fix insecure use of /tmp in EDSP solver 'dump'

As said in the bugreport, this is hardly a serious problem on a security
front, but it was always on the list to have the filename configurable
somehow and the stable filename is a problem for parallel executions.

Using an environment variable (APT_EDSP_DUMP_FILENAME) for this is more
or less the best we can do here as solvers do not get told about our
configuration and such.

Closes: 795600

1 files changed, 29 insertions, 12 deletions

diff --git a/cmdline/apt-dump-solver.cc b/cmdline/apt-dump-solver.cc
index 4729eac55..2e352931f 100644
--- a/cmdline/apt-dump-solver.cc
+++ b/cmdline/apt-dump-solver.cc
@@ -13,6 +13,7 @@
 #include <unistd.h>
 #include <cstdio>
 #include <iostream>
+#include <sstream>
 
 #include <config.h>
 									/*}}}*/
@@ -23,10 +24,11 @@
 static bool ShowHelp() {
 	ioprintf(std::cout, "%s %s (%s)\n", PACKAGE, PACKAGE_VERSION, COMMON_ARCH);
 	std::cout <<
-		"Usage: apt-dump-resolver\n"
+		"Usage: apt-dump-solver\n"
 		"\n"
-		"apt-dump-resolver is a dummy solver who just dumps its input to the\n"
-		"file /tmp/dump.edsp and exists with a proper EDSP error.\n"
+		"apt-dump-solver is a dummy solver who just dumps its input to the\n"
+		"file specified in the environment variable APT_EDSP_DUMP_FILENAME and\n"
+		"exists with a proper EDSP error.\n"
 		"\n"
 		"                       This dump has lost Super Cow Powers.\n";
 	return true;
@@ -39,16 +41,31 @@ int main(int argc,const char *argv[])					/*{{{*/
 		ShowHelp();
 		return 0;
 	}
-        // we really don't need anything
-        DropPrivileges();
 
-	FILE* input = fdopen(STDIN_FILENO, "r");
-	FILE* output = fopen("/tmp/dump.edsp", "w");
-	char buffer[400];
-	while (fgets(buffer, sizeof(buffer), input) != NULL)
-		fputs(buffer, output);
-	fclose(output);
-	fclose(input);
+	// we really don't need anything
+	DropPrivileges();
+	char const * const filename = getenv("APT_EDSP_DUMP_FILENAME");
+	if (filename == NULL || strlen(filename) == 0)
+	{
+	   EDSP::WriteError("ERR_NO_FILENAME", "You have to set the environment variable APT_EDSP_DUMP_FILENAME\n"
+		 "to a valid filename to store the dump of EDSP solver input in.\n"
+		 "For example with: export APT_EDSP_DUMP_FILENAME=/tmp/dump.edsp", stdout);
+	   return 0;
+	}
+
+	unlink(filename);
+	FileFd input, output;
+	if (input.OpenDescriptor(STDIN_FILENO, FileFd::ReadOnly) == false ||
+	      output.Open(filename, FileFd::WriteOnly | FileFd::Create | FileFd::Exclusive, 0600) == false ||
+	      CopyFile(input, output) == false || input.Close() == false || output.Close() == false)
+	{
+	   std::ostringstream out;
+	   out << "Writing EDSP solver input to file '" << filename << "' failed!\n";
+	   _error->DumpErrors(out);
+	   EDSP::WriteError("ERR_WRITE_ERROR", out.str(), stdout);
+	   return 0;
+	}
 
 	EDSP::WriteError("ERR_JUST_DUMPING", "I am too dumb, i can just dump!\nPlease use one of my friends instead!", stdout);
+	return 0;
 }