diff options
Diffstat (limited to 'src/crypto/aes-ccm.c')
| -rw-r--r-- | src/crypto/aes-ccm.c | 212 |
1 files changed, 212 insertions, 0 deletions
diff --git a/src/crypto/aes-ccm.c b/src/crypto/aes-ccm.c new file mode 100644 index 0000000..d14670d --- /dev/null +++ b/src/crypto/aes-ccm.c @@ -0,0 +1,212 @@ +/* + * Counter with CBC-MAC (CCM) with AES + * + * Copyright (c) 2010-2012, Jouni Malinen <j@w1.fi> + * + * This software may be distributed under the terms of the BSD license. + * See README for more details. + */ + +#include "includes.h" + +#include "common.h" +#include "aes.h" +#include "aes_wrap.h" + + +static void xor_aes_block(u8 *dst, const u8 *src) +{ + u32 *d = (u32 *) dst; + u32 *s = (u32 *) src; + *d++ ^= *s++; + *d++ ^= *s++; + *d++ ^= *s++; + *d++ ^= *s++; +} + + +static void aes_ccm_auth_start(void *aes, size_t M, size_t L, const u8 *nonce, + const u8 *aad, size_t aad_len, size_t plain_len, + u8 *x) +{ + u8 aad_buf[2 * AES_BLOCK_SIZE]; + u8 b[AES_BLOCK_SIZE]; + + /* Authentication */ + /* B_0: Flags | Nonce N | l(m) */ + b[0] = aad_len ? 0x40 : 0 /* Adata */; + b[0] |= (((M - 2) / 2) /* M' */ << 3); + b[0] |= (L - 1) /* L' */; + os_memcpy(&b[1], nonce, 15 - L); + WPA_PUT_BE16(&b[AES_BLOCK_SIZE - L], plain_len); + + wpa_hexdump_key(MSG_EXCESSIVE, "CCM B_0", b, AES_BLOCK_SIZE); + aes_encrypt(aes, b, x); /* X_1 = E(K, B_0) */ + + if (!aad_len) + return; + + WPA_PUT_BE16(aad_buf, aad_len); + os_memcpy(aad_buf + 2, aad, aad_len); + os_memset(aad_buf + 2 + aad_len, 0, sizeof(aad_buf) - 2 - aad_len); + + xor_aes_block(aad_buf, x); + aes_encrypt(aes, aad_buf, x); /* X_2 = E(K, X_1 XOR B_1) */ + + if (aad_len > AES_BLOCK_SIZE - 2) { + xor_aes_block(&aad_buf[AES_BLOCK_SIZE], x); + /* X_3 = E(K, X_2 XOR B_2) */ + aes_encrypt(aes, &aad_buf[AES_BLOCK_SIZE], x); + } +} + + +static void aes_ccm_auth(void *aes, const u8 *data, size_t len, u8 *x) +{ + size_t last = len % AES_BLOCK_SIZE; + size_t i; + + for (i = 0; i < len / AES_BLOCK_SIZE; i++) { + /* X_i+1 = E(K, X_i XOR B_i) */ + xor_aes_block(x, data); + data += AES_BLOCK_SIZE; + aes_encrypt(aes, x, x); + } + if (last) { + /* XOR zero-padded last block */ + for (i = 0; i < last; i++) + x[i] ^= *data++; + aes_encrypt(aes, x, x); + } +} + + +static void aes_ccm_encr_start(size_t L, const u8 *nonce, u8 *a) +{ + /* A_i = Flags | Nonce N | Counter i */ + a[0] = L - 1; /* Flags = L' */ + os_memcpy(&a[1], nonce, 15 - L); +} + + +static void aes_ccm_encr(void *aes, size_t L, const u8 *in, size_t len, u8 *out, + u8 *a) +{ + size_t last = len % AES_BLOCK_SIZE; + size_t i; + + /* crypt = msg XOR (S_1 | S_2 | ... | S_n) */ + for (i = 1; i <= len / AES_BLOCK_SIZE; i++) { + WPA_PUT_BE16(&a[AES_BLOCK_SIZE - 2], i); + /* S_i = E(K, A_i) */ + aes_encrypt(aes, a, out); + xor_aes_block(out, in); + out += AES_BLOCK_SIZE; + in += AES_BLOCK_SIZE; + } + if (last) { + WPA_PUT_BE16(&a[AES_BLOCK_SIZE - 2], i); + aes_encrypt(aes, a, out); + /* XOR zero-padded last block */ + for (i = 0; i < last; i++) + *out++ ^= *in++; + } +} + + +static void aes_ccm_encr_auth(void *aes, size_t M, u8 *x, u8 *a, u8 *auth) +{ + size_t i; + u8 tmp[AES_BLOCK_SIZE]; + + wpa_hexdump_key(MSG_EXCESSIVE, "CCM T", x, M); + /* U = T XOR S_0; S_0 = E(K, A_0) */ + WPA_PUT_BE16(&a[AES_BLOCK_SIZE - 2], 0); + aes_encrypt(aes, a, tmp); + for (i = 0; i < M; i++) + auth[i] = x[i] ^ tmp[i]; + wpa_hexdump_key(MSG_EXCESSIVE, "CCM U", auth, M); +} + + +static void aes_ccm_decr_auth(void *aes, size_t M, u8 *a, const u8 *auth, u8 *t) +{ + size_t i; + u8 tmp[AES_BLOCK_SIZE]; + + wpa_hexdump_key(MSG_EXCESSIVE, "CCM U", auth, M); + /* U = T XOR S_0; S_0 = E(K, A_0) */ + WPA_PUT_BE16(&a[AES_BLOCK_SIZE - 2], 0); + aes_encrypt(aes, a, tmp); + for (i = 0; i < M; i++) + t[i] = auth[i] ^ tmp[i]; + wpa_hexdump_key(MSG_EXCESSIVE, "CCM T", t, M); +} + + +/* AES-CCM with fixed L=2 and aad_len <= 30 assumption */ +int aes_ccm_ae(const u8 *key, size_t key_len, const u8 *nonce, + size_t M, const u8 *plain, size_t plain_len, + const u8 *aad, size_t aad_len, u8 *crypt, u8 *auth) +{ + const size_t L = 2; + void *aes; + u8 x[AES_BLOCK_SIZE], a[AES_BLOCK_SIZE]; + + if (aad_len > 30 || M > AES_BLOCK_SIZE) + return -1; + + aes = aes_encrypt_init(key, key_len); + if (aes == NULL) + return -1; + + aes_ccm_auth_start(aes, M, L, nonce, aad, aad_len, plain_len, x); + aes_ccm_auth(aes, plain, plain_len, x); + + /* Encryption */ + aes_ccm_encr_start(L, nonce, a); + aes_ccm_encr(aes, L, plain, plain_len, crypt, a); + aes_ccm_encr_auth(aes, M, x, a, auth); + + aes_encrypt_deinit(aes); + + return 0; +} + + +/* AES-CCM with fixed L=2 and aad_len <= 30 assumption */ +int aes_ccm_ad(const u8 *key, size_t key_len, const u8 *nonce, + size_t M, const u8 *crypt, size_t crypt_len, + const u8 *aad, size_t aad_len, const u8 *auth, u8 *plain) +{ + const size_t L = 2; + void *aes; + u8 x[AES_BLOCK_SIZE], a[AES_BLOCK_SIZE]; + u8 t[AES_BLOCK_SIZE]; + + if (aad_len > 30 || M > AES_BLOCK_SIZE) + return -1; + + aes = aes_encrypt_init(key, key_len); + if (aes == NULL) + return -1; + + /* Decryption */ + aes_ccm_encr_start(L, nonce, a); + aes_ccm_decr_auth(aes, M, a, auth, t); + + /* plaintext = msg XOR (S_1 | S_2 | ... | S_n) */ + aes_ccm_encr(aes, L, crypt, crypt_len, plain, a); + + aes_ccm_auth_start(aes, M, L, nonce, aad, aad_len, crypt_len, x); + aes_ccm_auth(aes, plain, crypt_len, x); + + aes_encrypt_deinit(aes); + + if (os_memcmp(x, t, M) != 0) { + wpa_printf(MSG_EXCESSIVE, "CCM: Auth mismatch"); + return -1; + } + + return 0; +} |