key;
- } else if (*synthetic_password_version == SYNTHETIC_PASSWORD_VERSION) {
- printf("spblob v2\n");
- /* Version 2 of the spblob is basically the same as version 1, but the order of getting the intermediate key and disk decryption key have been flip-flopped
+ } else if (*synthetic_password_version == SYNTHETIC_PASSWORD_VERSION_V2
+ || *synthetic_password_version == SYNTHETIC_PASSWORD_VERSION_V3) {
+ printf("spblob v2 / v3\n");
+ /* Version 2 / 3 of the spblob is basically the same as version 1, but the order of getting the intermediate key and disk decryption key have been flip-flopped
* as seen in https://android.googlesource.com/platform/frameworks/base/+/5025791ac6d1538224e19189397de8d71dcb1a12
*/
/* First decrypt call found in
@@ -926,7 +922,12 @@
//printf("secret key: "); output_hex((const unsigned char*)secret_key, secret_key_real_size); printf("\n");
// The payload data from the keystore update is further personalized at https://android.googlesource.com/platform/frameworks/base/+/android-8.0.0_r23/services/core/java/com/android/server/locksettings/SyntheticPasswordManager.java#153
// We now have the disk decryption key!
- disk_decryption_secret_key = PersonalizedHash(PERSONALIZATION_FBE_KEY, (const char*)secret_key, secret_key_real_size);
+ if (*synthetic_password_version == SYNTHETIC_PASSWORD_VERSION_V3) {
+ // V3 uses SP800 instead of SHA512
+ disk_decryption_secret_key = PersonalizedHashSP800(PERSONALIZATION_FBE_KEY, PERSONALISATION_CONTEXT, (const char*)secret_key, secret_key_real_size);
+ } else {
+ disk_decryption_secret_key = PersonalizedHash(PERSONALIZATION_FBE_KEY, (const char*)secret_key, secret_key_real_size);
+ }
//printf("disk_decryption_secret_key: '%s'\n", disk_decryption_secret_key.c_str());
free(secret_key);
return disk_decryption_secret_key;