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LibPDF: Add implementation of the Standard security handler

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Security handlers manage encryption and decription of PDF files. The
standard security handler uses RC4/MD5 to perform its crypto (AES as
well, but that is not yet implemented).
This commit is contained in:
Matthew Olsson 2022-03-20 14:24:23 -07:00 • committed by Andreas Kling
parent c98bda8ce6
commit 5b316462b2
9 changed files with 522 additions and 3 deletions
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70
Userland/Libraries/LibPDF/Encryption.h Normal file
View file

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/*
* Copyright (c) 2022, Matthew Olsson <mattco@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#pragma once
#include <AK/Span.h>
#include <LibPDF/ObjectDerivatives.h>
namespace PDF {
class SecurityHandler : public RefCounted<SecurityHandler> {
public:
static PDFErrorOr<NonnullRefPtr<SecurityHandler>> create(Document*, NonnullRefPtr<DictObject> encryption_dict);
virtual ~SecurityHandler() = default;
virtual bool try_provide_user_password(StringView password) = 0;
virtual bool has_user_password() const = 0;
virtual void encrypt(NonnullRefPtr<Object>, Reference reference) const = 0;
virtual void decrypt(NonnullRefPtr<Object>, Reference reference) const = 0;
};
class StandardSecurityHandler : public SecurityHandler {
public:
static PDFErrorOr<NonnullRefPtr<StandardSecurityHandler>> create(Document*, NonnullRefPtr<DictObject> encryption_dict);
StandardSecurityHandler(Document*, size_t revision, String const& o_entry, String const& u_entry, u32 flags, bool encrypt_metadata, size_t length);
~StandardSecurityHandler() override = default;
bool try_provide_user_password(StringView password_string) override;
bool has_user_password() const override { return m_encryption_key.has_value(); }
protected:
void encrypt(NonnullRefPtr<Object>, Reference reference) const override;
void decrypt(NonnullRefPtr<Object>, Reference reference) const override;
private:
template<bool is_revision_2>
ByteBuffer compute_user_password_value(ByteBuffer password_string);
ByteBuffer compute_encryption_key(ByteBuffer password_string);
Document* m_document;
size_t m_revision;
Optional<ByteBuffer> m_encryption_key;
String m_o_entry;
String m_u_entry;
u32 m_flags;
bool m_encrypt_metadata;
size_t m_length;
};
class RC4 {
public:
RC4(ReadonlyBytes key);
void generate_bytes(ByteBuffer&);
ByteBuffer encrypt(ReadonlyBytes bytes);
private:
Array<size_t, 256> m_bytes;
};
}