#!/bin/sh
set -e -u

# Example Proxy-Authorization:
#Digest username="*1337",realm="cy.sip.incenova.com",cnonce="6b8b4567",
#nc=00000001,qop="auth",uri="sip:*9000@cy.sip.incenova.com",
#nonce="c7903793-a86b-4129-98f0-e8893d44f3c1",
#response="0ea0ce64854f6d6251a051a0572d75aa",algorithm=MD5
if [ $# -ne 5 ]; then
    echo "Usage: username realm password digestUri nonce"
    exit 1
fi
username=$1
realm=$2
password=$3
method=INVITE
digestURI=$4
nonce=$5
qop=

DEBUG() {
    : "$@" >&2
}


# HA1=MD5(username:realm:password)
# HA2=MD5(method:digestURI)
# response=MD5(HA1:nonce:HA2)
# response=MD5(HA1:nonce:nonceCount:clientNonce:qop:HA2)    # when qop is given

MD5() {
    for arg; do DEBUG printf ' "%s"' "$arg"; done
    DEBUG echo
    printf "$@" | md5sum | cut -d' ' -f1 | tr -d '\n'
}

HA1=$(MD5 '%s:%s:%s' "$username" "$realm" "$password")
HA2=$(MD5 '%s:%s' "$method" "$digestURI")

if [ -z "$qop" ]; then
    MD5 "%s:%s:%s" "$HA1" "$nonce" "$HA2"
else
    MD5 "%s:%s:%s:%s:%s:%s" \
        "$HA1" "$nonce" "$nonceCount" "$clientNonce" "$qop" "$HA2"
fi
echo