A script to verify files match cryptographic hashses

assert-hash.sh

#!/bin/bash

usage() {
    echo "Usage: assert-hash [type] file hash"
    echo "[type] is the type of hash to use, it is optional, and defaults to sha256"
    echo "file is the file to hash"
    echo "hash is the hash you want to assert the file has"
}

if [[ $# == 2 ]]; then
    TYPE="sha256"
    FILE="$1";
    DESIRED_HASH="$2";
elif [[ $# == 3 ]]; then
    TYPE="$1";
    FILE="$2";
    DESIRED_HASH="$3";
else
    echo "Invalid number of arguments $#"
    usage
    exit 1;
fi;

DESIRED_HASH=$(echo "$DESIRED_HASH" | awk '{print(tolower($1))}')

if [ ! -f "$FILE" ]; then
    echo "File '$FILE' not found"
    exit 1;
fi;

case "$TYPE" in
    "md5" )
        echo "MD5 is insecure"
        echo "A bad person can fake the hash if they want too"
        echo "Do *NOT* rely on the validity of this hash for security"
        ;&
    "sha256" | "sha512" | "sha1" )
        HASH=$(openssl dgst -r -$TYPE $FILE | sed -r 's/(\w+).*/\1/')
        if [[ "$HASH" == "$DESIRED_HASH" ]]; then
            echo "OK $HASH";
            exit 0;
        else
            echo "INVALID $HASH";
            exit 2;
        fi;
        ;;
    "*" )
        echo "Unknown hash $TYPE"
        ;;
esac;