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-rw-r--r--src/lib/modes/aead/ocb/ocb.cpp185
-rw-r--r--src/lib/modes/aead/ocb/ocb.h11
2 files changed, 134 insertions, 62 deletions
diff --git a/src/lib/modes/aead/ocb/ocb.cpp b/src/lib/modes/aead/ocb/ocb.cpp
index 4e1076cba..a48f0751a 100644
--- a/src/lib/modes/aead/ocb/ocb.cpp
+++ b/src/lib/modes/aead/ocb/ocb.cpp
@@ -1,6 +1,6 @@
/*
* OCB Mode
-* (C) 2013 Jack Lloyd
+* (C) 2013,2017 Jack Lloyd
* (C) 2016 Daniel Neus, Rohde & Schwarz Cybersecurity
*
* Botan is released under the Simplified BSD License (see license.txt)
@@ -30,16 +30,18 @@ class L_computer
const secure_vector<uint8_t>& operator()(size_t i) const { return get(i); }
- const secure_vector<uint8_t>& compute_offsets(secure_vector<uint8_t>& offset,
- size_t block_index,
- size_t blocks) const
+ const secure_vector<uint8_t>&
+ compute_offsets(secure_vector<uint8_t>& offset,
+ size_t block_index,
+ size_t blocks,
+ size_t BS) const
{
- m_offset_buf.resize(blocks * 16);
+ m_offset_buf.resize(blocks * BS);
for(size_t i = 0; i != blocks; ++i)
{ // could be done in parallel
offset ^= get(ctz(block_index + 1 + i));
- copy_mem(&m_offset_buf[16*i], offset.data(), 16);
+ copy_mem(&m_offset_buf[BS*i], offset.data(), BS);
}
return m_offset_buf;
@@ -72,16 +74,17 @@ 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 BlockCipher& cipher,
+ const uint8_t ad[], size_t ad_len)
{
- secure_vector<uint8_t> sum(16);
- secure_vector<uint8_t> offset(16);
+ const size_t BS = cipher.block_size();
+ secure_vector<uint8_t> sum(BS);
+ secure_vector<uint8_t> offset(BS);
- secure_vector<uint8_t> buf(16);
+ secure_vector<uint8_t> buf(BS);
- const size_t ad_blocks = (ad_len / 16);
- const size_t ad_remainder = (ad_len % 16);
+ 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)
{
@@ -89,7 +92,7 @@ secure_vector<uint8_t> ocb_hash(const L_computer& L,
offset ^= L(ctz(i+1));
buf = offset;
- xor_buf(buf.data(), &ad[16*i], 16);
+ xor_buf(buf.data(), &ad[BS*i], BS);
cipher.encrypt(buf);
@@ -101,8 +104,8 @@ secure_vector<uint8_t> ocb_hash(const L_computer& L,
offset ^= L.star();
buf = offset;
- xor_buf(buf.data(), &ad[16*ad_blocks], ad_remainder);
- buf[ad_len % 16] ^= 0x80;
+ xor_buf(buf.data(), &ad[BS*ad_blocks], ad_remainder);
+ buf[ad_len % BS] ^= 0x80;
cipher.encrypt(buf);
@@ -117,14 +120,21 @@ secure_vector<uint8_t> ocb_hash(const L_computer& L,
OCB_Mode::OCB_Mode(BlockCipher* cipher, size_t tag_size) :
m_cipher(cipher),
m_checksum(m_cipher->parallel_bytes()),
- m_offset(16),
- m_ad_hash(16),
+ m_offset(m_cipher->block_size()),
+ m_ad_hash(m_cipher->block_size()),
m_tag_size(tag_size)
{
- if(m_cipher->block_size() != 16)
- throw Invalid_Argument("OCB requires 128 bit cipher");
+ const size_t BS = m_cipher->block_size();
- if(m_tag_size % 4 != 0 || m_tag_size < 8 || m_tag_size > 16)
+ /*
+ * 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.
+ */
+ if(BS != 16 && BS != 24 && BS != 32 && BS != 64)
+ throw Invalid_Argument("OCB does not support cipher " + m_cipher->name());
+
+ if(m_tag_size % 4 != 0 || m_tag_size < 8 || m_tag_size > BS || m_tag_size > 32)
throw Invalid_Argument("Invalid OCB tag length");
}
@@ -149,12 +159,17 @@ void OCB_Mode::reset()
bool OCB_Mode::valid_nonce_length(size_t length) const
{
- return (length > 0 && length < m_cipher->block_size());
+ if(length == 0)
+ return false;
+ if(m_cipher->block_size() == 16)
+ return length < 16;
+ else
+ return length < (m_cipher->block_size() - 1);
}
std::string OCB_Mode::name() const
{
- return m_cipher->name() + "/OCB"; // include tag size
+ return m_cipher->name() + "/OCB"; // include tag size?
}
size_t OCB_Mode::update_granularity() const
@@ -182,16 +197,25 @@ void OCB_Mode::set_associated_data(const uint8_t ad[], size_t ad_len)
secure_vector<uint8_t>
OCB_Mode::update_nonce(const uint8_t nonce[], size_t nonce_len)
{
- BOTAN_ASSERT(nonce_len < 16, "OCB nonce is less than cipher block size");
+ const size_t BS = m_cipher->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);
+
+ secure_vector<uint8_t> nonce_buf(BS);
- secure_vector<uint8_t> nonce_buf(16);
+ copy_mem(&nonce_buf[BS - nonce_len], nonce, nonce_len);
+ nonce_buf[0] = ((tag_size()*8) % (BS*8)) << (BS <= 16 ? 1 : 0);
- copy_mem(&nonce_buf[16 - nonce_len], nonce, nonce_len);
- nonce_buf[0] = ((tag_size() * 8) % 128) << 1;
- nonce_buf[16 - nonce_len - 1] = 1;
+ nonce_buf[BS - nonce_len - 1] ^= 1;
- const uint8_t bottom = nonce_buf[16-1] & 0x3F;
- nonce_buf[16-1] &= 0xC0;
+ const uint8_t bottom = nonce_buf[BS-1] & BOTTOM_MASK;
+ nonce_buf[BS-1] &= ~BOTTOM_MASK;
const bool need_new_stretch = (m_last_nonce != nonce_buf);
@@ -201,19 +225,58 @@ OCB_Mode::update_nonce(const uint8_t nonce[], size_t nonce_len)
m_cipher->encrypt(nonce_buf);
- for(size_t i = 0; i != 16 / 2; ++i)
- nonce_buf.push_back(nonce_buf[i] ^ nonce_buf[i+1]);
+ /*
+ 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)
+ nonce_buf.push_back(nonce_buf[i] ^ nonce_buf[i+1]);
+ }
+ else if(BS == 24)
+ {
+ for(size_t i = 0; i != 16; ++i)
+ nonce_buf.push_back(nonce_buf[i] ^ nonce_buf[i+5]);
+ }
+ else if(BS == 32)
+ {
+ for(size_t i = 0; i != BS; ++i)
+ nonce_buf.push_back(nonce_buf[i] ^ (nonce_buf[i] << 1) ^ (nonce_buf[i+1] >> 7));
+ }
+ else if(BS == 64)
+ {
+ for(size_t i = 0; i != BS / 2; ++i)
+ nonce_buf.push_back(nonce_buf[i] ^ nonce_buf[i+22]);
+ }
m_stretch = nonce_buf;
}
// now set the offset from stretch and bottom
-
const size_t shift_bytes = bottom / 8;
const size_t shift_bits = bottom % 8;
- secure_vector<uint8_t> offset(16);
- for(size_t i = 0; i != 16; ++i)
+ BOTAN_ASSERT(m_stretch.size() >= BS + shift_bytes + 1, "Size ok");
+
+ secure_vector<uint8_t> offset(BS);
+ for(size_t i = 0; i != BS; ++i)
{
offset[i] = (m_stretch[i+shift_bytes] << shift_bits);
offset[i] |= (m_stretch[i+shift_bytes+1] >> (8-shift_bits));
@@ -236,16 +299,17 @@ void OCB_Mode::start_msg(const uint8_t nonce[], size_t nonce_len)
void OCB_Encryption::encrypt(uint8_t buffer[], size_t blocks)
{
- const size_t par_blocks = m_checksum.size() / 16;
+ const size_t BS = m_cipher->block_size();
+ const size_t par_blocks = m_checksum.size() / BS;
while(blocks)
{
const size_t proc_blocks = std::min(blocks, par_blocks);
- const size_t proc_bytes = proc_blocks * 16;
+ const size_t proc_bytes = proc_blocks * BS;
BOTAN_ASSERT(m_L, "A key was set");
- const auto& offsets = m_L->compute_offsets(m_offset, m_block_index, proc_blocks);
+ const auto& offsets = m_L->compute_offsets(m_offset, m_block_index, proc_blocks, BS);
xor_buf(m_checksum.data(), buffer, proc_bytes);
@@ -261,27 +325,30 @@ void OCB_Encryption::encrypt(uint8_t buffer[], size_t blocks)
size_t OCB_Encryption::process(uint8_t buf[], size_t sz)
{
- BOTAN_ASSERT(sz % 16 == 0, "Invalid OCB input size");
- encrypt(buf, sz / 16);
+ const size_t BS = m_cipher->block_size();
+ BOTAN_ASSERT(sz % BS == 0, "Invalid OCB input size");
+ encrypt(buf, sz / BS);
return sz;
}
void OCB_Encryption::finish(secure_vector<uint8_t>& buffer, size_t offset)
{
+ const size_t BS = m_cipher->block_size();
+
BOTAN_ASSERT(buffer.size() >= offset, "Offset is sane");
const size_t sz = buffer.size() - offset;
uint8_t* buf = buffer.data() + offset;
if(sz)
{
- const size_t final_full_blocks = sz / 16;
- const size_t remainder_bytes = sz - (final_full_blocks * 16);
+ const size_t final_full_blocks = sz / BS;
+ const size_t remainder_bytes = sz - (final_full_blocks * BS);
encrypt(buf, final_full_blocks);
if(remainder_bytes)
{
- BOTAN_ASSERT(remainder_bytes < 16, "Only a partial block left");
+ 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);
@@ -289,13 +356,13 @@ void OCB_Encryption::finish(secure_vector<uint8_t>& buffer, size_t offset)
m_offset ^= m_L->star(); // Offset_*
- secure_vector<uint8_t> zeros(16);
+ secure_vector<uint8_t> zeros(BS);
m_cipher->encrypt(m_offset, zeros);
xor_buf(remainder, zeros.data(), remainder_bytes);
}
}
- secure_vector<uint8_t> checksum(16);
+ secure_vector<uint8_t> checksum(BS);
// fold checksum
for(size_t i = 0; i != m_checksum.size(); ++i)
@@ -305,9 +372,7 @@ void OCB_Encryption::finish(secure_vector<uint8_t>& buffer, size_t offset)
secure_vector<uint8_t> mac = m_offset;
mac ^= checksum;
mac ^= m_L->dollar();
-
m_cipher->encrypt(mac);
-
mac ^= m_ad_hash;
buffer += std::make_pair(mac.data(), tag_size());
@@ -319,18 +384,19 @@ void OCB_Encryption::finish(secure_vector<uint8_t>& buffer, size_t offset)
void OCB_Decryption::decrypt(uint8_t buffer[], size_t blocks)
{
+ const size_t BS = m_cipher->block_size();
const size_t par_bytes = m_cipher->parallel_bytes();
- BOTAN_ASSERT(par_bytes % 16 == 0, "Cipher is parallel in full blocks");
+ BOTAN_ASSERT(par_bytes % BS == 0, "Cipher is parallel in full blocks");
- const size_t par_blocks = par_bytes / 16;
+ const size_t par_blocks = par_bytes / BS;
while(blocks)
{
const size_t proc_blocks = std::min(blocks, par_blocks);
- const size_t proc_bytes = proc_blocks * 16;
+ const size_t proc_bytes = proc_blocks * BS;
- const auto& offsets = m_L->compute_offsets(m_offset, m_block_index, proc_blocks);
+ const auto& offsets = m_L->compute_offsets(m_offset, m_block_index, proc_blocks, BS);
xor_buf(buffer, offsets.data(), proc_bytes);
m_cipher->decrypt_n(buffer, buffer, proc_blocks);
@@ -346,13 +412,16 @@ void OCB_Decryption::decrypt(uint8_t buffer[], size_t blocks)
size_t OCB_Decryption::process(uint8_t buf[], size_t sz)
{
- BOTAN_ASSERT(sz % 16 == 0, "Invalid OCB input size");
- decrypt(buf, sz / 16);
+ const size_t BS = m_cipher->block_size();
+ BOTAN_ASSERT(sz % BS == 0, "Invalid OCB input size");
+ decrypt(buf, sz / BS);
return sz;
}
void OCB_Decryption::finish(secure_vector<uint8_t>& buffer, size_t offset)
{
+ const size_t BS = m_cipher->block_size();
+
BOTAN_ASSERT(buffer.size() >= offset, "Offset is sane");
const size_t sz = buffer.size() - offset;
uint8_t* buf = buffer.data() + offset;
@@ -363,20 +432,20 @@ void OCB_Decryption::finish(secure_vector<uint8_t>& buffer, size_t offset)
if(remaining)
{
- const size_t final_full_blocks = remaining / 16;
- const size_t final_bytes = remaining - (final_full_blocks * 16);
+ const size_t final_full_blocks = remaining / BS;
+ const size_t final_bytes = remaining - (final_full_blocks * BS);
decrypt(buf, final_full_blocks);
if(final_bytes)
{
- BOTAN_ASSERT(final_bytes < 16, "Only a partial block left");
+ BOTAN_ASSERT(final_bytes < BS, "Only a partial block left");
uint8_t* remainder = &buf[remaining - final_bytes];
m_offset ^= m_L->star(); // Offset_*
- secure_vector<uint8_t> pad(16);
+ secure_vector<uint8_t> pad(BS);
m_cipher->encrypt(m_offset, pad); // P_*
xor_buf(remainder, pad.data(), final_bytes);
@@ -386,7 +455,7 @@ void OCB_Decryption::finish(secure_vector<uint8_t>& buffer, size_t offset)
}
}
- secure_vector<uint8_t> checksum(16);
+ secure_vector<uint8_t> checksum(BS);
// fold checksum
for(size_t i = 0; i != m_checksum.size(); ++i)
diff --git a/src/lib/modes/aead/ocb/ocb.h b/src/lib/modes/aead/ocb/ocb.h
index 174812ee3..69f5fde60 100644
--- a/src/lib/modes/aead/ocb/ocb.h
+++ b/src/lib/modes/aead/ocb/ocb.h
@@ -22,6 +22,9 @@ class L_computer;
*
* @see "The OCB Authenticated-Encryption Algorithm" RFC 7253
* https://tools.ietf.org/html/rfc7253
+* @see "OCB For Block Ciphers Without 128-Bit Blocks"
+* (draft-krovetz-ocb-wide-d3) for the extension of OCB to
+* block ciphers with larger block sizes.
* @see Free Licenses http://www.cs.ucdavis.edu/~rogaway/ocb/license.htm
* @see OCB home page http://www.cs.ucdavis.edu/~rogaway/ocb
*/
@@ -47,7 +50,7 @@ class BOTAN_DLL OCB_Mode : public AEAD_Mode
~OCB_Mode();
protected:
/**
- * @param cipher the 128-bit block cipher to use
+ * @param cipher the block cipher to use
* @param tag_size is how big the auth tag will be
*/
OCB_Mode(BlockCipher* cipher, size_t tag_size);
@@ -68,7 +71,7 @@ class BOTAN_DLL OCB_Mode : public AEAD_Mode
secure_vector<uint8_t> update_nonce(const uint8_t nonce[], size_t nonce_len);
- size_t m_tag_size = 0;
+ const size_t m_tag_size = 0;
secure_vector<uint8_t> m_last_nonce;
secure_vector<uint8_t> m_stretch;
};
@@ -77,7 +80,7 @@ class BOTAN_DLL OCB_Encryption final : public OCB_Mode
{
public:
/**
- * @param cipher the 128-bit block cipher to use
+ * @param cipher the block cipher to use
* @param tag_size is how big the auth tag will be
*/
OCB_Encryption(BlockCipher* cipher, size_t tag_size = 16) :
@@ -99,7 +102,7 @@ class BOTAN_DLL OCB_Decryption final : public OCB_Mode
{
public:
/**
- * @param cipher the 128-bit block cipher to use
+ * @param cipher the block cipher to use
* @param tag_size is how big the auth tag will be
*/
OCB_Decryption(BlockCipher* cipher, size_t tag_size = 16) :
generated by cgit v1.2.3 (git 2.39.1) at 2024-12-29 11:23:22 +0000