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Fix AES-GCM code.

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This commit is contained in:
Michael Scire 2018-03-08 17:26:42 -08:00
parent 8e5228866c
commit 7e780301de
2 changed files with 25 additions and 22 deletions
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45
exosphere/src/gcm.c
View file

@ -22,7 +22,6 @@ static void shl_128(uint64_t *val) {
val[0] <<= 1;
}
/* Multiplies two 128-bit numbers X,Y in the GF(128) Galois Field. */
static void gf128_mul(uint8_t *dst, const uint8_t *x, const uint8_t *y) {
uint8_t x_work[0x10];
@ -59,24 +58,21 @@ static void gf128_mul(uint8_t *dst, const uint8_t *x, const uint8_t *y) {
/* Performs an AES-GCM GHASH operation over the data into dst. */
static void ghash(void *dst, const void *data, size_t data_size, const void *j_block, bool encrypt) {
uint8_t x[0x10];
uint8_t x[0x10] = {0};
uint8_t h[0x10];
uint64_t *p_x = (uint64_t *)(&x[0]);
uint64_t *p_data = (uint64_t *)data;
memset(x, 0, 0x10);
/* H = aes_ecb_encrypt(zeroes) */
se_aes_128_ecb_encrypt_block(KEYSLOT_SWITCH_TEMPKEY, h, 0x10, x, 0x10);
size_t total_size = data_size;
while (data_size >= 0x10) {
/* X = (X ^ current_block) * H */
p_x[0] ^= p_data[0];
p_x[1] ^= p_data[1];
gf128_mul(x, x, h);
/* Increment p_data by 0x10 bytes. */
@ -90,16 +86,19 @@ static void ghash(void *dst, const void *data, size_t data_size, const void *j_b
if (data_size & 0xF) {
gf128_mul(x, x, h);
}
uint64_t xor_size = total_size << 3;
xor_size = __builtin_bswap64(xor_size);
/* Due to a Nintendo bug, the wrong QWORD gets XOR'd in the "final output block" case. */
if (encrypt) {
p_x[1] ^= (uint64_t)(total_size << 3);
p_x[0] ^= xor_size;
} else {
p_x[0] ^= (uint64_t)(total_size << 3);
p_x[1] ^= xor_size;
}
gf128_mul(x, x, h);
/* If final output block, XOR with encrypted J block. */
if (encrypt) {
se_aes_128_ecb_encrypt_block(KEYSLOT_SWITCH_TEMPKEY, h, 0x10, j_block, 0x10);
@ -107,7 +106,6 @@ static void ghash(void *dst, const void *data, size_t data_size, const void *j_b
x[i] ^= h[i];
}
}
/* Copy output. */
memcpy(dst, x, 0x10);
}
@ -125,19 +123,22 @@ size_t gcm_decrypt_key(void *dst, size_t dst_size, const void *src, size_t src_s
generic_panic();
}
}
uint8_t intermediate_buf[0x400] = {0};
/* Unwrap the key */
unseal_key(KEYSLOT_SWITCH_TEMPKEY, sealed_kek, kek_size, usecase);
decrypt_data_into_keyslot(KEYSLOT_SWITCH_TEMPKEY, KEYSLOT_SWITCH_TEMPKEY, wrapped_key, key_size);
/* Decrypt the GCM keypair, AES-CTR with CTR = blob[:0x10]. */
se_aes_ctr_crypt(KEYSLOT_SWITCH_TEMPKEY, dst, dst_size, src + 0x10, src_size - 0x10, src, 0x10);
se_aes_ctr_crypt(KEYSLOT_SWITCH_TEMPKEY, intermediate_buf, dst_size, src + 0x10, src_size - 0x10, src, 0x10);
if (!is_personalized) {
/* Devkit non-personalized keys have no further authentication. */
memcpy(dst, intermediate_buf, src_size - 0x10);
memset(intermediate_buf, 0, sizeof(intermediate_buf));
return src_size - 0x10;
}
}
/* J = GHASH(CTR); */
uint8_t j_block[0x10];
@ -147,8 +148,8 @@ size_t gcm_decrypt_key(void *dst, size_t dst_size, const void *src, size_t src_s
/* Note: That MAC is calculated over plaintext is non-standard. */
/* It is supposed to be over the ciphertext. */
uint8_t calc_mac[0x10];
ghash(calc_mac, dst, src_size - 0x20, j_block, true);
ghash(calc_mac, intermediate_buf, src_size - 0x20, j_block, true);
/* Const-time memcmp. */
const uint8_t *src_bytes = src;
int different = 0;
@ -159,9 +160,11 @@ size_t gcm_decrypt_key(void *dst, size_t dst_size, const void *src, size_t src_s
return 0;
}
if (read64le(src_bytes, src_size - 0x28) != fuse_get_device_id()) {
if ((read64be(intermediate_buf, src_size - 0x28) & 0x00FFFFFFFFFFFFFFULL) != fuse_get_device_id()) {
return 0;
}
memcpy(dst, intermediate_buf, src_size - 0x30);
memset(intermediate_buf, 0, sizeof(intermediate_buf));
return src_size - 0x30;
}

2
exosphere/src/utils.h
View file

@ -78,7 +78,7 @@ static inline uint64_t read64le(const volatile void *qword, size_t offset) {
return *(uint64_t *)((uintptr_t)qword + offset);
}
static inline uint32_t read64be(const volatile void *qword, size_t offset) {
static inline uint64_t read64be(const volatile void *qword, size_t offset) {
return __builtin_bswap64(read64le(qword, offset));
}