Priviledge separation: use new monkeysphere user to handle
authorJameson Graef Rollins <jrollins@phys.columbia.edu>
Tue, 24 Jun 2008 17:53:22 +0000 (13:53 -0400)
committerJameson Graef Rollins <jrollins@phys.columbia.edu>
Tue, 24 Jun 2008 21:50:26 +0000 (17:50 -0400)
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.

debian/changelog
debian/control
debian/monkeysphere.postinst [new file with mode: 0755]
debian/monkeysphere.postrm [new file with mode: 0755]
man/man8/monkeysphere-server.8
src/common
src/monkeysphere
src/monkeysphere-server

index 82f274a02f442d2988eaf4a447f61944487c7eb7..c6b5de4ab95cef842d38403abbace95d65992bd5 100644 (file)
@@ -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
 
index 4f0e5f5ef72a9ab5f593748fb7840374a2e264f6..f5760d9af9300a6d6138ebe53c26663954122e20 100644 (file)
@@ -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 (executable)
index 0000000..50eaefa
--- /dev/null
@@ -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 (executable)
index 0000000..a103fc8
--- /dev/null
@@ -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
index 9bb7b2d51e8547f36e18df8a5df7b86a3e1e42cb..dbcc083f9bb7ec1c38883fd773f193a2174fa2ed 100644 (file)
@@ -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
index ead3736d7241ae1709dceff82494fc66b17e6dfb..42de18dda87e1088abcbf151ddbef33798ea2d07 100644 (file)
@@ -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)"
-}
index d8d4667c9201a6b286527d39aef6ce07916981dc..15a2a7aa48d32993112244223126ea6e758f02f0 100755 (executable)
@@ -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."
        ;;
index ac7c1cbca3cac6b12e3303338a3cc4b6470f4aff..4c403f2a2647ea4f074a8bad5637ad134190a97d 100755 (executable)
@@ -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 "$@"
        ;;