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/src/lib/modes/aead/ocb/ocb.cpp

/*
* OCB Mode
* (C) 2013,2017 Jack Lloyd
* (C) 2016 Daniel Neus, Rohde & Schwarz Cybersecurity
*
* Botan is released under the Simplified BSD License (see license.txt)
*/

#include <botan/internal/ocb.h>

#include <botan/block_cipher.h>
#include <botan/internal/bit_ops.h>
#include <botan/internal/ct_utils.h>
#include <botan/internal/poly_dbl.h>

namespace Botan {

// Has to be in Botan namespace so unique_ptr can reference it
class L_computer final {
   public:
      explicit L_computer(const BlockCipher& cipher) :
            m_BS(cipher.block_size()), m_max_blocks(cipher.parallel_bytes() / m_BS) {
         m_L_star.resize(m_BS);
         cipher.encrypt(m_L_star);
         m_L_dollar = poly_double(star());

         // Preallocate the m_L vector to the maximum expected size to avoid
         // re-allocations during runtime. This had caused a use-after-free in
         // earlier versions, due to references into this buffer becoming stale
         // in `compute_offset()`, after calling `get()` in the hot path.
         //
         // Note, that the list member won't be pre-allocated, so the expected
         // memory overhead is negligible.
         //
         // See also https://github.com/randombit/botan/issues/3812
         m_L.reserve(31);
         m_L.push_back(poly_double(dollar()));

         while(m_L.size() < 8) {
            m_L.push_back(poly_double(m_L.back()));
         }

         m_offset_buf.resize(m_BS * m_max_blocks);
      }

      void init(const secure_vector<uint8_t>& offset) { m_offset = offset; }

      bool initialized() const { return m_offset.empty() == false; }

      const secure_vector<uint8_t>& star() const { return m_L_star; }

      const secure_vector<uint8_t>& dollar() const { return m_L_dollar; }

      const secure_vector<uint8_t>& offset() const { return m_offset; }

      const secure_vector<uint8_t>& get(size_t i) const {
         while(m_L.size() <= i) {
            m_L.push_back(poly_double(m_L.back()));
         }

         return m_L[i];
      }

      const uint8_t* compute_offsets(size_t block_index, size_t blocks) {
         BOTAN_ASSERT(blocks <= m_max_blocks, "OCB offsets");

         uint8_t* offsets = m_offset_buf.data();

         if(block_index % 4 == 0) {
            const secure_vector<uint8_t>& L0 = get(0);
            const secure_vector<uint8_t>& L1 = get(1);

            while(blocks >= 4) {
               // ntz(4*i+1) == 0
               // ntz(4*i+2) == 1
               // ntz(4*i+3) == 0
               block_index += 4;
               const size_t ntz4 = var_ctz32(static_cast<uint32_t>(block_index));

               xor_buf(offsets, m_offset.data(), L0.data(), m_BS);
               offsets += m_BS;

               xor_buf(offsets, offsets - m_BS, L1.data(), m_BS);
               offsets += m_BS;

               xor_buf(m_offset.data(), L1.data(), m_BS);
               copy_mem(offsets, m_offset.data(), m_BS);
               offsets += m_BS;

               xor_buf(m_offset.data(), get(ntz4).data(), m_BS);
               copy_mem(offsets, m_offset.data(), m_BS);
               offsets += m_BS;

               blocks -= 4;
            }
         }

         for(size_t i = 0; i != blocks; ++i) {  // could be done in parallel
            const size_t ntz = var_ctz32(static_cast<uint32_t>(block_index + i + 1));
            xor_buf(m_offset.data(), get(ntz).data(), m_BS);
            copy_mem(offsets, m_offset.data(), m_BS);
            offsets += m_BS;
         }

         return m_offset_buf.data();
      }

   private:
      static secure_vector<uint8_t> poly_double(const secure_vector<uint8_t>& in) {
         secure_vector<uint8_t> out(in.size());
         poly_double_n(out.data(), in.data(), out.size());
         return out;
      }

      const size_t m_BS, m_max_blocks;
      secure_vector<uint8_t> m_L_dollar, m_L_star;
      secure_vector<uint8_t> m_offset;
      mutable std::vector<secure_vector<uint8_t>> m_L;
      secure_vector<uint8_t> m_offset_buf;
};

namespace {

/*
* OCB's HASH
*/
secure_vector<uint8_t> ocb_hash(const L_computer& L, const BlockCipher& cipher, const uint8_t ad[], size_t ad_len) {
   const size_t BS = cipher.block_size();
   secure_vector<uint8_t> sum(BS);
   secure_vector<uint8_t> offset(BS);

   secure_vector<uint8_t> buf(BS);

   const size_t ad_blocks = (ad_len / BS);
   const size_t ad_remainder = (ad_len % BS);

   for(size_t i = 0; i != ad_blocks; ++i) {
      // this loop could run in parallel
      offset ^= L.get(var_ctz32(static_cast<uint32_t>(i + 1)));
      buf = offset;
      xor_buf(buf.data(), &ad[BS * i], BS);
      cipher.encrypt(buf);
      sum ^= buf;
   }

   if(ad_remainder) {
      offset ^= L.star();
      buf = offset;
      xor_buf(buf.data(), &ad[BS * ad_blocks], ad_remainder);
      buf[ad_remainder] ^= 0x80;
      cipher.encrypt(buf);
      sum ^= buf;
   }

   return sum;
}

}  // namespace

OCB_Mode::OCB_Mode(std::unique_ptr<BlockCipher> cipher, size_t tag_size) :
      m_cipher(std::move(cipher)),
      m_checksum(m_cipher->parallel_bytes()),
      m_ad_hash(m_cipher->block_size()),
      m_tag_size(tag_size),
      m_block_size(m_cipher->block_size()),
      m_par_blocks(m_cipher->parallel_bytes() / m_block_size) {
   const size_t BS = block_size();

   /*
   * draft-krovetz-ocb-wide-d1 specifies OCB for several other block
   * sizes but only 128, 192, 256 and 512 bit are currently supported
   * by this implementation.
   */
   BOTAN_ARG_CHECK(BS == 16 || BS == 24 || BS == 32 || BS == 64, "Invalid block size for OCB");

   BOTAN_ARG_CHECK(m_tag_size % 4 == 0 && m_tag_size >= 8 && m_tag_size <= BS && m_tag_size <= 32,
                   "Invalid OCB tag length");
}

OCB_Mode::~OCB_Mode() = default;

void OCB_Mode::clear() {
   m_cipher->clear();
   m_L.reset();  // add clear here?
   reset();
}

void OCB_Mode::reset() {
   m_block_index = 0;
   zeroise(m_ad_hash);
   zeroise(m_checksum);
   m_last_nonce.clear();
   m_stretch.clear();
}

bool OCB_Mode::valid_nonce_length(size_t length) const {
   if(length == 0) {
      return false;
   }
   if(block_size() == 16) {
      return length < 16;
   } else {
      return length < (block_size() - 1);
   }
}

std::string OCB_Mode::name() const {
   return m_cipher->name() + "/OCB";  // include tag size?
}

size_t OCB_Mode::update_granularity() const {
   return block_size();
}

size_t OCB_Mode::ideal_granularity() const {
   return (m_par_blocks * block_size());
}

Key_Length_Specification OCB_Mode::key_spec() const {
   return m_cipher->key_spec();
}

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

void OCB_Mode::key_schedule(std::span<const uint8_t> key) {
   m_cipher->set_key(key);
   m_L = std::make_unique<L_computer>(*m_cipher);
}

void OCB_Mode::set_associated_data_n(size_t idx, std::span<const uint8_t> ad) {
   BOTAN_ARG_CHECK(idx == 0, "OCB: cannot handle non-zero index in set_associated_data_n");
   assert_key_material_set();
   m_ad_hash = ocb_hash(*m_L, *m_cipher, ad.data(), ad.size());
}

const secure_vector<uint8_t>& OCB_Mode::update_nonce(const uint8_t nonce[], size_t nonce_len) {
   const size_t BS = block_size();

   BOTAN_ASSERT(BS == 16 || BS == 24 || BS == 32 || BS == 64, "OCB block size is supported");

   const size_t MASKLEN = (BS == 16 ? 6 : ((BS == 24) ? 7 : 8));

   const uint8_t BOTTOM_MASK = static_cast<uint8_t>((static_cast<uint16_t>(1) << MASKLEN) - 1);

   m_nonce_buf.resize(BS);
   clear_mem(&m_nonce_buf[0], m_nonce_buf.size());

   copy_mem(&m_nonce_buf[BS - nonce_len], nonce, nonce_len);
   m_nonce_buf[0] = static_cast<uint8_t>(((tag_size() * 8) % (BS * 8)) << (BS <= 16 ? 1 : 0));

   m_nonce_buf[BS - nonce_len - 1] ^= 1;

   const uint8_t bottom = m_nonce_buf[BS - 1] & BOTTOM_MASK;
   m_nonce_buf[BS - 1] &= ~BOTTOM_MASK;

   const bool need_new_stretch = (m_last_nonce != m_nonce_buf);

   if(need_new_stretch) {
      m_last_nonce = m_nonce_buf;

      m_cipher->encrypt(m_nonce_buf);

      /*
      The loop bounds (BS vs BS/2) are derived from the relation
      between the block size and the MASKLEN. Using the terminology
      of draft-krovetz-ocb-wide, we have to derive enough bits in
      ShiftedKtop to read up to BLOCKLEN+bottom bits from Stretch.

                 +----------+---------+-------+---------+
                 | BLOCKLEN | RESIDUE | SHIFT | MASKLEN |
                 +----------+---------+-------+---------+
                 |       32 |     141 |    17 |    4    |
                 |       64 |      27 |    25 |    5    |
                 |       96 |    1601 |    33 |    6    |
                 |      128 |     135 |     8 |    6    |
                 |      192 |     135 |    40 |    7    |
                 |      256 |    1061 |     1 |    8    |
                 |      384 |    4109 |    80 |    8    |
                 |      512 |     293 |   176 |    8    |
                 |     1024 |  524355 |   352 |    9    |
                 +----------+---------+-------+---------+
      */
      if(BS == 16) {
         for(size_t i = 0; i != BS / 2; ++i) {
            m_nonce_buf.push_back(m_nonce_buf[i] ^ m_nonce_buf[i + 1]);
         }
      } else if(BS == 24) {
         for(size_t i = 0; i != 16; ++i) {
            m_nonce_buf.push_back(m_nonce_buf[i] ^ m_nonce_buf[i + 5]);
         }
      } else if(BS == 32) {
         for(size_t i = 0; i != BS; ++i) {
            m_nonce_buf.push_back(m_nonce_buf[i] ^ (m_nonce_buf[i] << 1) ^ (m_nonce_buf[i + 1] >> 7));
         }
      } else if(BS == 64) {
         for(size_t i = 0; i != BS / 2; ++i) {
            m_nonce_buf.push_back(m_nonce_buf[i] ^ m_nonce_buf[i + 22]);
         }
      }

      m_stretch = m_nonce_buf;
   }

   // now set the offset from stretch and bottom
   const size_t shift_bytes = bottom / 8;
   const size_t shift_bits = bottom % 8;

   BOTAN_ASSERT(m_stretch.size() >= BS + shift_bytes + 1, "Size ok");

   m_offset.resize(BS);
   for(size_t i = 0; i != BS; ++i) {
      m_offset[i] = (m_stretch[i + shift_bytes] << shift_bits);
      m_offset[i] |= (m_stretch[i + shift_bytes + 1] >> (8 - shift_bits));
   }

   return m_offset;
}

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

   assert_key_material_set();

   m_L->init(update_nonce(nonce, nonce_len));
   zeroise(m_checksum);
   m_block_index = 0;
}

void OCB_Encryption::encrypt(uint8_t buffer[], size_t blocks) {
   assert_key_material_set();
   BOTAN_STATE_CHECK(m_L->initialized());

   const size_t BS = block_size();

   while(blocks) {
      const size_t proc_blocks = std::min(blocks, par_blocks());
      const size_t proc_bytes = proc_blocks * BS;

      const uint8_t* offsets = m_L->compute_offsets(m_block_index, proc_blocks);

      xor_buf(m_checksum.data(), buffer, proc_bytes);

      m_cipher->encrypt_n_xex(buffer, offsets, proc_blocks);

      buffer += proc_bytes;
      blocks -= proc_blocks;
      m_block_index += proc_blocks;
   }
}

size_t OCB_Encryption::process_msg(uint8_t buf[], size_t sz) {
   BOTAN_ARG_CHECK(sz % update_granularity() == 0, "Invalid OCB input size");
   encrypt(buf, sz / block_size());
   return sz;
}

void OCB_Encryption::finish_msg(secure_vector<uint8_t>& buffer, size_t offset) {
   assert_key_material_set();
   BOTAN_STATE_CHECK(m_L->initialized());

   const size_t BS = block_size();

   BOTAN_ARG_CHECK(buffer.size() >= offset, "Offset is out of range");
   const size_t sz = buffer.size() - offset;
   uint8_t* buf = buffer.data() + offset;

   secure_vector<uint8_t> mac(BS);

   if(sz) {
      const size_t final_full_blocks = sz / BS;
      const size_t remainder_bytes = sz - (final_full_blocks * BS);

      encrypt(buf, final_full_blocks);
      mac = m_L->offset();

      if(remainder_bytes) {
         BOTAN_ASSERT(remainder_bytes < BS, "Only a partial block left");
         uint8_t* remainder = &buf[sz - remainder_bytes];

         xor_buf(m_checksum.data(), remainder, remainder_bytes);
         m_checksum[remainder_bytes] ^= 0x80;

         // Offset_*
         mac ^= m_L->star();

         secure_vector<uint8_t> pad(BS);
         m_cipher->encrypt(mac, pad);
         xor_buf(remainder, pad.data(), remainder_bytes);
      }
   } else {
      mac = m_L->offset();
   }

   // now compute the tag

   // fold checksum
   for(size_t i = 0; i != m_checksum.size(); i += BS) {
      xor_buf(mac.data(), m_checksum.data() + i, BS);
   }

   xor_buf(mac.data(), m_L->dollar().data(), BS);
   m_cipher->encrypt(mac);
   xor_buf(mac.data(), m_ad_hash.data(), BS);

   buffer += std::make_pair(mac.data(), tag_size());

   zeroise(m_checksum);
   m_block_index = 0;
}

void OCB_Decryption::decrypt(uint8_t buffer[], size_t blocks) {
   assert_key_material_set();
   BOTAN_STATE_CHECK(m_L->initialized());

   const size_t BS = block_size();

   while(blocks) {
      const size_t proc_blocks = std::min(blocks, par_blocks());
      const size_t proc_bytes = proc_blocks * BS;

      const uint8_t* offsets = m_L->compute_offsets(m_block_index, proc_blocks);

      m_cipher->decrypt_n_xex(buffer, offsets, proc_blocks);

      xor_buf(m_checksum.data(), buffer, proc_bytes);

      buffer += proc_bytes;
      blocks -= proc_blocks;
      m_block_index += proc_blocks;
   }
}

size_t OCB_Decryption::process_msg(uint8_t buf[], size_t sz) {
   BOTAN_ARG_CHECK(sz % update_granularity() == 0, "Invalid OCB input size");
   decrypt(buf, sz / block_size());
   return sz;
}

void OCB_Decryption::finish_msg(secure_vector<uint8_t>& buffer, size_t offset) {
   assert_key_material_set();
   BOTAN_STATE_CHECK(m_L->initialized());

   const size_t BS = block_size();

   BOTAN_ARG_CHECK(buffer.size() >= offset, "Offset is out of range");
   const size_t sz = buffer.size() - offset;
   uint8_t* buf = buffer.data() + offset;

   BOTAN_ARG_CHECK(sz >= tag_size(), "input did not include the tag");

   const size_t remaining = sz - tag_size();

   secure_vector<uint8_t> mac(BS);

   if(remaining) {
      const size_t final_full_blocks = remaining / BS;
      const size_t final_bytes = remaining - (final_full_blocks * BS);

      decrypt(buf, final_full_blocks);
      mac ^= m_L->offset();

      if(final_bytes) {
         BOTAN_ASSERT(final_bytes < BS, "Only a partial block left");

         uint8_t* remainder = &buf[remaining - final_bytes];

         mac ^= m_L->star();
         secure_vector<uint8_t> pad(BS);
         m_cipher->encrypt(mac, pad);  // P_*
         xor_buf(remainder, pad.data(), final_bytes);

         xor_buf(m_checksum.data(), remainder, final_bytes);
         m_checksum[final_bytes] ^= 0x80;
      }
   } else {
      mac = m_L->offset();
   }

   // compute the mac

   // fold checksum
   for(size_t i = 0; i != m_checksum.size(); i += BS) {
      xor_buf(mac.data(), m_checksum.data() + i, BS);
   }

   mac ^= m_L->dollar();
   m_cipher->encrypt(mac);
   mac ^= m_ad_hash;

   // reset state
   zeroise(m_checksum);
   m_block_index = 0;

   // compare mac
   const uint8_t* included_tag = &buf[remaining];

   if(!CT::is_equal(mac.data(), included_tag, tag_size()).as_bool()) {
      throw Invalid_Authentication_Tag("OCB tag check failed");
   }

   // remove tag from end of message
   buffer.resize(remaining + offset);
}

}  // namespace Botan

1	/*
2	* OCB Mode
3	* (C) 2013,2017 Jack Lloyd
4	* (C) 2016 Daniel Neus, Rohde & Schwarz Cybersecurity
5	*
6	* Botan is released under the Simplified BSD License (see license.txt)
7	*/
8
9	#include <botan/internal/ocb.h>
10
11	#include <botan/block_cipher.h>
12	#include <botan/internal/bit_ops.h>
13	#include <botan/internal/ct_utils.h>
14	#include <botan/internal/poly_dbl.h>
15
16	namespace Botan {
17
18	// Has to be in Botan namespace so unique_ptr can reference it
19	class L_computer final {
20	public:
21	explicit L_computer(const BlockCipher& cipher) :	245✔
22	m_BS(cipher.block_size()), m_max_blocks(cipher.parallel_bytes() / m_BS) {	490✔
23	m_L_star.resize(m_BS);	245✔
24	cipher.encrypt(m_L_star);	245✔
25	m_L_dollar = poly_double(star());	245✔
26
27	// Preallocate the m_L vector to the maximum expected size to avoid
28	// re-allocations during runtime. This had caused a use-after-free in
29	// earlier versions, due to references into this buffer becoming stale
30	// in `compute_offset()`, after calling `get()` in the hot path.
31	//
32	// Note, that the list member won't be pre-allocated, so the expected
33	// memory overhead is negligible.
34	//
35	// See also https://github.com/randombit/botan/issues/3812
36	m_L.reserve(31);	245✔
37	m_L.push_back(poly_double(dollar()));	245✔
38
39	while(m_L.size() < 8) {	1,960✔
40	m_L.push_back(poly_double(m_L.back()));	3,430✔
41	}
42
43	m_offset_buf.resize(m_BS * m_max_blocks);	245✔
44	}	245✔
45
46	void init(const secure_vector<uint8_t>& offset) { m_offset = offset; }	9,449✔
47
48	bool initialized() const { return m_offset.empty() == false; }	16,589✔
49
50	const secure_vector<uint8_t>& star() const { return m_L_star; }	6,068✔
51
52	const secure_vector<uint8_t>& dollar() const { return m_L_dollar; }	9,602✔
53
54	const secure_vector<uint8_t>& offset() const { return m_offset; }	9,357✔
55
56	const secure_vector<uint8_t>& get(size_t i) const {	121,741✔
57	while(m_L.size() <= i) {	121,828✔
58	m_L.push_back(poly_double(m_L.back()));	87✔
59	}
60
61	return m_L[i];	121,741✔
62	}
63
64	const uint8_t* compute_offsets(size_t block_index, size_t blocks) {	14,623✔
65	BOTAN_ASSERT(blocks <= m_max_blocks, "OCB offsets");	14,623✔
66
67	uint8_t* offsets = m_offset_buf.data();	14,623✔
68
69	if(block_index % 4 == 0) {	14,623✔
70	const secure_vector<uint8_t>& L0 = get(0);	14,169✔
71	const secure_vector<uint8_t>& L1 = get(1);	14,169✔
72
73	while(blocks >= 4) {	65,095✔
74	// ntz(4*i+1) == 0
75	// ntz(4*i+2) == 1
76	// ntz(4*i+3) == 0
77	block_index += 4;	36,757✔
78	const size_t ntz4 = var_ctz32(static_cast<uint32_t>(block_index));	36,757✔
79
80	xor_buf(offsets, m_offset.data(), L0.data(), m_BS);	36,757✔
81	offsets += m_BS;	36,757✔
82
83	xor_buf(offsets, offsets - m_BS, L1.data(), m_BS);	36,757✔
84	offsets += m_BS;	36,757✔
85
86	xor_buf(m_offset.data(), L1.data(), m_BS);	36,757✔
87	copy_mem(offsets, m_offset.data(), m_BS);	36,757✔
88	offsets += m_BS;	36,757✔
89
90	xor_buf(m_offset.data(), get(ntz4).data(), m_BS);	36,757✔
91	copy_mem(offsets, m_offset.data(), m_BS);	36,757✔
92	offsets += m_BS;	36,757✔
93
94	blocks -= 4;	36,757✔
95	}
96	}
97
98	for(size_t i = 0; i != blocks; ++i) { // could be done in parallel	24,239✔
99	const size_t ntz = var_ctz32(static_cast<uint32_t>(block_index + i + 1));	9,616✔
100	xor_buf(m_offset.data(), get(ntz).data(), m_BS);	9,616✔
101	copy_mem(offsets, m_offset.data(), m_BS);	9,616✔
102	offsets += m_BS;	9,616✔
103	}
104
105	return m_offset_buf.data();	14,623✔
106	}
107
108	private:
109	static secure_vector<uint8_t> poly_double(const secure_vector<uint8_t>& in) {	2,292✔
110	secure_vector<uint8_t> out(in.size());	2,292✔
111	poly_double_n(out.data(), in.data(), out.size());	2,292✔
112	return out;	2,292✔
113	}	×
114
115	const size_t m_BS, m_max_blocks;
116	secure_vector<uint8_t> m_L_dollar, m_L_star;
117	secure_vector<uint8_t> m_offset;
118	mutable std::vector<secure_vector<uint8_t>> m_L;
119	secure_vector<uint8_t> m_offset_buf;
120	};
121
122	namespace {
123
124	/*
125	* OCB's HASH
126	*/
127	secure_vector<uint8_t> ocb_hash(const L_computer& L, const BlockCipher& cipher, const uint8_t ad[], size_t ad_len) {	9,497✔
128	const size_t BS = cipher.block_size();	9,497✔
129	secure_vector<uint8_t> sum(BS);	9,497✔
130	secure_vector<uint8_t> offset(BS);	9,497✔
131
132	secure_vector<uint8_t> buf(BS);	9,497✔
133
134	const size_t ad_blocks = (ad_len / BS);	9,497✔
135	const size_t ad_remainder = (ad_len % BS);	9,497✔
136
137	for(size_t i = 0; i != ad_blocks; ++i) {	56,527✔
138	// this loop could run in parallel
139	offset ^= L.get(var_ctz32(static_cast<uint32_t>(i + 1)));	94,060✔
140	buf = offset;	47,030✔
141	xor_buf(buf.data(), &ad[BS * i], BS);	47,030✔
142	cipher.encrypt(buf);	47,030✔
143	sum ^= buf;	47,030✔
144	}
145
146	if(ad_remainder) {	9,497✔
147	offset ^= L.star();	5,867✔
148	buf = offset;	5,867✔
149	xor_buf(buf.data(), &ad[BS * ad_blocks], ad_remainder);	5,867✔
150	buf[ad_remainder] ^= 0x80;	5,867✔
151	cipher.encrypt(buf);	5,867✔
152	sum ^= buf;	5,867✔
153	}
154
155	return sum;	9,497✔
156	}	18,994✔
157
158	} // namespace
159
160	OCB_Mode::OCB_Mode(std::unique_ptr<BlockCipher> cipher, size_t tag_size) :	337✔
161	m_cipher(std::move(cipher)),	337✔
162	m_checksum(m_cipher->parallel_bytes()),	674✔
163	m_ad_hash(m_cipher->block_size()),	337✔
164	m_tag_size(tag_size),	337✔
165	m_block_size(m_cipher->block_size()),	337✔
166	m_par_blocks(m_cipher->parallel_bytes() / m_block_size) {	1,011✔
167	const size_t BS = block_size();	337✔
168
169	/*
170	* draft-krovetz-ocb-wide-d1 specifies OCB for several other block
171	* sizes but only 128, 192, 256 and 512 bit are currently supported
172	* by this implementation.
173	*/
174	BOTAN_ARG_CHECK(BS == 16 \|\| BS == 24 \|\| BS == 32 \|\| BS == 64, "Invalid block size for OCB");	337✔
175
176	BOTAN_ARG_CHECK(m_tag_size % 4 == 0 && m_tag_size >= 8 && m_tag_size <= BS && m_tag_size <= 32,	337✔
177	"Invalid OCB tag length");
178	}	337✔
179
180	OCB_Mode::~OCB_Mode() = default;	1,991✔
181
182	void OCB_Mode::clear() {	92✔
183	m_cipher->clear();	92✔
184	m_L.reset(); // add clear here?	92✔
185	reset();	92✔
186	}	92✔
187
188	void OCB_Mode::reset() {	410✔
189	m_block_index = 0;	410✔
190	zeroise(m_ad_hash);	410✔
191	zeroise(m_checksum);	410✔
192	m_last_nonce.clear();	410✔
193	m_stretch.clear();	410✔
194	}	410✔
195
196	bool OCB_Mode::valid_nonce_length(size_t length) const {	9,495✔
197	if(length == 0) {	9,495✔
198	return false;
199	}
200	if(block_size() == 16) {	9,495✔
201	return length < 16;	7,893✔
202	} else {
203	return length < (block_size() - 1);	1,602✔
204	}
205	}
206
207	std::string OCB_Mode::name() const {	506✔
208	return m_cipher->name() + "/OCB"; // include tag size?	1,012✔
209	}
210
211	size_t OCB_Mode::update_granularity() const {	1,321✔
212	return block_size();	1,321✔
213	}
214
215	size_t OCB_Mode::ideal_granularity() const {	276✔
216	return (m_par_blocks * block_size());	276✔
217	}
218
219	Key_Length_Specification OCB_Mode::key_spec() const {	245✔
220	return m_cipher->key_spec();	245✔
221	}
222
223	bool OCB_Mode::has_keying_material() const {	36,317✔
224	return m_cipher->has_keying_material();	36,317✔
225	}
226
227	void OCB_Mode::key_schedule(std::span<const uint8_t> key) {	245✔
228	m_cipher->set_key(key);	245✔
229	m_L = std::make_unique<L_computer>(*m_cipher);	245✔
230	}	245✔
231
232	void OCB_Mode::set_associated_data_n(size_t idx, std::span<const uint8_t> ad) {	9,681✔
233	BOTAN_ARG_CHECK(idx == 0, "OCB: cannot handle non-zero index in set_associated_data_n");	9,681✔
234	assert_key_material_set();	9,681✔
235	m_ad_hash = ocb_hash(m_L, m_cipher, ad.data(), ad.size());	9,497✔
236	}	9,497✔
237
238	const secure_vector<uint8_t>& OCB_Mode::update_nonce(const uint8_t nonce[], size_t nonce_len) {	9,449✔
239	const size_t BS = block_size();	9,449✔
240
241	BOTAN_ASSERT(BS == 16 \|\| BS == 24 \|\| BS == 32 \|\| BS == 64, "OCB block size is supported");	9,449✔
242
243	const size_t MASKLEN = (BS == 16 ? 6 : ((BS == 24) ? 7 : 8));	9,449✔
244
245	const uint8_t BOTTOM_MASK = static_cast<uint8_t>((static_cast<uint16_t>(1) << MASKLEN) - 1);	9,449✔
246
247	m_nonce_buf.resize(BS);	9,449✔
248	clear_mem(&m_nonce_buf[0], m_nonce_buf.size());	9,449✔
249
250	copy_mem(&m_nonce_buf[BS - nonce_len], nonce, nonce_len);	9,449✔
251	m_nonce_buf[0] = static_cast<uint8_t>(((tag_size() * 8) % (BS * 8)) << (BS <= 16 ? 1 : 0));	11,047✔
252
253	m_nonce_buf[BS - nonce_len - 1] ^= 1;	9,449✔
254
255	const uint8_t bottom = m_nonce_buf[BS - 1] & BOTTOM_MASK;	9,449✔
256	m_nonce_buf[BS - 1] &= ~BOTTOM_MASK;	9,449✔
257
258	const bool need_new_stretch = (m_last_nonce != m_nonce_buf);	9,449✔
259
260	if(need_new_stretch) {	9,449✔
261	m_last_nonce = m_nonce_buf;	683✔
262
263	m_cipher->encrypt(m_nonce_buf);	683✔
264
265	/*
266	The loop bounds (BS vs BS/2) are derived from the relation
267	between the block size and the MASKLEN. Using the terminology
268	of draft-krovetz-ocb-wide, we have to derive enough bits in
269	ShiftedKtop to read up to BLOCKLEN+bottom bits from Stretch.
270
271	+----------+---------+-------+---------+
272	\| BLOCKLEN \| RESIDUE \| SHIFT \| MASKLEN \|
273	+----------+---------+-------+---------+
274	\| 32 \| 141 \| 17 \| 4 \|
275	\| 64 \| 27 \| 25 \| 5 \|
276	\| 96 \| 1601 \| 33 \| 6 \|
277	\| 128 \| 135 \| 8 \| 6 \|
278	\| 192 \| 135 \| 40 \| 7 \|
279	\| 256 \| 1061 \| 1 \| 8 \|
280	\| 384 \| 4109 \| 80 \| 8 \|
281	\| 512 \| 293 \| 176 \| 8 \|
282	\| 1024 \| 524355 \| 352 \| 9 \|
283	+----------+---------+-------+---------+
284	*/
285	if(BS == 16) {	683✔
286	for(size_t i = 0; i != BS / 2; ++i) {	5,535✔
287	m_nonce_buf.push_back(m_nonce_buf[i] ^ m_nonce_buf[i + 1]);	4,920✔
288	}
289	} else if(BS == 24) {	68✔
290	for(size_t i = 0; i != 16; ++i) {	408✔
291	m_nonce_buf.push_back(m_nonce_buf[i] ^ m_nonce_buf[i + 5]);	384✔
292	}
293	} else if(BS == 32) {	44✔
294	for(size_t i = 0; i != BS; ++i) {	1,089✔
295	m_nonce_buf.push_back(m_nonce_buf[i] ^ (m_nonce_buf[i] << 1) ^ (m_nonce_buf[i + 1] >> 7));	1,056✔
296	}
297	} else if(BS == 64) {
298	for(size_t i = 0; i != BS / 2; ++i) {	363✔
299	m_nonce_buf.push_back(m_nonce_buf[i] ^ m_nonce_buf[i + 22]);	352✔
300	}
301	}
302
303	m_stretch = m_nonce_buf;	683✔
304	}
305
306	// now set the offset from stretch and bottom
307	const size_t shift_bytes = bottom / 8;	9,449✔
308	const size_t shift_bits = bottom % 8;	9,449✔
309
310	BOTAN_ASSERT(m_stretch.size() >= BS + shift_bytes + 1, "Size ok");	9,449✔
311
312	m_offset.resize(BS);	9,449✔
313	for(size_t i = 0; i != BS; ++i) {	195,569✔
314	m_offset[i] = (m_stretch[i + shift_bytes] << shift_bits);	186,120✔
315	m_offset[i] \|= (m_stretch[i + shift_bytes + 1] >> (8 - shift_bits));	186,120✔
316	}
317
318	return m_offset;	9,449✔
319	}
320
321	void OCB_Mode::start_msg(const uint8_t nonce[], size_t nonce_len) {	9,449✔
322	if(!valid_nonce_length(nonce_len)) {	9,449✔
323	throw Invalid_IV_Length(name(), nonce_len);	×
324	}
325
326	assert_key_material_set();	9,449✔
327
328	m_L->init(update_nonce(nonce, nonce_len));	9,449✔
329	zeroise(m_checksum);	9,449✔
330	m_block_index = 0;	9,449✔
331	}	9,449✔
332
333	void OCB_Encryption::encrypt(uint8_t buffer[], size_t blocks) {	4,195✔
334	assert_key_material_set();	4,195✔
335	BOTAN_STATE_CHECK(m_L->initialized());	4,149✔
336
337	const size_t BS = block_size();	4,103✔
338
339	while(blocks) {	11,814✔
340	const size_t proc_blocks = std::min(blocks, par_blocks());	7,711✔
341	const size_t proc_bytes = proc_blocks * BS;	7,711✔
342
343	const uint8_t* offsets = m_L->compute_offsets(m_block_index, proc_blocks);	7,711✔
344
345	xor_buf(m_checksum.data(), buffer, proc_bytes);	7,711✔
346
347	m_cipher->encrypt_n_xex(buffer, offsets, proc_blocks);	7,711✔
348
349	buffer += proc_bytes;	7,711✔
350	blocks -= proc_blocks;	7,711✔
351	m_block_index += proc_blocks;	7,711✔
352	}
353	}	4,103✔
354
355	size_t OCB_Encryption::process_msg(uint8_t buf[], size_t sz) {	500✔
356	BOTAN_ARG_CHECK(sz % update_granularity() == 0, "Invalid OCB input size");	500✔
357	encrypt(buf, sz / block_size());	500✔
358	return sz;	408✔
359	}
360
361	void OCB_Encryption::finish_msg(secure_vector<uint8_t>& buffer, size_t offset) {	5,704✔
362	assert_key_material_set();	5,704✔
363	BOTAN_STATE_CHECK(m_L->initialized());	5,612✔
364
365	const size_t BS = block_size();	5,566✔
366
367	BOTAN_ARG_CHECK(buffer.size() >= offset, "Offset is out of range");	5,566✔
368	const size_t sz = buffer.size() - offset;	5,566✔
369	uint8_t* buf = buffer.data() + offset;	5,566✔
370
371	secure_vector<uint8_t> mac(BS);	5,566✔
372
373	if(sz) {	5,566✔
374	const size_t final_full_blocks = sz / BS;	3,695✔
375	const size_t remainder_bytes = sz - (final_full_blocks * BS);	3,695✔
376
377	encrypt(buf, final_full_blocks);	3,695✔
378	mac = m_L->offset();	3,695✔
379
380	if(remainder_bytes) {	3,695✔
381	BOTAN_ASSERT(remainder_bytes < BS, "Only a partial block left");	3,492✔
382	uint8_t* remainder = &buf[sz - remainder_bytes];	3,492✔
383
384	xor_buf(m_checksum.data(), remainder, remainder_bytes);	3,492✔
385	m_checksum[remainder_bytes] ^= 0x80;	3,492✔
386
387	// Offset_*
388	mac ^= m_L->star();	3,492✔
389
390	secure_vector<uint8_t> pad(BS);	3,492✔
391	m_cipher->encrypt(mac, pad);	3,492✔
392	xor_buf(remainder, pad.data(), remainder_bytes);	3,492✔
393	}	3,492✔
394	} else {
395	mac = m_L->offset();	1,871✔
396	}
397
398	// now compute the tag
399
400	// fold checksum
401	for(size_t i = 0; i != m_checksum.size(); i += BS) {	72,870✔
402	xor_buf(mac.data(), m_checksum.data() + i, BS);	67,304✔
403	}
404
405	xor_buf(mac.data(), m_L->dollar().data(), BS);	5,566✔
406	m_cipher->encrypt(mac);	5,566✔
407	xor_buf(mac.data(), m_ad_hash.data(), BS);	5,566✔
408
409	buffer += std::make_pair(mac.data(), tag_size());	5,566✔
410
411	zeroise(m_checksum);	5,566✔
412	m_block_index = 0;	5,566✔
413	}	5,566✔
414
415	void OCB_Decryption::decrypt(uint8_t buffer[], size_t blocks) {	3,037✔
416	assert_key_material_set();	3,037✔
417	BOTAN_STATE_CHECK(m_L->initialized());	2,991✔
418
419	const size_t BS = block_size();	2,945✔
420
421	while(blocks) {	9,857✔
422	const size_t proc_blocks = std::min(blocks, par_blocks());	6,912✔
423	const size_t proc_bytes = proc_blocks * BS;	6,912✔
424
425	const uint8_t* offsets = m_L->compute_offsets(m_block_index, proc_blocks);	6,912✔
426
427	m_cipher->decrypt_n_xex(buffer, offsets, proc_blocks);	6,912✔
428
429	xor_buf(m_checksum.data(), buffer, proc_bytes);	6,912✔
430
431	buffer += proc_bytes;	6,912✔
432	blocks -= proc_blocks;	6,912✔
433	m_block_index += proc_blocks;	6,912✔
434	}
435	}	2,945✔
436
437	size_t OCB_Decryption::process_msg(uint8_t buf[], size_t sz) {	513✔
438	BOTAN_ARG_CHECK(sz % update_granularity() == 0, "Invalid OCB input size");	513✔
439	decrypt(buf, sz / block_size());	513✔
440	return sz;	421✔
441	}
442
443	void OCB_Decryption::finish_msg(secure_vector<uint8_t>& buffer, size_t offset) {	3,929✔
444	assert_key_material_set();	3,929✔
445	BOTAN_STATE_CHECK(m_L->initialized());	3,837✔
446
447	const size_t BS = block_size();	3,791✔
448
449	BOTAN_ARG_CHECK(buffer.size() >= offset, "Offset is out of range");	3,791✔
450	const size_t sz = buffer.size() - offset;	3,791✔
451	uint8_t* buf = buffer.data() + offset;	3,791✔
452
453	BOTAN_ARG_CHECK(sz >= tag_size(), "input did not include the tag");	3,791✔
454
455	const size_t remaining = sz - tag_size();	3,791✔
456
457	secure_vector<uint8_t> mac(BS);	3,791✔
458
459	if(remaining) {	3,791✔
460	const size_t final_full_blocks = remaining / BS;	2,524✔
461	const size_t final_bytes = remaining - (final_full_blocks * BS);	2,524✔
462
463	decrypt(buf, final_full_blocks);	2,524✔
464	mac ^= m_L->offset();	2,524✔
465
466	if(final_bytes) {	2,524✔
467	BOTAN_ASSERT(final_bytes < BS, "Only a partial block left");	2,331✔
468
469	uint8_t* remainder = &buf[remaining - final_bytes];	2,331✔
470
471	mac ^= m_L->star();	2,331✔
472	secure_vector<uint8_t> pad(BS);	2,469✔
473	m_cipher->encrypt(mac, pad); // P_*	2,331✔
474	xor_buf(remainder, pad.data(), final_bytes);	2,331✔
475
476	xor_buf(m_checksum.data(), remainder, final_bytes);	2,331✔
477	m_checksum[final_bytes] ^= 0x80;	2,331✔
478	}	2,331✔
479	} else {
480	mac = m_L->offset();	1,267✔
481	}
482
483	// compute the mac
484
485	// fold checksum
486	for(size_t i = 0; i != m_checksum.size(); i += BS) {	64,131✔
487	xor_buf(mac.data(), m_checksum.data() + i, BS);	60,340✔
488	}
489
490	mac ^= m_L->dollar();	3,791✔
491	m_cipher->encrypt(mac);	3,791✔
492	mac ^= m_ad_hash;	3,791✔
493
494	// reset state
495	zeroise(m_checksum);	3,791✔
496	m_block_index = 0;	3,791✔
497
498	// compare mac
499	const uint8_t* included_tag = &buf[remaining];	3,791✔
500
501	if(!CT::is_equal(mac.data(), included_tag, tag_size()).as_bool()) {	7,582✔
502	throw Invalid_Authentication_Tag("OCB tag check failed");	138✔
503	}
504
505	// remove tag from end of message
506	buffer.resize(remaining + offset);	3,653✔
507	}	3,653✔
508
509	} // namespace Botan

randombit / botan / 11087146043

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