cryptfs_hw/cryptfs_hw.c

/* Copyright (c) 2014, The Linux Foundation. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *   * Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 *   * Redistributions in binary form must reproduce the above
 *     copyright notice, this list of conditions and the following
 *     disclaimer in the documentation and/or other materials provided
 *     with the distribution.
 *   * Neither the name of The Linux Foundation nor the names of its
 *     contributors may be used to endorse or promote products derived
 *     from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED "AS IS" AND ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS
 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
 * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
 * OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN
 * IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include <cryptfs_hw.h>
#include <stdlib.h>
#include <sys/limits.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <dirent.h>
#include <dlfcn.h>
#include "cutils/log.h"
#include "cutils/properties.h"
#include "cutils/android_reboot.h"


// When device comes up or when user tries to change the password, user can
// try wrong password upto a certain number of times. If user enters wrong
// password further, HW would wipe all disk encryption related crypto data
// and would return an error ERR_MAX_PASSWORD_ATTEMPTS to VOLD. VOLD would
// wipe userdata partition once this error is received.
#define ERR_MAX_PASSWORD_ATTEMPTS -10
#define QSEECOM_DISK_ENCRYPTION 1
#define QSEECOM_ICE_DISK_ENCRYPTION 3
#define MAX_PASSWORD_LEN 32

/* Operations that be performed on HW based device encryption key */
#define SET_HW_DISK_ENC_KEY 1
#define UPDATE_HW_DISK_ENC_KEY 2

static int loaded_library = 0;
static unsigned char current_passwd[MAX_PASSWORD_LEN];
static int (*qseecom_create_key)(int, void*);
static int (*qseecom_update_key)(int, void*, void*);
static int (*qseecom_wipe_key)(int);

static int map_usage(int usage)
{
    return (is_ice_enabled() && (usage == QSEECOM_DISK_ENCRYPTION)) ?
                                          QSEECOM_ICE_DISK_ENCRYPTION : usage;
}


static unsigned char* get_tmp_passwd(const char* passwd)
{
    int passwd_len = 0;
    unsigned char * tmp_passwd = NULL;
    if(passwd) {
        tmp_passwd = (unsigned char*)malloc(MAX_PASSWORD_LEN);
        if(tmp_passwd) {
            memset(tmp_passwd, 0, MAX_PASSWORD_LEN);
            passwd_len = (strlen(passwd) > MAX_PASSWORD_LEN) ? MAX_PASSWORD_LEN : strlen(passwd);
            memcpy(tmp_passwd, passwd, passwd_len);
        } else {
            SLOGE("%s: Failed to allocate memory for tmp passwd \n", __func__);
        }
    } else {
        SLOGE("%s: Passed argument is NULL \n", __func__);
    }
    return tmp_passwd;
}

static void wipe_userdata()
{
    mkdir("/cache/recovery", 0700);
    int fd = open("/cache/recovery/command", O_RDWR|O_CREAT|O_TRUNC|O_NOFOLLOW, 0600);
    if (fd >= 0) {
        write(fd, "--wipe_data", strlen("--wipe_data") + 1);
        close(fd);
    } else {
        SLOGE("could not open /cache/recovery/command\n");
    }
    android_reboot(ANDROID_RB_RESTART2, 0, "recovery");
}

static int load_qseecom_library()
{
    const char *error = NULL;
    if (loaded_library)
        return loaded_library;

    void * handle = dlopen("/vendor/lib/libQSEEComAPI.so", RTLD_NOW);
    if(handle) {
        dlerror(); /* Clear any existing error */
        *(void **) (&qseecom_create_key) = dlsym(handle,"QSEECom_create_key");

        if((error = dlerror()) == NULL) {
            SLOGD("Success loading QSEECom_create_key \n");
            *(void **) (&qseecom_update_key) = dlsym(handle,"QSEECom_update_key_user_info");
            if ((error = dlerror()) == NULL) {
                SLOGD("Success loading QSEECom_update_key_user_info\n");
                *(void **) (&qseecom_wipe_key) = dlsym(handle,"QSEECom_wipe_key");
                if ((error = dlerror()) == NULL) {
                    loaded_library = 1;
                    SLOGD("Success loading QSEECom_wipe_key \n");
                }
                else
                    SLOGE("Error %s loading symbols for QSEECom APIs \n", error);
            }
            else
                SLOGE("Error %s loading symbols for QSEECom APIs \n", error);
        }
    } else {
        SLOGE("Could not load libQSEEComAPI.so \n");
    }

    if(error)
        dlclose(handle);

    return loaded_library;
}

/*
 * For NON-ICE targets, it would return 0 on success. On ICE based targets,
 * it would return key index in the ICE Key LUT
 */
static int set_key(const char* passwd, const char* enc_mode, int operation)
{
    int err = -1;
    if (is_hw_disk_encryption(enc_mode) && load_qseecom_library()) {
        unsigned char* tmp_passwd = get_tmp_passwd(passwd);
        if(tmp_passwd) {
            if (operation == UPDATE_HW_DISK_ENC_KEY)
                err = qseecom_update_key(map_usage(QSEECOM_DISK_ENCRYPTION), current_passwd, tmp_passwd);
            else if (operation == SET_HW_DISK_ENC_KEY)
                err = qseecom_create_key(map_usage(QSEECOM_DISK_ENCRYPTION), tmp_passwd);

            if(err >= 0) {
                memset(current_passwd, 0, MAX_PASSWORD_LEN);
                memcpy(current_passwd, tmp_passwd, MAX_PASSWORD_LEN);
            } else {
                if(ERR_MAX_PASSWORD_ATTEMPTS == err)
                    wipe_userdata();
            }
            free(tmp_passwd);
        }
    }
    return err;
}

int set_hw_device_encryption_key(const char* passwd, const char* enc_mode)
{
    return set_key(passwd, enc_mode, SET_HW_DISK_ENC_KEY);
}

int update_hw_device_encryption_key(const char* newpw, const char* enc_mode)
{

    return set_key(newpw, enc_mode, UPDATE_HW_DISK_ENC_KEY);
}

unsigned int is_hw_disk_encryption(const char* encryption_mode)
{
    int ret = 0;
    if(encryption_mode) {
        if (!strcmp(encryption_mode, "aes-xts")) {
            SLOGD("HW based disk encryption is enabled \n");
            ret = 1;
        }
    }
    return ret;
}

int is_ice_enabled(void)
{
    /* If (USE_ICE_FLAG) => return 1
     * if (property set to use gpce) return 0
     * we are using property to test UFS + GPCE, even though not required
     * if (storage is ufs) return 1
     * else return 0 so that emmc based device can work properly
     */
#ifdef USE_ICE_FOR_STORAGE_ENCRYPTION
    SLOGD("Ice enabled = true");
    return 1;
#else
    char enc_hw_type[PATH_MAX];
    char prop_storage[PATH_MAX];
    int ice = 0;
    int i;
    if (property_get("crypto.fde_enc_hw_type", enc_hw_type, "")) {
        if(!strncmp(enc_hw_type, "gpce", PROPERTY_VALUE_MAX)) {
            SLOGD("GPCE would be used for HW FDE");
            return 0;
        }
    }

    if (property_get("ro.boot.bootdevice", prop_storage, "")) {
        if(strstr(prop_storage, "ufs")) {
            SLOGD("ICE would be used for HW FDE");
            return 1;
        }
    }
    SLOGD("GPCE would be used for HW FDE");
    return 0;
#endif
}

int wipe_hw_device_encryption_key(const char* enc_mode)
{
    if (!enc_mode)
        return -1;

    if (is_hw_disk_encryption(enc_mode) && load_qseecom_library())
        return qseecom_wipe_key(map_usage(QSEECOM_DISK_ENCRYPTION));

    return 0;
}