Priviledge separation: use new monkeysphere user to handle

authentication keychain for server.  This required a bunch of changes
to all ms-server functions.  Seems to be working ok, although it feels
kind of hackish.

8 files changed, 258 insertions, 136 deletions

diff --git a/debian/changelog b/debian/changelog
index 82f274a..c6b5de4 100644
--- a/debian/changelog
+++ b/debian/changelog
@@ -3,7 +3,11 @@ monkeysphere (0.4-1) UNRELEASED; urgency=low
   [Daniel Kahn Gillmor]
   * New version (switch UNRELEASED to experimental when ready)
 
- -- Daniel Kahn Gillmor <dkg-debian.org@fifthhorseman.net>  Tue, 24 Jun 2008 01:25:45 -0400
+  [ Jameson Graef Rollins ]
+  * Privilege separation: use monkeysphere user to handle maintenance of
+    the gnupg authentication keychain for server.
+
+ -- Jameson Graef Rollins <jrollins@phys.columbia.edu>  Tue, 24 Jun 2008 13:52:28 -0400
 
 monkeysphere (0.3-1) experimental; urgency=low
 
diff --git a/debian/control b/debian/control
index 4f0e5f5..f5760d9 100644
--- a/debian/control
+++ b/debian/control
@@ -10,7 +10,7 @@ Dm-Upload-Allowed: yes
 
 Package: monkeysphere
 Architecture: any
-Depends: openssh-client, gnupg | gnupg2, coreutils (>= 6), moreutils, lockfile-progs, ${shlibs:Depends}
+Depends: openssh-client, gnupg | gnupg2, coreutils (>= 6), moreutils, lockfile-progs, adduser, ${shlibs:Depends}
 Recommends: netcat
 Enhances: openssh-client, openssh-server
 Description: use the OpenPGP web of trust to verify ssh connections
diff --git a/debian/monkeysphere.postinst b/debian/monkeysphere.postinst
new file mode 100755
index 0000000..50eaefa
--- /dev/null
+++ b/debian/monkeysphere.postinst
@@ -0,0 +1,17 @@
+#!/bin/sh -e
+
+# postinst script for monkeysphere
+
+# Author: Jameson Rollins <jrollins@fifthhorseman.net>
+# (c) 2008
+
+if ! getent passwd monkeysphere >/dev/null ; then
+    echo "adding monkeysphere user..."
+    adduser --quiet --system --no-create-home --home '/var/lib/monkeysphere' \
+    --shell '/bin/sh' --gecos 'monkeysphere authentication user,,,' monkeysphere
+fi
+
+# install host gnupg home directories
+install --mode 700 -d /var/lib/monkeysphere/gnupg-host
+# install authentication gnupg home directories
+install --mode 700 --owner monkeysphere -d /var/lib/monkeysphere/gnupg-authentication
diff --git a/debian/monkeysphere.postrm b/debian/monkeysphere.postrm
new file mode 100755
index 0000000..a103fc8
--- /dev/null
+++ b/debian/monkeysphere.postrm
@@ -0,0 +1,21 @@
+#!/bin/sh -e
+
+# postrm script for monkeysphere
+
+# Author: Jameson Rollins <jrollins@fifthhorseman.net>
+# (c) 2008
+
+case $1 in
+    purge)
+        rmdir --ignore-fail-on-non-empty /var/lib/monkeysphere || true
+        echo "removing monkeysphere user..."
+        userdel monkeysphere > /dev/null || true
+        ;;
+esac
+
+# dh_installdeb will replace this with shell code automatically
+# generated by other debhelper scripts.
+
+#DEBHELPER#
+
+exit 0
diff --git a/man/man8/monkeysphere-server.8 b/man/man8/monkeysphere-server.8
index 9bb7b2d..dbcc083 100644
--- a/man/man8/monkeysphere-server.8
+++ b/man/man8/monkeysphere-server.8
@@ -26,8 +26,8 @@ Update the admin-controlled authorized_keys files for user.  For each
 user specified, user ID's listed in the user's authorized_user_ids
 file are processed, and the user's authorized_keys file in
 /var/cache/monkeysphere/authorized_keys/USER.  See `man monkeysphere'
-for more info.  If the USER_CONTROLLED_AUTHORIZED_KEYS variable is
-set, then a user-controlled authorized_keys file (usually
+for more info.  If the RAW_AUTHORIZED_KEYS variable is set, then a
+user-controlled authorized_keys file (usually
 ~USER/.ssh/authorized_keys) is added to the authorized_keys file.  `u'
 may be used in place of `update-users.
 .TP
diff --git a/src/common b/src/common
index ead3736..42de18d 100644
--- a/src/common
+++ b/src/common
@@ -466,6 +466,8 @@ update_known_hosts() {
 process_known_hosts() {
     local returnCode
 
+    log "processing known_hosts file..."
+
     # default return code is 0, which assumes a key was found for
     # every host.  code will be set to 1 if a key is not found for at
     # least one host
@@ -551,6 +553,8 @@ process_authorized_user_ids() {
     local userid
     local returnCode
 
+    log "processing authorized_user_ids file..."
+
     # default return code is 0, and is set to 1 if a key for a user ID
     # is not found
     returnCode=0
@@ -609,85 +613,3 @@ process_authorized_keys() {
 
     return "$returnCode"
 }
-
-##################################################
-### GPG HELPER FUNCTIONS
-
-# retrieve key from web of trust, and set owner trust to "full"
-# if key is found.
-trust_key() {
-    local keyID
-    local trustLevel
-
-    keyID="$1"
-    trustLevel="$2"
-
-    if [ -z "$keyID" ] ; then
-	failure "You must specify key to trust."
-    fi
-
-    # get the key from the key server
-    if ! gpg --keyserver "$KEYSERVER" --recv-key "$keyID" ; then
-	failure "Could not retrieve key '$keyID'."
-    fi
-
-    # get key fingerprint
-    fingerprint=$(get_key_fingerprint "$keyID")
-
-    echo "key found:"
-    gpg --fingerprint "$fingerprint"
-
-    while [ -z "$trustLevel" ] ; do
-	cat <<EOF
-Please decide how far you trust this user to correctly verify other users' keys
-(by looking at passports, checking fingerprints from different sources, etc.)
-
-  1 = I don't know or won't say
-  2 = I do NOT trust
-  3 = I trust marginally
-  4 = I trust fully
-  5 = I trust ultimately
-
-EOF
-	read -p "Your decision? " trustLevel
-	if echo "$trustLevel" | grep -v "[1-5]" ; then
-	    echo "Unknown trust level '$trustLevel'."
-	    unset trustLevel
-	elif [ "$trustLevel" = 'q' ] ; then
-	    failure "Aborting."
-	fi
-    done
-
-    # attach a "non-exportable" signature to the key
-    # this is required for the key to have any validity at all
-    # the 'y's on stdin indicates "yes, i really want to sign"
-    echo -e 'y\ny' | gpg --quiet --lsign-key --command-fd 0 "$fingerprint"
-
-    # index trustLevel by one to difference between level in ui and level
-    # internally
-    trustLevel=$((trustLevel+1))
-
-    # import new owner trust level for key
-    echo "${fingerprint}:${trustLevel}:" | gpg --import-ownertrust
-    if [ $? = 0 ] ; then
-	log "Owner trust updated."
-    else
-	failure "There was a problem changing owner trust."
-    fi	
-}
-
-# publish server key to keyserver
-publish_server_key() {
-    read -p "really publish key to $KEYSERVER? [y|N]: " OK; OK=${OK:=N}
-    if [ ${OK/y/Y} != 'Y' ] ; then
-	failure "aborting."
-    fi
-
-    # publish host key
-    # FIXME: need to figure out better way to identify host key
-    # dummy command so as not to publish fakes keys during testing
-    # eventually:
-    #gpg --keyserver "$KEYSERVER" --send-keys $(hostname -f)
-    failure "NOT PUBLISHED (to avoid permanent publication errors during monkeysphere development).
-To publish manually, do: gpg --keyserver $KEYSERVER --send-keys $(hostname -f)"
-}
diff --git a/src/monkeysphere b/src/monkeysphere
index d8d4667..15a2a7a 100755
--- a/src/monkeysphere
+++ b/src/monkeysphere
@@ -168,7 +168,6 @@ case $COMMAND in
 	    if [ ! -s "$KNOWN_HOSTS" ] ; then
 		failure "known_hosts file '$KNOWN_HOSTS' is empty."
 	    fi
-	    log "processing known_hosts file..."
 	    process_known_hosts || ERR=1
 	fi
 
@@ -184,7 +183,6 @@ case $COMMAND in
 	fi
 
 	# process authorized_user_ids file
-	log "processing authorized_user_ids file..."
 	process_authorized_user_ids "$AUTHORIZED_USER_IDS" || ERR=1
 	log "authorized_keys file updated."
 	;;
diff --git a/src/monkeysphere-server b/src/monkeysphere-server
index ac7c1cb..4c403f2 100755
--- a/src/monkeysphere-server
+++ b/src/monkeysphere-server
@@ -10,6 +10,7 @@
 
 ########################################################################
 PGRM=$(basename $0)
+PGRM_PATH=$(dirname $0)
 
 SHARE=${SHARE:-"/usr/share/monkeysphere"}
 export SHARE
@@ -50,12 +51,16 @@ EOF
 # generate server gpg key
 gen_key() {
     local hostName
+    local userID
+    local keyParameters
+    local fingerprint
 
     hostName=${1:-$(hostname --fqdn)}
 
     SERVICE=${SERVICE:-"ssh"}
     userID="${SERVICE}://${hostName}"
 
+    GNUPGHOME="$GNUPGHOME_HOST"
     if gpg --list-key ="$userID" > /dev/null 2>&1 ; then
 	failure "Key for '$userID' already exists"
     fi
@@ -113,19 +118,32 @@ EOF
 EOF
 )
 
-    log "generating server key... "
+    log "generating server key..."
+    GNUPGHOME="$GNUPGHOME_HOST"
     echo "$keyParameters" | gpg --batch --gen-key
 
     # output the server fingerprint
     fingerprint_server_key "=${userID}"
 
     # find the key fingerprint of the server primary key
-    keyID=$(gpg --list-key --with-colons --with-fingerprint "=${userID}" | \
+    GNUPGHOME="$GNUPGHOME_HOST"
+    fingerprint=$(gpg --list-key --with-colons --with-fingerprint "=${userID}" | \
 	grep '^fpr:' | head -1 | cut -d: -f10)
 
+    # export the host key to the authentication keyring
+    GNUPGHOME="$GNUPGHOME_HOST" gpg --export "$fingerprint" | \
+	su --preserve-environment "$MONKEYSPHERE_USER" -c -- \
+	"GNUPGHOME=$GNUPGHOME_AUTHENTICATION gpg --import"
+
+    # set host key owner trust to ultimate in authentication keyring
+    echo "${fingerprint}:6:" | \
+        su --preserve-environment "$MONKEYSPHERE_USER" -c -- \
+        "GNUPGHOME=$GNUPGHOME_AUTHENTICATION gpg --import-ownertrust"
+
     # write the key to the file
     # NOTE: assumes that the primary key is the proper key to use
-    (umask 077 && gpgsecret2ssh "$keyID" > "${VARLIB}/ssh_host_rsa_key")
+    GNUPGHOME="$GNUPGHOME_HOST"
+    (umask 077 && gpgsecret2ssh "$fingerprint" > "${VARLIB}/ssh_host_rsa_key")
     log "Private SSH host key output to file: ${VARLIB}/ssh_host_rsa_key"
 }
 
@@ -133,7 +151,7 @@ EOF
 fingerprint_server_key() {
     local ID
 
-    if [ -z "$1" ] ; then
+    if [ "$1" ] ; then
 	ID="$1"
     else
 	ID="=ssh://$(hostname --fqdn)"
@@ -142,6 +160,113 @@ fingerprint_server_key() {
     gpg --fingerprint --list-secret-keys "$ID"
 }
 
+# publish server key to keyserver
+publish_server_key() {
+    read -p "really publish key to $KEYSERVER? [y|N]: " OK; OK=${OK:=N}
+    if [ ${OK/y/Y} != 'Y' ] ; then
+	failure "aborting."
+    fi
+
+    # publish host key
+    # FIXME: need to figure out better way to identify host key
+    # dummy command so as not to publish fakes keys during testing
+    # eventually:
+    #gpg --keyserver "$KEYSERVER" --send-keys $(hostname -f)
+    failure "NOT PUBLISHED (to avoid permanent publication errors during monkeysphere development).
+To publish manually, do: gpg --keyserver $KEYSERVER --send-keys $(hostname -f)"
+}
+
+
+# retrieve key from web of trust, and set owner trust to "full"
+# if key is found.
+trust_key() {
+    local keyID
+    local trustLevel
+
+    keyID="$1"
+    trustLevel="$2"
+
+    if [ -z "$keyID" ] ; then
+	failure "You must specify key to trust."
+    fi
+
+    export keyID
+
+    # get the key from the key server
+    GNUPGHOME="$GNUPGHOME_AUTHENTICATION"
+    su --preserve-environment "$MONKEYSPHERE_USER" -c -- \
+	"gpg --keyserver $KEYSERVER --recv-key $keyID"
+    if [ "$?" != 0 ] ; then
+	failure "Could not retrieve key '$keyID'."
+    fi
+
+    # move the key from the authentication keyring to the host keyring
+    GNUPGHOME="$GNUPGHOME_AUTHENTICATION"
+    su --preserve-environment "$MONKEYSPHERE_USER" -c -- \
+	"gpg --export $keyID" | \
+	GNUPGHOME="$GNUPGHOME_HOST" gpg --import
+
+    # get key fingerprint
+    GNUPGHOME="$GNUPGHOME_HOST"
+    fingerprint=$(get_key_fingerprint "$keyID")
+
+    echo "key found:"
+    GNUPGHOME="$GNUPGHOME_HOST"
+    gpg --fingerprint "$fingerprint"
+
+    while [ -z "$trustLevel" ] ; do
+	cat <<EOF
+Please decide how far you trust this user to correctly verify other users' keys
+(by looking at passports, checking fingerprints from different sources, etc.)
+
+  1 = I don't know or won't say
+  2 = I do NOT trust
+  3 = I trust marginally
+  4 = I trust fully
+  5 = I trust ultimately
+
+EOF
+	read -p "Your decision? " trustLevel
+	if echo "$trustLevel" | grep -v "[1-5]" ; then
+	    echo "Unknown trust level '$trustLevel'."
+	    unset trustLevel
+	elif [ "$trustLevel" = 'q' ] ; then
+	    failure "Aborting."
+	fi
+    done
+
+    # attach a "non-exportable" signature to the key
+    # this is required for the key to have any validity at all
+    # the 'y's on stdin indicates "yes, i really want to sign"
+    GNUPGHOME="$GNUPGHOME_HOST"
+    echo -e 'y\ny' | \
+	gpg --quiet --lsign-key --command-fd 0 "$fingerprint"
+
+    # copy the host keyring into the authentication keyring
+    mv "$GNUPGHOME_AUTHENTICATION"/pubring.gpg{,.old}
+    cp "$GNUPGHOME_HOST"/pubring.gpg "$GNUPGHOME_AUTHENTICATION"/pubring.gpg
+    chown "$MONKEYSPHERE_USER" "$GNUPGHOME_AUTHENTICATION"/pubring.gpg
+    GNUPGHOME="$GNUPGHOME_AUTHENTICATION"
+    su --preserve-environment "$MONKEYSPHERE_USER" -c -- \
+	"gpg --import ${GNUPGHOME_AUTHENTICATION}/pubring.gpg.old"
+
+    # index trustLevel by one to difference between level in ui and level
+    # internally
+    trustLevel=$((trustLevel+1))
+
+    # import new owner trust level for key
+    GNUPGHOME="$GNUPGHOME_AUTHENTICATION"
+    echo "${fingerprint}:${trustLevel}:" | \
+        su --preserve-environment "$MONKEYSPHERE_USER" -c -- \
+        "GNUPGHOME=$GNUPGHOME_AUTHENTICATION gpg --import-ownertrust"
+
+    if [ $? = 0 ] ; then
+	log "Owner trust updated."
+    else
+	failure "There was a problem changing owner trust."
+    fi
+}
+
 ########################################################################
 # MAIN
 ########################################################################
@@ -169,12 +294,15 @@ REQUIRED_USER_KEY_CAPABILITY=${REQUIRED_USER_KEY_CAPABILITY:-"a"}
 GNUPGHOME_HOST=${GNUPGHOME_HOST:-"${VARLIB}/gnupg-host"}
 GNUPGHOME_AUTHENTICATION=${GNUPGHOME_AUTHENTICATION:-"${VARLIB}/gnupg-authentication"}
 
-# set default GNUPGHOME, and make sure the directory exists.  this is
-# true for all functions expect user authentication
-# (ie. update-users).
-GNUPGHOME="$GNUPGHOME_HOST"
+# export variables
+export MODE
+export MONKEYSPHERE_USER
+export KEYSERVER
+export CHECK_KEYSERVER
+export REQUIRED_USER_KEY_CAPABILITY
+export GNUPGHOME_HOST
+export GNUPGHOME_AUTHENTICATION
 export GNUPGHOME
-mkdir -p -m 0700 "$GNUPGHOME"
 
 case $COMMAND in
     'update-users'|'update-user'|'u')
@@ -189,14 +317,17 @@ case $COMMAND in
 	# set mode
 	MODE="authorized_keys"
 
+	# set gnupg home
+	GNUPGHOME="$GNUPGHOME_AUTHENTICATION"
+
+	# check to see if the gpg trust database has been initialized
+	if [ ! -s "${GNUPGHOME}/trustdb.gpg" ] ; then
+	    failure "GNUPG trust database uninitialized.  Please see MONKEYSPHERE-SERVER(8)."
+	fi
+
         # make sure the authorized_keys directory exists
 	mkdir -p "${VARLIB}/authorized_keys"
 
-	# set GNUPGHOME, and make sure the directory exists
-	GNUPGHOME="$GNUPGHOME_AUTHENTICATION"
-	export GNUPGHOME
-	mkdir -p -m 0700 "$GNUPGHOME"
-
 	# loop over users
 	for uname in $unames ; do
 	    # check all specified users exist
@@ -211,67 +342,96 @@ case $COMMAND in
 	    rawAuthorizedKeys=$(translate_ssh_variables "$uname" "$RAW_AUTHORIZED_KEYS")
 
 	    # if neither is found, skip user
-	    if [ ! -s "$authorizedUserIDs" -a ! -s "$rawAuthorizedKeys" ] ; then
-		continue
+	    if [ ! -s "$authorizedUserIDs" ] ; then
+		if [ "$rawAuthorizedKeys" = '-' -o ! -s "$rawAuthorizedKeys" ] ; then
+		    continue
+		fi
 	    fi
 
 	    log "----- user: $uname -----"
 
-	    # temporary authorized_keys file
-	    AUTHORIZED_KEYS=$(mktemp)
+            # make temporary directory
+            TMPDIR=$(mktemp -d)
+
+	    # trap to delete temporary directory on exit
+	    trap "rm -rf $TMPDIR" EXIT
+
+            # create temporary authorized_user_ids file
+            TMP_AUTHORIZED_USER_IDS="${TMPDIR}/authorized_user_ids"
+            touch "$TMP_AUTHORIZED_USER_IDS"
 
-	    # trap to delete file on exit
-	    trap "rm -f $AUTHORIZE_KEYS" EXIT
+            # create temporary authorized_keys file
+            AUTHORIZED_KEYS="${TMPDIR}/authorized_keys"
+            touch "$AUTHORIZED_KEYS"
 
-	    # process authorized_user_ids file
+            # set restrictive permissions on the temporary files
+	    # FIXME: is there a better way to do this?
+            chmod 0700 "$TMPDIR"
+            chmod 0600 "$AUTHORIZED_KEYS"
+            chmod 0600 "$TMP_AUTHORIZED_USER_IDS"
+            chown -R "$MONKEYSPHERE_USER" "$TMPDIR"
+
+	    # if the authorized_user_ids file exists...
 	    if [ -s "$authorizedUserIDs" ] ; then
-		log "processing authorized_user_ids file..."
-		process_authorized_user_ids "$authorizedUserIDs"
+                # copy user authorized_user_ids file to temporary
+                # location
+		cat "$authorizedUserIDs" > "$TMP_AUTHORIZED_USER_IDS"
+
+		# export needed variables
+		export AUTHORIZED_KEYS
+		export TMP_AUTHORIZED_USER_IDS
+
+		# process authorized_user_ids file, as monkeysphere
+		# user
+		su --preserve-environment "$MONKEYSPHERE_USER" -c -- \
+		    ". ${SHARE}/common; process_authorized_user_ids $TMP_AUTHORIZED_USER_IDS"
 	    fi
 
 	    # add user-controlled authorized_keys file path if specified
-	    if [ "$RAW_AUTHORIZED_KEYS" != '-' ] ; then
-		if [ -s "$rawAuthorizedKeys" ] ; then
-		    log -n "adding raw authorized_keys file... "
-		    cat "$rawAuthorizedKeys" >> "$AUTHORIZED_KEYS"
-		    loge "done."
-		fi
+	    if [ "$rawAuthorizedKeys" != '-' -a -s "$rawAuthorizedKeys" ] ; then
+		log -n "adding raw authorized_keys file... "
+		cat "$rawAuthorizedKeys" >> "$AUTHORIZED_KEYS"
+		loge "done."
 	    fi
 
+	    # openssh appears to check the contents of the
+            # authorized_keys file as the user in question, so the
+            # file must be readable by that user at least.
+	    # FIXME: is there a better way to do this?
+	    chown root "$AUTHORIZED_KEYS"
+	    chgrp $(getent passwd "$uname" | cut -f4 -d:) "$AUTHORIZED_KEYS"
+	    chmod g+r "$AUTHORIZED_KEYS"
+
 	    # if the resulting authorized_keys file is not empty, move
-	    # the temp authorized_keys file into place
-	    if [ -s "$AUTHORIZED_KEYS" ] ; then
-		# openssh appears to check the contents of the
-                # authorized_keys file as the user in question, so the
-                # file must be readable by that user at least.
-		# FIXME: is there a better way to do this?
-		chgrp $(getent passwd "$uname" | cut -f4 -d:) "$AUTHORIZED_KEYS"
-		chmod g+r "$AUTHORIZED_KEYS"
-
-		mv -f "$AUTHORIZED_KEYS" "${VARLIB}/authorized_keys/${uname}"
-
-		log "authorized_keys file updated."
-
-	    # else destroy it
-	    else
-		rm -f "$AUTHORIZED_KEYS"
-	    fi
+	    # it into place
+	    mv -f "$AUTHORIZED_KEYS" "${VARLIB}/authorized_keys/${uname}"
+
+	    log "authorized_keys file updated."
+	    
+	    # destroy temporary directory
+	    rm -rf "$TMPDIR"
 	done
 	;;
 
     'gen-key'|'g')
-	gen_key "$1"
+	# set gnupg home
+	GNUPGHOME="$GNUPGHOME_HOST"
+	gen_key "$@"
 	;;
 
     'show-fingerprint'|'f')
+	# set gnupg home
+	GNUPGHOME="$GNUPGHOME_HOST"
 	fingerprint_server_key "$@"
 	;;
 
     'publish-key'|'p')
+	# set gnupg home
+	GNUPGHOME="$GNUPGHOME_HOST"
 	publish_server_key
 	;;
 
-    'trust-key'|'trust-key'|'t')
+    'trust-key'|'t')
 	trust_key "$@"
 	;;