avoid evaluating shell in paths used in apt-key

apt-key creates internally a script (since ~1.1) which it will call to
avoid dealing with an array of different options in the code itself, but
while writing this script it wraps the values in "", which will cause
the shell to evaluate its content upon execution.
To make 'use' of this either set a absolute gpg command or TMPDIR to
something as interesting as:
"/tmp/This is fü\$\$ing cràzy, \$(man man | head -n1 | cut -d' ' -f1)\$!"

If such paths can be encountered in reality is a different question…

1 files changed, 24 insertions, 20 deletions

diff --git a/cmdline/apt-key.in b/cmdline/apt-key.in
index f1d021e8a..4d1079a4b 100644
--- a/cmdline/apt-key.in
+++ b/cmdline/apt-key.in
@@ -4,17 +4,14 @@ set -e
 unset GREP_OPTIONS
 export IFS="$(printf "\n\b")"
 
-APT_DIR="/"
-eval $(apt-config shell APT_DIR Dir)
-
 MASTER_KEYRING='&keyring-master-filename;'
-eval $(apt-config shell MASTER_KEYRING APT::Key::MasterKeyring)
+eval "$(apt-config shell MASTER_KEYRING APT::Key::MasterKeyring)"
 ARCHIVE_KEYRING='&keyring-filename;'
-eval $(apt-config shell ARCHIVE_KEYRING APT::Key::ArchiveKeyring)
+eval "$(apt-config shell ARCHIVE_KEYRING APT::Key::ArchiveKeyring)"
 REMOVED_KEYS='&keyring-removed-filename;'
-eval $(apt-config shell REMOVED_KEYS APT::Key::RemovedKeys)
+eval "$(apt-config shell REMOVED_KEYS APT::Key::RemovedKeys)"
 ARCHIVE_KEYRING_URI='&keyring-uri;'
-eval $(apt-config shell ARCHIVE_KEYRING_URI APT::Key::ArchiveKeyringURI)
+eval "$(apt-config shell ARCHIVE_KEYRING_URI APT::Key::ArchiveKeyringURI)"
 
 aptkey_echo() { echo "$@"; }
 
@@ -40,6 +37,10 @@ command_available() {
     return 1
 }
 
+escape_shell() {
+    echo "$@" | sed -e "s#'#'\"'\"'#g"
+}
+
 get_fingerprints_of_keyring() {
     aptkey_execute "$GPG_SH" --keyring "$1" --with-colons --fingerprint | while read publine; do
 	# search for a public key
@@ -55,8 +56,8 @@ get_fingerprints_of_keyring() {
 }
 
 add_keys_with_verify_against_master_keyring() {
-    ADD_KEYRING=$1
-    MASTER=$2
+    ADD_KEYRING="$1"
+    MASTER="$2"
 
     if [ ! -f "$ADD_KEYRING" ]; then
 	echo >&2 "ERROR: '$ADD_KEYRING' not found"
@@ -72,8 +73,8 @@ add_keys_with_verify_against_master_keyring() {
     #   all keys that are exported must have a valid signature
     #   from a key in the $distro-master-keyring
     add_keys="$(get_fingerprints_of_keyring "$ADD_KEYRING")"
-    all_add_keys=`aptkey_execute "$GPG_SH" --keyring "$ADD_KEYRING" --with-colons --list-keys | grep ^[ps]ub | cut -d: -f5`
-    master_keys=`aptkey_execute "$GPG_SH" --keyring "$MASTER" --with-colons --list-keys | grep ^pub | cut -d: -f5`
+    all_add_keys="$(aptkey_execute "$GPG_SH" --keyring "$ADD_KEYRING" --with-colons --list-keys | grep ^[ps]ub | cut -d: -f5)"
+    master_keys="$(aptkey_execute "$GPG_SH" --keyring "$MASTER" --with-colons --list-keys | grep ^pub | cut -d: -f5)"
 
     # ensure there are no colisions LP: #857472
     for all_add_key in $all_add_keys; do
@@ -114,6 +115,9 @@ add_keys_with_verify_against_master_keyring() {
 # the archive-keyring keys needs to be signed with the master key
 # (otherwise it does not make sense from a security POV)
 net_update() {
+    local APT_DIR='/'
+    eval $(apt-config shell APT_DIR Dir)
+
     # Disabled for now as code is insecure (LP: #1013639 (and 857472, 1013128))
     APT_KEY_NET_UPDATE_ENABLED=""
     eval $(apt-config shell APT_KEY_NET_UPDATE_ENABLED APT::Key::Net-Update-Enabled)
@@ -137,7 +141,7 @@ net_update() {
     keyring="${APT_DIR}/var/lib/apt/keyrings/$(basename "$ARCHIVE_KEYRING_URI")"
     old_mtime=0
     if [ -e $keyring ]; then
-	old_mtime=$(stat -c %Y $keyring)
+	old_mtime=$(stat -c %Y "$keyring")
     fi
     (cd  "${APT_DIR}/var/lib/apt/keyrings"; wget --timeout=90 -q -N "$ARCHIVE_KEYRING_URI")
     if [ ! -e "$keyring" ]; then
@@ -228,7 +232,7 @@ foreach_keyring_do() {
 	    $ACTION "$TRUSTEDFILE" "$@"
 	fi
 	local TRUSTEDPARTS="/etc/apt/trusted.gpg.d"
-	eval $(apt-config shell TRUSTEDPARTS Dir::Etc::TrustedParts/d)
+	eval "$(apt-config shell TRUSTEDPARTS Dir::Etc::TrustedParts/d)"
 	if [ -d "$TRUSTEDPARTS" ]; then
 	    # strip / suffix as gpg will double-slash in that case (#665411)
 	    local STRIPPED_TRUSTEDPARTS="${TRUSTEDPARTS%/}"
@@ -360,7 +364,7 @@ setup_merged_keyring() {
 	FORCED_KEYRING="${GPGHOMEDIR}/forcedkeyid.gpg"
 	TRUSTEDFILE="${FORCED_KEYRING}"
 	echo "#!/bin/sh
-exec sh \"${GPG}\" --keyring \"${TRUSTEDFILE}\" \"\$@\"" > "${GPGHOMEDIR}/gpg.1.sh"
+exec sh '($(escape_shell "${GPG}")' --keyring '$(escape_shell "${TRUSTEDFILE}")' \"\$@\"" > "${GPGHOMEDIR}/gpg.1.sh"
 	GPG="${GPGHOMEDIR}/gpg.1.sh"
 	# ignore error as this "just" means we haven't found the forced keyid and the keyring will be empty
 	import_keyring_into_keyring '' "$TRUSTEDFILE" "$FORCED_KEYID" || true
@@ -372,12 +376,12 @@ exec sh \"${GPG}\" --keyring \"${TRUSTEDFILE}\" \"\$@\"" > "${GPGHOMEDIR}/gpg.1.
 	   touch "${GPGHOMEDIR}/pubring.gpg" "${GPGHOMEDIR}/pubring.orig.gpg"
 	fi
 	echo "#!/bin/sh
-exec sh \"${GPG}\" --keyring \"${GPGHOMEDIR}/pubring.gpg\" \"\$@\"" > "${GPGHOMEDIR}/gpg.1.sh"
+exec sh '$(escape_shell "${GPG}")' --keyring '$(escape_shell "${GPGHOMEDIR}/pubring.gpg")' \"\$@\"" > "${GPGHOMEDIR}/gpg.1.sh"
 	GPG="${GPGHOMEDIR}/gpg.1.sh"
     else
 	create_new_keyring "$TRUSTEDFILE"
 	echo "#!/bin/sh
-exec sh \"${GPG}\" --keyring \"${TRUSTEDFILE}\" \"\$@\"" > "${GPGHOMEDIR}/gpg.1.sh"
+exec sh '$(escape_shell "${GPG}")' --keyring '$(escape_shell "${TRUSTEDFILE}")' \"\$@\"" > "${GPGHOMEDIR}/gpg.1.sh"
 	GPG="${GPGHOMEDIR}/gpg.1.sh"
     fi
 }
@@ -479,13 +483,13 @@ create_gpg_home() {
 	fi
     fi
     GPGHOMEDIR="$(mktemp -d)"
-    CURRENTTRAP="${CURRENTTRAP} rm -rf '${GPGHOMEDIR}';"
+    CURRENTTRAP="${CURRENTTRAP} rm -rf '$(escape_shell "${GPGHOMEDIR}")';"
     trap "${CURRENTTRAP}" 0 HUP INT QUIT ILL ABRT FPE SEGV PIPE TERM
     chmod 700 "$GPGHOMEDIR"
 }
 
 prepare_gpg_home() {
-    eval $(apt-config shell GPG_EXE Apt::Key::gpgcommand)
+    eval "$(apt-config shell GPG_EXE Apt::Key::gpgcommand)"
 
     if [ -n "$GPG_EXE" ] && command_available "$GPG_EXE"; then
 	true
@@ -518,8 +522,8 @@ prepare_gpg_home() {
     fi
     # tell gpg that it shouldn't try to maintain a trustdb file
     echo "#!/bin/sh
-exec \"${GPG_EXE}\" --ignore-time-conflict --no-options --no-default-keyring \\
-   --homedir \"${GPGHOMEDIR}\" --no-auto-check-trustdb --trust-model always \"\$@\"" > "${GPGHOMEDIR}/gpg.0.sh"
+exec '$(escape_shell "${GPG_EXE}")' --ignore-time-conflict --no-options --no-default-keyring \\
+--homedir '$(escape_shell "${GPGHOMEDIR}")' --no-auto-check-trustdb --trust-model always \"\$@\"" > "${GPGHOMEDIR}/gpg.0.sh"
     GPG_SH="${GPGHOMEDIR}/gpg.0.sh"
     GPG="$GPG_SH"