Improve FILE(DOWNLOAD) and ExternalProject.

Improve FILE(DOWNLOAD ...):

- Add percent complete progress output to the FILE DOWNLOAD
  command. This progress output is off by default to
  preserve existing behavior. To turn it on, pass
  SHOW_PROGRESS as an argument.

- Add EXPECTED_MD5 argument. Verify that the downloaded
  file has the expected md5 sum after download is complete.

- Add documentation for SHOW_PROGRESS and EXPECTED_MD5.

  When the destination file exists already and has the
  expected md5 sum, then do not bother re-downloading
  the file. ("Short circuit" return.)

  Also, add a test that checks for the status output
  indicating that the short circuit behavior is actually
  occurring. Use a binary file for the test so that the
  md5 sum is guaranteed to be the same on all platforms
  regardless of "shifting text file line ending" issues.

Improve ExternalProject:

- Add argument URL_MD5.

- Add verify step that compares md5 sum of .tar.gz file
  before extracting it.

- Add md5 check to download step, too, to prevent
  unnecessary downloads.

- Emit a warning message when a file is not verified.
  Indicate that the file may be corrupt or that no
  checksum was specified.

Modules/ExternalProject.cmake

@@ -17,6 +17,7 @@
 #    [SVN_REPOSITORY url]        # URL of Subversion repo
 #    [SVN_REVISION rev]          # Revision to checkout from Subversion repo
 #    [URL /.../src.tgz]          # Full path or URL of source
+#    [URL_MD5 md5]               # MD5 checksum of file at URL
 #    [TIMEOUT seconds]           # Time allowed for file download operations
 #   #--Update/Patch step----------
 #    [UPDATE_COMMAND cmd...]     # Source work-tree update command
@@ -111,19 +112,19 @@
 #  License text for the above reference.)
 
 # Pre-compute a regex to match documented keywords for each command.
-file(STRINGS "${CMAKE_CURRENT_LIST_FILE}" lines LIMIT_COUNT 100
+file(STRINGS "${CMAKE_CURRENT_LIST_FILE}" lines LIMIT_COUNT 103
-     REGEX "^#  (  \\[[A-Z_]+ [^]]*\\] +#.*$|[A-Za-z_]+\\()")
+     REGEX "^#  (  \\[[A-Z0-9_]+ [^]]*\\] +#.*$|[A-Za-z0-9_]+\\()")
 foreach(line IN LISTS lines)
-  if("${line}" MATCHES "^#  [A-Za-z_]+\\(")
+  if("${line}" MATCHES "^#  [A-Za-z0-9_]+\\(")
     if(_ep_func)
       set(_ep_keywords_${_ep_func} "${_ep_keywords_${_ep_func}})$")
     endif()
-    string(REGEX REPLACE "^#  ([A-Za-z_]+)\\(.*" "\\1" _ep_func "${line}")
+    string(REGEX REPLACE "^#  ([A-Za-z0-9_]+)\\(.*" "\\1" _ep_func "${line}")
     #message("function [${_ep_func}]")
     set(_ep_keywords_${_ep_func} "^(")
     set(_ep_keyword_sep)
   else()
-    string(REGEX REPLACE "^#    \\[([A-Z_]+) .*" "\\1" _ep_key "${line}")
+    string(REGEX REPLACE "^#    \\[([A-Z0-9_]+) .*" "\\1" _ep_key "${line}")
     #message("  keyword [${_ep_key}]")
     set(_ep_keywords_${_ep_func}
       "${_ep_keywords_${_ep_func}}${_ep_keyword_sep}${_ep_key}")
@@ -148,7 +149,7 @@ function(_ep_parse_arguments f name ns args)
   foreach(arg IN LISTS args)
     set(is_value 1)
 
-    if(arg MATCHES "^[A-Z][A-Z_][A-Z_]+$" AND
+    if(arg MATCHES "^[A-Z][A-Z0-9_][A-Z0-9_]+$" AND
         NOT ((arg STREQUAL "${key}") AND (key STREQUAL "COMMAND")) AND
         NOT arg MATCHES "^(TRUE|FALSE)$")
       if(_ep_keywords_${f} AND arg MATCHES "${_ep_keywords_${f}}")
@@ -203,7 +204,7 @@ define_property(DIRECTORY PROPERTY "EP_PREFIX" INHERITED
   )
 
 
-function(_ep_write_downloadfile_script script_filename remote local timeout)
+function(_ep_write_downloadfile_script script_filename remote local timeout md5)
   if(timeout)
     set(timeout_args TIMEOUT ${timeout})
     set(timeout_msg "${timeout} seconds")
@@ -212,6 +213,12 @@ function(_ep_write_downloadfile_script script_filename remote local timeout)
     set(timeout_msg "none")
   endif()
 
+  if(md5)
+    set(md5_args EXPECTED_MD5 ${md5})
+  else()
+    set(md5_args "# no EXPECTED_MD5")
+  endif()
+
   file(WRITE ${script_filename}
 "message(STATUS \"downloading...
      src='${remote}'
@@ -221,6 +228,8 @@ function(_ep_write_downloadfile_script script_filename remote local timeout)
 file(DOWNLOAD
   \"${remote}\"
   \"${local}\"
+  SHOW_PROGRESS
+  ${md5_args}
   ${timeout_args}
   STATUS status
   LOG log)
@@ -243,6 +252,51 @@ message(STATUS \"downloading... done\")
 endfunction(_ep_write_downloadfile_script)
 
 
+function(_ep_write_verifyfile_script script_filename local md5)
+  file(WRITE ${script_filename}
+"message(STATUS \"verifying file...
+     file='${local}'\")
+
+set(verified 0)
+
+# If an expected md5 checksum exists, compare against it:
+#
+if(NOT \"${md5}\" STREQUAL \"\")
+  execute_process(COMMAND \${CMAKE_COMMAND} -E md5sum \"${local}\"
+    OUTPUT_VARIABLE ov
+    OUTPUT_STRIP_TRAILING_WHITESPACE
+    RESULT_VARIABLE rv)
+
+  if(NOT rv EQUAL 0)
+    message(FATAL_ERROR \"error: computing md5sum of '${local}' failed\")
+  endif()
+
+  string(REGEX MATCH \"^([0-9A-Fa-f]+)\" md5_actual \"\${ov}\")
+
+  string(TOLOWER \"\${md5_actual}\" md5_actual)
+  string(TOLOWER \"${md5}\" md5)
+
+  if(NOT \"\${md5}\" STREQUAL \"\${md5_actual}\")
+    message(FATAL_ERROR \"error: md5sum of '${local}' does not match expected value
+  md5_expected: \${md5}
+    md5_actual: \${md5_actual}
+\")
+  endif()
+
+  set(verified 1)
+endif()
+
+if(verified)
+  message(STATUS \"verifying file... done\")
+else()
+  message(STATUS \"verifying file... warning: did not verify file - no URL_MD5 checksum argument? corrupt file?\")
+endif()
+"
+)
+
+endfunction(_ep_write_verifyfile_script)
+
+
 function(_ep_write_extractfile_script script_filename filename tmp directory)
   set(args "")
 
@@ -678,9 +732,10 @@ function(_ep_add_download_command name)
     list(APPEND depends ${stamp_dir}/${name}-svninfo.txt)
   elseif(url)
     get_filename_component(work_dir "${source_dir}" PATH)
+    get_property(md5 TARGET ${name} PROPERTY _EP_URL_MD5)
     set(repository "external project URL")
     set(module "${url}")
-    set(tag "")
+    set(tag "${md5}")
     configure_file(
       "${CMAKE_ROOT}/Modules/RepositoryInfo.txt.in"
       "${stamp_dir}/${name}-urlinfo.txt"
@@ -701,14 +756,16 @@ function(_ep_add_download_command name)
         endif()
         set(file ${download_dir}/${fname})
         get_property(timeout TARGET ${name} PROPERTY _EP_TIMEOUT)
-        _ep_write_downloadfile_script("${stamp_dir}/download-${name}.cmake" "${url}" "${file}" "${timeout}")
+        _ep_write_downloadfile_script("${stamp_dir}/download-${name}.cmake" "${url}" "${file}" "${timeout}" "${md5}")
         set(cmd ${CMAKE_COMMAND} -P ${stamp_dir}/download-${name}.cmake
           COMMAND)
-        set(comment "Performing download step (download and extract) for '${name}'")
+        set(comment "Performing download step (download, verify and extract) for '${name}'")
       else()
         set(file "${url}")
-        set(comment "Performing download step (extract) for '${name}'")
+        set(comment "Performing download step (verify and extract) for '${name}'")
       endif()
+      _ep_write_verifyfile_script("${stamp_dir}/verify-${name}.cmake" "${file}" "${md5}")
+      list(APPEND cmd ${CMAKE_COMMAND} -P ${stamp_dir}/verify-${name}.cmake)
       # TODO: Support other archive formats.
       _ep_write_extractfile_script("${stamp_dir}/extract-${name}.cmake" "${file}" "${tmp_dir}" "${source_dir}")
       list(APPEND cmd ${CMAKE_COMMAND} -P ${stamp_dir}/extract-${name}.cmake)

Source/cmFileCommand.cxx

@@ -2443,7 +2443,8 @@ namespace{
     fout->write(chPtr, realsize);
     return realsize;
   }
-  
+
+
   static size_t
   cmFileCommandCurlDebugCallback(CURL *, curl_infotype, char *chPtr,
                                         size_t size, void *data)
@@ -2456,6 +2457,69 @@ namespace{
   }
 
 
+  class cURLProgressHelper
+  {
+  public:
+    cURLProgressHelper(cmFileCommand *fc)
+      {
+      this->CurrentPercentage = -1;
+      this->FileCommand = fc;
+      }
+
+    bool UpdatePercentage(double value, double total, std::string &status)
+      {
+      int OldPercentage = this->CurrentPercentage;
+
+      if (0.0 == total)
+        {
+        this->CurrentPercentage = 100;
+        }
+      else
+        {
+        this->CurrentPercentage = static_cast<int>(value/total*100.0 + 0.5);
+        }
+
+      bool updated = (OldPercentage != this->CurrentPercentage);
+
+      if (updated)
+        {
+        cmOStringStream oss;
+        oss << "[download " << this->CurrentPercentage << "% complete]";
+        status = oss.str();
+        }
+
+      return updated;
+      }
+
+    cmFileCommand *GetFileCommand()
+      {
+      return this->FileCommand;
+      }
+
+  private:
+    int CurrentPercentage;
+    cmFileCommand *FileCommand;
+  };
+
+
+  static int
+  cmFileCommandCurlProgressCallback(void *clientp,
+                                    double dltotal, double dlnow,
+                                    double ultotal, double ulnow)
+  {
+    cURLProgressHelper *helper =
+      reinterpret_cast<cURLProgressHelper *>(clientp);
+
+    std::string status;
+    if (helper->UpdatePercentage(dlnow, dltotal, status))
+      {
+      cmFileCommand *fc = helper->GetFileCommand();
+      cmMakefile *mf = fc->GetMakefile();
+      mf->DisplayStatus(status.c_str(), -1);
+      }
+
+    return 0;
+  }
 }
 
 #endif
@@ -2469,8 +2533,8 @@ namespace {
     cURLEasyGuard(CURL * easy)
       : Easy(easy)
       {}
-    
+
-    ~cURLEasyGuard(void) 
+    ~cURLEasyGuard(void)
       {
         if (this->Easy)
           {
@@ -2491,6 +2555,7 @@ namespace {
 }
 #endif
 
+
 bool
 cmFileCommand::HandleDownloadCommand(std::vector<std::string>
                                      const& args)
@@ -2508,9 +2573,13 @@ cmFileCommand::HandleDownloadCommand(std::vector<std::string>
   ++i;
   std::string file = *i;
   ++i;
+
   long timeout = 0;
   std::string verboseLog;
   std::string statusVar;
+  std::string expectedMD5sum;
+  bool showProgress = false;
+
   while(i != args.end())
     {
     if(*i == "TIMEOUT")
@@ -2549,9 +2618,65 @@ cmFileCommand::HandleDownloadCommand(std::vector<std::string>
         }
       statusVar = *i;
       }
+    else if(*i == "EXPECTED_MD5")
+      {
+      ++i;
+      if( i == args.end())
+        {
+        this->SetError("FILE(DOWNLOAD url file EXPECTED_MD5 sum) missing "
+                       "sum value for EXPECTED_MD5.");
+        return false;
+        }
+      expectedMD5sum = cmSystemTools::LowerCase(*i);
+      }
+    else if(*i == "SHOW_PROGRESS")
+      {
+      showProgress = true;
+      }
     ++i;
     }
 
+  // If file exists already, and caller specified an expected md5 sum,
+  // and the existing file already has the expected md5 sum, then simply
+  // return.
+  //
+  if(cmSystemTools::FileExists(file.c_str()) &&
+    !expectedMD5sum.empty())
+    {
+    char computedMD5[32];
+
+    if (!cmSystemTools::ComputeFileMD5(file.c_str(), computedMD5))
+      {
+      this->SetError("FILE(DOWNLOAD ) error; cannot compute MD5 sum on "
+        "pre-existing file");
+      return false;
+      }
+
+    std::string actualMD5sum = cmSystemTools::LowerCase(
+      std::string(computedMD5, 32));
+
+    if (expectedMD5sum == actualMD5sum)
+      {
+      this->Makefile->DisplayStatus(
+        "FILE(DOWNLOAD ) returning early: file already exists with "
+        "expected MD5 sum", -1);
+
+      if(statusVar.size())
+        {
+        cmOStringStream result;
+        result << (int)0 << ";\""
+          "returning early: file already exists with expected MD5 sum\"";
+        this->Makefile->AddDefinition(statusVar.c_str(),
+                                      result.str().c_str());
+        }
+
+      return true;
+      }
+    }
+
+  // Make sure parent directory exists so we can write to the file
+  // as we receive downloaded bits from curl...
+  //
   std::string dir = cmSystemTools::GetFilenamePath(file.c_str());
   if(!cmSystemTools::FileExists(dir.c_str()) &&
      !cmSystemTools::MakeDirectory(dir.c_str()))
@@ -2570,6 +2695,7 @@ cmFileCommand::HandleDownloadCommand(std::vector<std::string>
                        "file for write.");
     return false;
     }
+
   ::CURL *curl;
   ::curl_global_init(CURL_GLOBAL_DEFAULT);
   curl = ::curl_easy_init();
@@ -2585,28 +2711,31 @@ cmFileCommand::HandleDownloadCommand(std::vector<std::string>
   ::CURLcode res = ::curl_easy_setopt(curl, CURLOPT_URL, url.c_str());
   if (res != CURLE_OK)
     {
-      std::string errstring = "FILE(DOWNLOAD ) error; cannot set url: ";
+    std::string errstring = "FILE(DOWNLOAD ) error; cannot set url: ";
-      errstring += ::curl_easy_strerror(res);
+    errstring += ::curl_easy_strerror(res);
+    this->SetError(errstring.c_str());
     return false;
     }
 
   res = ::curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION,
-                             cmFileCommandWriteMemoryCallback);
+                           cmFileCommandWriteMemoryCallback);
   if (res != CURLE_OK)
-      {
+    {
-      std::string errstring =
+    std::string errstring =
-        "FILE(DOWNLOAD ) error; cannot set write function: ";
+      "FILE(DOWNLOAD ) error; cannot set write function: ";
-      errstring += ::curl_easy_strerror(res);
+    errstring += ::curl_easy_strerror(res);
+    this->SetError(errstring.c_str());
     return false;
     }
 
   res = ::curl_easy_setopt(curl, CURLOPT_DEBUGFUNCTION,
-                             cmFileCommandCurlDebugCallback);
+                           cmFileCommandCurlDebugCallback);
   if (res != CURLE_OK)
     {
-     std::string errstring =
+    std::string errstring =
-       "FILE(DOWNLOAD ) error; cannot set debug function: ";
+      "FILE(DOWNLOAD ) error; cannot set debug function: ";
-     errstring += ::curl_easy_strerror(res);
+    errstring += ::curl_easy_strerror(res);
+    this->SetError(errstring.c_str());
     return false;
     }
 
@@ -2618,14 +2747,16 @@ cmFileCommand::HandleDownloadCommand(std::vector<std::string>
     {
     std::string errstring = "FILE(DOWNLOAD ) error; cannot set write data: ";
     errstring += ::curl_easy_strerror(res);
+    this->SetError(errstring.c_str());
     return false;
     }
 
   res = ::curl_easy_setopt(curl, CURLOPT_DEBUGDATA, (void *)&chunkDebug);
   if (res != CURLE_OK)
     {
-    std::string errstring = "FILE(DOWNLOAD ) error; cannot set write data: ";
+    std::string errstring = "FILE(DOWNLOAD ) error; cannot set debug data: ";
     errstring += ::curl_easy_strerror(res);
+    this->SetError(errstring.c_str());
     return false;
     }
 
@@ -2637,24 +2768,70 @@ cmFileCommand::HandleDownloadCommand(std::vector<std::string>
       {
       std::string errstring = "FILE(DOWNLOAD ) error; cannot set verbose: ";
       errstring += ::curl_easy_strerror(res);
+      this->SetError(errstring.c_str());
       return false;
       }
     }
+
   if(timeout > 0)
     {
     res = ::curl_easy_setopt(curl, CURLOPT_TIMEOUT, timeout );
 
     if (res != CURLE_OK)
       {
-      std::string errstring = "FILE(DOWNLOAD ) error; cannot set verbose: ";
+      std::string errstring = "FILE(DOWNLOAD ) error; cannot set timeout: ";
       errstring += ::curl_easy_strerror(res);
+      this->SetError(errstring.c_str());
       return false;
       }
     }
+
+  // Need the progress helper's scope to last through the duration of
+  // the curl_easy_perform call... so this object is declared at function
+  // scope intentionally, rather than inside the "if(showProgress)"
+  // block...
+  //
+  cURLProgressHelper helper(this);
+
+  if(showProgress)
+    {
+    res = ::curl_easy_setopt(curl,
+      CURLOPT_NOPROGRESS, 0);
+    if (res != CURLE_OK)
+      {
+      std::string errstring = "FILE(DOWNLOAD ) error; cannot set noprogress value: ";
+      errstring += ::curl_easy_strerror(res);
+      this->SetError(errstring.c_str());
+      return false;
+      }
+
+    res = ::curl_easy_setopt(curl,
+      CURLOPT_PROGRESSFUNCTION, cmFileCommandCurlProgressCallback);
+    if (res != CURLE_OK)
+      {
+      std::string errstring = "FILE(DOWNLOAD ) error; cannot set progress function: ";
+      errstring += ::curl_easy_strerror(res);
+      this->SetError(errstring.c_str());
+      return false;
+      }
+
+    res = ::curl_easy_setopt(curl,
+      CURLOPT_PROGRESSDATA, reinterpret_cast<void*>(&helper));
+    if (res != CURLE_OK)
+      {
+      std::string errstring = "FILE(DOWNLOAD ) error; cannot set progress data: ";
+      errstring += ::curl_easy_strerror(res);
+      this->SetError(errstring.c_str());
+      return false;
+      }
+    }
+
   res = ::curl_easy_perform(curl);
+
   /* always cleanup */
   g_curl.release();
   ::curl_easy_cleanup(curl);
+
   if(statusVar.size())
     {
     cmOStringStream result;
@@ -2662,7 +2839,44 @@ cmFileCommand::HandleDownloadCommand(std::vector<std::string>
     this->Makefile->AddDefinition(statusVar.c_str(),
                                   result.str().c_str());
     }
+
   ::curl_global_cleanup();
+
+  // Explicitly flush/close so we can measure the md5 accurately.
+  //
+  fout.flush();
+  fout.close();
+
+  // Verify MD5 sum if requested:
+  //
+  if (!expectedMD5sum.empty())
+    {
+    char computedMD5[32];
+
+    if (!cmSystemTools::ComputeFileMD5(file.c_str(), computedMD5))
+      {
+      this->SetError("FILE(DOWNLOAD ) error; cannot compute MD5 sum on "
+        "downloaded file");
+      return false;
+      }
+
+    std::string actualMD5sum = cmSystemTools::LowerCase(
+      std::string(computedMD5, 32));
+
+    if (expectedMD5sum != actualMD5sum)
+      {
+      cmOStringStream oss;
+      oss << "FILE(DOWNLOAD ) error; expected and actual MD5 sums differ"
+        << std::endl
+        << "  for file: [" << file << "]" << std::endl
+        << "    expected MD5 sum: [" << expectedMD5sum << "]" << std::endl
+        << "      actual MD5 sum: [" << actualMD5sum << "]" << std::endl
+        ;
+      this->SetError(oss.str().c_str());
+      return false;
+      }
+    }
+
   if(chunkDebug.size())
     {
     chunkDebug.push_back(0);
@@ -2680,6 +2894,7 @@ cmFileCommand::HandleDownloadCommand(std::vector<std::string>
     this->Makefile->AddDefinition(verboseLog.c_str(),
                                   &*chunkDebug.begin());
     }
+
   return true;
 #else
   this->SetError("FILE(DOWNLOAD ) "

Source/cmFileCommand.h

@@ -80,7 +80,8 @@ public:
       "  file(RELATIVE_PATH variable directory file)\n"
       "  file(TO_CMAKE_PATH path result)\n"
       "  file(TO_NATIVE_PATH path result)\n"
-      "  file(DOWNLOAD url file [TIMEOUT timeout] [STATUS status] [LOG log])\n"
+      "  file(DOWNLOAD url file [TIMEOUT timeout] [STATUS status] [LOG log]\n"
+      "       [EXPECTED_MD5 sum] [SHOW_PROGRESS])\n"
       "WRITE will write a message into a file called 'filename'. It "
       "overwrites the file if it already exists, and creates the file "
       "if it does not exist.\n"
@@ -152,7 +153,12 @@ public:
       "and the second element is a string value for the error. A 0 "
       "numeric error means no error in the operation. "
       "If TIMEOUT time is specified, the operation will "
-      "timeout after time seconds, time should be specified as an integer."
+      "timeout after time seconds, time should be specified as an integer. "
+      "If EXPECTED_MD5 sum is specified, the operation will verify that the "
+      "downloaded file's actual md5 sum matches the expected value. If it "
+      "does not match, the operation fails with an error. "
+      "If SHOW_PROGRESS is specified, progress information will be printed "
+      "as status messages until the operation is complete."
       "\n"
       "The file() command also provides COPY and INSTALL signatures:\n"
       "  file(<COPY|INSTALL> files... DESTINATION <dir>\n"

Tests/CMakeTests/CMakeLists.txt

@@ -28,6 +28,11 @@ AddCMakeTest(Math "")
 AddCMakeTest(CMakeMinimumRequired "")
 AddCMakeTest(CompilerIdVendor "")
 
+AddCMakeTest(FileDownload "")
+set_property(TEST CMake.FileDownload PROPERTY
+  PASS_REGULAR_EXPRESSION "file already exists with expected MD5 sum"
+  )
+
 if(HAVE_ELF_H)
   AddCMakeTest(ELF "")
 endif()

Tests/CMakeTests/FileDownloadTest.cmake.in

@@ -0,0 +1,41 @@
+set(url "file://@CMAKE_CURRENT_SOURCE_DIR@/FileDownloadInput.png")
+set(dir "@CMAKE_CURRENT_BINARY_DIR@/downloads")
+
+message(STATUS "FileDownload:1")
+file(DOWNLOAD
+  ${url}
+  ${dir}/file1.png
+  TIMEOUT 2
+  )
+
+message(STATUS "FileDownload:2")
+file(DOWNLOAD
+  ${url}
+  ${dir}/file2.png
+  TIMEOUT 2
+  SHOW_PROGRESS
+  )
+
+# Two calls in a row, exactly the same arguments.
+# Since downloaded file should exist already for 2nd call,
+# the 2nd call will short-circuit and return early...
+#
+if(EXISTS ${dir}/file3.png)
+  file(REMOVE ${dir}/file3.png)
+endif()
+
+message(STATUS "FileDownload:3")
+file(DOWNLOAD
+  ${url}
+  ${dir}/file3.png
+  TIMEOUT 2
+  EXPECTED_MD5 d16778650db435bda3a8c3435c3ff5d1
+  )
+
+message(STATUS "FileDownload:4")
+file(DOWNLOAD
+  ${url}
+  ${dir}/file3.png
+  TIMEOUT 2
+  EXPECTED_MD5 d16778650db435bda3a8c3435c3ff5d1
+  )

Tests/ExternalProject/CMakeLists.txt

@@ -65,7 +65,9 @@ ExternalProject_Add(${proj}
   SVN_REPOSITORY ""
   SVN_REVISION ""
   TEST_COMMAND ""
+  TIMEOUT ""
   URL ""
+  URL_MD5 ""
   UPDATE_COMMAND ""
 )
 
@@ -96,6 +98,7 @@ endif()
 set(proj TutorialStep1-LocalTAR)
 ExternalProject_Add(${proj}
   URL "${CMAKE_CURRENT_SOURCE_DIR}/Step1.tar"
+  URL_MD5 a87c5b47c0201c09ddfe1d5738fdb1e3
   LIST_SEPARATOR ::
   PATCH_COMMAND ${CMAKE_COMMAND} -P ${CMAKE_CURRENT_SOURCE_DIR}/Step1Patch.cmake
   CMAKE_GENERATOR "${CMAKE_GENERATOR}"
@@ -107,6 +110,7 @@ ExternalProject_Add(${proj}
 set(proj TutorialStep1-LocalNoDirTAR)
 ExternalProject_Add(${proj}
   URL "${CMAKE_CURRENT_SOURCE_DIR}/Step1NoDir.tar"
+  URL_MD5 d09e3d370c5c908fa035c30939ee438e
   LIST_SEPARATOR @@
   CMAKE_ARGS -DCMAKE_INSTALL_PREFIX:PATH=<INSTALL_DIR> -G ${CMAKE_GENERATOR} <SOURCE_DIR>
              -DTEST_LIST:STRING=1@@2@@3
@@ -126,6 +130,7 @@ ExternalProject_Add_Step(${proj} mypatch
 set(proj TutorialStep1-LocalTGZ)
 ExternalProject_Add(${proj}
   URL "${CMAKE_CURRENT_SOURCE_DIR}/Step1.tgz"
+  URL_MD5 38c648e817339c356f6be00eeed79bd0
   CMAKE_ARGS -DCMAKE_INSTALL_PREFIX:PATH=<INSTALL_DIR> -G ${CMAKE_GENERATOR} <SOURCE_DIR>
   INSTALL_COMMAND ""
 )
@@ -133,6 +138,7 @@ ExternalProject_Add(${proj}
 set(proj TutorialStep1-LocalNoDirTGZ)
 ExternalProject_Add(${proj}
   URL "${CMAKE_CURRENT_SOURCE_DIR}/Step1NoDir.tgz"
+  URL_MD5 0b8182edcecdf40bf1c9d71d7d259f78
   CMAKE_GENERATOR "${CMAKE_GENERATOR}"
   CMAKE_ARGS -DCMAKE_INSTALL_PREFIX:PATH=<INSTALL_DIR>
   INSTALL_COMMAND ""
@@ -161,6 +167,7 @@ if(do_cvs_tests)
   ExternalProject_Add(${proj}
     SOURCE_DIR ${local_cvs_repo}
     URL ${CMAKE_CURRENT_SOURCE_DIR}/cvsrepo.tgz
+    URL_MD5 55fc85825ffdd9ed2597123c68b79f7e
     BUILD_COMMAND ""
     CONFIGURE_COMMAND ${CVS_EXECUTABLE} --version
     INSTALL_COMMAND ""
@@ -257,6 +264,7 @@ if(do_svn_tests)
   ExternalProject_Add(${proj}
     SOURCE_DIR ${local_svn_repo}
     URL ${CMAKE_CURRENT_SOURCE_DIR}/svnrepo.tgz
+    URL_MD5 2f468be4ed1fa96377fca0cc830819c4
     BUILD_COMMAND ""
     CONFIGURE_COMMAND ${Subversion_SVN_EXECUTABLE} --version
     INSTALL_COMMAND ""