create non-existent files in edit-sources with 644 instead of 640

If the sources file we want to edit doesn't exist yet GetLock will
create it with 640, which for a generic lockfile might be okay, but as
this is a sources file more relaxed permissions are in order – and
actually required as it wont be readable for unprivileged users causing
warnings/errors in apt calls.

Reported-By: J. Theede (musca) on IRC

apt-private/private-sources.cc

@@ -13,6 +13,8 @@
 #include <apt-private/private-sources.h>
 #include <apt-private/private-utils.h>
 
+#include <sys/types.h>
+#include <sys/stat.h>
 #include <stddef.h>
 #include <unistd.h>
 #include <iostream>
@@ -46,6 +48,12 @@ bool EditSources(CommandLine &CmdL)
    HashString before;
    if (FileExists(sourceslist))
        before.FromFile(sourceslist);
+   else
+   {
+      FileFd filefd;
+      if (filefd.Open(sourceslist, FileFd::Create | FileFd::WriteOnly, FileFd::None, 0644) == false)
+	 return false;
+   }
 
    ScopedGetLock lock(sourceslist);
    if (lock.fd < 0)
@@ -56,7 +64,13 @@ bool EditSources(CommandLine &CmdL)
    do {
       if (EditFileInSensibleEditor(sourceslist) == false)
 	 return false;
-      if (FileExists(sourceslist) && !before.VerifyFile(sourceslist))
+      if (before.empty())
+      {
+	 struct stat St;
+	 if (stat(sourceslist.c_str(), &St) == 0 && St.st_size == 0)
+	       RemoveFile("edit-sources", sourceslist);
+      }
+      else if (FileExists(sourceslist) && !before.VerifyFile(sourceslist))
       {
 	 file_changed = true;
 	 pkgCacheFile::RemoveCaches();

test/integration/test-apt-edit-sources

@@ -0,0 +1,39 @@
+#!/bin/sh
+set -e
+
+TESTDIR="$(readlink -f "$(dirname "$0")")"
+. "$TESTDIR/framework"
+
+setupenvironment
+configarchitecture 'native'
+
+echo 'Dir::Bin::Editor "cat";' > rootdir/etc/apt/apt.conf.d/editor.conf
+
+echo 'deb http://example.org/debian stable rocks' > rootdir/etc/apt/sources.list.d/rocks.list
+testsuccessequal "$(cat rootdir/etc/apt/sources.list.d/rocks.list)" apt edit-sources rocks.list
+
+cat >editor.sh <<EOF
+#!/bin/sh
+umask 077
+touch "\$@"
+EOF
+chmod +x ./editor.sh
+echo 'Dir::Bin::Editor "./editor.sh";' > rootdir/etc/apt/apt.conf.d/editor.conf
+testsuccess apt edit-sources blub.list
+testfailure test -e 'rootdir/etc/apt/sources.list.d/blub.list'
+
+cat >editor.sh <<EOF
+#!/bin/sh
+umask 077
+echo '#comment' > "\$1"
+EOF
+testsuccess apt edit-sources blub.list
+testfilestats 'rootdir/etc/apt/sources.list.d/blub.list' '%U:%G:%a' '=' "${TEST_DEFAULT_USER}:${TEST_DEFAULT_GROUP}:644"
+
+echo 'Dir::Bin::Editor "cat";' > rootdir/etc/apt/apt.conf.d/editor.conf
+echo 'blub' > rootdir/etc/apt/sources.list.d/blub.list
+testfailure apt edit-sources blub.list --assume-no
+
+echo 'deb http://example.org/debian stable rocks' > rootdir/etc/apt/sources.list.d/blub.list
+touch -m -d 'now + 1 hour' rootdir/etc/apt/sources.list.d/blub.list
+testwarning apt edit-sources blub.list --assume-no