/*************************************************************************** * __________ __ ___. * Open \______ \ ____ ____ | | _\_ |__ _______ ___ * Source | _// _ \_/ ___\| |/ /| __ \ / _ \ \/ / * Jukebox | | ( <_> ) \___| < | \_\ ( <_> > < < * Firmware |____|_ /\____/ \___ >__|_ \|___ /\____/__/\_ \ * \/ \/ \/ \/ \/ * * Copyright (C) 2017 Amaury Pouly * * This program is free software; you can redistribute it and/or * modify it under the terms of the GNU General Public License * as published by the Free Software Foundation; either version 2 * of the License, or (at your option) any later version. * * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY * KIND, either express or implied. * ****************************************************************************/ #include #include #include "misc.h" #include "fwu.h" #include "afi.h" #define check_field(v_exp, v_have, str_ok, str_bad) \ if((v_exp) != (v_have)) \ { cprintf(RED, str_bad); return 1; } \ else { cprintf(RED, str_ok); } #define check_field_soft(v_exp, v_have, str_ok, str_bad) \ if((v_exp) != (v_have)) \ { cprintf(RED, str_bad); } \ else { cprintf(RED, str_ok); } #define FWU_SIG_SIZE 16 #define FWU_BLOCK_SIZE 512 struct fwu_hdr_t { uint8_t sig[FWU_SIG_SIZE]; uint32_t fw_size; uint32_t block_size;// always 512 uint8_t version; uint8_t unk; uint8_t sig2[FWU_SIG_SIZE]; } __attribute__((packed)); const uint8_t g_fwu_signature[FWU_SIG_SIZE] = { 0x11, 0x22, 0x33, 0x44, 0x55, 0x66, 0x77, 0x88, 0x99, 0xaa, 0xbb, 0xcc, 0xdd, 0xee, 0xff, 0x75 }; struct fwu_crypto_hdr_t { uint8_t field0[16]; uint8_t unk; uint8_t key[32]; } __attribute__((packed)); struct fwu_sector0_tail_t { uint8_t unk_2; uint32_t unk_x808; uint32_t unk_8; uint8_t key_B[16]; uint8_t guid[16]; uint8_t unk_190; uint8_t super_secret_xor[16]; uint8_t timestamp[8]; uint8_t unk_0; uint8_t guid_filler[20]; uint8_t unk_1; uint8_t check[20]; } __attribute__((packed)); struct fwu_block_A_hdr_t { uint16_t block_A_size; uint8_t unk_0_a; uint8_t unk_1_a; uint8_t key_B[16]; uint8_t guid_filler[256]; uint8_t ec_sz; uint8_t unk_0_b; uint32_t unk_5; uint32_t unk_x505; uint16_t unk_1_b; uint8_t timestamp[8]; } __attribute__((packed)); struct fwu_block_B_hdr_t { uint16_t block_B_size; uint8_t unk_1_a; uint16_t unk_1_b; uint8_t timestamp[8]; uint16_t guid_filler_size; } __attribute__((packed)); struct fwu_tail_t { uint8_t length; /* in blocks? it's always 1 */ uint8_t type; /* always 7 */ uint8_t reserved[14]; uint32_t fwu_checksum; uint32_t flags; /* always 0x55aa55aa */ uint8_t desc[8]; /* always 'FwuTail' */ uint8_t fwu_crc_checksum[32]; /* always 0 */ uint8_t reserved2[444]; uint32_t fwutail_checksum; } __attribute__((packed)); struct version_desc_t { uint8_t version; uint8_t value; uint8_t unk; uint8_t sig2[FWU_SIG_SIZE]; }; struct version_desc_t g_version[] = { { 1, 0xd, 0xd0, { 0x76, 0x5c, 0x50, 0x94, 0x69, 0xb0, 0xa7, 0x03, 0x10, 0xf1, 0x7e, 0xdb, 0x88, 0x90, 0x86, 0x9d } }, { 1, 0xe, 0xd0, { 0x92, 0x22, 0x7a, 0x77, 0x08, 0x67, 0xae, 0x06, 0x16, 0x06, 0xb8, 0x65, 0xa6, 0x42, 0xf7, 0X52 } }, { 3, 0x7e, 0xe1, { 0x3f, 0xad, 0xf8, 0xb0, 0x2e, 0xaf, 0x67, 0x49, 0xb9, 0x85, 0x5f, 0x63, 0x4e, 0x5e, 0x8e, 0x2e } }, }; #define NR_VERSIONS (int)(sizeof(g_version)/sizeof(g_version[0])) typedef struct ec_point_t { uint32_t *x; uint32_t *y; }ec_point_t; struct ec_info_t { int nr_bits; int point_size; uint32_t *ec_a; // size uint32_t *ec_b; // size uint32_t *field_poly; // size uint32_t size; ec_point_t pt_G; ec_point_t pt_kG; // calculated ECIES public key uint32_t field_bits; int size_x2; int nr_bytes; int nr_dwords_m1; int nr_dwords_x2; int nr_dwords_x2_m1; int nr_dwords; }; struct ec_info_t g_ec_info; struct fwu_block_A_hdr_t g_subblock_A; uint8_t g_key_B[20]; uint8_t g_rc4_S[258]; uint8_t g_field_sz_byte; ec_point_t g_public_key; // from block A uint32_t *g_private_key; // from block B #include "atj_tables.h" #include void print_hex(const char *name, void *buf, size_t sz) { if(name) cprintf(BLUE, "%s\n", name); uint8_t *p = buf; for(size_t i = 0; i < sz; i += 16) { if(name) cprintf(OFF, " "); for(size_t j = i; j < i + 16; j++) if(j < sz) cprintf(YELLOW, "%02x ", p[j]); else cprintf(OFF, " "); cprintf(RED, " |"); for(size_t j = i; j < i + 16; j++) cprintf(GREEN, "%c", (j < sz && isprint(p[j])) ? p[j] : '.'); cprintf(RED, "|\n"); } } void compute_checksum(uint8_t *buf, size_t size, uint8_t t[20]) { memset(t, 0, 20); for(size_t i = 0; i < size; i++) t[i % 20] ^= buf[i]; for(int i = 0; i < 20; i++) t[i] = ~t[i]; } int check_block(uint8_t *buf, uint8_t ref[20], unsigned size) { uint8_t t[20]; compute_checksum(buf, size, t); return memcmp(ref, t, 20); } int get_version(uint8_t *buf, unsigned long size) { (void) size; struct fwu_hdr_t *hdr = (void *)buf; for(int i = 0; i < NR_VERSIONS; i++) if(hdr->version == g_version[i].value) return i; return -1; } static int decode_block_A(uint8_t block[1020]) { uint8_t *p = &g_decode_A_table[32 * (block[998] & 31)]; uint8_t key[32]; for(int i = 0; i < 20; i++) { block[1000 + i] ^= p[i]; key[i] = block[1000 + i]; } for(int i = 20; i < 32; i++) key[i] = key[i - 20]; for(int i = 0; i < 31 * 32; i++) block[i] ^= key[i % 32] ^ g_decode_A_table[i]; // FIXME dereferencing block - 1 is undefined behavior in standard C return check_block(block - 1, block + 1000, 1001); } // https://en.wikipedia.org/wiki/RC4#Key-scheduling_algorithm_(KSA) static void rc4_key_schedule(uint8_t *key, size_t keylength, uint8_t S[258]) { for(int i = 0; i < 256; i++) S[i] = i; S[256] = S[257] = 0; uint8_t j = 0; for(int i = 0; i < 256; i++) { j = (j + S[i] + key[i % keylength]) % 256; uint8_t tmp = S[i]; S[i] = S[j]; S[j] = tmp; } } // https://en.wikipedia.org/wiki/RC4#Pseudo-random_generation_algorithm_(PRGA) static void rc4_stream_cipher(uint8_t *buf, size_t size, uint8_t S[258]) { uint8_t i = S[256]; uint8_t j = S[257]; for(size_t k = 0; k < size; k++) { i = (i + 1) % 256; j = (j + S[i]) % 256; uint8_t tmp = S[i]; S[i] = S[j]; S[j] = tmp; buf[k] ^= S[(S[i] + S[j]) % 256]; } } static void rc4_cipher_block(uint8_t *keybuf, int keysize, uint8_t *buf, int bufsize, uint8_t S[258]) { rc4_key_schedule(keybuf, keysize, S); rc4_stream_cipher(buf, bufsize, S); } static void rc4_key_swap(uint8_t *inbuf, uint8_t *outbuf, size_t size, int swap) { memcpy(outbuf, inbuf, size); int a = swap & 0xf; int b = (swap >> 4) + 16; uint8_t v = outbuf[a]; outbuf[a] = outbuf[b]; outbuf[b] = v; } static void rc4_key_swap_and_decode(uint8_t keybuf[32], int swap, uint8_t *buf, int bufsize, uint8_t S[258]) { uint8_t keybuf_interm[32]; rc4_key_swap(keybuf, keybuf_interm, 32, swap); rc4_cipher_block(keybuf_interm, 32, buf, bufsize, S); } static void gf_zero(void *buf, size_t size_dwords) { memset(buf, 0, 4 * size_dwords); } static void set_bit(int bit_pos, uint32_t *buf) { buf[bit_pos / 32] |= 1 << (bit_pos % 32); } static int fill_ec_info(uint8_t sz) { if(sz == 2) sz = 233; else if(sz == 3) sz = 163; else return 1; g_ec_info.nr_bits = sz; g_ec_info.nr_bytes = sz / 8 + (sz % 8 != 0); g_ec_info.point_size = 2 * g_ec_info.nr_bytes; g_ec_info.nr_dwords = sz / 32 + (sz % 32 != 0); g_ec_info.size = 4 * g_ec_info.nr_dwords; g_ec_info.size_x2 = 8 * g_ec_info.nr_dwords; g_ec_info.nr_dwords_m1 = g_ec_info.nr_dwords - 1; g_ec_info.nr_dwords_x2 = 2 * g_ec_info.nr_dwords; g_ec_info.nr_dwords_x2_m1 = g_ec_info.nr_dwords_x2 - 1; g_ec_info.pt_G.x = malloc(4 * g_ec_info.nr_dwords); g_ec_info.pt_G.y = malloc(g_ec_info.size); g_ec_info.pt_kG.x = malloc(g_ec_info.size); g_ec_info.pt_kG.y = malloc(g_ec_info.size); g_ec_info.field_poly = malloc(g_ec_info.size); g_ec_info.ec_a = malloc(g_ec_info.size); g_ec_info.ec_b = malloc(g_ec_info.size); cprintf(BLUE, " Elliptic curve info:\n"); cprintf_field(" Field Bits: ", "%d\n", g_ec_info.nr_bits); cprintf_field(" Field Bytes: ", "%d\n", g_ec_info.nr_bytes); cprintf_field(" Point Size: ", "%d\n", g_ec_info.point_size); cprintf_field(" Field DWords: ", "%d\n", g_ec_info.nr_dwords); cprintf_field(" Size: ", "%d\n", g_ec_info.size); return 0; } static int process_block_A(uint8_t block[1024]) { cprintf(BLUE, "Block A\n"); int ret = decode_block_A(block + 4); cprintf(GREEN, " Check: "); check_field(ret, 0, "Pass\n", "Fail\n"); // print_hex("BlockA", block, 1024); memcpy(&g_subblock_A, block, sizeof(g_subblock_A)); // assert(offsetof(struct fwu_block_A_hdr_t, ec_sz) == 276); ret = fill_ec_info(g_subblock_A.ec_sz); cprintf(GREEN, " Info: "); check_field(ret, 0, "Pass\n", "Fail\n"); int tmp = 2 * g_ec_info.nr_bytes + 38; int offset = 1004 - tmp + 5; g_field_sz_byte = block[offset - 1]; g_public_key.x = malloc(g_ec_info.size); g_public_key.y = malloc(g_ec_info.size); memset(g_public_key.x, 0, g_ec_info.size); memset(g_public_key.y, 0, g_ec_info.size); memcpy(g_public_key.x, &block[offset], g_ec_info.nr_bytes); int offset2 = g_ec_info.nr_bytes + offset; memcpy(g_public_key.y, &block[offset2], g_ec_info.nr_bytes); // assert(offsetof(struct fwu_block_A_hdr_t, unk_1_b) == 286); cprintf_field(" Word: ", "%d ", g_subblock_A.unk_1_b); check_field(g_subblock_A.unk_1_b, 1, "Ok\n", "Mismatch\n"); return 0; } static void decode_key_B(uint8_t buf[20], uint8_t buf2[16], uint8_t key[20]) { for(int i = 0; i < 20; i++) { uint8_t v = buf[i] ^ g_decode_B_table[i]; key[i] = v; buf[i] = v ^ buf2[i % 16]; } } static void decode_block_B(uint8_t *buf, uint8_t key[16], size_t size) { decode_key_B(&buf[size], key, g_key_B); rc4_cipher_block(g_key_B, 20, buf, size, g_rc4_S); } static int find_last_bit_set(uint32_t *buf, bool a) { int i = a ? g_ec_info.nr_dwords_m1 : g_ec_info.nr_dwords_x2_m1; while(i >= 0 && buf[i] == 0) i--; if(i < 0) return -1; for(int j = 31; j >= 0; j--) if(buf[i] & (1 << j)) return 32 * i + j; return -1; // unreachable } static void gf_copy(uint32_t *to, uint32_t *from) { for(int i = 0; i < g_ec_info.nr_dwords; i++) to[i] = from[i]; } static void gf_swap(uint32_t *a, uint32_t *b) { for(int i = 0; i < g_ec_info.nr_dwords; i++) { uint32_t c = a[i]; a[i] = b[i]; b[i] = c; } } static void shift_left(uint32_t *buf, int nr_bits) { for(int i = g_ec_info.nr_dwords_m1; i >= 0; i--) buf[i + (nr_bits / 32)] = buf[i]; memset(buf, 0, 4 * (nr_bits / 32)); size_t size = g_ec_info.nr_dwords + (nr_bits + 31) / 32; nr_bits = nr_bits % 32; uint32_t acc = 0; for(size_t i = 0; i < size; i++) { uint32_t new_val = buf[i] << nr_bits | acc; /* WARNING if nr_bits = 0 then the right shift by 32 is undefined and so * the following code could break. The additional AND catches this case * and make sure the result is 0 */ acc = ((1 << nr_bits) - 1) & (buf[i] >> (32 - nr_bits)); buf[i] = new_val; } } static void gf_add_x2(uint32_t *res, uint32_t *a, uint32_t *b) { for(int i = 0; i < g_ec_info.nr_dwords_x2; i++) res[i] = a[i] ^ b[i]; } static void print_poly(const char *name, uint32_t *poly, int nr_dwords) { bool first = true; cprintf(RED, "%s", name); for(int dw = 0; dw < nr_dwords; dw++) { for(int i = 0; i < 32; i++) { if(!(poly[dw] & (1 << i))) continue; if(first) first = false; else cprintf(OFF, "+"); cprintf(OFF, "x^%d", dw * 32 + i); } } cprintf(OFF, "\n"); } /* https://en.wikipedia.org/wiki/Extended_Euclidean_algorithm#Simple_algebraic_field_extensions * invariant: p * s + a * t == r -> a * t == r (mod p) * loop until only lowest bit set (r == 1) -> inverse in t */ static void gf_inverse(uint32_t *newt, uint32_t *val) { uint32_t *tmp = malloc(g_ec_info.size_x2); uint32_t *r = malloc(g_ec_info.size_x2); uint32_t *newr = malloc(g_ec_info.size_x2); uint32_t *t = malloc(g_ec_info.size_x2); gf_zero(tmp, g_ec_info.nr_dwords_x2); /* newt := 1 */ gf_zero(newt, g_ec_info.nr_dwords); *newt = 1; /* t := 0 */ gf_zero(t, g_ec_info.nr_dwords); /* newr := a */ gf_copy(newr, val); /* r := p */ gf_copy(r, g_ec_info.field_poly); for(int i = find_last_bit_set(newr, 1); i; i = find_last_bit_set(newr, 1)) { /* pos := degree(newr) - degree(r) */ int pos = i - find_last_bit_set(r, 1); if(pos < 0) { gf_swap(newr, r); gf_swap(newt, t); pos = -pos; } /* newr := newr - x^pos * r */ gf_copy(tmp, r); shift_left(tmp, pos); gf_add_x2(newr, newr, tmp); /* newt := newt - x^pos * t */ gf_copy(tmp, t); shift_left(tmp, pos); gf_add_x2(newt, newt, tmp); } free(tmp); free(r); free(newr); free(t); } static void shift_left_one(uint32_t *a) { int pos = find_last_bit_set(a, 0) / 32 + 1; if(pos <= 0) return; uint32_t v = 0; for(int i = 0; i < pos; i++) { uint32_t new_val = v | a[i] << 1; v = a[i] >> 31; a[i] = new_val; } if(v) a[pos] = v; } #if 1 static void gf_mult(uint32_t *res, uint32_t *a2, uint32_t *a3) { uint32_t *tmp2 = malloc(g_ec_info.size_x2); gf_zero(tmp2, g_ec_info.nr_dwords_x2); gf_copy(tmp2, a3); int pos = g_ec_info.nr_dwords; uint32_t mask = 1; for(int i = 0; i < 32; i++) { for(int j = 0; j < g_ec_info.nr_dwords; j++) { if(a2[j] & mask) for(int k = 0; k < pos; k++) res[j + k] ^= tmp2[k]; } shift_left_one(tmp2); mask <<= 1; pos = find_last_bit_set(tmp2, 0) / 32 + 1; } free(tmp2); } #else static void gf_mult(uint32_t *res, uint32_t *a2, uint32_t *a3) { for(int i = 0; i < 32 * g_ec_info.nr_dwords; i++) for(int j = 0; j < 32 * g_ec_info.nr_dwords; j++) { int k = i + j; uint32_t v1 = (a2[i / 32] >> (i % 32)) & 1; uint32_t v2 = (a3[j / 32] >> (j % 32)) & 1; res[k / 32] ^= (v1 * v2) << (k % 32); } } #endif // https://en.wikipedia.org/wiki/Polynomial_long_division#Pseudocode static void gf_mod(uint32_t *r, uint32_t *field_poly) { uint32_t *tmp = malloc(g_ec_info.size_x2); int deg_d = g_ec_info.field_bits; int deg_r = find_last_bit_set(r, 0); /* i := degree(lead(r) / lead(d)) */ for(int i = deg_r - deg_d; i >= 0; i = find_last_bit_set(r, 0) - deg_d) { /* r := r - x^i * d */ gf_zero(tmp, g_ec_info.nr_dwords_x2); gf_copy(tmp, field_poly); shift_left(tmp, i); gf_add_x2(r, r, tmp); } free(tmp); } static void gf_add(uint32_t *res, uint32_t *a, uint32_t *b) { for(int i = 0; i < g_ec_info.nr_dwords; i++) res[i] = a[i] ^ b[i]; } static void print_point(const char *name, ec_point_t *ptr) { cprintf(BLUE, "%s\n", name); print_poly(" x: ", ptr->x, g_ec_info.nr_dwords); print_poly(" y: ", ptr->y, g_ec_info.nr_dwords); } static uint32_t g_gf_one[9] = { 1, 0, 0, 0, 0, 0, 0, 0, 0 }; static void ec_double(ec_point_t *point, ec_point_t *res) { uint32_t *v2 = malloc(g_ec_info.size_x2); uint32_t *v3 = malloc(g_ec_info.size_x2); uint32_t *v4 = malloc(g_ec_info.size_x2); uint32_t *v5 = malloc(g_ec_info.size_x2); uint32_t *v6 = malloc(g_ec_info.size_x2); gf_zero(res->x, g_ec_info.nr_dwords); gf_zero(res->y, g_ec_info.nr_dwords); gf_zero(v3, g_ec_info.nr_dwords_x2); gf_zero(v6, g_ec_info.nr_dwords_x2); gf_zero(v4, g_ec_info.nr_dwords_x2); /* v4 := 1/x */ gf_inverse(v4, point->x); gf_zero(v5, g_ec_info.nr_dwords_x2); /* v5 := y/x */ gf_mult(v5, v4, point->y); gf_mod(v5, g_ec_info.field_poly); /* v2 := x + y/x (lambda) */ gf_add(v2, point->x, v5); /* v4 := ec_a + lambda */ gf_add(v4, v2, g_ec_info.ec_a); gf_zero(v3, g_ec_info.nr_dwords_x2); /* v3 := lambda^2 */ gf_mult(v3, v2, v2); gf_mod(v3, g_ec_info.field_poly); /* x' := lambda + lambda^2 + ec_a */ gf_add(res->x, v4, v3); gf_zero(v5, g_ec_info.nr_dwords_x2); /* v4 := lambda + g_gf_one */ gf_add(v4, v2, g_gf_one); /* v5 := (lambda + 1) * x' = lambda.x' + x' */ gf_mult(v5, v4, res->x); gf_mod(v5, g_ec_info.field_poly); gf_zero(v6, g_ec_info.nr_dwords_x2); /* v6 := x1^2 */ gf_mult(v6, point->x, point->x); gf_mod(v6, g_ec_info.field_poly); /* y' = (lambda + g_gf_one) * x + x^2 = x^2 + lambda.x + x */ gf_add(res->y, v5, v6); free(v2); free(v3); free(v4); free(v5); free(v6); } static void ec_add(ec_point_t *a1, ec_point_t *a2, ec_point_t *res) { uint32_t *v3 = malloc(g_ec_info.size_x2); uint32_t *v4 = malloc(g_ec_info.size_x2); uint32_t *v5 = malloc(g_ec_info.size_x2); uint32_t *v6 = malloc(g_ec_info.size_x2); uint32_t *v7 = malloc(g_ec_info.size_x2); gf_zero(res->x, g_ec_info.nr_dwords); gf_zero(res->y, g_ec_info.nr_dwords); gf_zero(v4, g_ec_info.nr_dwords_x2); gf_zero(v7, g_ec_info.nr_dwords_x2); /* v5 = y1 + y2 */ gf_add(v5, a1->y, a2->y); /* v6 = x1 + x2 */ gf_add(v6, a1->x, a2->x); /* v7 = 1/(x1 + x2) */ gf_inverse(v7, v6); gf_zero(v3, g_ec_info.nr_dwords_x2); /* v3 = (y1 + y2) / (x1 + x2) (lambda) */ gf_mult(v3, v7, v5); gf_mod(v3, g_ec_info.field_poly); /* v5 = lambda + ec_a */ gf_add(v5, v3, g_ec_info.ec_a); gf_zero(v4, g_ec_info.nr_dwords_x2); /* v4 = lambda^2 */ gf_mult(v4, v3, v3); gf_mod(v4, g_ec_info.field_poly); /* v7 = lambda^2 + lambda + ec_a */ gf_add(v7, v5, v4); /* x' = ec_a + x1 + x2 + lambda + lambda^2 */ gf_add(res->x, v7, v6); /* v5 = x1 + x' */ gf_add(v5, a1->x, res->x); /* v6 = x' + y1 */ gf_add(v6, res->x, a1->y); gf_zero(v7, g_ec_info.nr_dwords_x2); /* v7 = (x1 + x').lambda */ gf_mult(v7, v5, v3); gf_mod(v7, g_ec_info.field_poly); /* y' = (x1 + x').lambda + x' + y1 */ gf_add(res->y, v7, v6); free(v3); free(v4); free(v5); free(v6); free(v7); } static int ec_mult(uint32_t *n, ec_point_t *point, ec_point_t *res) { ec_point_t res_others; res_others.x = malloc(g_ec_info.size); res_others.y = malloc(g_ec_info.size); gf_zero(res->x, g_ec_info.nr_dwords); gf_zero(res->y, g_ec_info.nr_dwords); gf_zero(res_others.x, g_ec_info.nr_dwords); gf_zero(res_others.y, g_ec_info.nr_dwords); int pos = find_last_bit_set(n, 1); /* res_other := point */ gf_copy(res_others.x, point->x); gf_copy(res_others.y, point->y); /* for all bit from SZ-1 downto 0 */ for(int bit = (pos % 32) - 1; bit >= 0; bit--) { /* res := 2 * res_other */ ec_double(&res_others, res); /* res_other := res = 2 * res_other */ gf_copy(res_others.x, res->x); gf_copy(res_others.y, res->y); /* if bit of n is set */ if(n[pos / 32] & (1 << bit)) { /* res := res_other + point */ ec_add(&res_others, point, res); gf_copy(res_others.x, res->x); gf_copy(res_others.y, res->y); } } /* same but optimized */ for(int i = pos / 32 - 1; i >= 0; i--) { for(int bit = 31; bit >= 0; bit--) { ec_double(&res_others, res); gf_copy(res_others.x, res->x); gf_copy(res_others.y, res->y); if(n[i] & (1 << bit)) { ec_add(&res_others, point, res); gf_copy(res_others.x, res->x); gf_copy(res_others.y, res->y); } } } gf_copy(res->x, res_others.x); gf_copy(res->y, res_others.y); free(res_others.x); free(res_others.y); return 0; } static void xor_with_point(uint8_t *buf, ec_point_t *point) { /* int sz = g_ec_info.nr_bytes - 1; if(sz <= 32) { for(int i = 0; i < sz; i++) buf[i] ^= point->x[i]; for(int i = sz; i < 32; i++) buf[i] ^= point->y[i - sz]; } else for(int i = 0; i < 32; i++) buf[i] ^= point->x[i]; */ uint8_t *ptrA = (uint8_t *)point->x; uint8_t *ptrB = (uint8_t *)point->y; int sz = MIN(g_ec_info.nr_bytes - 1, 32); for(int i = 0; i < sz; i++) buf[i] ^= ptrA[i]; for(int i = sz; i < 32; i++) buf[i] ^= ptrB[i - sz]; } // https://en.wikipedia.org/wiki/Integrated_Encryption_Scheme#Formal_description_of_ECIES static int xor_with_shared_secret(uint8_t *buf, ec_point_t *pt_rG, uint32_t *private_key) { ec_point_t shared_secret; shared_secret.x = malloc(g_ec_info.size); shared_secret.y = malloc(g_ec_info.size); gf_zero(shared_secret.x, g_ec_info.nr_dwords); gf_zero(shared_secret.y, g_ec_info.nr_dwords); int ret = ec_mult(private_key, pt_rG, &shared_secret); if(ret == 0) xor_with_point(buf, &shared_secret); free(shared_secret.x); free(shared_secret.y); return ret; } static int set_field_poly(uint32_t *field_poly, int field_sz) { gf_zero(field_poly, g_ec_info.nr_dwords); g_ec_info.field_bits = 0; if(field_sz == 4) { set_bit(0, field_poly); set_bit(74, field_poly); set_bit(233, field_poly); g_ec_info.field_bits = 233; return 0; } else if (field_sz == 5) { set_bit(0, field_poly); set_bit(3, field_poly); set_bit(6, field_poly); set_bit(7, field_poly); set_bit(163, field_poly); g_ec_info.field_bits = 163; return 0; } else return 1; } static int ec_init(ec_point_t *ec_G, char field_sz) { int ret = set_field_poly(g_ec_info.field_poly, field_sz); if(ret) return ret; if(field_sz == 4) { gf_copy(ec_G->x, g_sect233k1_G_x); gf_copy(ec_G->y, g_sect233k1_G_y); gf_copy(g_ec_info.ec_a, g_sect233k1_a); // zero gf_copy(g_ec_info.ec_b, g_sect233k1_b); // never used return 0; } else if(field_sz == 6 ) // yet to find even a single specimen { gf_copy(ec_G->x, g_sect163r2_G_x); gf_copy(ec_G->y, g_sect163r2_G_y); gf_copy(g_ec_info.ec_a, g_sect163r2_a); gf_copy(g_ec_info.ec_b, g_sect163r2_b); return 0; } else return 1; } static void create_guid(void *uid, int bit_size) { uint8_t *p = uid; for(int i = 0; i < bit_size / 8; i++) p[i] = rand() % 256; } static int process_block_B(uint8_t block[512]) { struct fwu_block_B_hdr_t *p_hdr = (void *)block; cprintf(BLUE, "Block B\n"); decode_block_B(block + 3, g_subblock_A.key_B, 492 - 3); cprintf_field(" Word: ", "%d ", p_hdr->unk_1_b); check_field(p_hdr->unk_1_b, 1, "Ok\n", "Mismatch\n"); int ret = check_block(block, block + 492, 492); cprintf(GREEN, " Check: "); check_field(ret, 0, "Pass\n", "Fail\n"); g_private_key = malloc(g_ec_info.size); memset(g_private_key, 0, g_ec_info.size); int offset = sizeof *p_hdr + p_hdr->guid_filler_size + 1; memcpy(g_private_key, &block[offset], g_ec_info.nr_bytes); return 0; } static int get_key_fwu_v3(size_t size, uint8_t *buf, uint8_t *blockA, uint8_t *blockB, uint8_t *keybuf, uint8_t *blo) { (void) size; uint8_t smallblock[512]; uint8_t bigblock[1024]; memset(smallblock, 0, sizeof(smallblock)); memset(bigblock, 0, sizeof(bigblock)); *blockA = buf[0x1ee] & 15; *blockB = buf[0x1fe] & 15; size_t offsetA = 512 * (1 + *blockA); size_t offsetB = 512 * (1 + *blockB); cprintf(BLUE, "Crypto\n"); cprintf_field(" Block A: ", "0x%zx\n", 512 + offsetA); cprintf_field(" Block B: ", "0x%zx\n", 512 + offsetA + 1024 + offsetB); memcpy(bigblock, &buf[512 + offsetA], sizeof(bigblock)); int ret = process_block_A(bigblock); if(ret != 0) return ret; memcpy(smallblock, &buf[512 + offsetA + 1024 + offsetB], sizeof(smallblock)); ret = process_block_B(smallblock); if(ret != 0) return ret; cprintf(BLUE, "Main\n"); struct fwu_crypto_hdr_t crypto_hdr; memcpy(&crypto_hdr, buf + sizeof(struct fwu_hdr_t), sizeof(crypto_hdr)); cprintf_field(" Byte: ", "%d ", crypto_hdr.unk); check_field(crypto_hdr.unk, 3, "Ok\n", "Mismatch\n"); size_t offset = sizeof(struct fwu_hdr_t) + sizeof(struct fwu_crypto_hdr_t); ec_point_t pt_rG; pt_rG.x = malloc(g_ec_info.size); pt_rG.y = malloc(g_ec_info.size); memset(pt_rG.x, 0, g_ec_info.size); memset(pt_rG.y, 0, g_ec_info.size); memcpy(pt_rG.x, buf + offset, g_ec_info.nr_bytes); memcpy(pt_rG.y, buf + offset + g_ec_info.nr_bytes, g_ec_info.nr_bytes); ret = ec_init(&g_ec_info.pt_G, g_field_sz_byte); cprintf(GREEN, " Elliptic curve init: "); check_field(ret, 0, "Pass\n", "Fail\n"); ec_mult(g_private_key, &g_ec_info.pt_G, &g_ec_info.pt_kG); cprintf(GREEN, " Public key check: "); if (memcmp(g_public_key.x, g_ec_info.pt_kG.x, g_ec_info.nr_bytes) || memcmp(g_public_key.y, g_ec_info.pt_kG.y, g_ec_info.nr_bytes)) { cprintf(RED, "Fail\n"); return 1; } else cprintf(RED, "Pass\n"); ret = xor_with_shared_secret(crypto_hdr.key, &pt_rG, g_private_key); cprintf(GREEN, " ECIES decryption: "); check_field(ret, 0, "Pass\n", "Fail\n"); memcpy(keybuf, crypto_hdr.key, 32); offset += g_ec_info.point_size; rc4_key_swap_and_decode(keybuf, 0, &buf[offset], 512 - offset, g_rc4_S); int pos = *(uint16_t *)&buf[offset]; cprintf_field(" Filler size: ", "%d ", pos); int tmp = offset + sizeof(struct fwu_sector0_tail_t); check_field(pos, 510 - tmp, "Ok\n", "Mismatch\n"); struct fwu_sector0_tail_t tail; memcpy(&tail, &buf[offset + 2 + pos], sizeof(tail)); cprintf_field(" Byte: ", "%d ", tail.unk_2); check_field(tail.unk_2, 2, "Ok\n", "Invalid\n"); cprintf_field(" DWord: ", "0x%x ", tail.unk_x808); check_field(tail.unk_x808, 0x808, "Ok\n", "Invalid\n"); cprintf_field(" DWord: ", "%d ", tail.unk_8); check_field(tail.unk_8, 8, "Ok\n", "Invalid\n"); cprintf_field(" Byte: ", "%d ", tail.unk_190); check_field(tail.unk_190, 190, "Ok\n", "Invalid\n"); /* encode super secret at random position in guid stream, never used */ memset(blo, 0, 512); create_guid(smallblock, 476 * 8); memcpy(smallblock + 476, tail.super_secret_xor, 16); compute_checksum(smallblock, 492, blo + 492); int bsz = blo[500]; memcpy(blo, smallblock, bsz); memcpy(blo + bsz, tail.super_secret_xor, 16); memcpy(blo + bsz + 16, smallblock + bsz, 476 - bsz); rc4_cipher_block(blo + 492, 16, blo, 492, g_rc4_S); ret = check_block(buf + sizeof(struct fwu_hdr_t), tail.check, 492 - sizeof(struct fwu_hdr_t)); cprintf(GREEN, " Check: "); check_field(ret, 0, "Pass\n", "Fail\n"); ret = memcmp(g_subblock_A.key_B, tail.key_B, 16); cprintf(GREEN, " Compare: "); check_field(ret, 0, "Pass\n", "Fail\n"); /* ret = memcmp(tail.guid, zero, sizeof(zero)); cprintf(GREEN, " Sanity: "); check_field(ret, 0, "Pass\n", "Fail\n"); */ return 0; } /* stolen from https://github.com/nfd/atj2127decrypt, I have no idea from where * he got this sequence of code. This code is really weird, I copy verbatim * his authors comment below. */ uint32_t atj2127_key[] = { 0x42146ea2, 0x892c8e85, 0x9f9f6d27, 0x545fedc3, 0x09e5c0ca, 0x2dfa7e61, 0x4e5322e6, 0xb19185b9 }; /* decrypt a 512-byte sector */ static void atj2127_decrypt_sector(void *inbuf, size_t size, uint32_t session_key[8], int rounds_to_perform) { uint32_t key[8]; for(int i = 0; i < 8; i++) key[i] = atj2127_key[i] ^ session_key[i]; uint32_t *buf = inbuf; if(size % 32) cprintf(GREY, "Size is not a multiple of 32!!!\n"); while(rounds_to_perform > 0) { uint32_t rollover = buf[7] ^ session_key[7]; buf[0] ^= key[1]; buf[1] ^= key[2]; buf[2] ^= key[3]; buf[3] ^= key[4]; buf[4] ^= key[5]; buf[5] ^= key[6]; buf[6] ^= key[7]; buf[7] ^= key[1] ^ key[4]; key[1] = key[2]; key[2] = key[3]; key[3] = key[4]; key[4] = key[5]; key[5] = key[6]; key[6] = key[7]; key[7] = rollover; buf += 8; rounds_to_perform -= 1; } } static void atj2127_decrypt(uint8_t *dst, const uint8_t *src, size_t size, uint8_t keybuf[32], int rounds_to_perform) { cprintf(BLUE, "ATJ2127:\n"); cprintf_field(" Rounds: ", "%d\n", rounds_to_perform); while(size > 0) { int sec_sz = MIN(size, 512); memcpy(dst, src, sec_sz); atj2127_decrypt_sector(dst, sec_sz, (uint32_t *)keybuf, rounds_to_perform); src += sec_sz; dst += sec_sz; size -= sec_sz; } } static int decrypt_fwu_v3(uint8_t *buf, size_t *size, uint8_t block[512], enum fwu_mode_t mode) { uint8_t blockA; uint8_t blockB; uint8_t keybuf[32]; struct fwu_hdr_t *hdr = (void *)buf; memset(keybuf, 0, sizeof(keybuf)); int ret = get_key_fwu_v3(*size, buf, &blockA, &blockB, keybuf, block); if(ret != 0) return ret; size_t file_size = *size; /* the input buffer is reorganized based on two offsets (blockA and blockB), * skip 2048 bytes of data used for crypto init */ *size = hdr->fw_size; /* use firmware size, not file size */ *size -= 512 + 1024 + 512; /* sector0 + blockA + blockB */ uint8_t *tmpbuf = malloc(*size); memset(tmpbuf, 0, *size); int offsetA = 512 * (1 + blockA); int offsetB = 512 * (1 + blockB); memcpy(tmpbuf, buf + 512, offsetA); memcpy(tmpbuf + offsetA, buf + 512 + offsetA + 1024, offsetB); memcpy(tmpbuf + offsetA + offsetB, buf + 512 + offsetA + 1024 + offsetB + 512, *size - offsetA - offsetB); /* stolen from https://github.com/nfd/atj2127decrypt, I have no idea from where * he got this sequence of code. This code is really weird, I copy verbatim * his authors comment below. * * This is really weird. This is passed to the decrypt-sector function and * determines how much of each 512-byte sector to decrypt, where for every * 32MB of size above the first 32MB, one 32 byte chunk of each sector * (starting from the end) will remain unencrypted, up to a maximum of 480 * bytes of plaintext. Was this a speed-related thing? It just seems * completely bizarre. */ /* NOTE: the original code uses the file length to determine how much * to encrypt and not the size reported in the header. Since * the file size can be different from the size reported in the header * (the infamous 512 bytes described above), this might be wrong. */ int rounds_to_perform = 16 - (file_size >> 0x19); if(rounds_to_perform <= 0) rounds_to_perform = 1; /* the ATJ213x and ATJ2127 do not use the same encryption at this point, and I * don't see any obvious way to tell which encryption is used (since they * use the same version above). */ bool is_atj2127 = false; if(mode == FWU_AUTO) { uint8_t hdr_buf[512]; atj2127_decrypt(hdr_buf, tmpbuf, sizeof(hdr_buf), keybuf, rounds_to_perform); is_atj2127 = afi_check(hdr_buf, sizeof(hdr_buf)); if(is_atj2127) cprintf(BLUE, "File looks like an ATJ2127 firmware\n"); else cprintf(BLUE, "File does not looks like an ATJ2127 firmware\n"); } else if(mode == FWU_ATJ2127) is_atj2127 = true; if(is_atj2127) atj2127_decrypt(buf, tmpbuf, *size, keybuf, rounds_to_perform); else { rc4_key_schedule(keybuf, 32, g_rc4_S); rc4_stream_cipher(tmpbuf, *size, g_rc4_S); memcpy(buf, tmpbuf, *size); } return 0; } uint32_t fwu_checksum(void *buf, size_t size) { if(size % 4) cprintf(GREY, "WARNING: checksum of buffer whose length is not a multiple of 4"); uint32_t *p = buf; uint32_t sum = 0; for(size_t i = 0; i < size / 4; i++) sum += *p++; return sum; } int fwu_decrypt(uint8_t *buf, size_t *size, enum fwu_mode_t mode) { struct fwu_hdr_t *hdr = (void *)buf; if(*size < sizeof(struct fwu_hdr_t)) { cprintf(GREY, "File too small\n"); return 1; } cprintf(BLUE, "Header\n"); cprintf(GREEN, " Signature:"); for(int i = 0; i < FWU_SIG_SIZE; i++) cprintf(YELLOW, " %02x", hdr->sig[i]); if(memcmp(hdr->sig, g_fwu_signature, FWU_SIG_SIZE) == 0) cprintf(RED, " Ok\n"); else { cprintf(RED, " Mismatch\n"); return 1; } cprintf_field(" FW size: ", "%d ", hdr->fw_size); if(hdr->fw_size == *size) cprintf(RED, " Ok\n"); else if(hdr->fw_size < *size) cprintf(RED, " Ok (file greater than firmware)\n"); else { cprintf(RED, " Error (file too small)\n"); return 1; } cprintf_field(" Block size: ", "%d ", hdr->block_size); check_field(hdr->block_size, FWU_BLOCK_SIZE, "Ok\n", "Invalid\n"); cprintf_field(" Version: ", "0x%x ", hdr->version); int ver = get_version(buf, *size); if(ver < 0) { cprintf(RED, "(Unknown)\n"); return 1; } else cprintf(RED, "(Ver. %d)\n", g_version[ver].version); cprintf_field(" Unknown: ", "0x%x ", hdr->unk); check_field(hdr->unk, g_version[ver].unk, "Ok\n", "Invalid\n"); cprintf(GREEN, " Signature:"); for(int i = 0; i < FWU_SIG_SIZE; i++) cprintf(YELLOW, " %02x", hdr->sig2[i]); if(memcmp(hdr->sig2, g_version[ver].sig2, FWU_SIG_SIZE) == 0) cprintf(RED, " Ok\n"); else { cprintf(RED, " Mismatch\n"); return 2; } /* check whether the firmware has a FwuTail (as far as I know, there is no flag anywhere that * indicates its presence or not) */ struct fwu_tail_t *tail = (void *)(buf + hdr->fw_size - sizeof(struct fwu_tail_t)); if(tail->flags == 0x55aa55aa && strcmp((char *)tail->desc, "FwuTail") == 0) { cprintf(BLUE, "Tail\n"); cprintf_field(" Length: ", "%d ", tail->length); check_field_soft(tail->length, 1, "Ok\n", "Fail\n"); cprintf_field(" Type: ", "%d ", tail->type); check_field_soft(tail->type, 7, "Ok\n", "Fail\n"); cprintf_field(" FW checksum: ", "%x ", tail->fwu_checksum); check_field_soft(fwu_checksum(buf, hdr->fw_size - sizeof(struct fwu_tail_t)), tail->fwu_checksum, "Ok\n", "Mismatch\n"); cprintf(GREEN, " FW CRC Checksum: "); for(unsigned i = 0; i < sizeof(tail->fwu_crc_checksum); i++) cprintf(YELLOW, "%02x", tail->fwu_crc_checksum[i]); cprintf(RED, " Ignored (should be 0)\n"); cprintf_field(" Tail checksum: ", "%x ", tail->fwutail_checksum); check_field_soft(fwu_checksum(tail, sizeof(struct fwu_tail_t) - 4), tail->fwutail_checksum, "Ok\n", "Mismatch\n"); /* if it has a tail, the firmware size includes it, so we need to decrease it to avoid * "decrypting" the tail and output garbage */ hdr->fw_size -= sizeof(struct fwu_tail_t); } else cprintf(BLUE, "Firmware does not seem to have a tail\n"); if(g_version[ver].version == 3) { uint8_t block[512]; memset(block, 0, sizeof(block)); return decrypt_fwu_v3(buf, size, block, mode); } else { cprintf(GREY, "Unsupported version: %d\n", g_version[ver].version); return 1; } } bool fwu_check(uint8_t *buf, size_t size) { struct fwu_hdr_t *hdr = (void *)buf; if(size < sizeof(struct fwu_hdr_t)) return false; return memcmp(hdr->sig, g_fwu_signature, FWU_SIG_SIZE) == 0; }