#!/bin/sh

# @(#)pmcheck	1.9 (PGP Moose) 96/03/04
# Authorisation checking script for PGP Moose
# Written by Greg Rose, RoSecure Software, Copyright C 1995.

# Configuration:
    # Where to create temporary files.
    TMP=/tmp

    # Name of the file with valid moderator's/individual's names
    ACCEPT=PGP_Moose_accept

# End Configuration

# Be neat and tidy.
TF=$TMP/pmcheck$$
trap "rm -f $TF.?; exit 1" 1 2 3 15

VERBOSE=false
# Usage: $0 [newsgroup|user] [filename]
case $# in
0)
    VERBOSE=true
    NEWSGROUP=any
    cat >$TF.f
    FILE=$TF.f
    FILENAME="standard input"
    ;;
1)
    if [ -f "$1" ]; then
	VERBOSE=true
	NEWSGROUP=any
	FILE="$1"
	FILENAME="$1"
    else
	cat >$TF.f
	FILE=$TF.f
	FILENAME="standard input"
	NEWSGROUP="$1"
    fi
    ;;
2)
    NEWSGROUP="$1"
    FILE="$2"
    FILENAME="$2"
    ;;
*)
    echo >&2 "Usage: $0 [newsgroup|user] [article]"
    echo >&2 "       newsgroup may be "any" to check all signatures."
    exit 1
    ;;
esac

# Find all the authentication headers we can handle
grep -i '^X-Auth.*:  *PGPMoose ' $FILE | \
    sed -e 's/.* //' >$TF.g

# For the time being, simply avoid cancel messages.
# Note that pmdaemon authenticates them, but you probably don't
# want to cancel them.
if grep -i -s '^Control:[ 	]*cancel' $FILE >/dev/null; then
    rm -f $TF.?
    exit 0
fi

# The designated newsgroup must be validated.
if [ "x$NEWSGROUP" != "xany" ]; then
    grep -i -s "^$NEWSGROUP\$" $TF.g >/dev/null || {
	echo >&2 "$0: Posting for $NEWSGROUP not approved with PGP Moose."
	rm -f $TF.?
	exit 1
    }
    # Uncomment this line if you only want to check this one group
    echo "$NEWSGROUP" >$TF.g
fi

# Make the document we are going to check signatures on.
pmcanon $FILE >$TF.m
    
# Loop checking all X-Auth: lines required
echo 0 >$TF.b
while read GROUP; do
    # Check whether this is an interesting X-Auth: line.
    # This is determined by the existence of the $ACCEPT file.
    # If it exists, only the groups/individuals mentioned are
    # relevent. Otherwise, check everything in sight, but don't
    # worry if you can't find a key or the signature doesn't match.
    # CONTROLLED is 0 if there is a $ACCEPT file and this group/user is
    # in it.
    [ -f "$ACCEPT" ] && grep -i -s "^$GROUP[ 	]" "$ACCEPT" >/dev/null
    CONTROLLED=$?
    if [ "$CONTROLLED" != 0 -a "$NEWSGROUP" != "any" ]; then
	continue
    fi
    # $1      $2       $3   $4  $5
    # X-Auth: PGPMoose V1.1 PGP sci.crypt.research
    set -- `grep -i "^X-Auth.*:  *PGPMoose .* $GROUP\$" $FILE`

    # Check for version mismatch, but at the moment we just warn.
    # It is pretty hard to know just what to do in this case.
    if [ "$3" != "V2.0" -o "$4" != "PGP" ]; then
	echo >&2 "$0: warning: version mismatch V2.0 PGP != $3 $4"
    fi

    # reconstruct the input signature file.
    cat <<-END_OF_SIG >$TF.s
	-----BEGIN PGP SIGNATURE-----
	Version: GnuPG v1.4.5 (NetBSD)

	END_OF_SIG
    sed -n -e "1,/^[Xx]-[Aa][Uu][Tt][Hh].*:  *PGPMoose .* $GROUP\$/d" \
	-e '/^ *$/,$d' \
	-e '/^[^ 	]/,$d' \
	-e 's/^[ 	]*//p' \
	$FILE >>$TF.s
    cat <<-END_OF_SIG >>$TF.s
	-----END PGP SIGNATURE-----
	END_OF_SIG

    # Now we can check the signature.
    gpg --verify $TF.s $TF.m >$TF.e 2>&1
    STATUS=$?
#    cat >&2 $TF.s 
#    echo ====
#    cat >&2 $TF.m 
#    echo ====
#    cat >&2 $TF.e 

    # If this is a target newsgroup/user, any error is bad news.
    if [ "$CONTROLLED" = 0 -a $STATUS != 0 ]; then
	echo >&2 "$0: Invalid designated signature from $GROUP"
	echo 2 >$TF.b
	continue
    fi
    # There are various understood error codes, not to mention the others...
    # These codes come from the PGP source, and are probably not immutable.
    case "$STATUS" in
    0)
	# signature checks out... handle that case below
	;;
    11)
	# Non-existent key
	if [ "$VERBOSE" = true ]; then
	    echo "No public key for signature $GROUP"
	fi
	continue
	;;
    30)
	# Signature check error
	$VERBOSE || echo >&2 "Signature doesn't match $FILE for $GROUP"
	echo 2 >$TF.b
	continue
	;;
    *)
	# Some other unknown error. Treat same as Non-existent key.
	if [ "$VERBOSE" = true ]; then
	    echo "Unknown PGP error, status = $STATUS"
	    cat $TF.e
	fi
	continue
	;;
    esac

    SIG=`sed -n 's/gpg: Good signature from "\(.*\)"/\1/p' $TF.e`
    if [ "x$SIG" = "x" ]; then
	# this one "can't happen"
	echo >&2 "$0: MOOSE ERROR: Invalid signature for $GROUP on $FILE."
    fi
    if [ "$VERBOSE" = "true" ]; then
	echo "$0: Verified signature from '$SIG'."
    fi

    # Finally, was it signed by the right person?
    if [ "$CONTROLLED" = 0 ]; then
	grep -i -s "^$GROUP[	 ]*$SIG\$" "$ACCEPT" >/dev/null || {
	    echo >&2 "$0: '$SIG' not accepted for $GROUP."
	    echo 2 >$TF.b
	}
    fi
done <$TF.g

BADSIG=`cat $TF.b`
rm -f $TF.?
exit $BADSIG