Do not parse Status fields from remote sources

This could allow an attacker to mark a package as installed in a
remote package index, as long as the package was not listed in
the dpkg status file.

This way, an attacker could force the installation of a package
during a dist-upgrade, by providing two packages in an index,
an older marked as installed, and a newer - apt would "upgrade"
to the newer version.

4 files changed, 44 insertions, 2 deletions

diff --git a/apt-pkg/deb/debindexfile.cc b/apt-pkg/deb/debindexfile.cc
index 504db919b..de6371ace 100644
--- a/apt-pkg/deb/debindexfile.cc
+++ b/apt-pkg/deb/debindexfile.cc
@@ -621,7 +621,7 @@ bool debStatusIndex::Merge(pkgCacheGenerator &Gen,OpProgress *Prog) const
    FileFd Pkg(File,FileFd::ReadOnly, FileFd::Extension);
    if (_error->PendingError() == true)
       return false;
-   debListParser Parser(&Pkg);
+   debStatusListParser Parser(&Pkg);
    if (_error->PendingError() == true)
       return false;
 
diff --git a/apt-pkg/deb/deblistparser.cc b/apt-pkg/deb/deblistparser.cc
index 6d4fd9ac1..336414775 100644
--- a/apt-pkg/deb/deblistparser.cc
+++ b/apt-pkg/deb/deblistparser.cc
@@ -333,7 +333,7 @@ unsigned short debListParser::VersionHash()
    return Result;
 }
 									/*}}}*/
-// ListParser::ParseStatus - Parse the status field			/*{{{*/
+// StatusListParser::ParseStatus - Parse the status field		/*{{{*/
 // ---------------------------------------------------------------------
 /* Status lines are of the form,
      Status: want flag status
@@ -345,6 +345,11 @@ unsigned short debListParser::VersionHash()
 bool debListParser::ParseStatus(pkgCache::PkgIterator &Pkg,
 				pkgCache::VerIterator &Ver)
 {
+   return true;
+}
+bool debStatusListParser::ParseStatus(pkgCache::PkgIterator &Pkg,
+				pkgCache::VerIterator &Ver)
+{
    const char *Start;
    const char *Stop;
    if (Section.Find("Status",Start,Stop) == false)
diff --git a/apt-pkg/deb/deblistparser.h b/apt-pkg/deb/deblistparser.h
index db7afa73c..d479997a3 100644
--- a/apt-pkg/deb/deblistparser.h
+++ b/apt-pkg/deb/deblistparser.h
@@ -117,4 +117,11 @@ class debTranslationsParser : public debListParser
       : debListParser(File, Arch) {};
 };
 
+class APT_HIDDEN debStatusListParser : public debListParser
+{
+ public:
+   virtual bool ParseStatus(pkgCache::PkgIterator &Pkg,pkgCache::VerIterator &Ver);
+   debStatusListParser(FileFd *File)
+      : debListParser(File) {};
+};
 #endif
diff --git a/test/integration/test-security-no-remote-status b/test/integration/test-security-no-remote-status
new file mode 100755
index 000000000..b7cd0b0d1
--- /dev/null
+++ b/test/integration/test-security-no-remote-status
@@ -0,0 +1,30 @@
+#!/bin/sh
+#
+# Test that packages from remote sources cannot set the Status field.
+#
+set -e
+
+TESTDIR=$(readlink -f $(dirname $0))
+. $TESTDIR/framework
+setupenvironment
+configarchitecture 'amd64'
+
+TMPDIR=$(readlink -f .)
+
+insertpackage 'unstable' 'pretends-installed' 'all' '1' 'Status: install ok installed'
+insertinstalledpackage 'really-installed' 'all' '1'
+setupaptarchive
+
+testequal "pretends-installed:
+  Installed: (none)
+  Candidate: 1
+  Version table:
+     1 0
+        500 file:${TMPDIR}/aptarchive/ unstable/main amd64 Packages" aptcache policy pretends-installed
+
+testequal "really-installed:
+  Installed: 1
+  Candidate: 1
+  Version table:
+ *** 1 0
+        100 ${TMPDIR}/rootdir/var/lib/dpkg/status" aptcache policy really-installed