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|
# sasl.tcl - Copyright (C) 2005 Pat Thoyts <patthoyts@users.sourceforge.net>
#
# This is an implementation of a general purpose SASL library for use in
# Tcl scripts.
#
# References:
# Myers, J., "Simple Authentication and Security Layer (SASL)",
# RFC 2222, October 1997.
# Rose, M.T., "TclSASL", "http://beepcore-tcl.sourceforge.net/tclsasl.html"
#
# -------------------------------------------------------------------------
# See the file "license.terms" for information on usage and redistribution
# of this file, and for a DISCLAIMER OF ALL WARRANTIES.
# -------------------------------------------------------------------------
package require Tcl 8.2
namespace eval ::SASL {
variable uid
if {![info exists uid]} { set uid 0 }
variable mechanisms
if {![info exists mechanisms]} {
set mechanisms [list]
}
}
# SASL::mechanisms --
#
# Return a list of available SASL mechanisms. By default only the
# client implementations are given but if type is set to server then
# the list of available server mechanisms is returned.
# No mechanism with a preference value less than 'minimum' will be
# returned.
# The list is sorted by the security preference with the most secure
# mechanisms given first.
#
proc ::SASL::mechanisms {{type client} {minimum 0}} {
variable mechanisms
set r [list]
foreach mech $mechanisms {
if {[lindex $mech 0] < $minimum} { continue }
switch -exact -- $type {
client {
if {[string length [lindex $mech 2]] > 0} {
lappend r [lindex $mech 1]
}
}
server {
if {[string length [lindex $mech 3]] > 0} {
lappend r [lindex $mech 1]
}
}
default {
return -code error "invalid type \"$type\":\
must be either client or server"
}
}
}
return $r
}
# SASL::register --
#
# Register a new SASL mechanism with a security preference. Higher
# preference values are chosen before lower valued mechanisms.
# If no server implementation is available then an empty string
# should be provided for the serverproc parameter.
#
proc ::SASL::register {mechanism preference clientproc {serverproc {}}} {
variable mechanisms
set ndx [lsearch -regexp $mechanisms $mechanism]
set mech [list $preference $mechanism $clientproc $serverproc]
if {$ndx == -1} {
lappend mechanisms $mech
} else {
set mechanisms [lreplace $mechanisms $ndx $ndx $mech]
}
set mechanisms [lsort -index 0 -decreasing -integer $mechanisms]
return
}
# SASL::uid --
#
# Return a unique integer.
#
proc ::SASL::uid {} {
variable uid
return [incr uid]
}
# SASL::response --
#
# Get the reponse string from the SASL state.
#
proc ::SASL::response {context} {
upvar #0 $context ctx
return $ctx(response)
}
# SASL::reset --
#
# Reset the SASL state. This permits the same instance to be reused
# for a new round of authentication.
#
proc ::SASL::reset {context {step 0}} {
upvar #0 $context ctx
array set ctx [list step $step response "" valid false count 0]
return $context
}
# SASL::cleanup --
#
# Free any resources used with the SASL state.
#
proc ::SASL::cleanup {context} {
if {[info exists $context]} {
unset $context
}
return
}
# SASL::new --
#
# Create a new SASL instance.
#
proc ::SASL::new {args} {
set context [namespace current]::[uid]
upvar #0 $context ctx
array set ctx [list mech {} callback {} proc {} service smtp server {} \
step 0 response "" valid false type client count 0]
eval [linsert $args 0 [namespace origin configure] $context]
return $context
}
# SASL::configure --
#
# Configure the SASL state.
#
proc ::SASL::configure {context args} {
variable mechanisms
upvar #0 $context ctx
while {[string match -* [set option [lindex $args 0]]]} {
switch -exact -- $option {
-service {
set ctx(service) [Pop args 1]
}
-server - -serverFQDN {
set ctx(server) [Pop args 1]
}
-mech - -mechanism {
set mech [string toupper [Pop args 1]]
set ctx(proc) {}
foreach m $mechanisms {
if {[string equal [lindex $m 1] $mech]} {
set ctx(mech) $mech
if {[string equal $ctx(type) "server"]} {
set ctx(proc) [lindex $m 3]
} else {
set ctx(proc) [lindex $m 2]
}
break
}
}
if {[string equal $ctx(proc) {}]} {
return -code error "mechanism \"$mech\" not available:\
must be one of those given by \[sasl::mechanisms\]"
}
}
-callback - -callbacks {
set ctx(callback) [Pop args 1]
}
-type {
set type [Pop args 1]
if {[lsearch -exact {server client} $type] != -1} {
set ctx(type) $type
if {![string equal $ctx(mech) ""]} {
configure $context -mechanism $ctx(mech)
}
} else {
return -code error "bad value \"$type\":\
must be either client or server"
}
}
default {
return -code error "bad option \"$option\":\
must be one of -mechanism, -service, -server -type\
or -callbacks"
}
}
Pop args
}
}
proc ::SASL::step {context challenge args} {
upvar #0 $context ctx
incr ctx(count)
return [eval [linsert $args 0 $ctx(proc) $context $challenge]]
}
proc ::SASL::Pop {varname {nth 0}} {
upvar $varname args
set r [lindex $args $nth]
set args [lreplace $args $nth $nth]
return $r
}
proc ::SASL::md5_init {} {
variable md5_inited
if {[info exists md5_inited]} {return} else {set md5_inited 1}
# Deal with either version of md5. We'd like version 2 but someone
# may have already loaded version 1.
set md5major [lindex [split [package require md5] .] 0]
if {$md5major < 2} {
# md5 v1, no options, and returns a hex string ready for us.
proc ::SASL::md5_hex {data} { return [::md5::md5 $data] }
proc ::SASL::md5_bin {data} { return [binary format H* [::md5::md5 $data]] }
proc ::SASL::hmac_hex {pass data} { return [::md5::hmac $pass $data] }
proc ::SASL::hmac_bin {pass data} { return [binary format H* [::md5::hmac $pass $data]] }
} else {
# md5 v2 requires -hex to return hash as hex-encoded non-binary string.
proc ::SASL::md5_hex {data} { return [string tolower [::md5::md5 -hex $data]] }
proc ::SASL::md5_bin {data} { return [::md5::md5 $data] }
proc ::SASL::hmac_hex {pass data} { return [::md5::hmac -hex -key $pass $data] }
proc ::SASL::hmac_bin {pass data} { return [::md5::hmac -key $pass $data] }
}
}
# -------------------------------------------------------------------------
# CRAM-MD5 SASL MECHANISM
#
# Implementation of the Challenge-Response Authentication Mechanism
# (RFC2195).
#
# Comments:
# This mechanism passes a server generated string containing
# a timestamp and has the client generate an MD5 HMAC using the
# shared secret as the key and the server string as the data.
# The downside of this protocol is that the server must have access
# to the plaintext password.
#
proc ::SASL::CRAM-MD5:client {context challenge args} {
upvar #0 $context ctx
md5_init
if {$ctx(step) != 0} {
return -code error "unexpected state: CRAM-MD5 has only 1 step"
}
if {[string length $challenge] == 0} {
set ctx(response) ""
return 1
}
set password [eval $ctx(callback) [list $context password]]
set username [eval $ctx(callback) [list $context username]]
set reply [hmac_hex $password $challenge]
set reply "$username [string tolower $reply]"
set ctx(response) $reply
incr ctx(step)
return 0
}
proc ::SASL::CRAM-MD5:server {context clientrsp args} {
upvar #0 $context ctx
md5_init
incr ctx(step)
switch -exact -- $ctx(step) {
1 {
set ctx(realm) [eval $ctx(callback) [list $context realm]]
set ctx(response) "<[pid].[clock seconds]@$ctx(realm)>"
return 1
}
2 {
foreach {user hash} $clientrsp break
set hash [string tolower $hash]
set pass [eval $ctx(callback) [list $context password $user $ctx(realm)]]
set check [hmac_bin $pass $ctx(response)]
binary scan $check H* cx
if {[string equal $cx $hash]} {
return 0
} else {
return -code error "authentication failed"
}
}
default {
return -code error "invalid state"
}
}
}
::SASL::register CRAM-MD5 30 ::SASL::CRAM-MD5:client ::SASL::CRAM-MD5:server
# -------------------------------------------------------------------------
# PLAIN SASL MECHANISM
#
# Implementation of the single step login SASL mechanism (RFC2595).
#
# Comments:
# A single step mechanism in which the authorization ID, the
# authentication ID and password are all transmitted in plain
# text. This should not be used unless the channel is secured by
# some other means (such as SSL/TLS).
#
proc ::SASL::PLAIN:client {context challenge args} {
upvar #0 $context ctx
incr ctx(step)
set authzid [eval $ctx(callback) [list $context login]]
set username [eval $ctx(callback) [list $context username]]
set password [eval $ctx(callback) [list $context password]]
set ctx(response) "$authzid\x00$username\x00$password"
return 0
}
proc ::SASL::PLAIN:server {context clientrsp args} {
upvar \#0 $context ctx
if {[string length $clientrsp] < 1} {
set ctx(response) ""
return 1
} else {
foreach {authzid authid pass} [split $clientrsp \0] break
set realm [eval $ctx(callback) [list $context realm]]
set check [eval $ctx(callback) [list $context password $authid $realm]]
if {[string equal $pass $check]} {
return 0
} else {
return -code error "authentication failed"
}
}
}
::SASL::register PLAIN 10 ::SASL::PLAIN:client ::SASL::PLAIN:server
# -------------------------------------------------------------------------
# LOGIN SASL MECHANISM
#
# Implementation of the two step login SASL mechanism.
#
# Comments:
# This is an unofficial but widely deployed SASL mechanism somewhat
# akin to the PLAIN mechanism. Both the authentication ID and password
# are transmitted in plain text in response to server prompts.
#
# NOT RECOMMENDED for use in new protocol implementations.
#
proc ::SASL::LOGIN:client {context challenge args} {
upvar #0 $context ctx
if {$ctx(step) == 0 && [string length $challenge] == 0} {
set ctx(response) ""
return 1
}
incr ctx(step)
switch -exact -- $ctx(step) {
1 {
set ctx(response) [eval $ctx(callback) [list $context username]]
set r 1
}
2 {
set ctx(response) [eval $ctx(callback) [list $context password]]
set r 0
}
default {
return -code error "unexpected state \"$ctx(step)\":\
LOGIN has only 2 steps"
}
}
return $r
}
proc ::SASL::LOGIN:server {context clientrsp args} {
upvar #0 $context ctx
incr ctx(step)
switch -exact -- $ctx(step) {
1 {
set ctx(response) "Username:"
return 1
}
2 {
set ctx(username) $clientrsp
set ctx(response) "Password:"
return 1
}
3 {
set user $ctx(username)
set realm [eval $ctx(callback) [list $context realm]]
set pass [eval $ctx(callback) [list $context password $user $realm]]
if {[string equal $clientrsp $pass]} {
return 0
} else {
return -code error "authentication failed"
}
}
default {
return -code error "invalid state"
}
}
}
::SASL::register LOGIN 20 ::SASL::LOGIN:client ::SASL::LOGIN:server
# -------------------------------------------------------------------------
# ANONYMOUS SASL MECHANISM
#
# Implementation of the ANONYMOUS SASL mechanism (RFC2245).
#
# Comments:
#
#
proc ::SASL::ANONYMOUS:client {context challenge args} {
upvar #0 $context ctx
set user [eval $ctx(callback) [list $context username]]
set realm [eval $ctx(callback) [list $context realm]]
set ctx(response) $user@$realm
return 0
}
proc ::SASL::ANONYMOUS:server {context clientrsp args} {
upvar #0 $context ctx
set ctx(response) ""
if {[string length $clientrsp] < 1} {
if {$ctx(count) > 2} {
return -code error "authentication failed"
}
return 1
} else {
set ctx(trace) $clientrsp
return 0
}
}
::SASL::register ANONYMOUS 5 ::SASL::ANONYMOUS:client ::SASL::ANONYMOUS:server
# -------------------------------------------------------------------------
# DIGEST-MD5 SASL MECHANISM
#
# Implementation of the DIGEST-MD5 SASL mechanism (RFC2831).
#
# Comments:
#
proc ::SASL::DIGEST-MD5:client {context challenge args} {
upvar #0 $context ctx
md5_init
if {$ctx(step) == 0 && [string length $challenge] == 0} {
if {[info exists ctx(challenge)]} {
set challenge $ctx(challenge)
} else {
set ctx(response) ""
return 1
}
}
incr ctx(step)
set result 0
switch -exact -- $ctx(step) {
1 {
set ctx(challenge) $challenge
array set params [DigestParameters $challenge]
if {![info exists ctx(noncecount)]} {
set ctx(noncecount) 0
}
set nonce $params(nonce)
set cnonce [CreateNonce]
set noncecount [format %08u [incr ctx(noncecount)]]
set qop auth
# support the 'charset' parameter.
set username [eval $ctx(callback) [list $context username]]
set password [eval $ctx(callback) [list $context password]]
set encoding iso8859-1
if {[info exists params(charset)]} {
set encoding $params(charset)
}
set username [encoding convertto $encoding $username]
set password [encoding convertto $encoding $password]
if {[info exists params(realm)]} {
set realm $params(realm)
} else {
set realm [eval $ctx(callback) [list $context realm]]
}
set uri "$ctx(service)/$realm"
set R [DigestResponse $username $realm $password $uri \
$qop $nonce $noncecount $cnonce]
set ctx(response) "username=\"$username\",realm=\"$realm\",nonce=\"$nonce\",nc=\"$noncecount\",cnonce=\"$cnonce\",digest-uri=\"$uri\",response=\"$R\",qop=$qop"
if {[info exists params(charset)]} {
append ctx(response) ",charset=$params(charset)"
}
set result 1
}
2 {
set ctx(response) ""
set result 0
}
default {
return -code error "invalid state"
}
}
return $result
}
proc ::SASL::DIGEST-MD5:server {context challenge args} {
upvar #0 $context ctx
md5_init
incr ctx(step)
set result 0
switch -exact -- $ctx(step) {
1 {
set realm [eval $ctx(callback) [list $context realm]]
set ctx(nonce) [CreateNonce]
set ctx(nc) 0
set ctx(response) "realm=\"$realm\",nonce=\"$ctx(nonce)\",qop=\"auth\",charset=utf-8,algorithm=md5-sess"
set result 1
}
2 {
array set params [DigestParameters $challenge]
set realm [eval $ctx(callback) [list $context realm]]
set password [eval $ctx(callback)\
[list $context password $params(username) $realm]]
set uri "$ctx(service)/$realm"
set nc [format %08u [expr {$ctx(nc) + 1}]]
set R [DigestResponse $params(username) $realm $password \
$uri auth $ctx(nonce) $nc $params(cnonce)]
if {[string equal $R $params(response)]} {
set R2 [DigestResponse $params(username) $realm $password \
$uri auth $ctx(nonce) $nc $params(cnonce)]
set ctx(response) "rspauth=$R2"
incr ctx(nc)
set result 1
} else {
return -code error "authentication failed"
}
}
3 {
set ctx(response) ""
set result 0
}
default {
return -code error "invalid state"
}
}
return $result
}
# RFC 2831 2.1
# Char categories as per spec...
# Build up a regexp for splitting the challenge into key value pairs.
proc ::SASL::DigestParameters {challenge} {
set sep "\\\]\\\[\\\\()<>@,;:\\\"\\\?=\\\{\\\} \t"
set tok {0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz\-\|\~\!\#\$\%\&\*\+\.\^\_\`}
set sqot {(?:\'(?:\\.|[^\'\\])*\')}
set dqot {(?:\"(?:\\.|[^\"\\])*\")}
set parameters {}
regsub -all "(\[${tok}\]+)=(${dqot}|(?:\[${tok}\]+))(?:\[${sep}\]+|$)" $challenge {\1 \2 } parameters
return $parameters
}
# RFC 2831 2.1.2.1
#
proc ::SASL::DigestResponse {user realm pass uri qop nonce noncecount cnonce} {
set A1 [md5_bin "$user:$realm:$pass"]
set A2 "AUTHENTICATE:$uri"
if {![string equal $qop "auth"]} {
append A2 :[string repeat 0 32]
}
set A1h [md5_hex "${A1}:$nonce:$cnonce"]
set A2h [md5_hex $A2]
set R [md5_hex $A1h:$nonce:$noncecount:$cnonce:$qop:$A2h]
return $R
}
# RFC 2831 2.1.2.2
#
proc ::SASL::DigestResponse2 {user realm pass uri qop nonce noncecount cnonce} {
set A1 [md5_bin "$user:$realm:$pass"]
set A2 ":$uri"
if {![string equal $qop "auth"]} {
append A2 :[string repeat 0 32]
}
set A1h [md5_hex "${A1}:$nonce:$cnonce"]
set A2h [md5_hex $A2]
set R [md5_hex $A1h:$nonce:$noncecount:$cnonce:$qop:$A2h]
return $R
}
# Get 16 random bytes for a nonce value. If we can use /dev/random, do so
# otherwise we hash some values.
#
proc ::SASL::CreateNonce {} {
set bytes {}
if {[file readable /dev/urandom]} {
catch {
set f [open /dev/urandom r]
fconfigure $f -translation binary -buffering none
set bytes [read $f 16]
close $f
}
}
if {[string length $bytes] < 1} {
md5_init
set bytes [md5_bin [clock seconds]:[pid]:[expr {rand()}]]
}
return [binary scan $bytes h* r; set r]
}
::SASL::register DIGEST-MD5 40 \
::SASL::DIGEST-MD5:client ::SASL::DIGEST-MD5:server
# -------------------------------------------------------------------------
# OTP SASL MECHANISM
#
# Implementation of the OTP SASL mechanism (RFC2444).
#
# Comments:
#
# RFC 2289: A One-Time Password System
# RFC 2444: OTP SASL Mechanism
# RFC 2243: OTP Extended Responses
# Client initializes with authid\0authzid
# Server responds with extended OTP responses
# eg: otp-md5 498 bi32123 ext
# Client responds with otp result as:
# hex:xxxxxxxxxxxxxxxx
# or
# word:WWWW WWW WWWW WWWW WWWW
#
# To support changing the otp sequence the extended commands have:
# init-hex:<current>:<new params>:<new>
# eg: init-hex:xxxxxxxxxxxx:md5 499 seed987:xxxxxxxxxxxxxx
# or init-word
proc ::SASL::OTP:client {context challenge args} {
upvar #0 $context ctx
package require otp
incr ctx(step)
switch -exact -- $ctx(step) {
1 {
set authzid [eval $ctx(callback) [list $context login]]
set username [eval $ctx(callback) [list $context username]]
set ctx(response) "$authzid\x00$username"
set cont 1
}
2 {
foreach {type count seed ext} $challenge break
set type [lindex [split $type -] 1]
if {[lsearch -exact {md4 md5 sha1 rmd160} $type] == -1} {
return -code error "unsupported digest algorithm \"$type\":\
must be one of md4, md5, sha1 or rmd160"
}
set challenge [lrange $challenge 3 end]
set password [eval $ctx(callback) [list $context password]]
set otp [::otp::otp-$type -word -seed $seed \
-count $count $password]
if {[string match "ext*" $ext]} {
set otp word:$otp
}
set ctx(response) $otp
set cont 0
}
default {
return -code error "unexpected state \"$ctx(step)\":\
the SASL OTP mechanism only has 2 steps"
}
}
return $cont
}
::SASL::register OTP 45 ::SASL::OTP:client
# -------------------------------------------------------------------------
package provide SASL 1.3.3
# -------------------------------------------------------------------------
#
# Local variables:
# indent-tabs-mode: nil
# End:
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