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1.1 misho 1: /*
2: * Copyright (C) 2013-2016 Andreas Steffen
3: * HSR Hochschule fuer Technik Rapperswil
4: *
5: * This program is free software; you can redistribute it and/or modify it
6: * under the terms of the GNU General Public License as published by the
7: * Free Software Foundation; either version 2 of the License, or (at your
8: * option) any later version. See <http://www.fsf.org/copyleft/gpl.txt>.
9: *
10: * This program is distributed in the hope that it will be useful, but
11: * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
12: * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
13: * for more details.
14: */
15:
16: #include "mgf1_xof.h"
17:
18: #include "crypto/hashers/hasher.h"
19: #include "utils/debug.h"
20:
21: typedef struct private_mgf1_xof_t private_mgf1_xof_t;
22:
23: /**
24: * Private data of an mgf1_xof_t object.
25: */
26: struct private_mgf1_xof_t {
27:
28: /**
29: * Public mgf1_xof_t interface.
30: */
31: mgf1_xof_t public;
32:
33: /**
34: * XOF type of the MGF1 Mask Generation Function
35: */
36: ext_out_function_t type;
37:
38: /**
39: * Hasher the MGF1 Mask Generation Function is based on
40: */
41: hasher_t *hasher;
42:
43: /**
44: * Is the seed hashed before using it as a seed for MGF1 ?
45: */
46: bool hash_seed;
47:
48: /**
49: * Counter
50: */
51: uint32_t counter;
52:
53: /**
54: * Set if counter has reached 2^32
55: */
56: bool overflow;
57:
58: /**
59: * Current state to be hashed
60: */
61: chunk_t state;
62:
63: /**
64: * Position of the 4 octet counter string
65: */
66: uint8_t *ctr_str;
67:
68: /**
69: * Latest hash block
70: */
71: uint8_t buf[HASH_SIZE_SHA512];
72:
73: /**
74: * Index pointing to the current position in the hash block
75: */
76: size_t buf_index;
77:
78: };
79:
80: METHOD(xof_t, get_type, ext_out_function_t,
81: private_mgf1_xof_t *this)
82: {
83: return this->type;
84: }
85:
86: static bool get_next_block(private_mgf1_xof_t *this, uint8_t *buffer)
87: {
88: /* detect overflow, set counter string and increment counter */
89: if (this->overflow)
90: {
91: DBG1(DBG_LIB, "MGF1 overflow occurred");
92: return FALSE;
93: }
94: htoun32(this->ctr_str, this->counter++);
95: if (this->counter == 0)
96: {
97: this->overflow = TRUE;
98: }
99:
100: /* get the next block from the hash function */
101: if (!this->hasher->get_hash(this->hasher, this->state, buffer))
102: {
103: return FALSE;
104: }
105:
106: return TRUE;
107: }
108:
109: METHOD(xof_t, get_bytes, bool,
110: private_mgf1_xof_t *this, size_t out_len, uint8_t *buffer)
111: {
112: size_t index = 0, blocks, len, hash_size;
113:
114: hash_size = this->hasher->get_hash_size(this->hasher);
115:
116: /* empty the current hash block buffer first */
117: len = min(out_len, hash_size - this->buf_index);
118: if (len)
119: {
120: memcpy(buffer, this->buf + this->buf_index, len);
121: index += len;
122: this->buf_index += len;
123: }
124:
125: /* copy whole hash blocks directly to output buffer */
126: blocks = (out_len - index) / hash_size;
127: while (blocks--)
128: {
129: if (!get_next_block(this, buffer + index))
130: {
131: return FALSE;
132: }
133: index += hash_size;
134: }
135:
136: /* get another hash block if some more output bytes are needed */
137: len = out_len - index;
138: if (len)
139: {
140: if (!get_next_block(this, this->buf))
141: {
142: return FALSE;
143: }
144: memcpy(buffer + index, this->buf, len);
145: this->buf_index = len;
146: }
147:
148: return TRUE;
149: }
150:
151: METHOD(xof_t, allocate_bytes, bool,
152: private_mgf1_xof_t *this, size_t out_len, chunk_t *chunk)
153: {
154: *chunk = chunk_alloc(out_len);
155:
156: if (!get_bytes(this, out_len, chunk->ptr))
157: {
158: chunk_free(chunk);
159: return FALSE;
160: }
161:
162: return TRUE;
163: }
164:
165: METHOD(xof_t, get_block_size, size_t,
166: private_mgf1_xof_t *this)
167: {
168: return this->hasher->get_hash_size(this->hasher);
169: }
170:
171: METHOD(xof_t, get_seed_size, size_t,
172: private_mgf1_xof_t *this)
173: {
174: return this->hasher->get_hash_size(this->hasher);
175: }
176:
177: METHOD(xof_t, set_seed, bool,
178: private_mgf1_xof_t *this, chunk_t seed)
179: {
180: size_t hash_size, state_len;
181:
182: if (seed.len == 0)
183: {
184: DBG1(DBG_LIB, "empty seed for MGF1");
185: return FALSE;
186: }
187:
188: /* determine state size and allocate space accordingly */
189: hash_size = this->hasher->get_hash_size(this->hasher);
190: state_len = (this->hash_seed ? hash_size : seed.len) + 4;
191: chunk_clear(&this->state);
192: this->state = chunk_alloc(state_len);
193:
194: /* hash block buffer is empty */
195: this->buf_index = hash_size;
196:
197: /* reset counter */
198: this->counter = 0;
199:
200: /* determine position of the 4 octet counter string */
201: this->ctr_str = this->state.ptr + state_len - 4;
202:
203: if (this->hash_seed)
204: {
205: if (!this->hasher->get_hash(this->hasher, seed, this->state.ptr))
206: {
207: DBG1(DBG_LIB, "failed to hash seed for MGF1");
208: return FALSE;
209: }
210: }
211: else
212: {
213: memcpy(this->state.ptr, seed.ptr, seed.len);
214: }
215:
216: return TRUE;
217: }
218:
219: METHOD(xof_t, destroy, void,
220: private_mgf1_xof_t *this)
221: {
222: this->hasher->destroy(this->hasher);
223: chunk_clear(&this->state);
224: free(this);
225: }
226:
227: METHOD(mgf1_t, set_hash_seed, void,
228: private_mgf1_xof_t *this, bool yes)
229: {
230: this->hash_seed = yes;
231: }
232:
233: /*
234: * Described in header.
235: */
236: mgf1_xof_t *mgf1_xof_create(ext_out_function_t algorithm)
237: {
238: private_mgf1_xof_t *this;
239: hash_algorithm_t hash_alg;
240: hasher_t *hasher;
241:
242: switch (algorithm)
243: {
244: case XOF_MGF1_SHA1:
245: hash_alg = HASH_SHA1;
246: break;
247: case XOF_MGF1_SHA224:
248: hash_alg = HASH_SHA224;
249: break;
250: case XOF_MGF1_SHA256:
251: hash_alg = HASH_SHA256;
252: break;
253: case XOF_MGF1_SHA384:
254: hash_alg = HASH_SHA384;
255: break;
256: case XOF_MGF1_SHA512:
257: hash_alg = HASH_SHA512;
258: break;
259: default:
260: return NULL;
261: }
262:
263: hasher = lib->crypto->create_hasher(lib->crypto, hash_alg);
264: if (!hasher)
265: {
266: DBG1(DBG_LIB, "failed to create %N hasher for MGF1",
267: hash_algorithm_names, hash_alg);
268: return NULL;
269: }
270:
271: INIT(this,
272: .public = {
273: .mgf1_interface = {
274: .xof_interface = {
275: .get_type = _get_type,
276: .get_bytes = _get_bytes,
277: .allocate_bytes = _allocate_bytes,
278: .get_block_size = _get_block_size,
279: .get_seed_size = _get_seed_size,
280: .set_seed = _set_seed,
281: .destroy = _destroy,
282: },
283: .set_hash_seed = _set_hash_seed,
284: },
285: },
286: .type = algorithm,
287: .hasher = hasher,
288: );
289:
290: return &this->public;
291: }