Bug#579028: pbuilder: installs untrusted packages without asking

Package: pbuilder
Version: 0.206
Tags: patch
Followup-For: Bug #579028

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA256

Dear Maintainer,

The attached patch changes the defaults to always enforce signed
repositories and aborts if an untrusted/manipulated package is
installed. It adds the new option --keyring (APTKEYRINGS) to add
additional keyrings, which are then used to verify the (local)
signed repositories. This way no untrusted packages can be
installed.

To still allow untrusted/unsigned repositories - they are a very
bad idea and allow remote attackers performing a MITM to take
over the system, including all built packages - the new option
- --allow-untrusted (ALLOWUNTRUSTED) was added.

I tested it with the official Debian repository, signed and
unsigned local repositories and it works fine for me. But I'm
only a "normal" pbuilder user, so I might have missed something.
Please test the patch.

I haven't tested it with cdebootstrap, but it should work as
well.

The old PBUILDERSATISFYDEPENDSOPT --check-key option was
deprecated and is no longer used (it emits a warning now) as
validation is the default now.

The patch also contains documentation updates for the new
options/variables and updates for the NEWS file describing the
necessary changes to continue using untrusted packages (but
please don't do that - especially as a Debian developer).

Please have a look and include the patch as soon as possible to
fix this security issue.

Regards,
Simon

- -- System Information:
Debian Release: wheezy/sid
  APT prefers unstable
  APT policy: (500, 'unstable')
Architecture: amd64 (x86_64)

Kernel: Linux 3.2.0-1-amd64 (SMP w/8 CPU cores)
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash

Versions of packages pbuilder depends on:
ii  cdebootstrap           0.5.8+b1
ii  coreutils              8.13-3
ii  debconf [debconf-2.0]  1.5.41
ii  debianutils            4.2.1
ii  debootstrap            1.0.38
ii  dpkg-dev               1.16.1.2
ii  wget                   1.13.4-2

Versions of packages pbuilder recommends:
pn  devscripts  2.11.4
pn  fakeroot    1.18.2-1
pn  sudo        <none>

Versions of packages pbuilder suggests:
pn  cowdancer     <none>
pn  gdebi-core    <none>
pn  pbuilder-uml  <none>

- -- debconf information excluded

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>From cadc48fb599d436577a6efedc7f25e175652a3a1 Mon Sep 17 00:00:00 2001
Message-Id: <cadc48fb599d436577a6efedc7f25e175652a3a1.1330997290.git.simon@ruderich.org>
From: Simon Ruderich <simon@ruderich.org>
Date: Tue, 6 Mar 2012 02:00:48 +0100
Subject: [PATCH] Enforce valid signed repositories by default.

10 files changed, 124 insertions, 26 deletions

diff --git a/debian/NEWS b/debian/NEWS
index 6d144b9..80d36e9 100644
--- a/debian/NEWS
+++ b/debian/NEWS
@@ -1,3 +1,22 @@
+pbuilder (0.207) unstable; urgency=low
+
+  The default configuration will now only install trusted packages.  This
+  prevents building packages with manipulated sources or a system compromise
+  due to a man-in-the-middle attack.
+
+  However this also prevents installing packages from unsigned repositories by
+  default.
+
+  If you really want to continue using unsigned repositories, you have to set
+  ALLOWUNTRUSTED=yes in your .pbuilderrc or use the --allow-untrusted option.
+  But if possible use a signed repository and set the used keys with the new
+  --keyring option (can be passed multiple times).
+
+  Due to this change the PBUILDERSATISFYDEPENDSOPT option --check-key is no
+  longer necessary and thus deprecated.
+
+ -- Simon Ruderich <simon@ruderich.org>  Tue, 06 Mar 2012 02:02:38 +0100
+
 pbuilder (0.197) unstable; urgency=low
 
   The default configuration will now enable ccache.  To disable installation
diff --git a/debian/pbuilder-test/00_prepinstall b/debian/pbuilder-test/00_prepinstall
index 0c1d44c..1769cdd 100755
--- a/debian/pbuilder-test/00_prepinstall
+++ b/debian/pbuilder-test/00_prepinstall
@@ -1,4 +1,4 @@
 #!/bin/bash
 # Prepare and install packages used in the tests.
 
-apt-get install -y --force-yes sudo
+apt-get install -y sudo
diff --git a/pbuilder-checkparams b/pbuilder-checkparams
index c031f18..3cdc48e 100755
--- a/pbuilder-checkparams
+++ b/pbuilder-checkparams
@@ -207,6 +207,14 @@ while [ -n "$1" ]; do
 	    DEBOOTSTRAP="$2";
 	    shift; shift;
 	    ;;
+	--allow-untrusted)
+	    ALLOWUNTRUSTED=yes;
+	    shift;
+	    ;;
+	--keyring)
+	    APTKEYRINGS[${#APTKEYRINGS[@]}]="$2";
+	    shift; shift;
+	    ;;
 	--save-after-login|--save-after-exec)
 	    SAVE_AFTER_LOGIN=yes;
 	    shift;
@@ -312,3 +320,13 @@ fi
 
 # sort BINDMOUNTS to ensure that deeper directories are mounted last
 BINDMOUNTS="$(for i in $BINDMOUNTS; do echo $i; done | sort -u)"
+
+if [ "$ALLOWUNTRUSTED" = "yes" ]; then
+    PBUILDERSATISFYDEPENDSOPT[${#PBUILDERSATISFYDEPENDSOPT[@]}]='--allow-untrusted'
+    # Also duplicated in pbuilder-satisfydepends-checkparams!
+    # apt flag to accept untrusted packages
+    APTGETOPT[${#APTGETOPT[@]}]='--force-yes'
+    # aptitude flag to accept untrusted packages
+    APTITUDEOPT[${#APTITUDEOPT[@]}]='-o'
+    APTITUDEOPT[${#APTITUDEOPT[@]}]='Aptitude::CmdLine::Ignore-Trust-Violations=true'
+fi
diff --git a/pbuilder-createbuildenv b/pbuilder-createbuildenv
index 6c69f98..b23c343 100755
--- a/pbuilder-createbuildenv
+++ b/pbuilder-createbuildenv
@@ -78,6 +78,11 @@ mkdir -p "$BUILDPLACE/tmp/buildd"
 
 copy_local_configuration
 installaptlines
+# To support package verification inside the repository we may have to import
+# additional keys.
+for KEY in "${APTKEYRINGS[@]}"; do
+    $CHROOTEXEC /usr/bin/apt-key add - < "${KEY}" > /dev/null
+done
 
 executehooks "G"
 
diff --git a/pbuilder-satisfydepends-aptitude b/pbuilder-satisfydepends-aptitude
index 6ea6cb0..35a8374 100755
--- a/pbuilder-satisfydepends-aptitude
+++ b/pbuilder-satisfydepends-aptitude
@@ -89,7 +89,7 @@ EOF
     $CHROOTEXEC sh -c "cat \"$BUILD_DEP_DEB_CONTROL\""
     $CHROOTEXEC sh -c "dpkg-deb -b \"$BUILD_DEP_DEB_DIR/pbuilder-satisfydepends-dummy\""
     $CHROOTEXEC dpkg --force-depends --force-conflicts -i "$BUILD_DEP_DEB_DIR/pbuilder-satisfydepends-dummy.deb" || true
-    $CHROOTEXEC aptitude -y --without-recommends -o APT::Install-Recommends=false "${PBUILDER_APTITUDE_CHECK_OPTS[@]}" -o Aptitude::ProblemResolver::StepScore=100 -o "Aptitude::ProblemResolver::Hints::KeepDummy=reject pbuilder-satisfydepends-dummy :UNINST" -o Aptitude::ProblemResolver::Keep-All-Level=55000 -o Aptitude::ProblemResolver::Remove-Essential-Level=maximum install pbuilder-satisfydepends-dummy
+    $CHROOTEXEC aptitude -y --without-recommends -o APT::Install-Recommends=false "${APTITUDEOPT[@]}" -o Aptitude::ProblemResolver::StepScore=100 -o "Aptitude::ProblemResolver::Hints::KeepDummy=reject pbuilder-satisfydepends-dummy :UNINST" -o Aptitude::ProblemResolver::Keep-All-Level=55000 -o Aptitude::ProblemResolver::Remove-Essential-Level=maximum install pbuilder-satisfydepends-dummy
     # check whether the aptitude's resolver kept the package
     if ! $CHROOTEXEC dpkg -l pbuilder-satisfydepends-dummy 2>/dev/null | grep -q ^ii; then
         echo "Aptitude couldn't satisfy the build dependencies"
diff --git a/pbuilder-satisfydepends-checkparams b/pbuilder-satisfydepends-checkparams
index 249b67e..b81c765 100755
--- a/pbuilder-satisfydepends-checkparams
+++ b/pbuilder-satisfydepends-checkparams
@@ -27,13 +27,6 @@ FORCEVERSION=""
 CONTINUE_FAIL="no"
 CHROOTEXEC_AFTER_INTERNAL_CHROOTEXEC=no
 
-# aptitude flag to ignore key verification
-PBUILDER_APTITUDE_CHECK_OPTS=(
-    '-o'
-    'Aptitude::CmdLine::Ignore-Trust-Violations=true' )
-# apt flag to ignore key verification
-PBUILDER_APT_GET_CHECK_OPTS="--force-yes"
-
 while [ -n "$1" ]; do
     case "$1" in
 	--control|-c)
@@ -80,8 +73,16 @@ while [ -n "$1" ]; do
 	    shift;
 	    ;;
 	--check-key)
-	    unset PBUILDER_APTITUDE_CHECK_OPTS
-	    unset PBUILDER_APT_GET_CHECK_OPTS
+	    log 'W: --check-key is now enabled by default and thus deprecated.'
+	    shift;
+	    ;;
+	--allow-untrusted)
+	    # Also duplicated in pbuilder-checkparams!
+	    # apt flag to accept untrusted packages
+	    APTGETOPT[${#APTGETOPT[@]}]='--force-yes'
+	    # aptitude flag to accept untrusted packages
+	    APTITUDEOPT[${#APTITUDEOPT[@]}]='-o'
+	    APTITUDEOPT[${#APTITUDEOPT[@]}]='Aptitude::CmdLine::Ignore-Trust-Violations=true'
 	    shift;
 	    ;;
 	--help|-h|*)
diff --git a/pbuilder-updatebuildenv b/pbuilder-updatebuildenv
index cdcc22c..737f53d 100755
--- a/pbuilder-updatebuildenv
+++ b/pbuilder-updatebuildenv
@@ -72,6 +72,12 @@ $CHROOTEXEC /usr/bin/apt-get -q -y "${APTGETOPT[@]}" autoremove || true
 $CHROOTEXEC /usr/bin/apt-get -q -y "${APTGETOPT[@]}" install build-essential dpkg-dev $EXTRAPACKAGES
 save_aptcache
 
+# To support package verification inside the repository we may have to import
+# additional keys.
+for KEY in "${APTKEYRINGS[@]}"; do
+    $CHROOTEXEC /usr/bin/apt-key add - < "${KEY}" > /dev/null
+done
+
 # optionally auto-clean apt-cache
 if [ "${AUTOCLEANAPTCACHE}" = "yes" -a -n "$APTCACHE" ]; then
     log "I: Cleaning the cached apt archive"
diff --git a/pbuilder.8 b/pbuilder.8
index 478be40..a2f37c3 100644
--- a/pbuilder.8
+++ b/pbuilder.8
@@ -361,7 +361,7 @@ specified in a space-delimited manner, surrounded in double quotations, like:
 .B """/srv /somedir /someotherdir"""
 
 .TP
-.BI "\-\-debootstrapopts " "\-\-variant=buildd"
+.BI "\-\-debootstrapopts " "\-\-variant=buildd" " " "\-\-keyring" " " "/usr/share/keyrings/debian\-archive\-keyring.gpg"
 Add extra command-line options to debootstrap.
 
 Specify multiple options through multiple instance of this
@@ -380,6 +380,24 @@ and default is to use
 .B debootstrap.
 
 .TP
+.BI "\-\-allow\-untrusted "
+Allow untrusted (no key installed) and unsigned repositories.
+.BI Warning:
+Enabling this option may allow remote attackers to compromise the system.
+Better use signed repositories and
+.B "\-\-keyring"
+to add the key(s).
+
+.TP
+.BI "\-\-keyring " "path/to/keyring"
+Additional keyrings to use for package verification with apt, not used for
+debootstrap (use
+.B "\-\-debootstrapopts"
+). Use this to add (local) signed repositories. By default the
+debian-archive-keyring package inside the chroot is used. Can be specified
+multiple times.
+
+.TP
 .BI "\-\-save\-after\-login "
 .TP
 .BI "\-\-save\-after\-exec "
diff --git a/pbuilderrc b/pbuilderrc
index 6ade93b..8774f46 100644
--- a/pbuilderrc
+++ b/pbuilderrc
@@ -53,11 +53,19 @@ PBUILDERROOTCMD="sudo -E"
 # not support unsigned APT repositories
 PBUILDERSATISFYDEPENDSCMD="/usr/lib/pbuilder/pbuilder-satisfydepends"
 
-# You can optionally make pbuilder check key by setting the following flags
-# PBUILDERSATISFYDEPENDSOPT=('--check-key')
-# unset PBUILDERSATISFYDEPENDSOPT
-# option to pass to apt-get always.
-export APTGETOPT=('--force-yes')
+# Arguments for $PBUILDERSATISFYDEPENDSCMD.
+# PBUILDERSATISFYDEPENDSOPT=()
+
+# You can optionally make pbuilder accept untrusted repositories by setting
+# this option to yes, but this may allow remote attackers to compromise the
+# system. Better set a valid key for the signed (local) repository with
+# $APTKEYRINGS (see below).
+ALLOWUNTRUSTED=no
+
+# Option to pass to apt-get always.
+export APTGETOPT=()
+# Option to pass to aptitude always.
+export APTITUDEOPT=()
 
 #Command-line option passed on to dpkg-buildpackage.
 #DEBBUILDOPTS="-IXXX -iXXX"
@@ -82,6 +90,11 @@ DEBOOTSTRAPOPTS=(
 # or unset it to make it not a buildd type.
 # unset DEBOOTSTRAPOPTS
 
+# Keyrings to use for package verification with apt, not used for debootstrap
+# (use DEBOOTSTRAPOPTS). By default the debian-archive-keyring package inside
+# the chroot is used.
+APTKEYRINGS=()
+
 # Set the PATH I am going to use inside pbuilder: default is "/usr/sbin:/usr/bin:/sbin:/bin"
 export PATH="/usr/sbin:/usr/bin:/sbin:/bin"
 
diff --git a/pbuilderrc.5 b/pbuilderrc.5
index 14fde73..40fc8bb 100644
--- a/pbuilderrc.5
+++ b/pbuilderrc.5
@@ -178,17 +178,25 @@ may also be used to reset the list of options.
 
 The default value is to build source and binary package.
 .TP
-.BI "DEBOOTSTRAPOPTS=" "( '\-\-variant=buildd' )"
+.BI "DEBOOTSTRAPOPTS=" "( '\-\-variant=buildd' '\-\-keyring' '/usr/share/keyrings/debian\-archive\-keyring.gpg' )"
 When this option is set to
 .B "\-\-variant=buildd"
 .B "pbuilder"
 will invoke
 .B "$DEBOOTSTRAP"
-with "\-\-variant=buildd"
+with
+.B "\-\-variant=buildd"
 option, which results in debootstrap creating a minimal chroot for
 buildd instead of trying to create a minimal installation chroot.
-.B "DEBOOTSTRAP"
-is another directive in this file.
+.B "\-\-keyring"
+is used to specify a keyring for debootstrap.
+.TP
+.BI "APTKEYRINGS=" "()"
+Additional keyrings to use for package verification with apt, not used for
+debootstrap (use
+.B "$DEBOOTSTRAPOPTS"
+). Use this to add (local) signed repositories. By default the
+debian-archive-keyring package inside the chroot is used.
 .TP
 .BI "DEBOOTSTRAP=" "debootstrap"
 Use this option to switch the implementation of
@@ -329,15 +337,25 @@ used until 0.172.
 
 The default is now "aptitude".
 .TP
-.BI "PBUILDERSATISFYDEPENDSOPT=" "('\-\-check\-key')"
+.BI "PBUILDERSATISFYDEPENDSOPT=" "()"
 Array of flags to give to pbuilder\-satisfydepends.
-Specifying \-\-check\-key here will try to verify key signatures.
 
 .TP
-.BI "APTGETOPT=" "('\-\-force\-yes')"
+.BI "ALLOWUNTRUSTED=" "no"
+Allow untrusted (no key installed) and unsigned repositories.
+.BI Warning:
+Enabling this option may allow remote attackers to compromise the system.
+Better use signed repositories and
+.B "$APTKEYRINGS"
+to add the key(s).
+
+.TP
+.BI "APTGETOPT=" "()"
 Extra flags to give to apt\-get.
-Default is \-\-force\-yes, which will skip key verification of packages
-to be installed. Unset if you want to enable key verification.
+
+.TP
+.BI "APTITUDEGETOPT=" "()"
+Extra flags to give to aptitude.
 
 .TP
 .BI "REMOVEPACKAGES=" "lilo"