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LibPDF: Extract aes helper in StandardSecurityHandler::crypt()

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No behavior change, pure code move.

We'll use this for AESV3.
This commit is contained in:
Nico Weber 2023-07-19 21:43:13 -04:00 • committed by Andreas Kling
parent 9cbdb334ab
commit 6d0dbaf9d7
1 changed files with 31 additions and 28 deletions
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59
Userland/Libraries/LibPDF/Encryption.cpp
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@ -633,6 +633,36 @@ void StandardSecurityHandler::crypt(NonnullRefPtr<Object> object, Reference refe
if (m_method == CryptFilterMethod::None)
return;
auto aes = [&](ReadonlyBytes bytes, ByteBuffer const& key) {
auto cipher = Crypto::Cipher::AESCipher::CBCMode(key, m_length * 8, direction, Crypto::Cipher::PaddingMode::CMS);
// "The block size parameter is 16 bytes, and the initialization vector is a 16-byte random number
// that is stored as the first 16 bytes of the encrypted stream or string."
static_assert(Crypto::Cipher::AESCipher::block_size() == 16);
if (direction == Crypto::Cipher::Intent::Encryption) {
auto output = cipher.create_aligned_buffer(16 + bytes.size()).release_value_but_fixme_should_propagate_errors();
auto iv_span = output.bytes().trim(16);
auto encrypted_span = output.bytes().slice(16);
fill_with_random(iv_span);
cipher.encrypt(bytes, encrypted_span, iv_span);
return output;
} else {
VERIFY(direction == Crypto::Cipher::Intent::Decryption);
auto iv = bytes.trim(16);
bytes = bytes.slice(16);
auto decrypted = cipher.create_aligned_buffer(bytes.size()).release_value_but_fixme_should_propagate_errors();
auto decrypted_span = decrypted.bytes();
cipher.decrypt(bytes, decrypted_span, iv);
decrypted.resize(decrypted_span.size());
return decrypted;
}
};
if (m_method == CryptFilterMethod::AESV3) {
// ISO 32000 (PDF 2.0), 7.6.3.3 Algorithm 1.A: Encryption of data using the AES algorithms
@ -717,34 +747,7 @@ void StandardSecurityHandler::crypt(NonnullRefPtr<Object> object, Reference refe
key.resize(encryption_key.size());
if (m_method == CryptFilterMethod::AESV2) {
auto cipher = Crypto::Cipher::AESCipher::CBCMode(key, m_length * 8, direction, Crypto::Cipher::PaddingMode::CMS);
// "The block size parameter is 16 bytes, and the initialization vector is a 16-byte random number
// that is stored as the first 16 bytes of the encrypted stream or string."
static_assert(Crypto::Cipher::AESCipher::block_size() == 16);
if (direction == Crypto::Cipher::Intent::Encryption) {
auto output = cipher.create_aligned_buffer(16 + bytes.size()).release_value_but_fixme_should_propagate_errors();
auto iv_span = output.bytes().trim(16);
auto encrypted_span = output.bytes().slice(16);
fill_with_random(iv_span);
cipher.encrypt(bytes, encrypted_span, iv_span);
assign(move(output));
} else {
VERIFY(direction == Crypto::Cipher::Intent::Decryption);
auto iv = bytes.trim(16);
bytes = bytes.slice(16);
auto decrypted = cipher.create_aligned_buffer(bytes.size()).release_value_but_fixme_should_propagate_errors();
auto decrypted_span = decrypted.bytes();
cipher.decrypt(bytes, decrypted_span, iv);
decrypted.resize(decrypted_span.size());
assign(move(decrypted));
}
assign(aes(bytes, key));
return;
}