1 /*
2 * Galois/Counter Mode (GCM) and GMAC with AES
3 *
4 * Copyright (c) 2012, Jouni Malinen <j@w1.fi>
5 *
6 * This software may be distributed under the terms of the BSD license.
7 * See README for more details.
8 */
9
10 #include "includes.h"
11
12 #include "common.h"
13 #include "aes.h"
14 #include "aes_wrap.h"
15
inc32(u8 * block)16 static void inc32(u8 *block)
17 {
18 u32 val;
19 val = WPA_GET_BE32(block + AES_BLOCK_SIZE - 4);
20 val++;
21 WPA_PUT_BE32(block + AES_BLOCK_SIZE - 4, val);
22 }
23
24
xor_block(u8 * dst,const u8 * src)25 static void xor_block(u8 *dst, const u8 *src)
26 {
27 u32 *d = (u32 *) dst;
28 u32 *s = (u32 *) src;
29 *d++ ^= *s++;
30 *d++ ^= *s++;
31 *d++ ^= *s++;
32 *d++ ^= *s++;
33 }
34
35
shift_right_block(u8 * v)36 static void shift_right_block(u8 *v)
37 {
38 u32 val;
39
40 val = WPA_GET_BE32(v + 12);
41 val >>= 1;
42 if (v[11] & 0x01)
43 val |= 0x80000000;
44 WPA_PUT_BE32(v + 12, val);
45
46 val = WPA_GET_BE32(v + 8);
47 val >>= 1;
48 if (v[7] & 0x01)
49 val |= 0x80000000;
50 WPA_PUT_BE32(v + 8, val);
51
52 val = WPA_GET_BE32(v + 4);
53 val >>= 1;
54 if (v[3] & 0x01)
55 val |= 0x80000000;
56 WPA_PUT_BE32(v + 4, val);
57
58 val = WPA_GET_BE32(v);
59 val >>= 1;
60 WPA_PUT_BE32(v, val);
61 }
62
63
64 /* Multiplication in GF(2^128) */
gf_mult(const u8 * x,const u8 * y,u8 * z)65 static void gf_mult(const u8 *x, const u8 *y, u8 *z)
66 {
67 u8 v[16];
68 int i, j;
69
70 os_memset(z, 0, 16); /* Z_0 = 0^128 */
71 os_memcpy(v, y, 16); /* V_0 = Y */
72
73 for (i = 0; i < 16; i++) {
74 for (j = 0; j < 8; j++) {
75 if (x[i] & BIT(7 - j)) {
76 /* Z_(i + 1) = Z_i XOR V_i */
77 xor_block(z, v);
78 } else {
79 /* Z_(i + 1) = Z_i */
80 }
81
82 if (v[15] & 0x01) {
83 /* V_(i + 1) = (V_i >> 1) XOR R */
84 shift_right_block(v);
85 /* R = 11100001 || 0^120 */
86 v[0] ^= 0xe1;
87 } else {
88 /* V_(i + 1) = V_i >> 1 */
89 shift_right_block(v);
90 }
91 }
92 }
93 }
94
95
ghash_start(u8 * y)96 static void ghash_start(u8 *y)
97 {
98 /* Y_0 = 0^128 */
99 os_memset(y, 0, 16);
100 }
101
102
ghash(const u8 * h,const u8 * x,size_t xlen,u8 * y)103 static void ghash(const u8 *h, const u8 *x, size_t xlen, u8 *y)
104 {
105 size_t m, i;
106 const u8 *xpos = x;
107 u8 tmp[16];
108
109 m = xlen / 16;
110
111 for (i = 0; i < m; i++) {
112 /* Y_i = (Y^(i-1) XOR X_i) dot H */
113 xor_block(y, xpos);
114 xpos += 16;
115
116 /* dot operation:
117 * multiplication operation for binary Galois (finite) field of
118 * 2^128 elements */
119 gf_mult(y, h, tmp);
120 os_memcpy(y, tmp, 16);
121 }
122
123 if (x + xlen > xpos) {
124 /* Add zero padded last block */
125 size_t last = x + xlen - xpos;
126 os_memcpy(tmp, xpos, last);
127 os_memset(tmp + last, 0, sizeof(tmp) - last);
128
129 /* Y_i = (Y^(i-1) XOR X_i) dot H */
130 xor_block(y, tmp);
131
132 /* dot operation:
133 * multiplication operation for binary Galois (finite) field of
134 * 2^128 elements */
135 gf_mult(y, h, tmp);
136 os_memcpy(y, tmp, 16);
137 }
138
139 /* Return Y_m */
140 }
141
142
aes_gctr(void * aes,const u8 * icb,const u8 * x,size_t xlen,u8 * y)143 static void aes_gctr(void *aes, const u8 *icb, const u8 *x, size_t xlen, u8 *y)
144 {
145 size_t i, n, last;
146 u8 cb[AES_BLOCK_SIZE], tmp[AES_BLOCK_SIZE];
147 const u8 *xpos = x;
148 u8 *ypos = y;
149
150 if (xlen == 0)
151 return;
152
153 n = xlen / 16;
154
155 os_memcpy(cb, icb, AES_BLOCK_SIZE);
156 /* Full blocks */
157 for (i = 0; i < n; i++) {
158 aes_encrypt(aes, cb, ypos);
159 xor_block(ypos, xpos);
160 xpos += AES_BLOCK_SIZE;
161 ypos += AES_BLOCK_SIZE;
162 inc32(cb);
163 }
164
165 last = x + xlen - xpos;
166 if (last) {
167 /* Last, partial block */
168 aes_encrypt(aes, cb, tmp);
169 for (i = 0; i < last; i++)
170 *ypos++ = *xpos++ ^ tmp[i];
171 }
172 }
173
174
aes_gcm_init_hash_subkey(const u8 * key,size_t key_len,u8 * H)175 static void * aes_gcm_init_hash_subkey(const u8 *key, size_t key_len, u8 *H)
176 {
177 void *aes;
178
179 aes = aes_encrypt_init(key, key_len);
180 if (aes == NULL)
181 return NULL;
182
183 /* Generate hash subkey H = AES_K(0^128) */
184 os_memset(H, 0, AES_BLOCK_SIZE);
185 aes_encrypt(aes, H, H);
186 wpa_hexdump_key(MSG_EXCESSIVE, "Hash subkey H for GHASH",
187 H, AES_BLOCK_SIZE);
188 return aes;
189 }
190
191
aes_gcm_prepare_j0(const u8 * iv,size_t iv_len,const u8 * H,u8 * J0)192 static void aes_gcm_prepare_j0(const u8 *iv, size_t iv_len, const u8 *H, u8 *J0)
193 {
194 u8 len_buf[16];
195
196 if (iv_len == 12) {
197 /* Prepare block J_0 = IV || 0^31 || 1 [len(IV) = 96] */
198 os_memcpy(J0, iv, iv_len);
199 os_memset(J0 + iv_len, 0, AES_BLOCK_SIZE - iv_len);
200 J0[AES_BLOCK_SIZE - 1] = 0x01;
201 } else {
202 /*
203 * s = 128 * ceil(len(IV)/128) - len(IV)
204 * J_0 = GHASH_H(IV || 0^(s+64) || [len(IV)]_64)
205 */
206 ghash_start(J0);
207 ghash(H, iv, iv_len, J0);
208 WPA_PUT_BE64(len_buf, 0);
209 WPA_PUT_BE64(len_buf + 8, iv_len * 8);
210 ghash(H, len_buf, sizeof(len_buf), J0);
211 }
212 }
213
214
aes_gcm_gctr(void * aes,const u8 * J0,const u8 * in,size_t len,u8 * out)215 static void aes_gcm_gctr(void *aes, const u8 *J0, const u8 *in, size_t len,
216 u8 *out)
217 {
218 u8 J0inc[AES_BLOCK_SIZE];
219
220 if (len == 0)
221 return;
222
223 os_memcpy(J0inc, J0, AES_BLOCK_SIZE);
224 inc32(J0inc);
225 aes_gctr(aes, J0inc, in, len, out);
226 }
227
228
aes_gcm_ghash(const u8 * H,const u8 * aad,size_t aad_len,const u8 * crypt,size_t crypt_len,u8 * S)229 static void aes_gcm_ghash(const u8 *H, const u8 *aad, size_t aad_len,
230 const u8 *crypt, size_t crypt_len, u8 *S)
231 {
232 u8 len_buf[16];
233
234 /*
235 * u = 128 * ceil[len(C)/128] - len(C)
236 * v = 128 * ceil[len(A)/128] - len(A)
237 * S = GHASH_H(A || 0^v || C || 0^u || [len(A)]64 || [len(C)]64)
238 * (i.e., zero padded to block size A || C and lengths of each in bits)
239 */
240 ghash_start(S);
241 ghash(H, aad, aad_len, S);
242 ghash(H, crypt, crypt_len, S);
243 WPA_PUT_BE64(len_buf, aad_len * 8);
244 WPA_PUT_BE64(len_buf + 8, crypt_len * 8);
245 ghash(H, len_buf, sizeof(len_buf), S);
246
247 wpa_hexdump_key(MSG_EXCESSIVE, "S = GHASH_H(...)", S, 16);
248 }
249
250
251 /**
252 * aes_gcm_ae - GCM-AE_K(IV, P, A)
253 */
aes_gcm_ae(const u8 * key,size_t key_len,const u8 * iv,size_t iv_len,const u8 * plain,size_t plain_len,const u8 * aad,size_t aad_len,u8 * crypt,u8 * tag)254 int aes_gcm_ae(const u8 *key, size_t key_len, const u8 *iv, size_t iv_len,
255 const u8 *plain, size_t plain_len,
256 const u8 *aad, size_t aad_len, u8 *crypt, u8 *tag)
257 {
258 u8 H[AES_BLOCK_SIZE];
259 u8 J0[AES_BLOCK_SIZE];
260 u8 S[16];
261 void *aes;
262
263 aes = aes_gcm_init_hash_subkey(key, key_len, H);
264 if (aes == NULL)
265 return -1;
266
267 aes_gcm_prepare_j0(iv, iv_len, H, J0);
268
269 /* C = GCTR_K(inc_32(J_0), P) */
270 aes_gcm_gctr(aes, J0, plain, plain_len, crypt);
271
272 aes_gcm_ghash(H, aad, aad_len, crypt, plain_len, S);
273
274 /* T = MSB_t(GCTR_K(J_0, S)) */
275 aes_gctr(aes, J0, S, sizeof(S), tag);
276
277 /* Return (C, T) */
278
279 aes_encrypt_deinit(aes);
280
281 return 0;
282 }
283
284
285 /**
286 * aes_gcm_ad - GCM-AD_K(IV, C, A, T)
287 */
aes_gcm_ad(const u8 * key,size_t key_len,const u8 * iv,size_t iv_len,const u8 * crypt,size_t crypt_len,const u8 * aad,size_t aad_len,const u8 * tag,u8 * plain)288 int aes_gcm_ad(const u8 *key, size_t key_len, const u8 *iv, size_t iv_len,
289 const u8 *crypt, size_t crypt_len,
290 const u8 *aad, size_t aad_len, const u8 *tag, u8 *plain)
291 {
292 u8 H[AES_BLOCK_SIZE];
293 u8 J0[AES_BLOCK_SIZE];
294 u8 S[16], T[16];
295 void *aes;
296
297 aes = aes_gcm_init_hash_subkey(key, key_len, H);
298 if (aes == NULL)
299 return -1;
300
301 aes_gcm_prepare_j0(iv, iv_len, H, J0);
302
303 /* P = GCTR_K(inc_32(J_0), C) */
304 aes_gcm_gctr(aes, J0, crypt, crypt_len, plain);
305
306 aes_gcm_ghash(H, aad, aad_len, crypt, crypt_len, S);
307
308 /* T' = MSB_t(GCTR_K(J_0, S)) */
309 aes_gctr(aes, J0, S, sizeof(S), T);
310
311 aes_encrypt_deinit(aes);
312
313 if (os_memcmp_const(tag, T, 16) != 0) {
314 wpa_printf(MSG_EXCESSIVE, "GCM: Tag mismatch");
315 return -1;
316 }
317
318 return 0;
319 }
320
321
aes_gmac(const u8 * key,size_t key_len,const u8 * iv,size_t iv_len,const u8 * aad,size_t aad_len,u8 * tag)322 int aes_gmac(const u8 *key, size_t key_len, const u8 *iv, size_t iv_len,
323 const u8 *aad, size_t aad_len, u8 *tag)
324 {
325 return aes_gcm_ae(key, key_len, iv, iv_len, NULL, 0, aad, aad_len, NULL,
326 tag);
327 }
328