Atmosphere/fusee/fusee-secondary/src/key_derivation.c

/*
 * Copyright (c) 2018-2020 Atmosphère-NX
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms and conditions of the GNU General Public License,
 * version 2, as published by the Free Software Foundation.
 *
 * This program is distributed in the hope it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
 * more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <stdio.h>
#include "lib/log.h"
#include "key_derivation.h"
#include "masterkey.h"
#include "se.h"
#include "exocfg.h"
#include "fuse.h"
#include "extkeys.h"
#include "utils.h"

#define AL16 ALIGN(16)

static const uint8_t AL16 keyblob_seeds[MASTERKEY_REVISION_MAX][0x10] = {
    {0xDF, 0x20, 0x6F, 0x59, 0x44, 0x54, 0xEF, 0xDC, 0x70, 0x74, 0x48, 0x3B, 0x0D, 0xED, 0x9F, 0xD3},   /* Keyblob seed 00. */
    {0x0C, 0x25, 0x61, 0x5D, 0x68, 0x4C, 0xEB, 0x42, 0x1C, 0x23, 0x79, 0xEA, 0x82, 0x25, 0x12, 0xAC},   /* Keyblob seed 01. */
    {0x33, 0x76, 0x85, 0xEE, 0x88, 0x4A, 0xAE, 0x0A, 0xC2, 0x8A, 0xFD, 0x7D, 0x63, 0xC0, 0x43, 0x3B},   /* Keyblob seed 02. */
    {0x2D, 0x1F, 0x48, 0x80, 0xED, 0xEC, 0xED, 0x3E, 0x3C, 0xF2, 0x48, 0xB5, 0x65, 0x7D, 0xF7, 0xBE},   /* Keyblob seed 03. */
    {0xBB, 0x5A, 0x01, 0xF9, 0x88, 0xAF, 0xF5, 0xFC, 0x6C, 0xFF, 0x07, 0x9E, 0x13, 0x3C, 0x39, 0x80},   /* Keyblob seed 04. */
    {0xD8, 0xCC, 0xE1, 0x26, 0x6A, 0x35, 0x3F, 0xCC, 0x20, 0xF3, 0x2D, 0x3B, 0x51, 0x7D, 0xE9, 0xC0}    /* Keyblob seed 05. */
};

static const uint8_t AL16 keyblob_mac_seed[0x10] = {
    0x59, 0xC7, 0xFB, 0x6F, 0xBE, 0x9B, 0xBE, 0x87, 0x65, 0x6B, 0x15, 0xC0, 0x53, 0x73, 0x36, 0xA5
};

static const uint8_t AL16 masterkey_seed[0x10] = {
    0xD8, 0xA2, 0x41, 0x0A, 0xC6, 0xC5, 0x90, 0x01, 0xC6, 0x1D, 0x6A, 0x26, 0x7C, 0x51, 0x3F, 0x3C
};

static const uint8_t AL16 devicekey_seed[0x10] = {
    0x4F, 0x02, 0x5F, 0x0E, 0xB6, 0x6D, 0x11, 0x0E, 0xDC, 0x32, 0x7D, 0x41, 0x86, 0xC2, 0xF4, 0x78
};

static const uint8_t AL16 devicekey_4x_seed[0x10] = {
    0x0C, 0x91, 0x09, 0xDB, 0x93, 0x93, 0x07, 0x81, 0x07, 0x3C, 0xC4, 0x16, 0x22, 0x7C, 0x6C, 0x28
};

static const uint8_t AL16 masterkey_4x_seed[0x10] = {
    0x2D, 0xC1, 0xF4, 0x8D, 0xF3, 0x5B, 0x69, 0x33, 0x42, 0x10, 0xAC, 0x65, 0xDA, 0x90, 0x46, 0x66
};

/* TODO: Bother adding 8.1.0 here? We'll never call into here... */
static const uint8_t AL16 new_master_kek_seeds[MASTERKEY_REVISION_700_800 - MASTERKEY_REVISION_600_610][0x10] = {
    {0x37, 0x4B, 0x77, 0x29, 0x59, 0xB4, 0x04, 0x30, 0x81, 0xF6, 0xE5, 0x8C, 0x6D, 0x36, 0x17, 0x9A}, /* MasterKek seed 06. */
    {0x9A, 0x3E, 0xA9, 0xAB, 0xFD, 0x56, 0x46, 0x1C, 0x9B, 0xF6, 0x48, 0x7F, 0x5C, 0xFA, 0x09, 0x5C}, /* MasterKek seed 07. */
};

static nx_dec_keyblob_t AL16 g_dec_keyblobs[32];

static int get_keyblob(nx_keyblob_t *dst, uint32_t revision, const nx_keyblob_t *keyblobs, uint32_t available_revision) {
    if (revision >= 0x20) {
        return -1;
        /* TODO: what should we do? */
    }

    if (keyblobs != NULL) {
        *dst = keyblobs[revision];
    } else {
        return -1;
        /* TODO: what should we do? */
    }

    return 0;
}

static bool safe_memcmp(uint8_t *a, uint8_t *b, size_t sz) {
    uint8_t different = 0;
    for (unsigned int i = 0; i < sz; i++) {
        different |= a[i] ^ b[i];
    }
    return different != 0;
}

static int decrypt_keyblob(const nx_keyblob_t *keyblobs, uint32_t revision, uint32_t available_revision) {
    nx_keyblob_t AL16 keyblob;
    uint8_t AL16 work_buffer[0x10];
    unsigned int keyslot = revision == MASTERKEY_REVISION_100_230 ? 0xF : KEYSLOT_SWITCH_TEMPKEY;

    if (get_keyblob(&keyblob, revision, keyblobs, available_revision) != 0) {
        return -1;
    }

    se_aes_ecb_decrypt_block(0xD, work_buffer, 0x10, keyblob_seeds[revision], 0x10);
    decrypt_data_into_keyslot(keyslot, 0xE, work_buffer, 0x10);
    decrypt_data_into_keyslot(0xB, keyslot, keyblob_mac_seed, 0x10);

    /* Validate keyblob. */
    se_compute_aes_128_cmac(0xB, work_buffer, 0x10, keyblob.mac + sizeof(keyblob.mac), sizeof(keyblob) - sizeof(keyblob.mac));
    if (safe_memcmp(keyblob.mac, work_buffer, 0x10)) {
        return -1;
    }

    /* Decrypt keyblob. */
    se_aes_ctr_crypt(keyslot, &g_dec_keyblobs[revision], sizeof(g_dec_keyblobs[revision]), keyblob.data, sizeof(keyblob.data), keyblob.ctr, sizeof(keyblob.ctr));
    return 0;
}

int load_package1_key(uint32_t revision) {
    if (revision > MASTERKEY_REVISION_600_610) {
        return -1;
    }

    set_aes_keyslot(0xB, g_dec_keyblobs[revision].package1_key, 0x10);
    return 0;
}

/* Derive all Switch keys. */
int derive_nx_keydata(uint32_t target_firmware, const nx_keyblob_t *keyblobs, uint32_t available_revision, const void *tsec_key, void *tsec_root_keys, unsigned int *out_keygen_type) {
    uint8_t AL16 work_buffer[0x10];
    uint8_t AL16 zeroes[0x10] = {0};

    /* Initialize keygen type. */
    *out_keygen_type = 0;

    /* TODO: Set keyslot flags properly in preparation of derivation. */
    set_aes_keyslot_flags(0xE, 0x15);
    set_aes_keyslot_flags(0xD, 0x15);

    /* Set the TSEC key. */
    set_aes_keyslot(0xD, tsec_key, 0x10);

    /* Decrypt all keyblobs, setting keyslot 0xF correctly. */
    for (unsigned int rev = 0; rev <= MASTERKEY_REVISION_600_610; rev++) {
        int ret = decrypt_keyblob(keyblobs, rev, available_revision);
        if (ret) {
            return ret;
        }
    }

    /* Do 6.2.0+ keygen. */
    if (target_firmware >= ATMOSPHERE_TARGET_FIRMWARE_6_2_0) {
        uint32_t desired_keyblob;

        if (target_firmware >= ATMOSPHERE_TARGET_FIRMWARE_8_1_0) {
            /* NOTE: We load in the current key for all >= 8.1.0 firmwares to reduce sept binaries. */
            desired_keyblob = MASTERKEY_REVISION_910_CURRENT;
        } else if (target_firmware >= ATMOSPHERE_TARGET_FIRMWARE_7_0_0) {
            desired_keyblob = MASTERKEY_REVISION_700_800;
        } else {
            desired_keyblob = MASTERKEY_REVISION_620;
        }

        /* Try emulation result. */
        for (unsigned int rev = MASTERKEY_REVISION_620; rev < MASTERKEY_REVISION_MAX; rev++) {
            void *tsec_root_key = (void *)((uintptr_t)tsec_root_keys + 0x10 * (rev - MASTERKEY_REVISION_620));
            if (memcmp(tsec_root_key, zeroes, 0x10) != 0) {
                /* We got a valid key from emulation. */
                set_aes_keyslot(0xD, tsec_root_key, 0x10);
                se_aes_ecb_decrypt_block(0xD, work_buffer, 0x10, new_master_kek_seeds[rev - MASTERKEY_REVISION_620], 0x10);
                memcpy(g_dec_keyblobs[rev].master_kek, work_buffer, 0x10);
            }
        }

        if (memcmp(g_dec_keyblobs[desired_keyblob].master_kek, zeroes, 0x10) == 0) {
            /* Try reading the keys from a file. */
            const char *keyfile = fuse_get_retail_type() != 0 ? "atmosphere/prod.keys" : "atmosphere/dev.keys";
            FILE *extkey_file = fopen(keyfile, "r");
            AL16 fusee_extkeys_t extkeys = {0};
            if (extkey_file == NULL) {
                fatal_error("Error: failed to read %s, needed for 6.2.0+ key derivation!", keyfile);
            }
            extkeys_initialize_keyset(&extkeys, extkey_file);
            fclose(extkey_file);
            for (unsigned int rev = MASTERKEY_REVISION_620; rev < MASTERKEY_REVISION_MAX; rev++) {
                if (memcmp(extkeys.tsec_root_keys[rev - MASTERKEY_REVISION_620], zeroes, 0x10) != 0) {
                    set_aes_keyslot(0xD, extkeys.tsec_root_keys[rev - MASTERKEY_REVISION_620], 0x10);
                    se_aes_ecb_decrypt_block(0xD, work_buffer, 0x10, new_master_kek_seeds[rev - MASTERKEY_REVISION_620], 0x10);
                    memcpy(g_dec_keyblobs[rev].master_kek, work_buffer, 0x10);
                } else {
                    memcpy(g_dec_keyblobs[rev].master_kek, extkeys.master_keks[rev], 0x10);
                }
            }
        }


        if (memcmp(g_dec_keyblobs[available_revision].master_kek, zeroes, 0x10) == 0) {
            fatal_error("Error: failed to derive master_kek_%02x!", available_revision);
        }
    }

    /* Clear the SBK. */
    clear_aes_keyslot(0xE);

    /* Get needed data. */
    set_aes_keyslot(0xD, g_dec_keyblobs[available_revision].master_kek, 0x10);

    /* Also set the Package1 key for the revision that is stored on the eMMC boot0 partition. */
    if (target_firmware < ATMOSPHERE_TARGET_FIRMWARE_6_2_0) {
        load_package1_key(available_revision);
    }

    /* Derive keys for Exosphere, lock critical keyslots. */
    decrypt_data_into_keyslot(0xA, 0xF, devicekey_4x_seed, 0x10);
    decrypt_data_into_keyslot(0xF, 0xF, devicekey_seed,    0x10);
    decrypt_data_into_keyslot(0xC, 0xD, masterkey_4x_seed, 0x10);
    decrypt_data_into_keyslot(0xD, 0xD, masterkey_seed,    0x10);

    /* Setup master key revision, derive older master keys for use. */
    return mkey_detect_revision(fuse_get_retail_type() != 0);
}

static void generate_specific_aes_key(void *dst, const void *wrapped_key, bool should_mask, uint32_t target_firmware, uint32_t generation) {
    unsigned int keyslot = devkey_get_keyslot(generation);

    if (fuse_get_bootrom_patch_version() < 0x7F) {
        /* On dev units, use a fixed "all-zeroes" seed. */
        /* Yes, this data really is all-zero in actual TrustZone .rodata. */
        static const uint8_t AL16 dev_specific_aes_key_source[0x10] = {0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00};
        static const uint8_t AL16 dev_specific_aes_key_ctr[0x10] = {0x3C, 0xD5, 0x92, 0xEC, 0x68, 0x31, 0x4A, 0x06, 0xD4, 0x1B, 0x0C, 0xD9, 0xF6, 0x2E, 0xD9, 0xE9};
        static const uint8_t AL16 dev_specific_aes_key_mask[0x10] = {0xAC, 0xCA, 0x9A, 0xCA, 0xFF, 0x2E, 0xB9, 0x22, 0xCC, 0x1F, 0x4F, 0xAD, 0xDD, 0x77, 0x21, 0x1E};

        se_aes_ctr_crypt(keyslot, dst, 0x10, dev_specific_aes_key_source, 0x10, dev_specific_aes_key_ctr, 0x10);

        if (should_mask) {
            for (unsigned int i = 0; i < 0x10; i++) {
                ((uint8_t *)dst)[i] ^= dev_specific_aes_key_mask[i];
            }
        }
    } else {
        /* On retail, standard kek->key decryption. */
        static const uint8_t AL16 retail_specific_aes_key_source[0x10] = {0xE2, 0xD6, 0xB8, 0x7A, 0x11, 0x9C, 0xB8, 0x80, 0xE8, 0x22, 0x88, 0x8A, 0x46, 0xFB, 0xA1, 0x95};
        decrypt_data_into_keyslot(KEYSLOT_SWITCH_TEMPKEY, keyslot, retail_specific_aes_key_source, 0x10);
        se_aes_ecb_decrypt_block(KEYSLOT_SWITCH_TEMPKEY, dst, 0x10, wrapped_key, 0x10);
    }
}

static void generate_personalized_aes_key_for_bis(void *dst, const void *wrapped_kek, const void *wrapped_key, uint32_t target_firmware, uint32_t generation) {
    static const uint8_t AL16 kek_source[0x10] = {
        0x4D, 0x87, 0x09, 0x86, 0xC4, 0x5D, 0x20, 0x72, 0x2F, 0xBA, 0x10, 0x53, 0xDA, 0x92, 0xE8, 0xA9
    };
    static const uint8_t AL16 key_source[0x10] = {
        0x89, 0x61, 0x5E, 0xE0, 0x5C, 0x31, 0xB6, 0x80, 0x5F, 0xE5, 0x8F, 0x3D, 0xA2, 0x4F, 0x7A, 0xA8
    };

    unsigned int keyslot = devkey_get_keyslot(generation);
    /* Derive kek. */
    decrypt_data_into_keyslot(KEYSLOT_SWITCH_TEMPKEY, keyslot, kek_source, 0x10);
    decrypt_data_into_keyslot(KEYSLOT_SWITCH_TEMPKEY, KEYSLOT_SWITCH_TEMPKEY, wrapped_kek, 0x10);
    /* Derive key. */
    decrypt_data_into_keyslot(KEYSLOT_SWITCH_TEMPKEY, KEYSLOT_SWITCH_TEMPKEY, key_source, 0x10);
    se_aes_ecb_decrypt_block(KEYSLOT_SWITCH_TEMPKEY, dst, 0x10, wrapped_key, 0x10);
}

void derive_bis_key(void *dst, BisPartition partition_id, uint32_t target_firmware) {
    static const uint8_t AL16 key_source_for_bis[3][2][0x10] = {
        {
            {0xF8, 0x3F, 0x38, 0x6E, 0x2C, 0xD2, 0xCA, 0x32, 0xA8, 0x9A, 0xB9, 0xAA, 0x29, 0xBF, 0xC7, 0x48},
            {0x7D, 0x92, 0xB0, 0x3A, 0xA8, 0xBF, 0xDE, 0xE1, 0xA7, 0x4C, 0x3B, 0x6E, 0x35, 0xCB, 0x71, 0x06}
        },
        {
            {0x41, 0x00, 0x30, 0x49, 0xDD, 0xCC, 0xC0, 0x65, 0x64, 0x7A, 0x7E, 0xB4, 0x1E, 0xED, 0x9C, 0x5F},
            {0x44, 0x42, 0x4E, 0xDA, 0xB4, 0x9D, 0xFC, 0xD9, 0x87, 0x77, 0x24, 0x9A, 0xDC, 0x9F, 0x7C, 0xA4}
        },
        {
            {0x52, 0xC2, 0xE9, 0xEB, 0x09, 0xE3, 0xEE, 0x29, 0x32, 0xA1, 0x0C, 0x1F, 0xB6, 0xA0, 0x92, 0x6C},
            {0x4D, 0x12, 0xE1, 0x4B, 0x2A, 0x47, 0x4C, 0x1C, 0x09, 0xCB, 0x03, 0x59, 0xF0, 0x15, 0xF4, 0xE4}
        }
    };

    uint32_t bis_key_generation = fuse_get_5x_key_generation();
    if (bis_key_generation > 0) {
        bis_key_generation -= 1;
    }

    static const uint8_t AL16 bis_kek_source[0x10] = {0x34, 0xC1, 0xA0, 0xC4, 0x82, 0x58, 0xF8, 0xB4, 0xFA, 0x9E, 0x5E, 0x6A, 0xDA, 0xFC, 0x7E, 0x4F};
    switch (partition_id) {
        case BisPartition_Calibration:
            generate_specific_aes_key(dst, key_source_for_bis[partition_id][0], false, target_firmware, bis_key_generation);
            generate_specific_aes_key(dst + 0x10, key_source_for_bis[partition_id][1], false, target_firmware, bis_key_generation);
            break;
        case BisPartition_Safe:
        case BisPartition_UserSystem:
            generate_personalized_aes_key_for_bis(dst, bis_kek_source, key_source_for_bis[partition_id][0], target_firmware, bis_key_generation);
            generate_personalized_aes_key_for_bis(dst + 0x10, bis_kek_source, key_source_for_bis[partition_id][1], target_firmware, bis_key_generation);
            break;
        default:
            generic_panic();
    }
}