gpgv: Pass the current configuration settings to apt-key

This makes stuff like RootDir, Dir, and friends work if they are
set in the parent process.

LP: #1607283

apt-pkg/contrib/gpgv.cc

@@ -18,6 +18,7 @@
 #include <stddef.h>
 
 #include <algorithm>
+#include <fstream>
 #include <iostream>
 #include <string>
 #include <vector>
@@ -97,6 +98,7 @@ void ExecGPGV(std::string const &File, std::string const &FileGPG,
    std::vector<std::string> dataHeader;
    char * sig = NULL;
    char * data = NULL;
+   char * conf = nullptr;
 
    if (releaseSignature == DETACHED)
    {
@@ -107,6 +109,7 @@ void ExecGPGV(std::string const &File, std::string const &FileGPG,
    {
       sig = GenerateTemporaryFileTemplate("apt.sig");
       data = GenerateTemporaryFileTemplate("apt.data");
+      conf = GenerateTemporaryFileTemplate("apt.conf");
       if (sig == NULL || data == NULL)
       {
 	 ioprintf(std::cerr, "Couldn't create tempfile names for splitting up %s", File.c_str());
@@ -115,8 +118,11 @@ void ExecGPGV(std::string const &File, std::string const &FileGPG,
 
       int const sigFd = mkstemp(sig);
       int const dataFd = mkstemp(data);
-      if (sigFd == -1 || dataFd == -1)
+      int const confFd = mkstemp(conf);
+      if (sigFd == -1 || dataFd == -1 || confFd == -1 )
       {
+	 if (confFd != -1)
+	    unlink(conf);
 	 if (dataFd != -1)
 	    unlink(data);
 	 if (sigFd != -1)
@@ -129,14 +135,20 @@ void ExecGPGV(std::string const &File, std::string const &FileGPG,
       signature.OpenDescriptor(sigFd, FileFd::WriteOnly, true);
       FileFd message;
       message.OpenDescriptor(dataFd, FileFd::WriteOnly, true);
+      std::ofstream configStream(conf);
 
-      if (signature.Failed() == true || message.Failed() == true ||
+      _config->Dump(configStream);
+      close(confFd);
+
+      if (signature.Failed() == true || message.Failed() == true || configStream.fail() == true ||
 	    SplitClearSignedFile(File, &message, &dataHeader, &signature) == false)
       {
 	 if (dataFd != -1)
 	    unlink(data);
 	 if (sigFd != -1)
 	    unlink(sig);
+	 if (confFd != -1)
+	    unlink(conf);
 	 ioprintf(std::cerr, "Splitting up %s into data and signature failed", File.c_str());
 	 exit(112);
       }
@@ -180,7 +192,7 @@ void ExecGPGV(std::string const &File, std::string const &FileGPG,
    else
    {
 //#define UNLINK_EXIT(X) exit(X)
-#define UNLINK_EXIT(X) unlink(sig);unlink(data);exit(X)
+#define UNLINK_EXIT(X) unlink(sig);unlink(data);unlink(conf);exit(X)
 
       // for clear-signed files we have created tempfiles we have to clean up
       // and we do an additional check, so fork yet another time …
@@ -191,6 +203,7 @@ void ExecGPGV(std::string const &File, std::string const &FileGPG,
       }
       if(pid == 0)
       {
+	 setenv("APT_CONFIG", conf, 1);
 	 if (statusfd != -1)
 	    dup2(fd[1], statusfd);
 	 execvp(Args[0], (char **) &Args[0]);
@@ -211,8 +224,10 @@ void ExecGPGV(std::string const &File, std::string const &FileGPG,
       // we don't need the files any longer
       unlink(sig);
       unlink(data);
+      unlink(conf);
       free(sig);
       free(data);
+      free(conf);
 
       // check if it exit'ed normally …
       if (WIFEXITED(Status) == false)