/src/botan/src/lib/modes/cbc/cbc.cpp

Source (jump to first uncovered line)
/*
* CBC Mode
* (C) 1999-2007,2013,2017 Jack Lloyd
* (C) 2016 Daniel Neus, Rohde & Schwarz Cybersecurity
* (C) 2018 Ribose Inc
*
* Botan is released under the Simplified BSD License (see license.txt)
*/

#include <botan/internal/cbc.h>

#include <botan/internal/fmt.h>
#include <botan/internal/mode_pad.h>
#include <botan/internal/rounding.h>

namespace Botan {

CBC_Mode::CBC_Mode(std::unique_ptr<BlockCipher> cipher, std::unique_ptr<BlockCipherModePaddingMethod> padding) :
      m_cipher(std::move(cipher)), m_padding(std::move(padding)), m_block_size(m_cipher->block_size()) {
   if(m_padding && !m_padding->valid_blocksize(m_block_size)) {
      throw Invalid_Argument(fmt("Padding {} cannot be used with {} in CBC mode", m_padding->name(), m_cipher->name()));
   }
}

void CBC_Mode::clear() {
   m_cipher->clear();
   reset();
}

void CBC_Mode::reset() {
   m_state.clear();
}

std::string CBC_Mode::name() const {
   if(m_padding) {
      return fmt("{}/CBC/{}", cipher().name(), padding().name());
   } else {
      return fmt("{}/CBC/CTS", cipher().name());
   }
}

size_t CBC_Mode::update_granularity() const {
   return cipher().block_size();
}

size_t CBC_Mode::ideal_granularity() const {
   return cipher().parallel_bytes();
}

Key_Length_Specification CBC_Mode::key_spec() const {
   return cipher().key_spec();
}

size_t CBC_Mode::default_nonce_length() const {
   return block_size();
}

bool CBC_Mode::valid_nonce_length(size_t n) const {
   return (n == 0 || n == block_size());
}

bool CBC_Mode::has_keying_material() const {
   return m_cipher->has_keying_material();
}

void CBC_Mode::key_schedule(std::span<const uint8_t> key) {
   m_cipher->set_key(key);
   m_state.clear();
}

void CBC_Mode::start_msg(const uint8_t nonce[], size_t nonce_len) {
   if(!valid_nonce_length(nonce_len)) {
      throw Invalid_IV_Length(name(), nonce_len);
   }

   /*
   * A nonce of zero length means carry the last ciphertext value over
   * as the new IV, as unfortunately some protocols require this. If
   * this is the first message then we use an IV of all zeros.
   */
   if(nonce_len) {
      m_state.assign(nonce, nonce + nonce_len);
   } else if(m_state.empty()) {
      m_state.resize(m_cipher->block_size());
   }
   // else leave the state alone
}

size_t CBC_Encryption::minimum_final_size() const {
   return 0;
}

size_t CBC_Encryption::output_length(size_t input_length) const {
   if(input_length == 0) {
      return block_size();
   } else {
      return round_up(input_length, block_size());
   }
}

size_t CBC_Encryption::process_msg(uint8_t buf[], size_t sz) {
   BOTAN_STATE_CHECK(state().empty() == false);
   const size_t BS = block_size();

   BOTAN_ARG_CHECK(sz % BS == 0, "CBC input is not full blocks");
   const size_t blocks = sz / BS;

   if(blocks > 0) {
      xor_buf(&buf[0], state_ptr(), BS);
      cipher().encrypt(&buf[0]);

      for(size_t i = 1; i != blocks; ++i) {
         xor_buf(&buf[BS * i], &buf[BS * (i - 1)], BS);
         cipher().encrypt(&buf[BS * i]);
      }

      state().assign(&buf[BS * (blocks - 1)], &buf[BS * blocks]);
   }

   return sz;
}

void CBC_Encryption::finish_msg(secure_vector<uint8_t>& buffer, size_t offset) {
   BOTAN_STATE_CHECK(state().empty() == false);
   BOTAN_ARG_CHECK(buffer.size() >= offset, "Offset is out of range");

   const size_t BS = block_size();

   const size_t bytes_in_final_block = (buffer.size() - offset) % BS;

   padding().add_padding(buffer, bytes_in_final_block, BS);

   BOTAN_ASSERT_EQUAL(buffer.size() % BS, offset % BS, "Padded to block boundary");

   update(buffer, offset);
}

bool CTS_Encryption::valid_nonce_length(size_t n) const {
   return (n == block_size());
}

size_t CTS_Encryption::minimum_final_size() const {
   return block_size() + 1;
}

size_t CTS_Encryption::output_length(size_t input_length) const {
   return input_length;  // no ciphertext expansion in CTS
}

void CTS_Encryption::finish_msg(secure_vector<uint8_t>& buffer, size_t offset) {
   BOTAN_STATE_CHECK(state().empty() == false);
   BOTAN_ARG_CHECK(buffer.size() >= offset, "Offset is out of range");
   uint8_t* buf = buffer.data() + offset;
   const size_t sz = buffer.size() - offset;

   const size_t BS = block_size();

   if(sz < BS + 1) {
      throw Encoding_Error(name() + ": insufficient data to encrypt");
   }

   if(sz % BS == 0) {
      update(buffer, offset);

      // swap last two blocks
      for(size_t i = 0; i != BS; ++i) {
         std::swap(buffer[buffer.size() - BS + i], buffer[buffer.size() - 2 * BS + i]);
      }
   } else {
      const size_t full_blocks = ((sz / BS) - 1) * BS;
      const size_t final_bytes = sz - full_blocks;
      BOTAN_ASSERT(final_bytes > BS && final_bytes < 2 * BS, "Left over size in expected range");

      secure_vector<uint8_t> last(buf + full_blocks, buf + full_blocks + final_bytes);
      buffer.resize(full_blocks + offset);
      update(buffer, offset);

      xor_buf(last.data(), state_ptr(), BS);
      cipher().encrypt(last.data());

      for(size_t i = 0; i != final_bytes - BS; ++i) {
         last[i] ^= last[i + BS];
         last[i + BS] ^= last[i];
      }

      cipher().encrypt(last.data());

      buffer += last;
   }
}

size_t CBC_Decryption::output_length(size_t input_length) const {
   return input_length;  // precise for CTS, worst case otherwise
}

size_t CBC_Decryption::minimum_final_size() const {
   return block_size();
}

size_t CBC_Decryption::process_msg(uint8_t buf[], size_t sz) {
   BOTAN_STATE_CHECK(state().empty() == false);

   const size_t BS = block_size();

   BOTAN_ARG_CHECK(sz % BS == 0, "Input is not full blocks");
   size_t blocks = sz / BS;

   while(blocks) {
      const size_t to_proc = std::min(BS * blocks, m_tempbuf.size());

      cipher().decrypt_n(buf, m_tempbuf.data(), to_proc / BS);

      xor_buf(m_tempbuf.data(), state_ptr(), BS);
      xor_buf(&m_tempbuf[BS], buf, to_proc - BS);
      copy_mem(state_ptr(), buf + (to_proc - BS), BS);

      copy_mem(buf, m_tempbuf.data(), to_proc);

      buf += to_proc;
      blocks -= to_proc / BS;
   }

   return sz;
}

void CBC_Decryption::finish_msg(secure_vector<uint8_t>& buffer, size_t offset) {
   BOTAN_STATE_CHECK(state().empty() == false);
   BOTAN_ARG_CHECK(buffer.size() >= offset, "Offset is out of range");
   const size_t sz = buffer.size() - offset;

   const size_t BS = block_size();

   if(sz == 0 || sz % BS) {
      throw Decoding_Error(name() + ": Ciphertext not a multiple of block size");
   }

   update(buffer, offset);

   const size_t pad_bytes = BS - padding().unpad(&buffer[buffer.size() - BS], BS);
   buffer.resize(buffer.size() - pad_bytes);  // remove padding
   if(pad_bytes == 0 && padding().name() != "NoPadding") {
      throw Decoding_Error("Invalid CBC padding");
   }
}

void CBC_Decryption::reset() {
   CBC_Mode::reset();
   zeroise(m_tempbuf);
}

bool CTS_Decryption::valid_nonce_length(size_t n) const {
   return (n == block_size());
}

size_t CTS_Decryption::minimum_final_size() const {
   return block_size() + 1;
}

void CTS_Decryption::finish_msg(secure_vector<uint8_t>& buffer, size_t offset) {
   BOTAN_STATE_CHECK(state().empty() == false);
   BOTAN_ARG_CHECK(buffer.size() >= offset, "Offset is out of range");
   const size_t sz = buffer.size() - offset;
   uint8_t* buf = buffer.data() + offset;

   const size_t BS = block_size();

   if(sz < BS + 1) {
      throw Encoding_Error(name() + ": insufficient data to decrypt");
   }

   if(sz % BS == 0) {
      // swap last two blocks

      for(size_t i = 0; i != BS; ++i) {
         std::swap(buffer[buffer.size() - BS + i], buffer[buffer.size() - 2 * BS + i]);
      }

      update(buffer, offset);
   } else {
      const size_t full_blocks = ((sz / BS) - 1) * BS;
      const size_t final_bytes = sz - full_blocks;
      BOTAN_ASSERT(final_bytes > BS && final_bytes < 2 * BS, "Left over size in expected range");

      secure_vector<uint8_t> last(buf + full_blocks, buf + full_blocks + final_bytes);
      buffer.resize(full_blocks + offset);
      update(buffer, offset);

      cipher().decrypt(last.data());

      xor_buf(last.data(), &last[BS], final_bytes - BS);

      for(size_t i = 0; i != final_bytes - BS; ++i) {
         std::swap(last[i], last[i + BS]);
      }

      cipher().decrypt(last.data());
      xor_buf(last.data(), state_ptr(), BS);

      buffer += last;
   }
}

}  // namespace Botan

Coverage Report

Created: 2023-12-08 07:00

Line	Count	Source (jump to first uncovered line)
1		/*
2		* CBC Mode
3		* (C) 1999-2007,2013,2017 Jack Lloyd
4		* (C) 2016 Daniel Neus, Rohde & Schwarz Cybersecurity
5		* (C) 2018 Ribose Inc
6		*
7		* Botan is released under the Simplified BSD License (see license.txt)
8		*/
9
10		#include <botan/internal/cbc.h>
11
12		#include <botan/internal/fmt.h>
13		#include <botan/internal/mode_pad.h>
14		#include <botan/internal/rounding.h>
15
16		namespace Botan {
17
18		CBC_Mode::CBC_Mode(std::unique_ptr<BlockCipher> cipher, std::unique_ptr<BlockCipherModePaddingMethod> padding) :
19	0	m_cipher(std::move(cipher)), m_padding(std::move(padding)), m_block_size(m_cipher->block_size()) {
20	0	if(m_padding && !m_padding->valid_blocksize(m_block_size)) {
21	0	throw Invalid_Argument(fmt("Padding {} cannot be used with {} in CBC mode", m_padding->name(), m_cipher->name()));
22	0	}
23	0	}
24
25	0	void CBC_Mode::clear() {
26	0	m_cipher->clear();
27	0	reset();
28	0	}
29
30	0	void CBC_Mode::reset() {
31	0	m_state.clear();
32	0	}
33
34	0	std::string CBC_Mode::name() const {
35	0	if(m_padding) {
36	0	return fmt("{}/CBC/{}", cipher().name(), padding().name());
37	0	} else {
38	0	return fmt("{}/CBC/CTS", cipher().name());
39	0	}
40	0	}
41
42	0	size_t CBC_Mode::update_granularity() const {
43	0	return cipher().block_size();
44	0	}
45
46	0	size_t CBC_Mode::ideal_granularity() const {
47	0	return cipher().parallel_bytes();
48	0	}
49
50	0	Key_Length_Specification CBC_Mode::key_spec() const {
51	0	return cipher().key_spec();
52	0	}
53
54	0	size_t CBC_Mode::default_nonce_length() const {
55	0	return block_size();
56	0	}
57
58	0	bool CBC_Mode::valid_nonce_length(size_t n) const {
59	0	return (n == 0 \|\| n == block_size());
60	0	}
61
62	0	bool CBC_Mode::has_keying_material() const {
63	0	return m_cipher->has_keying_material();
64	0	}
65
66	0	void CBC_Mode::key_schedule(std::span<const uint8_t> key) {
67	0	m_cipher->set_key(key);
68	0	m_state.clear();
69	0	}
70
71	0	void CBC_Mode::start_msg(const uint8_t nonce[], size_t nonce_len) {
72	0	if(!valid_nonce_length(nonce_len)) {
73	0	throw Invalid_IV_Length(name(), nonce_len);
74	0	}
75
76		/*
77		* A nonce of zero length means carry the last ciphertext value over
78		* as the new IV, as unfortunately some protocols require this. If
79		* this is the first message then we use an IV of all zeros.
80		*/
81	0	if(nonce_len) {
82	0	m_state.assign(nonce, nonce + nonce_len);
83	0	} else if(m_state.empty()) {
84	0	m_state.resize(m_cipher->block_size());
85	0	}
86		// else leave the state alone
87	0	}
88
89	0	size_t CBC_Encryption::minimum_final_size() const {
90	0	return 0;
91	0	}
92
93	0	size_t CBC_Encryption::output_length(size_t input_length) const {
94	0	if(input_length == 0) {
95	0	return block_size();
96	0	} else {
97	0	return round_up(input_length, block_size());
98	0	}
99	0	}
100
101	0	size_t CBC_Encryption::process_msg(uint8_t buf[], size_t sz) {
102	0	BOTAN_STATE_CHECK(state().empty() == false);
103	0	const size_t BS = block_size();
104
105	0	BOTAN_ARG_CHECK(sz % BS == 0, "CBC input is not full blocks");
106	0	const size_t blocks = sz / BS;
107
108	0	if(blocks > 0) {
109	0	xor_buf(&buf[0], state_ptr(), BS);
110	0	cipher().encrypt(&buf[0]);
111
112	0	for(size_t i = 1; i != blocks; ++i) {
113	0	xor_buf(&buf[BS * i], &buf[BS * (i - 1)], BS);
114	0	cipher().encrypt(&buf[BS * i]);
115	0	}
116
117	0	state().assign(&buf[BS * (blocks - 1)], &buf[BS * blocks]);
118	0	}
119
120	0	return sz;
121	0	}
122
123	0	void CBC_Encryption::finish_msg(secure_vector<uint8_t>& buffer, size_t offset) {
124	0	BOTAN_STATE_CHECK(state().empty() == false);
125	0	BOTAN_ARG_CHECK(buffer.size() >= offset, "Offset is out of range");
126
127	0	const size_t BS = block_size();
128
129	0	const size_t bytes_in_final_block = (buffer.size() - offset) % BS;
130
131	0	padding().add_padding(buffer, bytes_in_final_block, BS);
132
133	0	BOTAN_ASSERT_EQUAL(buffer.size() % BS, offset % BS, "Padded to block boundary");
134
135	0	update(buffer, offset);
136	0	}
137
138	0	bool CTS_Encryption::valid_nonce_length(size_t n) const {
139	0	return (n == block_size());
140	0	}
141
142	0	size_t CTS_Encryption::minimum_final_size() const {
143	0	return block_size() + 1;
144	0	}
145
146	0	size_t CTS_Encryption::output_length(size_t input_length) const {
147	0	return input_length; // no ciphertext expansion in CTS
148	0	}
149
150	0	void CTS_Encryption::finish_msg(secure_vector<uint8_t>& buffer, size_t offset) {
151	0	BOTAN_STATE_CHECK(state().empty() == false);
152	0	BOTAN_ARG_CHECK(buffer.size() >= offset, "Offset is out of range");
153	0	uint8_t* buf = buffer.data() + offset;
154	0	const size_t sz = buffer.size() - offset;
155
156	0	const size_t BS = block_size();
157
158	0	if(sz < BS + 1) {
159	0	throw Encoding_Error(name() + ": insufficient data to encrypt");
160	0	}
161
162	0	if(sz % BS == 0) {
163	0	update(buffer, offset);
164
165		// swap last two blocks
166	0	for(size_t i = 0; i != BS; ++i) {
167	0	std::swap(buffer[buffer.size() - BS + i], buffer[buffer.size() - 2 * BS + i]);
168	0	}
169	0	} else {
170	0	const size_t full_blocks = ((sz / BS) - 1) * BS;
171	0	const size_t final_bytes = sz - full_blocks;
172	0	BOTAN_ASSERT(final_bytes > BS && final_bytes < 2 * BS, "Left over size in expected range");
173
174	0	secure_vector<uint8_t> last(buf + full_blocks, buf + full_blocks + final_bytes);
175	0	buffer.resize(full_blocks + offset);
176	0	update(buffer, offset);
177
178	0	xor_buf(last.data(), state_ptr(), BS);
179	0	cipher().encrypt(last.data());
180
181	0	for(size_t i = 0; i != final_bytes - BS; ++i) {
182	0	last[i] ^= last[i + BS];
183	0	last[i + BS] ^= last[i];
184	0	}
185
186	0	cipher().encrypt(last.data());
187
188	0	buffer += last;
189	0	}
190	0	}
191
192	0	size_t CBC_Decryption::output_length(size_t input_length) const {
193	0	return input_length; // precise for CTS, worst case otherwise
194	0	}
195
196	0	size_t CBC_Decryption::minimum_final_size() const {
197	0	return block_size();
198	0	}
199
200	0	size_t CBC_Decryption::process_msg(uint8_t buf[], size_t sz) {
201	0	BOTAN_STATE_CHECK(state().empty() == false);
202
203	0	const size_t BS = block_size();
204
205	0	BOTAN_ARG_CHECK(sz % BS == 0, "Input is not full blocks");
206	0	size_t blocks = sz / BS;
207
208	0	while(blocks) {
209	0	const size_t to_proc = std::min(BS * blocks, m_tempbuf.size());
210
211	0	cipher().decrypt_n(buf, m_tempbuf.data(), to_proc / BS);
212
213	0	xor_buf(m_tempbuf.data(), state_ptr(), BS);
214	0	xor_buf(&m_tempbuf[BS], buf, to_proc - BS);
215	0	copy_mem(state_ptr(), buf + (to_proc - BS), BS);
216
217	0	copy_mem(buf, m_tempbuf.data(), to_proc);
218
219	0	buf += to_proc;
220	0	blocks -= to_proc / BS;
221	0	}
222
223	0	return sz;
224	0	}
225
226	0	void CBC_Decryption::finish_msg(secure_vector<uint8_t>& buffer, size_t offset) {
227	0	BOTAN_STATE_CHECK(state().empty() == false);
228	0	BOTAN_ARG_CHECK(buffer.size() >= offset, "Offset is out of range");
229	0	const size_t sz = buffer.size() - offset;
230
231	0	const size_t BS = block_size();
232
233	0	if(sz == 0 \|\| sz % BS) {
234	0	throw Decoding_Error(name() + ": Ciphertext not a multiple of block size");
235	0	}
236
237	0	update(buffer, offset);
238
239	0	const size_t pad_bytes = BS - padding().unpad(&buffer[buffer.size() - BS], BS);
240	0	buffer.resize(buffer.size() - pad_bytes); // remove padding
241	0	if(pad_bytes == 0 && padding().name() != "NoPadding") {
242	0	throw Decoding_Error("Invalid CBC padding");
243	0	}
244	0	}
245
246	0	void CBC_Decryption::reset() {
247	0	CBC_Mode::reset();
248	0	zeroise(m_tempbuf);
249	0	}
250
251	0	bool CTS_Decryption::valid_nonce_length(size_t n) const {
252	0	return (n == block_size());
253	0	}
254
255	0	size_t CTS_Decryption::minimum_final_size() const {
256	0	return block_size() + 1;
257	0	}
258
259	0	void CTS_Decryption::finish_msg(secure_vector<uint8_t>& buffer, size_t offset) {
260	0	BOTAN_STATE_CHECK(state().empty() == false);
261	0	BOTAN_ARG_CHECK(buffer.size() >= offset, "Offset is out of range");
262	0	const size_t sz = buffer.size() - offset;
263	0	uint8_t* buf = buffer.data() + offset;
264
265	0	const size_t BS = block_size();
266
267	0	if(sz < BS + 1) {
268	0	throw Encoding_Error(name() + ": insufficient data to decrypt");
269	0	}
270
271	0	if(sz % BS == 0) {
272		// swap last two blocks
273
274	0	for(size_t i = 0; i != BS; ++i) {
275	0	std::swap(buffer[buffer.size() - BS + i], buffer[buffer.size() - 2 * BS + i]);
276	0	}
277
278	0	update(buffer, offset);
279	0	} else {
280	0	const size_t full_blocks = ((sz / BS) - 1) * BS;
281	0	const size_t final_bytes = sz - full_blocks;
282	0	BOTAN_ASSERT(final_bytes > BS && final_bytes < 2 * BS, "Left over size in expected range");
283
284	0	secure_vector<uint8_t> last(buf + full_blocks, buf + full_blocks + final_bytes);
285	0	buffer.resize(full_blocks + offset);
286	0	update(buffer, offset);
287
288	0	cipher().decrypt(last.data());
289
290	0	xor_buf(last.data(), &last[BS], final_bytes - BS);
291
292	0	for(size_t i = 0; i != final_bytes - BS; ++i) {
293	0	std::swap(last[i], last[i + BS]);
294	0	}
295
296	0	cipher().decrypt(last.data());
297	0	xor_buf(last.data(), state_ptr(), BS);
298
299	0	buffer += last;
300	0	}
301	0	}
302
303		} // namespace Botan