1/* Part of SWI-Prolog 2 3 Author: Matt Lilley 4 E-mail: thetrime@gmail.com 5 WWW: http://www.swi-prolog.org 6 Copyright (c) 2004-2016, SWI-Prolog Foundation 7 VU University Amsterdam 8 All rights reserved. 9 10 Redistribution and use in source and binary forms, with or without 11 modification, are permitted provided that the following conditions 12 are met: 13 14 1. Redistributions of source code must retain the above copyright 15 notice, this list of conditions and the following disclaimer. 16 17 2. Redistributions in binary form must reproduce the above copyright 18 notice, this list of conditions and the following disclaimer in 19 the documentation and/or other materials provided with the 20 distribution. 21 22 THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 23 "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 24 LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS 25 FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 26 COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, 27 INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, 28 BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 29 LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER 30 CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 31 LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN 32 ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 33 POSSIBILITY OF SUCH DAMAGE. 34*/ 35 36:-module(saml, 37 [saml_authenticate/4]). 38 39:- autoload(library(base64),[base64/2]). 40:- autoload(library(crypto),[rsa_sign/4,hex_bytes/2]). 41:- use_module(library(debug),[debug/3,debugging/1]). 42:- autoload(library(error), 43 [domain_error/2,existence_error/2,permission_error/3]). 44:- autoload(library(lists),[member/2,subtract/3,select/3]). 45:- autoload(library(memfile), 46 [ new_memory_file/1, 47 open_memory_file/4, 48 memory_file_to_atom/2, 49 free_memory_file/1 50 ]). 51:- autoload(library(quintus),[otherwise/0]). 52:- autoload(library(sgml),[load_structure/3]). 53:- autoload(library(sgml_write),[xml_write/3]). 54:- autoload(library(sha),[sha_hash/3]). 55:- autoload(library(ssl), 56 [load_private_key/3,load_certificate/2,same_certificate/2]). 57:- autoload(library(url),[parse_url/2,parse_url_search/2]). 58:- autoload(library(uuid),[uuid/1]). 59:- autoload(library(xmldsig),[xmld_verify_signature/4]). 60:- autoload(library(xmlenc), 61 [load_certificate_from_base64_string/2,decrypt_xml/4]). 62:- autoload(library(zlib),[zopen/3]). 63:- autoload(library(http/http_client),[http_read_data/3]). 64:- autoload(library(http/http_dispatch),[http_redirect/3]). 65:- autoload(library(http/http_path),[http_absolute_location/3]). 66:- autoload(library(http/http_open),[http_open/3]).

SAML Authentication

This library uses SAML to exchange messages with an Identity Provider to establish assertions about the current user's session. It operates only as the service end, not the identity provider end.

There are four primary integration points for applications to use this code: 1) You must declare at least one service provider (SP) 2) You must declare at least one identity provider (IdP) per SP 3) Finally, you can call saml_authenticate(+SP, +IdP, +Callback, +Request) to obtain assertions The asynchronous nature of the SAML process means that a callback must be used. Assuming that the IdP was able to provide at least some valid assertions about the user, after calling Callback with 2 extra arguments (a list of the assertion terms and the URL being request by the user), the user will be redirected back to their original URL. It is therefore up to the callback to ensure that this does not simply trigger another round of SAML negotiations - for example, by throwing http_reply(forbidden(RequestURL)) if the assertions are not strong enough 4) Finally, your SP metadata will be available from the web server directly. This is required to configure the IdP. This will be available at './metadata.xml', relative to the LocationSpec provided when the SP was declared.

Configuring an SP: To declare an SP, use the declaration :-

saml_sp(+ServiceProvider: atom,
+LocationSpec: term,
+PrivateKeySpec: term,
+Password: atom
+CertificateSpec: term,
+Options: list)

The ServiceProvider is the identifier of your service. Ideally, this should be a fully-qualified URI The LocationSpec is a location that the HTTP dispatch layer will understand for example '.' or root('saml'). The Private KeySpec is a 'file specifier' that resolves to a private key (see below for specifiers) The Password is a password used for reading the private key. If the key is not encrypted, any atom can be supplied as it will be ignored The CertificateSpec is a file specifier that resolves to a certificate holding the public key corresponding to PrivateKeySPec There are currently no implemented options (the list is ignored).

Configuring an IdP: To declare an IdP, use the declaration :-

saml_idp(+ServiceProvider: atom,
+MetadataSpec: term)

. ServiceProvider is the identifier used when declaring your SP. You do not need to declare them in a particular order, but both must be present in the system before running saml_authenticate/4. MetadataSpec is a file specifier that resolves to the metadata for the IdP. Most IdPs will be able to provide this on request

File Specifiers: The following specifiers are supported for locating files:

file(Filename): The local file Filename
resource(Resource): The prolog resource Resource. See resource/3
url(URL): The file identified by the HTTP (or HTTPS if you have the HTTPS plugin loaded) URL

129user:term_expansion(:-saml_idp(ServiceProvider, MetadataFile), Clauses):- 130 saml_idp_clauses(ServiceProvider, MetadataFile, Clauses). 131 132user:term_expansion(:-saml_sp(ServiceProvider, Spec, KeyFile, Password, CertFile, Options), 133 [saml:saml_acs_path(ServiceProvider, ACSPath), 134 saml:saml_sp_certificate(ServiceProvider, Certificate, PEMData, PrivateKey), 135 ( :-http_handler(MetadataPath, saml:saml_metadata(ServiceProvider, Options), [])), 136 ( :-http_handler(ACSPath, saml:saml_acs_handler(ServiceProvider, Options), []))]):- 137 http_absolute_location(Spec, Root, []), 138 atom_concat(Root, '/auth', ACSPath), 139 atom_concat(Root, '/metadata.xml', MetadataPath), 140 read_key(KeyFile, Password, PrivateKey), 141 read_certificate(CertFile, Certificate, PEMData). 142 143read_key(Spec, Password, Key):- 144 setup_call_cleanup(open_spec(Spec, Stream), 145 load_private_key(Stream, Password, Key), 146 close(Stream)). 147 148read_certificate(Spec, Certificate, PEMData):- 149 setup_call_cleanup(open_spec(Spec, Stream1), 150 read_string(Stream1, _, PEMData), 151 close(Stream1)), 152 setup_call_cleanup(open_string(PEMData, Stream2), 153 load_certificate(Stream2, Certificate), 154 close(Stream2)). 155 156open_spec(Spec, Stream):- 157 ( Spec = file(Filename) 158 -> open(Filename, read, Stream) 159 ; Spec = resource(Name) 160 -> open_resource(Name, read, Stream) 161 ; Spec = url(URL) 162 -> http_open(URL, Stream, []) 163 ; domain_error(file_specification, Spec) 164 ). 165 166:-multifile(saml:saml_sp_certificate/4). 167:-multifile(saml:saml_idp/3). 168:-multifile(saml:saml_idp_certificate/4). 169:-multifile(saml:saml_idp_binding/4). 170:-multifile(saml:saml_acs_path/2). 171 172saml_idp_clauses(ServiceProvider, MetadataSpec, Clauses):- 173 setup_call_cleanup(open_spec(MetadataSpec, Stream), 174 load_structure(Stream, Metadata, [dialect(xmlns)]), 175 close(Stream)), 176 ( memberchk(element('urn:oasis:names:tc:SAML:2.0:metadata':'EntitiesDescriptor', _, EntitiesDescriptor), Metadata) 177 -> ( memberchk(element('urn:oasis:names:tc:SAML:2.0:metadata':'EntityDescriptor', EntityDescriptorAttributes, EntityDescriptor), EntitiesDescriptor), 178 memberchk(element('urn:oasis:names:tc:SAML:2.0:metadata':'IDPSSODescriptor', IDPSSODescriptorAttributes, IDPSSODescriptor), EntityDescriptor) 179 -> trust_saml_idp_descriptor(ServiceProvider, EntityDescriptorAttributes, IDPSSODescriptorAttributes, IDPSSODescriptor, Clauses) 180 ; existence_error(idp_descriptor, MetadataSpec) 181 ) 182 ; memberchk(element('urn:oasis:names:tc:SAML:2.0:metadata':'EntityDescriptor', EntityDescriptorAttributes, EntityDescriptor), Metadata), 183 memberchk(element('urn:oasis:names:tc:SAML:2.0:metadata':'IDPSSODescriptor', IDPSSODescriptorAttributes, IDPSSODescriptor), EntityDescriptor) 184 -> trust_saml_idp_descriptor(ServiceProvider, EntityDescriptorAttributes, IDPSSODescriptorAttributes, IDPSSODescriptor, Clauses) 185 ; existence_error(idp_descriptor, MetadataSpec) 186 ). 187 188trust_saml_idp_descriptor(ServiceProvider, 189 EntityDescriptorAttributes, 190 IDPSSODescriptorAttributes, 191 IDPSSODescriptor, 192 [saml:saml_idp(ServiceProvider, EntityID, MustSign)|Clauses]):- 193 memberchk(entityID=EntityID, EntityDescriptorAttributes), 194 findall(saml:saml_idp_binding(ServiceProvider, EntityID, Binding, BindingInfo), 195 ( member(element('urn:oasis:names:tc:SAML:2.0:metadata':'SingleSignOnService', SingleSignOnServiceAttributes, SingleSignOnService), IDPSSODescriptor), 196 process_saml_binding(SingleSignOnServiceAttributes, SingleSignOnService, Binding, BindingInfo) 197 ), 198 Clauses, 199 Tail), 200 ( Tail == Clauses 201 -> existence_error(supported_binding, IDPSSODescriptor) 202 ; true 203 ), 204 findall(saml:saml_idp_certificate(ServiceProvider, EntityID, CertificateUse, Certificate), 205 idp_certificate(IDPSSODescriptor, CertificateUse, Certificate), 206 Tail), 207 ( memberchk('WantAuthnRequestsSigned'=true, IDPSSODescriptorAttributes) 208 -> MustSign = true 209 ; MustSign = false 210 ). 211 212idp_certificate(IDPSSODescriptor, CertificateUse, Certificate):- 213 member(element('urn:oasis:names:tc:SAML:2.0:metadata':'KeyDescriptor', KeyDescriptorAttributes, KeyDescriptor), IDPSSODescriptor), 214 memberchk(use=CertificateUse, KeyDescriptorAttributes), 215 memberchk(element('http://www.w3.org/2000/09/xmldsig#':'KeyInfo', _, KeyInfo), KeyDescriptor), 216 memberchk(element('http://www.w3.org/2000/09/xmldsig#':'X509Data', _, X509Data), KeyInfo), 217 memberchk(element('http://www.w3.org/2000/09/xmldsig#':'X509Certificate', _, [X509CertificateData]), X509Data), 218 load_certificate_from_base64_string(X509CertificateData, Certificate). 219 220 221process_saml_binding(SingleSignOnServiceAttributes, _, 'urn:oasis:names:tc:SAML:2.0:bindings:HTTP-Redirect', Location):- 222 memberchk('Binding'='urn:oasis:names:tc:SAML:2.0:bindings:HTTP-Redirect', SingleSignOnServiceAttributes), 223 !, 224 memberchk('Location'=Location, SingleSignOnServiceAttributes). 225 226process_saml_binding(SingleSignOnServiceAttributes, _, 'urn:oasis:names:tc:SAML:2.0:bindings:HTTP-POST', Location):- 227 memberchk('Binding'='urn:oasis:names:tc:SAML:2.0:bindings:HTTP-POST', SingleSignOnServiceAttributes), 228 !, 229 memberchk('Location'=Location, SingleSignOnServiceAttributes). 230 231 232 233form_authn_request(Request, ID, Destination, Date, ServiceProvider, ExtraElements, XML):- 234 saml_acs_path(ServiceProvider, Path), 235 subtract(Request, [path(_), search(_)], Request1), 236 parse_url(ACSURL, [path(Path)|Request1]), 237 SAMLP = 'urn:oasis:names:tc:SAML:2.0:protocol', 238 SAML = 'urn:oasis:names:tc:SAML:2.0:assertion', 239 XML = element(SAMLP:'AuthnRequest', ['ID'=ID, 240 'Version'='2.0', 241 'IssueInstant'=Date, 242 'Destination'=Destination, 243 'IsPassive'=false, 244 'ProtocolBinding'='urn:oasis:names:tc:SAML:2.0:bindings:HTTP-POST', 245 'AssertionConsumerServiceURL'=ACSURL], 246 [element(SAML:'Issuer', [], [ServiceProvider]), 247 element(SAMLP:'NameIDPolicy', ['AllowCreate'=true, 248 'Format'='urn:oasis:names:tc:SAML:1.1:nameid-format:unspecified'], [])|ExtraElements]). 249 250 251:-meta_predicate(saml_authenticate(+, +, 2, +)). 252saml_authenticate(ServiceProvider, IdentityProvider, Callback, Request):- 253 memberchk(request_uri(RequestingURI), Request), 254 format(atom(RelayState), '~q', [saml(RequestingURI, Callback)]), 255 get_xml_timestamp(Date), 256 uuid(UUID), 257 % the ID must start with a letter but the UUID may start with a number. Resolve this by prepending an 'a' 258 atom_concat(a, UUID, ID), 259 saml_idp(ServiceProvider, IdentityProvider, _MustSign), 260 % Always sign the request 261 MustSign = true, 262 XMLOptions = [header(false), layout(false)], 263 ( saml_idp_binding(ServiceProvider, IdentityProvider, 'urn:oasis:names:tc:SAML:2.0:bindings:HTTP-Redirect', BaseURL) 264 -> parse_url(BaseURL, Parts), 265 form_authn_request(Request, ID, BaseURL, Date, ServiceProvider, [], XML), 266 with_output_to(string(XMLString), xml_write(current_output, XML, XMLOptions)), 267 debug(saml, 'XML:~n~s~n', [XMLString]), 268 setup_call_cleanup(new_memory_file(MemFile), 269 (setup_call_cleanup(open_memory_file(MemFile, write, MemWrite, [encoding(octet)]), 270 (setup_call_cleanup(zopen(MemWrite, Write, [format(raw_deflate), level(9), close_parent(false)]), 271 format(Write, '~s', [XMLString]), 272 close(Write)) 273 ), 274 close(MemWrite)), 275 memory_file_to_atom(MemFile, SAMLRequestRaw) 276 ), 277 free_memory_file(MemFile)), 278 base64(SAMLRequestRaw, SAMLRequest), 279 debug(saml, 'Encoded request: ~w~n', [SAMLRequest]), 280 ( MustSign == true 281 -> saml_sp_certificate(ServiceProvider, _, _, PrivateKey), 282 saml_sign(PrivateKey, XMLString, SAMLRequest, RelayState, ExtraParameters) 283 ; ExtraParameters = [] 284 ) 285 ; domain_error(supported_binding, IdentityProvider) % Other bindings could be implemented here, most obviously HTTP-POST and HTTP-POST-SimpleSign 286 ), 287 parse_url(IdPURL, [search(['SAMLRequest'=SAMLRequest, 'RelayState'=RelayState|ExtraParameters])|Parts]), 288 debug(saml, 'Redirecting user to~n~w~n', [IdPURL]), 289 http_redirect(moved_temporary, IdPURL, Request). 290 291saml_simple_sign(PrivateKey, XMLString, _SAMLRequest, RelayState, ['SigAlg'=SigAlg,'Signature'=Signature]):- 292 SigAlg = 'http://www.w3.org/2000/09/xmldsig#rsa-sha1', 293 format(string(DataToSign), 'SAMLRequest=~s&RelayState=~w&SigAlg=~w', [XMLString, RelayState, SigAlg]), 294 debug(saml, 'Data to sign with HTTP-Redirect-SimpleSign:~n~s~n', [DataToSign]), 295 sha_hash(DataToSign, Digest, [algorithm(sha1)]), 296 rsa_sign(PrivateKey, Digest, RawSignature, 297 [ type(sha1), 298 encoding(octet) 299 ]), 300 base64(RawSignature, Signature), 301 debug(saml, 'Signature:~n~w~n', [Signature]). 302 303saml_sign(PrivateKey, _XMLString, SAMLRequest, RelayState, ['SigAlg'=SigAlg,'Signature'=Base64Signature]):- 304 SigAlg = 'http://www.w3.org/2000/09/xmldsig#rsa-sha1', 305 parse_url_search(CodesToSign, ['SAMLRequest'=SAMLRequest, 'RelayState'=RelayState, 'SigAlg'=SigAlg]), 306 string_codes(DataToSign, CodesToSign), 307 debug(saml, 'Data to sign with HTTP-Redirect binding:~n~s~n', [DataToSign]), 308 sha_hash(DataToSign, Digest, [algorithm(sha1)]), 309 rsa_sign(PrivateKey, Digest, HexSignature, 310 [ type(sha1), 311 encoding(octet) 312 ]), 313 hex_bytes(HexSignature, SignatureBytes), 314 atom_codes(SignatureAtom, SignatureBytes), 315 base64(SignatureAtom, Base64Signature), 316 debug(saml, '~nSignature:~n~w~n', [Base64Signature]). 317 318saml_acs_handler(ServiceProvider, Options, Request):- 319 debug(saml, 'Got a message back from IdP!~n', []), 320 http_read_data(Request, PostedData, []), 321 debug(saml, '~w~n', [PostedData]), 322 memberchk('SAMLResponse'=Atom, PostedData), 323 memberchk('RelayState'=Relay, PostedData), 324 ( atom_to_term(Relay, saml(OriginalURI, Callback), _) 325 -> true 326 ; throw(error(invalid_request, _)) 327 ), 328 base64(RawData, Atom), 329 atom_string(RawData, RawString), 330 setup_call_cleanup(open_string(RawString, Stream), 331 load_structure(Stream, XML, [dialect(xmlns), keep_prefix(true)]), 332 close(Stream)), 333 ( debugging(saml) 334 -> xml_write(user_error, XML, []) 335 ; true 336 ), 337 process_saml_response(XML, ServiceProvider, Callback, OriginalURI, Options), 338 debug(saml, 'Redirecting successfully authenticated user to ~w~n', [OriginalURI]), 339 http_redirect(moved_temporary, OriginalURI, Request). 340 341 342propagate_ns([], _, []):- !. 343propagate_ns([element(Tag, Attributes, Children)|Siblings], 344 NS, 345 [element(Tag, NewAttributes, NewChildren)|NewSiblings]):- 346 !, 347 merge_ns(NS, Attributes, NewAttributes, NewNS), 348 propagate_ns(Children, NewNS, NewChildren), 349 propagate_ns(Siblings, NS, NewSiblings). 350propagate_ns([X|Siblings], NS, [X|NewSiblings]):- 351 propagate_ns(Siblings, NS, NewSiblings). 352 353merge_ns([xmlns:Prefix=Value|NS], Attributes, NewAttributes, NewNS):- 354 ( select(xmlns:Prefix=NewValue, Attributes, A1) 355 -> NewNS = [xmlns:Prefix=NewValue|T], 356 NewAttributes = [xmlns:Prefix=NewValue|N] 357 ; A1 = Attributes, 358 NewNS = [xmlns:Prefix=Value|T], 359 NewAttributes = [xmlns:Prefix=Value|N] 360 ), 361 merge_ns(NS, A1, N, T). 362 363merge_ns([], A, A, NS):- 364 findall(xmlns:Prefix=Value, member(xmlns:Prefix=Value, A), NS). 365 366 367:-meta_predicate(process_saml_response(+, +, 2, +, +)). 368process_saml_response(XML0, ServiceProvider, Callback, RequestURL, Options):- 369 SAMLP = 'urn:oasis:names:tc:SAML:2.0:protocol', 370 SAML = 'urn:oasis:names:tc:SAML:2.0:assertion', 371 DS = 'http://www.w3.org/2000/09/xmldsig#', 372 propagate_ns(XML0, [], XML), 373 XML = [element(ns(_, SAMLP):'Response', _, Response)], 374 % Response MAY contain the following elements : Issuer, Signature, Extensions 375 % Response MAY contain the following attributes: InResponseTo, Destination, Consent 376 % Response MUST contain the following elements : Status 377 % Response MUST contain the following attributes: ID, IssueInstant, Version 378 ( memberchk(element(ns(_, SAMLP):'Status', _StatusAttributes, Status), Response)-> 379 % Status MUST contain a StatusCode element, and MAY contain a StatusMessage and or StatusDetail element 380 ( memberchk(element(ns(_, SAMLP):'StatusCode', StatusCodeAttributes, _StatusCode), Status)-> 381 % StatusCode MUST contain a Value attribute 382 ( memberchk('Value'=StatusCodeValue, StatusCodeAttributes)-> 383 true 384 ; domain_error(legal_saml_response, XML0) 385 ) 386 ; domain_error(legal_saml_response, XML0) 387 ) 388 ; domain_error(legal_saml_response, XML0) 389 ), 390 ( memberchk(element(ns(_, SAML):'Issuer', _, [IssuerName]), Response) 391 -> true 392 ; IssuerName = {null} 393 ), 394 395 ( member(element(ns(_, DS):'Signature', _, Signature), Response)-> 396 xmld_verify_signature(XML, Signature, Certificate, []), 397 % Check that the certificate used to sign was one in the metadata 398 ( saml_idp_certificate(ServiceProvider, IssuerName, signing, IDPCertificate), 399 same_certificate(Certificate, IDPCertificate) 400 -> true 401 ; domain_error(trusted_certificate, Certificate) 402 ) 403 ; otherwise-> 404 % Warning: Message is not signed. Assertions may be though 405 % FIXME: Determine a policy for handling this - if the SP wants them signed, we must make sure they are 406 true 407 ), 408 409 ( StatusCodeValue == 'urn:oasis:names:tc:SAML:2.0:status:Success'-> 410 % The user has authenticated in some capacity. 411 % Note that we cannot say anything ABOUT the user yet. That will come once we process the assertions 412 true 413 ; StatusCodeValue == 'urn:oasis:names:tc:SAML:2.0:status:Requester'-> 414 throw(saml_rejected(requester)) 415 ; StatusCodeValue == 'urn:oasis:names:tc:SAML:2.0:status:Responder'-> 416 throw(saml_rejected(responder)) 417 ; StatusCodeValue == 'urn:oasis:names:tc:SAML:2.0:status:VersionMismatch'-> 418 throw(saml_rejected(version_mismatch)) 419 ; throw(saml_rejected(illegal_response)) 420 ), 421 422 % Response MAY also contain 0..N of the following elements: Assertion, EncryptedAssertion. 423 findall(Attribute, 424 ( ( member(element(ns(SAMLPrefix, SAML):'Assertion', AssertionAttributes, Assertion), Response), 425 process_assertion(ServiceProvider, IssuerName, XML, AssertionAttributes, Assertion, Attribute)) 426 ; member(element(ns(SAMLPrefix, SAML):'EncryptedAssertion', _, EncryptedAssertion), Response), 427 decrypt_xml(EncryptedAssertion, DecryptedAssertion, saml:saml_key_callback(ServiceProvider), Options), 428 member(element(ns(_, SAML):'Assertion', AssertionAttributes, Assertion), DecryptedAssertion), 429 process_assertion(ServiceProvider, IssuerName, XML, AssertionAttributes, Assertion, Attribute) 430 ), 431 AcceptedAttributes), 432 debug(saml, 'Calling SAML callback with these attributes: ~w', [AcceptedAttributes]), 433 call(Callback, RequestURL, AcceptedAttributes). 434 435process_assertion(ServiceProvider, _EntityID, Document, Attributes, Assertion, AssertedAttribute):- 436 SAML = ns(_, 'urn:oasis:names:tc:SAML:2.0:assertion'), 437 DS = ns(_, 'http://www.w3.org/2000/09/xmldsig#'), 438 ( memberchk('ID'=_AssertionID, Attributes)-> 439 true 440 ; throw(missing_assertion_id) 441 ), 442 % An Assertion MUST contain an Issuer, and MAY contain a Signature, Subject, Conditions, Advice, plus 0..N of the following: 443 % Statement 444 % AuthnStatement 445 % AuthzDecisionStatement 446 % AttributeStatement 447 % It must also have all the following attributes, Version, ID, IssueInstant 448 memberchk(element(SAML:'Issuer', _, [IssuerName]), Assertion), 449 debug(saml, 'Received assertion from IdP ~w', [IssuerName]), 450 ( member(element(DS:'Signature', _, Signature), Assertion)-> 451 xmld_verify_signature(Document, Signature, Certificate, []), 452 % Check that the certificate used to sign was one in the metadata 453 ( saml_idp_certificate(ServiceProvider, IssuerName, signing, IDPCertificate), 454 same_certificate(Certificate, IDPCertificate) 455 -> true 456 ; domain_error(trusted_certificate, Certificate) 457 ) 458 ; otherwise-> 459 % Technically the standard allows this, but it seems like practically it would be useless? 460 % Which part of the response SHOULD be signed? The entire thing or the assertions? 461 true 462 %throw(unsigned_response) 463 ), 464 ( memberchk(element(SAML:'Conditions', ConditionsAttributes, Conditions), Assertion)-> 465 % If conditions are present, we MUST check them. These can include arbitrary, user-defined conditions 466 % and things like ProxyRestriction and OneTimeUse 467 get_xml_timestamp(Date), 468 ( memberchk('NotOnOrAfter'=Expiry, ConditionsAttributes)-> 469 Date @< Expiry 470 ; true 471 ), 472 ( memberchk('NotBefore'=Expiry, ConditionsAttributes)-> 473 Date @> Expiry 474 ; true 475 ), 476 forall(member(element(SAML:'Condition', ConditionAttributes, Condition), Conditions), 477 condition_holds(ConditionAttributes, Condition)), 478 forall(member(element(SAML:'AudienceRestriction', _AudienceRestrictionAttributes, AudienceRestriction), Conditions), 479 ( member(element(SAML:'Audience', _, [Audience]), AudienceRestriction), 480 Audience == ServiceProvider 481 -> true 482 ; permission_error(accept, assertion, AudienceRestriction) 483 )), 484 ( memberchk(element(SAML:'OneTimeUse', _, _), Conditions)-> 485 throw(one_time_use_not_supported) 486 ; true 487 ), 488 ( memberchk(element(SAML:'ProxyRestriction', _, _), Conditions)-> 489 throw(proxy_restriction_not_supported) 490 ; true 491 ) 492 ; true 493 ), 494 % The Subject element is not mandatory. In the introduction to section 2, the specification states 495 % "the <Subject> element is optional, and other specifications and profiles may utilize the SAML assertion 496 % structure to make similar statements without specifying a subject, or possibly specifying the subject in an 497 % alternate way" 498 % However, 2.3.3 goes on to say that 499 % "SAML itself defines no such statements, and an assertion without a subject has no defined meaning in this specification." 500 % Specifically, 2.7.2, 2.7.3, 2.7.4 enumerate all the SAML-defined statements, and all of them say that the assertion MUST 501 % contain a subject 502 ( memberchk(element(SAML:'Subject', _, Subject), Assertion)-> 503 memberchk(element(SAML:'NameID', _, [IdPName]), Subject), 504 debug(saml, 'Assertion is for subject ~w', [IdPName]), 505 % Note that it is not mandatory for there to be any SubjectConfirmation in the message, however, since we must verify at least one 506 % confirmation in order to trust that the subject has really associated with the IdP, a subject with no confirmations is useless anyway 507 ( member(element(SAML:'SubjectConfirmation', SubjectConfirmationAttributes, SubjectConfirmation), Subject), 508 subject_confirmation_is_valid(SubjectConfirmationAttributes, SubjectConfirmation)-> 509 debug(saml, 'Subject is confirmed', []) 510 ; debug(saml, 'No valid subject confirmation could be found', []), 511 throw(no_subject_confirmation) 512 ) 513 ; throw(not_supported(assertion_without_subject)) 514 ), 515 !, 516 memberchk(element(SAML:'AttributeStatement', _, AttributeStatement), Assertion), 517 member(element(SAML:'Attribute', AttributeAttributes, Attribute), AttributeStatement), 518 memberchk('Name'=AttributeName, AttributeAttributes), 519 ( memberchk('FriendlyName'=FriendlyName, AttributeAttributes) 520 -> true 521 ; FriendlyName = '' 522 ), 523 memberchk(element(SAML:'AttributeValue', _, [AttributeValue]), Attribute), 524 AssertedAttribute = attribute(AttributeName, FriendlyName, AttributeValue). 525 526process_assertion(_Attributes, _Assertion, _, _, _, _):- 527 debug(saml, 'Warning: Assertion was not valid', []). 528 529condition_holds(_ConditionAttributes, _Condition):- 530 throw(conditions_not_implemented). 531 532get_xml_timestamp(Date):- 533 get_time(Time), 534 stamp_date_time(Time, date(Y, M, D, HH, MM, SSF, _, 'UTC', _), 'UTC'), 535 SS is floor(SSF), 536 format(atom(Date), '~w-~|~`0t~w~2+-~|~`0t~w~2+T~|~`0t~w~2+:~|~`0t~w~2+:~|~`0t~w~2+Z', [Y,M,D,HH,MM,SS]). 537 538 539subject_confirmation_is_valid(SubjectConfirmationAttributes, SubjectConfirmation):- 540 SAML = ns(_, 'urn:oasis:names:tc:SAML:2.0:assertion'), 541 memberchk('Method'='urn:oasis:names:tc:SAML:2.0:cm:bearer', SubjectConfirmationAttributes), % this is the only method we support 542 memberchk(element(SAML:'SubjectConfirmationData', Attributes, _SubjectConfirmationData), SubjectConfirmation), 543 get_xml_timestamp(Date), 544 ( memberchk('NotOnOrAfter'=Expiry, Attributes)-> 545 Date @< Expiry 546 ; true 547 ), 548 ( memberchk('NotBefore'=Expiry, Attributes)-> 549 Date @> Expiry 550 ; true 551 ), 552 ( memberchk('InResponseTo'=_InResponseTo, Attributes)-> 553 % FIXME: Check that we sent the message, somehow? 554 true 555 ; true 556 ), 557 ( memberchk('Recipient'=_Recipient, Attributes)-> 558 % FIXME: Check that this is us, somehow? 559 true 560 ; true 561 ), 562 % FIXME: We can also have other arbitrary elements and attributes in here for user-defined extensions. These are ignored. 563 true. 564 565saml_key_callback(ServiceProvider, certificate, KeyHint, Key):- 566 saml_sp_certificate(ServiceProvider, KeyHint, _, Key), 567 !. 568 569 570saml_metadata(ServiceProvider, _Options, Request):- 571 MD = 'urn:oasis:names:tc:SAML:2.0:metadata', 572 DS = 'http://www.w3.org/2000/09/xmldsig#', 573 saml_sp_certificate(ServiceProvider, _X509Certificate, X509Certificate, _PrivateKey), 574 575 % All of this should be configurable, eventually? 576 EncryptionMethod = 'http://www.w3.org/2009/xmlenc11#rsa-oaep', 577 NameIDFormat = 'urn:oasis:names:tc:SAML:1.1:nameid-format:unspecified', 578 ACSBinding = 'urn:oasis:names:tc:SAML:2.0:bindings:HTTP-POST', 579 580 parse_url(RequestURL, Request), 581 http_absolute_location('./auth', ACSLocation, [relative_to(RequestURL)]), 582 583 % Extract the part of the certificate between the BEGIN and END delimiters 584 ( sub_string(X509Certificate, CertMarkerStart, CertMarkerLength, _, "-----BEGIN CERTIFICATE-----\n"), 585 sub_string(X509Certificate, CertEnd, _, _, "\n-----END CERTIFICATE-----"), 586 CertStart is CertMarkerStart + CertMarkerLength, 587 CertEnd > CertStart-> 588 CertLength is CertEnd - CertStart, 589 sub_string(X509Certificate, CertStart, CertLength, _, PresentableCertificate) 590 ; existence_error(certificate_data, X509Certificate) 591 ), 592 format(current_output, 'Content-type: text/xml~n~n', []), 593 XML = [element(MD:'EntitiesDescriptor', [], [EntityDescriptor])], 594 EntityDescriptor = element(MD:'EntityDescriptor', [entityID=ServiceProvider], [SPSSODescriptor]), 595 SPSSODescriptor = element(MD:'SPSSODescriptor', ['AuthnRequestsSigned'=true, 596 protocolSupportEnumeration='urn:oasis:names:tc:SAML:2.0:protocol'], [EncryptionKeyDescriptor, 597 SigningKeyDescriptor, 598 element(MD:'NameIDFormat', [], [NameIDFormat]), 599 AssertionConsumerService]), 600 EncryptionKeyDescriptor = element(MD:'KeyDescriptor', [use=encryption], [KeyInfo, 601 element(MD:'EncryptionMethod', ['Algorithm'=EncryptionMethod], [])]), 602 SigningKeyDescriptor = element(MD:'KeyDescriptor', [use=signing], [KeyInfo, 603 element(MD:'EncryptionMethod', ['Algorithm'=EncryptionMethod], [])]), 604 605 KeyInfo = element(DS:'KeyInfo', [], [X509Data]), 606 X509Data = element(DS:'X509Data', [], [element(DS:'X509Certificate', [], [PresentableCertificate])]), 607 AssertionConsumerService = element(MD:'AssertionConsumerService', [index='0', isDefault=true, 'Binding'=ACSBinding, 'Location'=ACSLocation], []), 608 xml_write(current_output, XML, [])