fpdfsdk/fpdfattachment.cpp

// Copyright 2017 PDFium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "public/fpdf_attachment.h"

#include <memory>
#include <utility>

#include "core/fdrm/crypto/fx_crypt.h"
#include "core/fpdfapi/parser/cpdf_array.h"
#include "core/fpdfapi/parser/cpdf_document.h"
#include "core/fpdfapi/parser/cpdf_name.h"
#include "core/fpdfapi/parser/cpdf_number.h"
#include "core/fpdfapi/parser/cpdf_reference.h"
#include "core/fpdfapi/parser/cpdf_string.h"
#include "core/fpdfapi/parser/fpdf_parser_decode.h"
#include "core/fpdfdoc/cpdf_filespec.h"
#include "core/fpdfdoc/cpdf_nametree.h"
#include "core/fxcrt/cfx_datetime.h"
#include "core/fxcrt/fx_extension.h"
#include "fpdfsdk/fsdk_define.h"

namespace {

constexpr char kChecksumKey[] = "CheckSum";

CPDF_Object* CPDFObjectFromFPDFAttachment(FPDF_ATTACHMENT attachment) {
  return static_cast<CPDF_Object*>(attachment);
}

ByteString CFXByteStringHexDecode(const ByteString& bsHex) {
  uint8_t* result = nullptr;
  uint32_t size = 0;
  HexDecode(bsHex.raw_str(), bsHex.GetLength(), &result, &size);
  ByteString bsDecoded(result, size);
  FX_Free(result);
  return bsDecoded;
}

ByteString GenerateMD5Base16(const void* contents, const unsigned long len) {
  uint8_t digest[16];
  CRYPT_MD5Generate(reinterpret_cast<const uint8_t*>(contents), len, digest);
  char buf[32];
  for (int i = 0; i < 16; ++i)
    FXSYS_IntToTwoHexChars(digest[i], &buf[i * 2]);

  return ByteString(buf, 32);
}

}  // namespace

FPDF_EXPORT int FPDF_CALLCONV
FPDFDoc_GetAttachmentCount(FPDF_DOCUMENT document) {
  CPDF_Document* pDoc = CPDFDocumentFromFPDFDocument(document);
  if (!pDoc)
    return 0;

  return CPDF_NameTree(pDoc, "EmbeddedFiles").GetCount();
}

FPDF_EXPORT FPDF_ATTACHMENT FPDF_CALLCONV
FPDFDoc_AddAttachment(FPDF_DOCUMENT document, FPDF_WIDESTRING name) {
  CPDF_Document* pDoc = CPDFDocumentFromFPDFDocument(document);
  WideString wsName =
      WideString::FromUTF16LE(name, WideString::WStringLength(name));
  if (!pDoc || wsName.IsEmpty())
    return nullptr;

  CPDF_Dictionary* pRoot = pDoc->GetRoot();
  if (!pRoot)
    return nullptr;

  // Retrieve the document's Names dictionary; create it if missing.
  CPDF_Dictionary* pNames = pRoot->GetDictFor("Names");
  if (!pNames) {
    pNames = pDoc->NewIndirect<CPDF_Dictionary>();
    pRoot->SetNewFor<CPDF_Reference>("Names", pDoc, pNames->GetObjNum());
  }

  // Create the EmbeddedFiles dictionary if missing.
  if (!pNames->GetDictFor("EmbeddedFiles")) {
    CPDF_Dictionary* pFiles = pDoc->NewIndirect<CPDF_Dictionary>();
    pFiles->SetNewFor<CPDF_Array>("Names");
    pNames->SetNewFor<CPDF_Reference>("EmbeddedFiles", pDoc,
                                      pFiles->GetObjNum());
  }

  // Set up the basic entries in the filespec dictionary.
  CPDF_Dictionary* pFile = pDoc->NewIndirect<CPDF_Dictionary>();
  pFile->SetNewFor<CPDF_Name>("Type", "Filespec");
  pFile->SetNewFor<CPDF_String>("UF", wsName);
  pFile->SetNewFor<CPDF_String>("F", wsName);

  // Add the new attachment name and filespec into the document's EmbeddedFiles.
  CPDF_NameTree nameTree(pDoc, "EmbeddedFiles");
  if (!nameTree.AddValueAndName(
          pdfium::MakeUnique<CPDF_Reference>(pDoc, pFile->GetObjNum()),
          wsName)) {
    return nullptr;
  }

  return pFile;
}

FPDF_EXPORT FPDF_ATTACHMENT FPDF_CALLCONV
FPDFDoc_GetAttachment(FPDF_DOCUMENT document, int index) {
  CPDF_Document* pDoc = CPDFDocumentFromFPDFDocument(document);
  if (!pDoc || index < 0)
    return nullptr;

  CPDF_NameTree nameTree(pDoc, "EmbeddedFiles");
  if (static_cast<size_t>(index) >= nameTree.GetCount())
    return nullptr;

  WideString csName;
  return nameTree.LookupValueAndName(index, &csName);
}

FPDF_EXPORT FPDF_BOOL FPDF_CALLCONV
FPDFDoc_DeleteAttachment(FPDF_DOCUMENT document, int index) {
  CPDF_Document* pDoc = CPDFDocumentFromFPDFDocument(document);
  if (!pDoc || index < 0)
    return false;

  CPDF_NameTree nameTree(pDoc, "EmbeddedFiles");
  if (static_cast<size_t>(index) >= nameTree.GetCount())
    return false;

  return nameTree.DeleteValueAndName(index);
}

FPDF_EXPORT unsigned long FPDF_CALLCONV
FPDFAttachment_GetName(FPDF_ATTACHMENT attachment,
                       void* buffer,
                       unsigned long buflen) {
  CPDF_Object* pFile = CPDFObjectFromFPDFAttachment(attachment);
  if (!pFile)
    return 0;

  return Utf16EncodeMaybeCopyAndReturnLength(CPDF_FileSpec(pFile).GetFileName(),
                                             buffer, buflen);
}

FPDF_EXPORT FPDF_BOOL FPDF_CALLCONV
FPDFAttachment_HasKey(FPDF_ATTACHMENT attachment, FPDF_BYTESTRING key) {
  CPDF_Object* pFile = CPDFObjectFromFPDFAttachment(attachment);
  if (!pFile)
    return 0;

  CPDF_Dictionary* pParamsDict = CPDF_FileSpec(pFile).GetParamsDict();
  return pParamsDict ? pParamsDict->KeyExist(key) : 0;
}

FPDF_EXPORT FPDF_OBJECT_TYPE FPDF_CALLCONV
FPDFAttachment_GetValueType(FPDF_ATTACHMENT attachment, FPDF_BYTESTRING key) {
  if (!FPDFAttachment_HasKey(attachment, key))
    return FPDF_OBJECT_UNKNOWN;

  CPDF_FileSpec spec(CPDFObjectFromFPDFAttachment(attachment));
  CPDF_Object* pObj = spec.GetParamsDict()->GetObjectFor(key);
  return pObj ? pObj->GetType() : FPDF_OBJECT_UNKNOWN;
}

FPDF_EXPORT FPDF_BOOL FPDF_CALLCONV
FPDFAttachment_SetStringValue(FPDF_ATTACHMENT attachment,
                              FPDF_BYTESTRING key,
                              FPDF_WIDESTRING value) {
  CPDF_Object* pFile = CPDFObjectFromFPDFAttachment(attachment);
  if (!pFile)
    return false;

  CPDF_Dictionary* pParamsDict = CPDF_FileSpec(pFile).GetParamsDict();
  if (!pParamsDict)
    return false;

  ByteString bsKey = key;
  ByteString bsValue = CFXByteStringFromFPDFWideString(value);
  bool bEncodedAsHex = bsKey == kChecksumKey;
  if (bEncodedAsHex)
    bsValue = CFXByteStringHexDecode(bsValue);

  pParamsDict->SetNewFor<CPDF_String>(bsKey, bsValue, bEncodedAsHex);
  return true;
}

FPDF_EXPORT unsigned long FPDF_CALLCONV
FPDFAttachment_GetStringValue(FPDF_ATTACHMENT attachment,
                              FPDF_BYTESTRING key,
                              void* buffer,
                              unsigned long buflen) {
  CPDF_Object* pFile = CPDFObjectFromFPDFAttachment(attachment);
  if (!pFile)
    return 0;

  CPDF_Dictionary* pParamsDict = CPDF_FileSpec(pFile).GetParamsDict();
  if (!pParamsDict)
    return 0;

  ByteString bsKey = key;
  WideString value = pParamsDict->GetUnicodeTextFor(bsKey);
  if (bsKey == kChecksumKey && !value.IsEmpty()) {
    CPDF_String* stringValue = pParamsDict->GetObjectFor(bsKey)->AsString();
    if (stringValue->IsHex()) {
      ByteString encoded = PDF_EncodeString(stringValue->GetString(), true);
      value = CPDF_String(nullptr, encoded, false).GetUnicodeText();
    }
  }

  return Utf16EncodeMaybeCopyAndReturnLength(value, buffer, buflen);
}

FPDF_EXPORT FPDF_BOOL FPDF_CALLCONV
FPDFAttachment_SetFile(FPDF_ATTACHMENT attachment,
                       FPDF_DOCUMENT document,
                       const void* contents,
                       const unsigned long len) {
  CPDF_Object* pFile = CPDFObjectFromFPDFAttachment(attachment);
  CPDF_Document* pDoc = CPDFDocumentFromFPDFDocument(document);
  if (!pFile || !pFile->IsDictionary() || !pDoc || len > INT_MAX)
    return false;

  // An empty content must have a zero length.
  if (!contents && len != 0)
    return false;

  // Create a dictionary for the new embedded file stream.
  auto pFileStreamDict = pdfium::MakeUnique<CPDF_Dictionary>();
  CPDF_Dictionary* pParamsDict =
      pFileStreamDict->SetNewFor<CPDF_Dictionary>("Params");

  // Set the size of the new file in the dictionary.
  pFileStreamDict->SetNewFor<CPDF_Number>("DL", static_cast<int>(len));
  pParamsDict->SetNewFor<CPDF_Number>("Size", static_cast<int>(len));

  // Set the creation date of the new attachment in the dictionary.
  CFX_DateTime dateTime = CFX_DateTime::Now();
  pParamsDict->SetNewFor<CPDF_String>(
      "CreationDate",
      ByteString::Format("D:%d%02d%02d%02d%02d%02d", dateTime.GetYear(),
                         dateTime.GetMonth(), dateTime.GetDay(),
                         dateTime.GetHour(), dateTime.GetMinute(),
                         dateTime.GetSecond()),
      false);

  // Set the checksum of the new attachment in the dictionary.
  pParamsDict->SetNewFor<CPDF_String>(
      kChecksumKey, CFXByteStringHexDecode(GenerateMD5Base16(contents, len)),
      true);

  // Create the file stream and have the filespec dictionary link to it.
  std::unique_ptr<uint8_t, FxFreeDeleter> stream(FX_Alloc(uint8_t, len));
  memcpy(stream.get(), contents, len);
  CPDF_Stream* pFileStream = pDoc->NewIndirect<CPDF_Stream>(
      std::move(stream), len, std::move(pFileStreamDict));
  CPDF_Dictionary* pEFDict =
      pFile->AsDictionary()->SetNewFor<CPDF_Dictionary>("EF");
  pEFDict->SetNewFor<CPDF_Reference>("F", pDoc, pFileStream->GetObjNum());
  return true;
}

FPDF_EXPORT unsigned long FPDF_CALLCONV
FPDFAttachment_GetFile(FPDF_ATTACHMENT attachment,
                       void* buffer,
                       unsigned long buflen) {
  CPDF_Object* pFile = CPDFObjectFromFPDFAttachment(attachment);
  if (!pFile)
    return 0;

  CPDF_Stream* pFileStream = CPDF_FileSpec(pFile).GetFileStream();
  if (!pFileStream)
    return 0;

  return DecodeStreamMaybeCopyAndReturnLength(pFileStream, buffer, buflen);
}