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LibCrypto: Fix broken CTR mode, implement RFC 3686 Test Vectors

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This commit is contained in:
Ben Wiederhake 2020-07-25 23:40:55 +02:00 • committed by Andreas Kling
parent ef4ce54b02
commit a51cbc2978
2 changed files with 241 additions and 12 deletions
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24
Libraries/LibCrypto/Cipher/Mode/CTR.h
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@ -82,8 +82,9 @@ namespace Cipher {
*
* Due to this plethora of mutually-incompatible counters,
* the method of counting should be a template parameter.
* This currently implements BIGINT_MIXEDENDIAN_INCR_0, which is not used
* anywhere else.
* This currently implements BIGINT_INCR_0, which means perfect
* interoperability with openssl. The test vectors from RFC 3686 just need to be
* incremented by 1.
* TODO: Implement other counters?
*/
@ -112,6 +113,8 @@ public:
virtual Optional<ByteBuffer> encrypt(const ByteBuffer& in, ByteBuffer& out, Optional<ByteBuffer> ivec = {}) override
{
// Our interpretation of "ivec" is what AES-CTR
// would define as nonce + IV + 4 zero bytes.
return this->encrypt_or_stream(&in, out, ivec);
}
@ -129,20 +132,17 @@ public:
}
private:
static ByteBuffer increment(const ByteBuffer& in)
static void increment_inplace(ByteBuffer& in)
{
ByteBuffer new_buffer(in);
size_t* num_view = (size_t*)new_buffer.data();
for (size_t i = 0; i < in.size() / sizeof(size_t); ++i) {
if (num_view[i] == (size_t)-1) {
num_view[i] = 0;
for (size_t i = in.size(); i > 0;) {
--i;
if (in[i] == (u8)-1) {
in[i] = 0;
} else {
num_view[i]++;
in[i]++;
break;
}
}
return new_buffer;
}
Optional<ByteBuffer> encrypt_or_stream(const ByteBuffer* in, ByteBuffer& out, Optional<ByteBuffer> ivec)
@ -178,7 +178,7 @@ private:
auto write_size = min(block_size, length);
out.overwrite(offset, block.get().data(), write_size);
iv = increment(iv);
increment_inplace(iv);
length -= write_size;
offset += write_size;
}