Linux Virtual Printer Driver

cloud_print/virtual_driver/posix/virtual_driver_posix.cc

+// Copyright (c) 2011 The Chromium 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 <pwd.h>
+#include <stdio.h>
+
+#include <cups/backend.h>
+
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+
+#include "base/at_exit.h"
+#include "base/base_paths.h"
+#include "base/command_line.h"
+#include "base/file_path.h"
+#include "base/logging.h"
+#include "base/path_service.h"
+
+#include "cloud_print/virtual_driver/posix/printer_driver_util_posix.h"
+
+using namespace std;
+
+int WriteToTemp(FILE* input_pdf, FilePath output_path) {
+  FILE* output_pdf;
+  char buffer[128];
+  output_pdf = fopen(output_path.value().c_str(),"w");
+  if(output_pdf == NULL) {
+    LOG(ERROR) <<"Unable to open file handle for writing output file";
+     exit(CUPS_BACKEND_CANCEL);
+  }
+  // Read from input file or stdin and write to output file.
+  while(fgets(buffer,128,input_pdf) != NULL){
+    fputs(buffer, output_pdf);
+  }
+
+  LOG(INFO) << "Successfully wrote output file";
+  // ensure everything is written, then close the files.
+  fflush(output_pdf);
+  fclose(input_pdf);
+  fclose(output_pdf);
+}
+
+void SetUser(const char* user) {
+  struct passwd* calling_user=NULL;
+  calling_user=getpwnam(user);
+  if(calling_user == NULL) {
+    LOG(ERROR) << "Unable to get calling user";
+    exit(CUPS_BACKEND_CANCEL);
+  }
+  if(setgid(calling_user->pw_gid)==-1) {
+    LOG(ERROR) << "Unable to set group ID";
+    exit(CUPS_BACKEND_CANCEL);
+  }
+  if(!setuid(calling_user->pw_uid)==-1)  {
+    LOG(ERROR) << "Unable to set UID";
+    exit(CUPS_BACKEND_CANCEL);
+  }
+
+  LOG(INFO) << "Successfully set user and group ID";
+}
+
+
+
+// Main function for backend.
+int main(int argc, const char* argv[]) {
+  // With no arguments, send identification string as required by CUPS.
+  if (argc==1) {

[Albert Bodenhamer, 2011/07/11 19:21:32]

You're accessing argc and argv directly in some places and using CommandLine in
others.  Can you use CommandLine for everything?  If not, you should comment
why.

+    printf("file GCP-driver:/ \"GCP Virtual Driver\" \"GCP Virtual Driver\" "
+            "\"MFG:Google Inc.;MDL:GCP Virtual Driver;DES:GCP Virtual Driver;"
+            "CLS:PRINTER;CMD:POSTSCRIPT;\"\n");
+    return 0;
+  }
+
+  if (argc<6 || argc>7) {
+    fprintf(stderr,"Usage: GCP-Driver job-id user"
+                    "title copies options [file]\n");
+    return 0;
+  }
+
+  //AtExitManager is necessary to use the path service.
+  base::AtExitManager aemanager;
+  // File handler for the temporary PDF we pass onto Chrome.
+  FILE* output_pdf;
+  // Enable Logging.
+  CommandLine::Init(argc,argv);
+  // Location for the log file.
+  std::string log_location="/var/log/GCP-Driver.log";
+
+  // Set up logging.
+  logging::InitLogging(log_location.c_str(),
+                       logging::LOG_ONLY_TO_FILE,
+                       logging::LOCK_LOG_FILE,
+                       logging::APPEND_TO_OLD_LOG_FILE,
+                       logging::DISABLE_DCHECK_FOR_NON_OFFICIAL_RELEASE_BUILDS);
+
+  // Temporary directory to hold the output file.
+  FilePath temp_dir;
+  // Strings to hold details of current job.
+  std::string current_user;
+  std::string set_var;
+  std::string job_title;
+  std::string job_id;
+  std::string file_name;
+
+  // Get temp directory to hold spool file.
+  if(!PathService::Get(base::DIR_TEMP, &temp_dir)) {
+    LOG(ERROR) << "Unable to get DIR_TEMP";
+    return CUPS_BACKEND_CANCEL;
+  }
+  // Get details from command line and set spool path.
+  current_user = argv[2];
+  job_title = argv[3];
+  job_id = argv[1];
+  file_name = current_user + "-"  + job_title + "-" + job_id;
+  FilePath output_path = temp_dir.Append(file_name);
+
+  // Read from file if specified.
+  if(argc==7){
+    FILE* input_pdf=fopen(argv[6],"r");
+    if(input_pdf == NULL) {
+      LOG(ERROR) << "Unable to read input PDF";
+      return CUPS_BACKEND_CANCEL;
+    }
+    // File is opened.
+    WriteToTemp(input_pdf,output_path);
+  }
+  // Otherwise, read from stdin.
+  else{
+    WriteToTemp(stdin, output_path);
+  }
+
+  // Set File permissions to allow non-sudo user to read spool file.
+  if(chmod(output_path.value().c_str(),S_IRUSR|S_IWUSR|S_IROTH|S_IWOTH)!=0) {
+    LOG(ERROR)<<"Unable to change file permissions";

[Albert Bodenhamer, 2011/07/11 19:21:32]

Should you return an error here?

+  }
+
+  pid_t pid=fork();
+
+  if(!pid) {
+    // In child process.
+
+    // Set the user to the one that initiated print job.
+    SetUser(argv[2]);
+
+    // Launch Chrome and pass the print job onto Cloud Print.
+    LaunchPrintDialog(output_path.value(), job_title, current_user);
+
+    return 0;
+  }// back in parent process.
+  // wait for child, then terminate.
+  waitpid(pid,NULL,0);
+  return 0;
+}// main