#!/bin/bash

#
# Black Magic - the script
# by: Aaron Conole <apconole@yahoo.com>
#

# Released under the 3-clause BSD License, which I won't include here verbatim.
# Essentially, give me credit and don't you forget it.

PATH=/usr/bin:/bin

GDB=`which gdb`
WHO=`id -un`
PS=`which ps`
GREP=`which grep`
HEAD=`which head`
AWK=`which awk`
READLINK=`which readlink`
MKTEMP=`which mktemp`
RM=`which rm`

BINARY=""

print_help()
{
    echo "Black Magic shell script. WARNING: this does dangerous and completely"
    echo "-INSANE- things to running processes. Don't blame me if you create"
    echo "extreme havok on your systems."
    echo ""
    echo "Options:"
    echo ""
    echo "Set one or the other (or both)"
    echo "--pid <number>"
    echo "--binary <path>"
    echo ""
    echo "Specify the posix function to run"
    echo "--function <function>"
    echo ""
    echo "Arguments to function (provide in-order)"
    echo "--string \"<some value>\""
    echo "--literal <some value>"
    echo ""
    echo "String's are quoted. Literals are not."
}

if [ "$1" = "-h" -o "$1" = "--help" ]; then
    print_help
    
    exit 0
fi

PROCESS_PID=0
PROCESS_BINARY=""

POSIX_FUNCTION=""
POSIX_FUNCTION_ARGS=""

while [ $# -gt 0 ]; do
    case "$1" in
        --pid)
            shift
            echo "Setting PID: $1"
            PROCESS_PID=$1
            ;;
        --binary)
            shift
            echo "Setting binary: $1"
            PROCESS_BINARY=$1
            ;;
        --function)
            shift
            echo "Will call: $1"
            POSIX_FUNCTION=$1
            ;;

        --string)
            shift
            if [ "$POSIX_FUNCTION_ARGS" != "" ]; then
                POSIX_FUNCTION_ARGS="$POSIX_FUNCTION_ARGS, \"$1\""
            else
                POSIX_FUNCTION_ARGS="\"$1\""
            fi
            ;;

        --literal)
            shift
            if [ "$POSIX_FUNCTION_ARGS" != "" ]; then
                POSIX_FUNCTION_ARGS="$POSIX_FUNCTION_ARGS, $1"
            else
                POSIX_FUNCTION_ARGS="$1"
            fi
            ;;
        *)
            print_help
            echo "Error: Unknown option \"$1\""
            exit 1
            ;;
        esac
    shift
done

if [ $PROCESS_PID -eq 0 -a "$PROCESS_BINARY" == "" ]; then
    print_help
    echo "ERROR: Must set at LEAST process PID or BINARY"
    exit 1
fi

if [ "$POSIX_FUNCTION" == "" ]; then
    print_help
    echo "ERROR: Must set at LEAST a posix function"
    exit 1
fi

if [ $PROCESS_PID -eq 0 ]; then
    PROCESS_PID=`$PS aux | $GREP ${WHO} | $GREP ${PROCESS_BINARY} | $HEAD -n 1 | $CUT -d" " -f2`
    if [ "$PROCESS_PID" == "" ]; then
        PROCESS_BIN_NAME=`$BASENAME ${PROCESS_BINARY}`
        PROCESS_PID=`$PS aux | $GREP ${WHO} | $GREP ${PROCESS_BIN_NAME} | $HEAD -n 1 | $AWK '{print $2}'`
    fi
    if [ "$PROCESS_PID" == "" ]; then
        print_help
        echo "ERROR: unknown binary. best specify both on the command line."
        exit 1
    fi
fi

if [ "$PROCESS_BINARY" == "" ]; then
    PROCESS_BINARY=`$READLINK -f /proc/${PROCESS_PID}/exe`
    if [ "$PROCESS_BINARY" == "" ]; then
        print_help
        echo "ERROR: couldn't get process name from ID. Best specify both."
        exit 1
    fi
    
fi

POSIX_CALL="$POSIX_FUNCTION($POSIX_FUNCTION_ARGS)"
TMPFILE=`$MKTEMP`

echo "Black magic about to happen"
echo "---------------------------"
echo ""
echo "Modify running image of: $PROCESS_BINARY"
echo "Image PID: $PROCESS_PID"
echo "Function call looks like: ${POSIX_CALL}"
echo "Temporary file: $TMPFILE"
echo ""
echo "Pray!"

cat > $TMPFILE <<EOF
attach ${PROCESS_PID}
call ${POSIX_CALL}
detach
quit
EOF

$GDB $PROCESS_BINARY -x $TMPFILE

$RM $TMPFILE

echo "Done - hope it worked"