1 /*
2 * AES-256 file encryption program
3 *
4 * Copyright (C) 2006-2015, ARM Limited, All Rights Reserved
5 * SPDX-License-Identifier: Apache-2.0
6 *
7 * Licensed under the Apache License, Version 2.0 (the "License"); you may
8 * not use this file except in compliance with the License.
9 * You may obtain a copy of the License at
10 *
11 * http://www.apache.org/licenses/LICENSE-2.0
12 *
13 * Unless required by applicable law or agreed to in writing, software
14 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
15 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
16 * See the License for the specific language governing permissions and
17 * limitations under the License.
18 *
19 * This file is part of mbed TLS (https://tls.mbed.org)
20 */
21
22 #if !defined(MBEDTLS_CONFIG_FILE)
23 #include "mbedtls/config.h"
24 #else
25 #include MBEDTLS_CONFIG_FILE
26 #endif
27
28 #if defined(MBEDTLS_PLATFORM_C)
29 #include "mbedtls/platform.h"
30 #else
31 #include <stdio.h>
32 #define mbedtls_fprintf fprintf
33 #define mbedtls_printf printf
34 #endif
35
36 #include "mbedtls/aes.h"
37 #include "mbedtls/md.h"
38
39 #include <stdio.h>
40 #include <stdlib.h>
41 #include <string.h>
42
43 #if defined(_WIN32)
44 #include <windows.h>
45 #if !defined(_WIN32_WCE)
46 #include <io.h>
47 #endif
48 #else
49 #include <sys/types.h>
50 #include <unistd.h>
51 #endif
52
53 #define MODE_ENCRYPT 0
54 #define MODE_DECRYPT 1
55
56 #define USAGE \
57 "\n aescrypt2 <mode> <input filename> <output filename> <key>\n" \
58 "\n <mode>: 0 = encrypt, 1 = decrypt\n" \
59 "\n example: aescrypt2 0 file file.aes hex:E76B2413958B00E193\n" \
60 "\n"
61
62 #if !defined(MBEDTLS_AES_C) || !defined(MBEDTLS_SHA256_C) || \
63 !defined(MBEDTLS_FS_IO) || !defined(MBEDTLS_MD_C)
main(void)64 int main( void )
65 {
66 mbedtls_printf("MBEDTLS_AES_C and/or MBEDTLS_SHA256_C "
67 "and/or MBEDTLS_FS_IO and/or MBEDTLS_MD_C "
68 "not defined.\n");
69 return( 0 );
70 }
71 #else
main(int argc,char * argv[])72 int main( int argc, char *argv[] )
73 {
74 int ret = 1;
75
76 unsigned int i, n;
77 int mode, lastn;
78 size_t keylen;
79 FILE *fkey, *fin = NULL, *fout = NULL;
80
81 char *p;
82 unsigned char IV[16];
83 unsigned char key[512];
84 unsigned char digest[32];
85 unsigned char buffer[1024];
86 unsigned char diff;
87
88 mbedtls_aes_context aes_ctx;
89 mbedtls_md_context_t sha_ctx;
90
91 #if defined(_WIN32_WCE)
92 long filesize, offset;
93 #elif defined(_WIN32)
94 LARGE_INTEGER li_size;
95 __int64 filesize, offset;
96 #else
97 off_t filesize, offset;
98 #endif
99
100 mbedtls_aes_init( &aes_ctx );
101 mbedtls_md_init( &sha_ctx );
102
103 ret = mbedtls_md_setup( &sha_ctx, mbedtls_md_info_from_type( MBEDTLS_MD_SHA256 ), 1 );
104 if( ret != 0 )
105 {
106 mbedtls_printf( " ! mbedtls_md_setup() returned -0x%04x\n", -ret );
107 goto exit;
108 }
109
110 /*
111 * Parse the command-line arguments.
112 */
113 if( argc != 5 )
114 {
115 mbedtls_printf( USAGE );
116
117 #if defined(_WIN32)
118 mbedtls_printf( "\n Press Enter to exit this program.\n" );
119 fflush( stdout ); getchar();
120 #endif
121
122 goto exit;
123 }
124
125 mode = atoi( argv[1] );
126 memset(IV, 0, sizeof(IV));
127 memset(key, 0, sizeof(key));
128 memset(digest, 0, sizeof(digest));
129 memset(buffer, 0, sizeof(buffer));
130
131 if( mode != MODE_ENCRYPT && mode != MODE_DECRYPT )
132 {
133 mbedtls_fprintf( stderr, "invalide operation mode\n" );
134 goto exit;
135 }
136
137 if( strcmp( argv[2], argv[3] ) == 0 )
138 {
139 mbedtls_fprintf( stderr, "input and output filenames must differ\n" );
140 goto exit;
141 }
142
143 if( ( fin = fopen( argv[2], "rb" ) ) == NULL )
144 {
145 mbedtls_fprintf( stderr, "fopen(%s,rb) failed\n", argv[2] );
146 goto exit;
147 }
148
149 if( ( fout = fopen( argv[3], "wb+" ) ) == NULL )
150 {
151 mbedtls_fprintf( stderr, "fopen(%s,wb+) failed\n", argv[3] );
152 goto exit;
153 }
154
155 /*
156 * Read the secret key and clean the command line.
157 */
158 if( ( fkey = fopen( argv[4], "rb" ) ) != NULL )
159 {
160 keylen = fread( key, 1, sizeof( key ), fkey );
161 fclose( fkey );
162 }
163 else
164 {
165 if( memcmp( argv[4], "hex:", 4 ) == 0 )
166 {
167 p = &argv[4][4];
168 keylen = 0;
169
170 while( sscanf( p, "%02X", &n ) > 0 &&
171 keylen < (int) sizeof( key ) )
172 {
173 key[keylen++] = (unsigned char) n;
174 p += 2;
175 }
176 }
177 else
178 {
179 keylen = strlen( argv[4] );
180
181 if( keylen > (int) sizeof( key ) )
182 keylen = (int) sizeof( key );
183
184 memcpy( key, argv[4], keylen );
185 }
186 }
187
188 memset( argv[4], 0, strlen( argv[4] ) );
189
190 #if defined(_WIN32_WCE)
191 filesize = fseek( fin, 0L, SEEK_END );
192 #else
193 #if defined(_WIN32)
194 /*
195 * Support large files (> 2Gb) on Win32
196 */
197 li_size.QuadPart = 0;
198 li_size.LowPart =
199 SetFilePointer( (HANDLE) _get_osfhandle( _fileno( fin ) ),
200 li_size.LowPart, &li_size.HighPart, FILE_END );
201
202 if( li_size.LowPart == 0xFFFFFFFF && GetLastError() != NO_ERROR )
203 {
204 mbedtls_fprintf( stderr, "SetFilePointer(0,FILE_END) failed\n" );
205 goto exit;
206 }
207
208 filesize = li_size.QuadPart;
209 #else
210 if( ( filesize = lseek( fileno( fin ), 0, SEEK_END ) ) < 0 )
211 {
212 perror( "lseek" );
213 goto exit;
214 }
215 #endif
216 #endif
217
218 if( fseek( fin, 0, SEEK_SET ) < 0 )
219 {
220 mbedtls_fprintf( stderr, "fseek(0,SEEK_SET) failed\n" );
221 goto exit;
222 }
223
224 if( mode == MODE_ENCRYPT )
225 {
226 /*
227 * Generate the initialization vector as:
228 * IV = SHA-256( filesize || filename )[0..15]
229 */
230 for( i = 0; i < 8; i++ )
231 buffer[i] = (unsigned char)( filesize >> ( i << 3 ) );
232
233 p = argv[2];
234
235 mbedtls_md_starts( &sha_ctx );
236 mbedtls_md_update( &sha_ctx, buffer, 8 );
237 mbedtls_md_update( &sha_ctx, (unsigned char *) p, strlen( p ) );
238 mbedtls_md_finish( &sha_ctx, digest );
239
240 memcpy( IV, digest, 16 );
241
242 /*
243 * The last four bits in the IV are actually used
244 * to store the file size modulo the AES block size.
245 */
246 lastn = (int)( filesize & 0x0F );
247
248 IV[15] = (unsigned char)
249 ( ( IV[15] & 0xF0 ) | lastn );
250
251 /*
252 * Append the IV at the beginning of the output.
253 */
254 if( fwrite( IV, 1, 16, fout ) != 16 )
255 {
256 mbedtls_fprintf( stderr, "fwrite(%d bytes) failed\n", 16 );
257 goto exit;
258 }
259
260 /*
261 * Hash the IV and the secret key together 8192 times
262 * using the result to setup the AES context and HMAC.
263 */
264 memset( digest, 0, 32 );
265 memcpy( digest, IV, 16 );
266
267 for( i = 0; i < 8192; i++ )
268 {
269 mbedtls_md_starts( &sha_ctx );
270 mbedtls_md_update( &sha_ctx, digest, 32 );
271 mbedtls_md_update( &sha_ctx, key, keylen );
272 mbedtls_md_finish( &sha_ctx, digest );
273 }
274
275 memset( key, 0, sizeof( key ) );
276 mbedtls_aes_setkey_enc( &aes_ctx, digest, 256 );
277 mbedtls_md_hmac_starts( &sha_ctx, digest, 32 );
278
279 /*
280 * Encrypt and write the ciphertext.
281 */
282 for( offset = 0; offset < filesize; offset += 16 )
283 {
284 n = ( filesize - offset > 16 ) ? 16 : (int)
285 ( filesize - offset );
286
287 if( fread( buffer, 1, n, fin ) != (size_t) n )
288 {
289 mbedtls_fprintf( stderr, "fread(%d bytes) failed\n", n );
290 goto exit;
291 }
292
293 for( i = 0; i < 16; i++ )
294 buffer[i] = (unsigned char)( buffer[i] ^ IV[i] );
295
296 mbedtls_aes_crypt_ecb( &aes_ctx, MBEDTLS_AES_ENCRYPT, buffer, buffer );
297 mbedtls_md_hmac_update( &sha_ctx, buffer, 16 );
298
299 if( fwrite( buffer, 1, 16, fout ) != 16 )
300 {
301 mbedtls_fprintf( stderr, "fwrite(%d bytes) failed\n", 16 );
302 goto exit;
303 }
304
305 memcpy( IV, buffer, 16 );
306 }
307
308 /*
309 * Finally write the HMAC.
310 */
311 mbedtls_md_hmac_finish( &sha_ctx, digest );
312
313 if( fwrite( digest, 1, 32, fout ) != 32 )
314 {
315 mbedtls_fprintf( stderr, "fwrite(%d bytes) failed\n", 16 );
316 goto exit;
317 }
318 }
319
320 if( mode == MODE_DECRYPT )
321 {
322 unsigned char tmp[16];
323
324 /*
325 * The encrypted file must be structured as follows:
326 *
327 * 00 .. 15 Initialization Vector
328 * 16 .. 31 AES Encrypted Block #1
329 * ..
330 * N*16 .. (N+1)*16 - 1 AES Encrypted Block #N
331 * (N+1)*16 .. (N+1)*16 + 32 HMAC-SHA-256(ciphertext)
332 */
333 if( filesize < 48 )
334 {
335 mbedtls_fprintf( stderr, "File too short to be encrypted.\n" );
336 goto exit;
337 }
338
339 if( ( filesize & 0x0F ) != 0 )
340 {
341 mbedtls_fprintf( stderr, "File size not a multiple of 16.\n" );
342 goto exit;
343 }
344
345 /*
346 * Subtract the IV + HMAC length.
347 */
348 filesize -= ( 16 + 32 );
349
350 /*
351 * Read the IV and original filesize modulo 16.
352 */
353 if( fread( buffer, 1, 16, fin ) != 16 )
354 {
355 mbedtls_fprintf( stderr, "fread(%d bytes) failed\n", 16 );
356 goto exit;
357 }
358
359 memcpy( IV, buffer, 16 );
360 lastn = IV[15] & 0x0F;
361
362 /*
363 * Hash the IV and the secret key together 8192 times
364 * using the result to setup the AES context and HMAC.
365 */
366 memset( digest, 0, 32 );
367 memcpy( digest, IV, 16 );
368
369 for( i = 0; i < 8192; i++ )
370 {
371 mbedtls_md_starts( &sha_ctx );
372 mbedtls_md_update( &sha_ctx, digest, 32 );
373 mbedtls_md_update( &sha_ctx, key, keylen );
374 mbedtls_md_finish( &sha_ctx, digest );
375 }
376
377 memset( key, 0, sizeof( key ) );
378 mbedtls_aes_setkey_dec( &aes_ctx, digest, 256 );
379 mbedtls_md_hmac_starts( &sha_ctx, digest, 32 );
380
381 /*
382 * Decrypt and write the plaintext.
383 */
384 for( offset = 0; offset < filesize; offset += 16 )
385 {
386 if( fread( buffer, 1, 16, fin ) != 16 )
387 {
388 mbedtls_fprintf( stderr, "fread(%d bytes) failed\n", 16 );
389 goto exit;
390 }
391
392 memcpy( tmp, buffer, 16 );
393
394 mbedtls_md_hmac_update( &sha_ctx, buffer, 16 );
395 mbedtls_aes_crypt_ecb( &aes_ctx, MBEDTLS_AES_DECRYPT, buffer, buffer );
396
397 for( i = 0; i < 16; i++ )
398 buffer[i] = (unsigned char)( buffer[i] ^ IV[i] );
399
400 memcpy( IV, tmp, 16 );
401
402 n = ( lastn > 0 && offset == filesize - 16 )
403 ? lastn : 16;
404
405 if( fwrite( buffer, 1, n, fout ) != (size_t) n )
406 {
407 mbedtls_fprintf( stderr, "fwrite(%d bytes) failed\n", n );
408 goto exit;
409 }
410 }
411
412 /*
413 * Verify the message authentication code.
414 */
415 mbedtls_md_hmac_finish( &sha_ctx, digest );
416
417 if( fread( buffer, 1, 32, fin ) != 32 )
418 {
419 mbedtls_fprintf( stderr, "fread(%d bytes) failed\n", 32 );
420 goto exit;
421 }
422
423 /* Use constant-time buffer comparison */
424 diff = 0;
425 for( i = 0; i < 32; i++ )
426 diff |= digest[i] ^ buffer[i];
427
428 if( diff != 0 )
429 {
430 mbedtls_fprintf( stderr, "HMAC check failed: wrong key, "
431 "or file corrupted.\n" );
432 goto exit;
433 }
434 }
435
436 ret = 0;
437
438 exit:
439 if( fin )
440 fclose( fin );
441 if( fout )
442 fclose( fout );
443
444 memset( buffer, 0, sizeof( buffer ) );
445 memset( digest, 0, sizeof( digest ) );
446
447 mbedtls_aes_free( &aes_ctx );
448 mbedtls_md_free( &sha_ctx );
449
450 return( ret );
451 }
452 #endif /* MBEDTLS_AES_C && MBEDTLS_SHA256_C && MBEDTLS_FS_IO */
453
