Sometimes, you are asked to implement some unusual Single Sign On methods. This code helps to deal with Digest based SSO when configured. This specific implementation support a Quality-of-protection set to "auth".
How to use this snippet:
Proof of Concept
Generate a valid Digest response
when hitting "/test", the irule build the Digest response and log it to the ltm log file.
when RULE_INIT {
set static::nonce "MDgvMjUvMjAxNyAwOToyNTo0Nw"
set static::user "testuser"
set static::password "testpass"
set static::realm "testrealm"
set static::method "GET"
set static::uri "/testuri"
set static::client_nonce "389db6597243daf2"
set static::nonce_count "00000001"
}
when HTTP_REQUEST {
# working test
if { [HTTP::uri] eq "/test" } {
binary scan [md5 "$static::user:$static::realm:$static::password"] H* ha1
log local0. "HA1 = $ha1"
binary scan [md5 "$static::method:$static::uri"] H* ha2
log local0. "HA2 = $ha2"
binary scan [md5 "$ha1:$static::nonce:$static::nonce_count:$static::client_nonce:auth:$ha2"] H* response
log local0. "response = $response"
}
}
Play Digest SSO when receiving a 401 response from the backend
note : Client Nonce is currently a static variable. Must be generated within the irule instead.
when RULE_INIT {
set static::user "testuser"
set static::password "testpass"
set static::client_nonce "389db6597243daf2"
set static::nonce_count "00000001"
}
when HTTP_REQUEST {
# set vars required for Digest SSO
set uri [HTTP::uri]
set method [HTTP::method]
set retried 0
# insert a dummy text. Help to inject Digest SSO
HTTP::header replace Authorization "irule-test-digest-sso"
set request [HTTP::request]
HTTP::header remove Authorization
}
when HTTP_RESPONSE {
if { [HTTP::status] contains "401" and [HTTP::header exists "WWW-Authenticate"] and [HTTP::header "WWW-Authenticate"] contains "Digest" and $retried == 0 } {
set www_auth [HTTP::header "WWW-Authenticate"]
set fields [split $www_auth ","]
set realm [lindex [split [lindex $fields 0] "="] 1]
set nonce [lindex [split [lindex $fields 1] "="] 1]
# retrieve username and password from wherever you want. Can be APM, Basic authentication, ...
binary scan [md5 "$static::user:$realm:$static::password"] H* ha1
binary scan [md5 "$method:$uri"] H* ha2
binary scan [md5 "$ha1:$nonce:$static::nonce_count:$static::client_nonce:auth:$ha2"] H* response
set retried 1
set auth_value "Digest username=\"$static::user\", realm=\"$realm\", nonce=\"$nonce\", uri=\"$uri\", algorithm=MD5, response=\"$response\", opaque=\"0000000000000000\", qop=auth, nc=$static::nonce_count, cnonce=\"$static::client_nonce\""
# insert Authorization header with Digest
set updated_request [string map "$find $auth_value" $request]
# resend the request with the Authorization header filled
HTTP::retry $updated_request
} else {
set retried 0
}
}
Code :
when RULE_INIT {
set static::user "testuser"
set static::password "testpass"
set static::client_nonce "389db6597243daf2"
set static::nonce_count "00000001"
}
when HTTP_REQUEST {
# set vars required for Digest SSO
set uri [HTTP::uri]
set method [HTTP::method]
set retried 0
# insert a dummy text. Help to inject Digest SSO
HTTP::header replace Authorization "irule-test-digest-sso"
set request [HTTP::request]
HTTP::header remove Authorization
}
when HTTP_RESPONSE {
if { [HTTP::status] contains "401" and [HTTP::header exists "WWW-Authenticate"] and [HTTP::header "WWW-Authenticate"] contains "Digest" and $retried == 0 } {
set www_auth [HTTP::header "WWW-Authenticate"]
set fields [split $www_auth ","]
set realm [lindex [split [lindex $fields 0] "="] 1]
set nonce [lindex [split [lindex $fields 1] "="] 1]
# retrieve username and password from wherever you want. Can be APM, Basic authentication, ...
binary scan [md5 "$static::user:$realm:$static::password"] H* ha1
binary scan [md5 "$method:$uri"] H* ha2
binary scan [md5 "$ha1:$nonce:$static::nonce_count:$static::client_nonce:auth:$ha2"] H* response
set retried 1
set auth_value "Digest username=\"$static::user\", realm=\"$realm\", nonce=\"$nonce\", uri=\"$uri\", algorithm=MD5, response=\"$response\", opaque=\"0000000000000000\", qop=auth, nc=$static::nonce_count, cnonce=\"$static::client_nonce\""
# insert Authorization header with Digest
set updated_request [string map "$find $auth_value" $request]
# resend the request with the Authorization header filled
HTTP::retry $updated_request
} else {
set retried 0
}
}
1/ The server nonce value might contain equal sign so the above code will chop it off in an unintended way.
2/ It would need a condition block in HTTP_REQUEST to identify if it is a request from HTTP::retry.
when RULE_INIT {
set static::user "testuser"
set static::password "testpass"
set static::client_nonce "389db6597243daf2"
set static::nonce_count "00000001"
}
when CLIENT_ACCEPTED {
set retried 0
}
when HTTP_REQUEST {
if { ${retried} == 0 } {
set vars required for Digest SSO
set uri [HTTP::uri]
set method [HTTP::method]
set retried 0
insert a dummy text. Help to inject Digest SSO
HTTP::header replace Authorization "irule-test-digest-sso"
set request [HTTP::request]
HTTP::header remove Authorization
}
}
when HTTP_RESPONSE {
if { [HTTP::status] contains "401" and [HTTP::header exists "WWW-Authenticate"] and [HTTP::header "WWW-Authenticate"] contains "Digest" and $retried == 0 } {
set www_auth [HTTP::header "WWW-Authenticate"]
basically chop the "realm=" and "nonce=" using strictly string functions
set realm [string range ${www_auth} [expr {[string first "realm=" ${www_auth}] + 7}] [expr {[string first "," ${www_auth} [string first "realm=" ${www_auth}]] - 2}]]
set nonce [string range ${www_auth} [expr {[string first "nonce=" ${www_auth}] + 7}] [expr {[string first "," ${www_auth} [string first "nonce=" ${www_auth}]] - 2}]]
retrieve username and password from wherever you want. Can be APM, Basic authentication, ...
binary scan [md5 "$static::user:$realm:$static::password"] H* ha1
binary scan [md5 "$method:$uri"] H* ha2
binary scan [md5 "$ha1:$nonce:$static::nonce_count:$static::client_nonce:auth:$ha2"] H* response
set retried 1
set auth_value "Digest username=\"$static::user\", realm=\"$realm\", nonce=\"$nonce\", uri=\"$uri\", algorithm=MD5, response=\"$response\", qop=auth, nc=$static::nonce_count, cnonce=\"$static::client_nonce\""
insert Authorization header with Digest
set updated_request [string map [list "irule-test-digest-sso" "$auth_value"] $request]
resend the request with the Authorization header filled
HTTP::retry $updated_request
} else {
set retried 0
}
}
Hopefully this would help someone working on this trick.
