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service_provider.go
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service_provider.go
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package saml
import (
"bytes"
"compress/flate"
"context"
"crypto/rsa"
"crypto/tls"
"crypto/x509"
"encoding/base64"
"encoding/xml"
"errors"
"fmt"
"html/template"
"io"
"net/http"
"net/url"
"regexp"
"time"
"github.com/beevik/etree"
xrv "github.com/mattermost/xml-roundtrip-validator"
dsig "github.com/russellhaering/goxmldsig"
"github.com/russellhaering/goxmldsig/etreeutils"
"github.com/crewjam/saml/logger"
"github.com/crewjam/saml/xmlenc"
)
// NameIDFormat is the format of the id
type NameIDFormat string
// Element returns an XML element representation of n.
func (n NameIDFormat) Element() *etree.Element {
el := etree.NewElement("")
el.SetText(string(n))
return el
}
// Name ID formats
const (
UnspecifiedNameIDFormat NameIDFormat = "urn:oasis:names:tc:SAML:1.1:nameid-format:unspecified"
TransientNameIDFormat NameIDFormat = "urn:oasis:names:tc:SAML:2.0:nameid-format:transient"
EmailAddressNameIDFormat NameIDFormat = "urn:oasis:names:tc:SAML:1.1:nameid-format:emailAddress"
PersistentNameIDFormat NameIDFormat = "urn:oasis:names:tc:SAML:2.0:nameid-format:persistent"
)
// SignatureVerifier verifies a signature
//
// Can be implemented in order to override ServiceProvider's default
// way of verifying signatures.
type SignatureVerifier interface {
VerifySignature(validationContext *dsig.ValidationContext, el *etree.Element) error
}
// ServiceProvider implements SAML Service provider.
//
// In SAML, service providers delegate responsibility for identifying
// clients to an identity provider. If you are writing an application
// that uses passwords (or whatever) stored somewhere else, then you
// are service provider.
//
// See the example directory for an example of a web application using
// the service provider interface.
type ServiceProvider struct {
// Entity ID is optional - if not specified then MetadataURL will be used
EntityID string
// Key is the RSA private key we use to sign requests.
Key *rsa.PrivateKey
// Certificate is the RSA public part of Key.
Certificate *x509.Certificate
Intermediates []*x509.Certificate
// HTTPClient to use during SAML artifact resolution
HTTPClient *http.Client
// MetadataURL is the full URL to the metadata endpoint on this host,
// i.e. https://example.com/saml/metadata
MetadataURL url.URL
// AcsURL is the full URL to the SAML Assertion Customer Service endpoint
// on this host, i.e. https://example.com/saml/acs
AcsURL url.URL
// SloURL is the full URL to the SAML Single Logout endpoint on this host.
// i.e. https://example.com/saml/slo
SloURL url.URL
// IDPMetadata is the metadata from the identity provider.
IDPMetadata *EntityDescriptor
// AuthnNameIDFormat is the format used in the NameIDPolicy for
// authentication requests
AuthnNameIDFormat NameIDFormat
// MetadataValidDuration is a duration used to calculate validUntil
// attribute in the metadata endpoint
MetadataValidDuration time.Duration
// ForceAuthn allows you to force re-authentication of users even if the user
// has a SSO session at the IdP.
ForceAuthn *bool
// RequestedAuthnContext allow you to specify the requested authentication
// context in authentication requests
RequestedAuthnContext *RequestedAuthnContext
// AllowIdpInitiated
AllowIDPInitiated bool
// DefaultRedirectURI where untracked requests (as of IDPInitiated) are redirected to
DefaultRedirectURI string
// SignatureVerifier, if non-nil, allows you to implement an alternative way
// to verify signatures.
SignatureVerifier SignatureVerifier
// SignatureMethod, if non-empty, authentication requests will be signed
SignatureMethod string
// LogoutBindings specify the bindings available for SLO endpoint. If empty,
// HTTP-POST binding is used.
LogoutBindings []string
}
// MaxIssueDelay is the longest allowed time between when a SAML assertion is
// issued by the IDP and the time it is received by ParseResponse. This is used
// to prevent old responses from being replayed (while allowing for some clock
// drift between the SP and IDP).
var MaxIssueDelay = time.Second * 90
// MaxClockSkew allows for leeway for clock skew between the IDP and SP when
// validating assertions. It defaults to 180 seconds (matches shibboleth).
var MaxClockSkew = time.Second * 180
// DefaultValidDuration is how long we assert that the SP metadata is valid.
const DefaultValidDuration = time.Hour * 24 * 2
// DefaultCacheDuration is how long we ask the IDP to cache the SP metadata.
const DefaultCacheDuration = time.Hour * 24 * 1
// Metadata returns the service provider metadata
func (sp *ServiceProvider) Metadata() *EntityDescriptor {
validDuration := DefaultValidDuration
if sp.MetadataValidDuration > 0 {
validDuration = sp.MetadataValidDuration
}
authnRequestsSigned := len(sp.SignatureMethod) > 0
wantAssertionsSigned := true
validUntil := TimeNow().Add(validDuration)
var keyDescriptors []KeyDescriptor
if sp.Certificate != nil {
certBytes := sp.Certificate.Raw
for _, intermediate := range sp.Intermediates {
certBytes = append(certBytes, intermediate.Raw...)
}
keyDescriptors = []KeyDescriptor{
{
Use: "encryption",
KeyInfo: KeyInfo{
X509Data: X509Data{
X509Certificates: []X509Certificate{
{Data: base64.StdEncoding.EncodeToString(certBytes)},
},
},
},
EncryptionMethods: []EncryptionMethod{
{Algorithm: "http://www.w3.org/2001/04/xmlenc#aes128-cbc"},
{Algorithm: "http://www.w3.org/2001/04/xmlenc#aes192-cbc"},
{Algorithm: "http://www.w3.org/2001/04/xmlenc#aes256-cbc"},
{Algorithm: "http://www.w3.org/2001/04/xmlenc#rsa-oaep-mgf1p"},
},
},
}
if len(sp.SignatureMethod) > 0 {
keyDescriptors = append(keyDescriptors, KeyDescriptor{
Use: "signing",
KeyInfo: KeyInfo{
X509Data: X509Data{
X509Certificates: []X509Certificate{
{Data: base64.StdEncoding.EncodeToString(certBytes)},
},
},
},
})
}
}
sloEndpoints := make([]Endpoint, len(sp.LogoutBindings))
for i, binding := range sp.LogoutBindings {
sloEndpoints[i] = Endpoint{
Binding: binding,
Location: sp.SloURL.String(),
ResponseLocation: sp.SloURL.String(),
}
}
return &EntityDescriptor{
EntityID: firstSet(sp.EntityID, sp.MetadataURL.String()),
ValidUntil: validUntil,
SPSSODescriptors: []SPSSODescriptor{
{
SSODescriptor: SSODescriptor{
RoleDescriptor: RoleDescriptor{
ProtocolSupportEnumeration: "urn:oasis:names:tc:SAML:2.0:protocol",
KeyDescriptors: keyDescriptors,
ValidUntil: &validUntil,
},
SingleLogoutServices: sloEndpoints,
NameIDFormats: []NameIDFormat{sp.AuthnNameIDFormat},
},
AuthnRequestsSigned: &authnRequestsSigned,
WantAssertionsSigned: &wantAssertionsSigned,
AssertionConsumerServices: []IndexedEndpoint{
{
Binding: HTTPPostBinding,
Location: sp.AcsURL.String(),
Index: 1,
},
{
Binding: HTTPArtifactBinding,
Location: sp.AcsURL.String(),
Index: 2,
},
},
},
},
}
}
// MakeRedirectAuthenticationRequest creates a SAML authentication request using
// the HTTP-Redirect binding. It returns a URL that we will redirect the user to
// in order to start the auth process.
func (sp *ServiceProvider) MakeRedirectAuthenticationRequest(relayState string) (*url.URL, error) {
req, err := sp.MakeAuthenticationRequest(sp.GetSSOBindingLocation(HTTPRedirectBinding), HTTPRedirectBinding, HTTPPostBinding)
if err != nil {
return nil, err
}
return req.Redirect(relayState, sp)
}
// Redirect returns a URL suitable for using the redirect binding with the request
func (r *AuthnRequest) Redirect(relayState string, sp *ServiceProvider) (*url.URL, error) {
w := &bytes.Buffer{}
w1 := base64.NewEncoder(base64.StdEncoding, w)
w2, _ := flate.NewWriter(w1, 9)
doc := etree.NewDocument()
doc.SetRoot(r.Element())
if _, err := doc.WriteTo(w2); err != nil {
panic(err)
}
if err := w2.Close(); err != nil {
panic(err)
}
if err := w1.Close(); err != nil {
panic(err)
}
rv, _ := url.Parse(r.Destination)
// We can't depend on Query().set() as order matters for signing
query := rv.RawQuery
if len(query) > 0 {
query += "&SAMLRequest=" + url.QueryEscape(w.String())
} else {
query += "SAMLRequest=" + url.QueryEscape(w.String())
}
if relayState != "" {
query += "&RelayState=" + relayState
}
if len(sp.SignatureMethod) > 0 {
query += "&SigAlg=" + url.QueryEscape(sp.SignatureMethod)
signingContext, err := GetSigningContext(sp)
if err != nil {
return nil, err
}
sig, err := signingContext.SignString(query)
if err != nil {
return nil, err
}
query += "&Signature=" + url.QueryEscape(base64.StdEncoding.EncodeToString(sig))
}
rv.RawQuery = query
return rv, nil
}
// GetSSOBindingLocation returns URL for the IDP's Single Sign On Service binding
// of the specified type (HTTPRedirectBinding or HTTPPostBinding)
func (sp *ServiceProvider) GetSSOBindingLocation(binding string) string {
for _, idpSSODescriptor := range sp.IDPMetadata.IDPSSODescriptors {
for _, singleSignOnService := range idpSSODescriptor.SingleSignOnServices {
if singleSignOnService.Binding == binding {
return singleSignOnService.Location
}
}
}
return ""
}
// GetArtifactBindingLocation returns URL for the IDP's Artifact binding of the
// specified type
func (sp *ServiceProvider) GetArtifactBindingLocation(binding string) string {
for _, idpSSODescriptor := range sp.IDPMetadata.IDPSSODescriptors {
for _, artifactResolutionService := range idpSSODescriptor.ArtifactResolutionServices {
if artifactResolutionService.Binding == binding {
return artifactResolutionService.Location
}
}
}
return ""
}
// GetSLOBindingLocation returns URL for the IDP's Single Log Out Service binding
// of the specified type (HTTPRedirectBinding or HTTPPostBinding)
func (sp *ServiceProvider) GetSLOBindingLocation(binding string) string {
for _, idpSSODescriptor := range sp.IDPMetadata.IDPSSODescriptors {
for _, singleLogoutService := range idpSSODescriptor.SingleLogoutServices {
if singleLogoutService.Binding == binding {
return singleLogoutService.Location
}
}
}
return ""
}
// getIDPSigningCerts returns the certificates which we can use to verify things
// signed by the IDP in PEM format, or nil if no such certificate is found.
func (sp *ServiceProvider) getIDPSigningCerts() ([]*x509.Certificate, error) {
var certStrs []string
// We need to include non-empty certs where the "use" attribute is
// either set to "signing" or is missing
for _, idpSSODescriptor := range sp.IDPMetadata.IDPSSODescriptors {
for _, keyDescriptor := range idpSSODescriptor.KeyDescriptors {
if len(keyDescriptor.KeyInfo.X509Data.X509Certificates) != 0 {
switch keyDescriptor.Use {
case "", "signing":
for _, certificate := range keyDescriptor.KeyInfo.X509Data.X509Certificates {
certStrs = append(certStrs, certificate.Data)
}
}
}
}
}
if len(certStrs) == 0 {
return nil, errors.New("cannot find any signing certificate in the IDP SSO descriptor")
}
certs := make([]*x509.Certificate, len(certStrs))
// cleanup whitespace
regex := regexp.MustCompile(`\s+`)
for i, certStr := range certStrs {
certStr = regex.ReplaceAllString(certStr, "")
certBytes, err := base64.StdEncoding.DecodeString(certStr)
if err != nil {
return nil, fmt.Errorf("cannot parse certificate: %s", err)
}
parsedCert, err := x509.ParseCertificate(certBytes)
if err != nil {
return nil, err
}
certs[i] = parsedCert
}
return certs, nil
}
// MakeArtifactResolveRequest produces a new ArtifactResolve object to send to the idp's Artifact resolver
func (sp *ServiceProvider) MakeArtifactResolveRequest(artifactID string) (*ArtifactResolve, error) {
req := ArtifactResolve{
ID: fmt.Sprintf("id-%x", randomBytes(20)),
IssueInstant: TimeNow(),
Version: "2.0",
Issuer: &Issuer{
Format: "urn:oasis:names:tc:SAML:2.0:nameid-format:entity",
Value: firstSet(sp.EntityID, sp.MetadataURL.String()),
},
Artifact: artifactID,
}
if len(sp.SignatureMethod) > 0 {
if err := sp.SignArtifactResolve(&req); err != nil {
return nil, err
}
}
return &req, nil
}
// MakeAuthenticationRequest produces a new AuthnRequest object to send to the idpURL
// that uses the specified binding (HTTPRedirectBinding or HTTPPostBinding)
func (sp *ServiceProvider) MakeAuthenticationRequest(idpURL string, binding string, resultBinding string) (*AuthnRequest, error) {
allowCreate := true
nameIDFormat := sp.nameIDFormat()
req := AuthnRequest{
AssertionConsumerServiceURL: sp.AcsURL.String(),
Destination: idpURL,
ProtocolBinding: resultBinding, // default binding for the response
ID: fmt.Sprintf("id-%x", randomBytes(20)),
IssueInstant: TimeNow(),
Version: "2.0",
Issuer: &Issuer{
Format: "urn:oasis:names:tc:SAML:2.0:nameid-format:entity",
Value: firstSet(sp.EntityID, sp.MetadataURL.String()),
},
NameIDPolicy: &NameIDPolicy{
AllowCreate: &allowCreate,
// TODO(ross): figure out exactly policy we need
// urn:mace:shibboleth:1.0:nameIdentifier
// urn:oasis:names:tc:SAML:2.0:nameid-format:transient
Format: &nameIDFormat,
},
ForceAuthn: sp.ForceAuthn,
RequestedAuthnContext: sp.RequestedAuthnContext,
}
// We don't need to sign the XML document if the IDP uses HTTP-Redirect binding
if len(sp.SignatureMethod) > 0 && binding == HTTPPostBinding {
if err := sp.SignAuthnRequest(&req); err != nil {
return nil, err
}
}
return &req, nil
}
// GetSigningContext returns a dsig.SigningContext initialized based on the Service Provider's configuration
func GetSigningContext(sp *ServiceProvider) (*dsig.SigningContext, error) {
keyPair := tls.Certificate{
Certificate: [][]byte{sp.Certificate.Raw},
PrivateKey: sp.Key,
Leaf: sp.Certificate,
}
// TODO: add intermediates for SP
// for _, cert := range sp.Intermediates {
// keyPair.Certificate = append(keyPair.Certificate, cert.Raw)
// }
keyStore := dsig.TLSCertKeyStore(keyPair)
if sp.SignatureMethod != dsig.RSASHA1SignatureMethod &&
sp.SignatureMethod != dsig.RSASHA256SignatureMethod &&
sp.SignatureMethod != dsig.RSASHA512SignatureMethod {
return nil, fmt.Errorf("invalid signing method %s", sp.SignatureMethod)
}
signatureMethod := sp.SignatureMethod
signingContext := dsig.NewDefaultSigningContext(keyStore)
signingContext.Canonicalizer = dsig.MakeC14N10ExclusiveCanonicalizerWithPrefixList(canonicalizerPrefixList)
if err := signingContext.SetSignatureMethod(signatureMethod); err != nil {
return nil, err
}
return signingContext, nil
}
// SignArtifactResolve adds the `Signature` element to the `ArtifactResolve`.
func (sp *ServiceProvider) SignArtifactResolve(req *ArtifactResolve) error {
signingContext, err := GetSigningContext(sp)
if err != nil {
return err
}
assertionEl := req.Element()
signedRequestEl, err := signingContext.SignEnveloped(assertionEl)
if err != nil {
return err
}
sigEl := signedRequestEl.Child[len(signedRequestEl.Child)-1]
req.Signature = sigEl.(*etree.Element)
return nil
}
// SignAuthnRequest adds the `Signature` element to the `AuthnRequest`.
func (sp *ServiceProvider) SignAuthnRequest(req *AuthnRequest) error {
signingContext, err := GetSigningContext(sp)
if err != nil {
return err
}
assertionEl := req.Element()
signedRequestEl, err := signingContext.SignEnveloped(assertionEl)
if err != nil {
return err
}
sigEl := signedRequestEl.Child[len(signedRequestEl.Child)-1]
req.Signature = sigEl.(*etree.Element)
return nil
}
// MakePostAuthenticationRequest creates a SAML authentication request using
// the HTTP-POST binding. It returns HTML text representing an HTML form that
// can be sent presented to a browser to initiate the login process.
func (sp *ServiceProvider) MakePostAuthenticationRequest(relayState string) ([]byte, error) {
req, err := sp.MakeAuthenticationRequest(sp.GetSSOBindingLocation(HTTPPostBinding), HTTPPostBinding, HTTPPostBinding)
if err != nil {
return nil, err
}
return req.Post(relayState), nil
}
// Post returns an HTML form suitable for using the HTTP-POST binding with the request
func (r *AuthnRequest) Post(relayState string) []byte {
doc := etree.NewDocument()
doc.SetRoot(r.Element())
reqBuf, err := doc.WriteToBytes()
if err != nil {
panic(err)
}
encodedReqBuf := base64.StdEncoding.EncodeToString(reqBuf)
tmpl := template.Must(template.New("saml-post-form").Parse(`` +
`<form method="post" action="{{.URL}}" id="SAMLRequestForm">` +
`<input type="hidden" name="SAMLRequest" value="{{.SAMLRequest}}" />` +
`<input type="hidden" name="RelayState" value="{{.RelayState}}" />` +
`<input id="SAMLSubmitButton" type="submit" value="Submit" />` +
`</form>` +
`<script>document.getElementById('SAMLSubmitButton').style.visibility="hidden";` +
`document.getElementById('SAMLRequestForm').submit();</script>`))
data := struct {
URL string
SAMLRequest string
RelayState string
}{
URL: r.Destination,
SAMLRequest: encodedReqBuf,
RelayState: relayState,
}
rv := bytes.Buffer{}
if err := tmpl.Execute(&rv, data); err != nil {
panic(err)
}
return rv.Bytes()
}
// AssertionAttributes is a list of AssertionAttribute
type AssertionAttributes []AssertionAttribute
// Get returns the assertion attribute whose Name or FriendlyName
// matches name, or nil if no matching attribute is found.
func (aa AssertionAttributes) Get(name string) *AssertionAttribute {
for _, attr := range aa {
if attr.Name == name {
return &attr
}
if attr.FriendlyName == name {
return &attr
}
}
return nil
}
// AssertionAttribute represents an attribute of the user extracted from
// a SAML Assertion.
type AssertionAttribute struct {
FriendlyName string
Name string
Value string
}
// InvalidResponseError is the error produced by ParseResponse when it fails.
// The underlying error is in PrivateErr. Response is the response as it was
// known at the time validation failed. Now is the time that was used to validate
// time-dependent parts of the assertion.
type InvalidResponseError struct {
PrivateErr error
Response string
Now time.Time
}
func (ivr *InvalidResponseError) Error() string {
return "Authentication failed"
}
// ErrBadStatus is returned when the assertion provided is valid but the
// status code is not "urn:oasis:names:tc:SAML:2.0:status:Success".
type ErrBadStatus struct {
Status string
}
func (e ErrBadStatus) Error() string {
return e.Status
}
// ParseResponse extracts the SAML IDP response received in req, resolves
// artifacts when necessary, validates it, and returns the verified assertion.
func (sp *ServiceProvider) ParseResponse(req *http.Request, possibleRequestIDs []string) (*Assertion, error) {
if artifactID := req.Form.Get("SAMLart"); artifactID != "" {
return sp.handleArtifactRequest(req.Context(), artifactID, possibleRequestIDs)
}
return sp.parseResponseHTTP(req, possibleRequestIDs)
}
func (sp *ServiceProvider) handleArtifactRequest(ctx context.Context, artifactID string, possibleRequestIDs []string) (*Assertion, error) {
retErr := &InvalidResponseError{Now: TimeNow()}
artifactResolveRequest, err := sp.MakeArtifactResolveRequest(artifactID)
if err != nil {
retErr.PrivateErr = fmt.Errorf("cannot generate artifact resolution request: %s", err)
return nil, retErr
}
requestBody, err := elementToBytes(artifactResolveRequest.SoapRequest())
if err != nil {
retErr.PrivateErr = err
return nil, retErr
}
req, err := http.NewRequestWithContext(ctx, "POST", sp.GetArtifactBindingLocation(SOAPBinding),
bytes.NewReader(requestBody))
if err != nil {
retErr.PrivateErr = err
return nil, retErr
}
req.Header.Set("Content-Type", "text/xml")
httpClient := sp.HTTPClient
if httpClient == nil {
httpClient = http.DefaultClient
}
response, err := httpClient.Do(req)
if err != nil {
retErr.PrivateErr = fmt.Errorf("cannot resolve artifact: %s", err)
return nil, retErr
}
defer func() {
if err := response.Body.Close(); err != nil {
logger.DefaultLogger.Printf("Error while closing response body during artifact resolution: %v", err)
}
}()
if response.StatusCode != 200 {
retErr.PrivateErr = fmt.Errorf("Error during artifact resolution: HTTP status %d (%s)", response.StatusCode, response.Status)
return nil, retErr
}
responseBody, err := io.ReadAll(response.Body)
if err != nil {
retErr.PrivateErr = fmt.Errorf("Error during artifact resolution: %s", err)
return nil, retErr
}
assertion, err := sp.ParseXMLArtifactResponse(responseBody, possibleRequestIDs, artifactResolveRequest.ID)
if err != nil {
return nil, err
}
return assertion, nil
}
func (sp *ServiceProvider) parseResponseHTTP(req *http.Request, possibleRequestIDs []string) (*Assertion, error) {
retErr := &InvalidResponseError{
Now: TimeNow(),
}
rawResponseBuf, err := base64.StdEncoding.DecodeString(req.PostForm.Get("SAMLResponse"))
if err != nil {
retErr.PrivateErr = fmt.Errorf("cannot parse base64: %s", err)
return nil, retErr
}
assertion, err := sp.ParseXMLResponse(rawResponseBuf, possibleRequestIDs)
if err != nil {
return nil, err
}
return assertion, nil
}
// ParseXMLArtifactResponse validates the SAML Artifact resolver response
// and returns the verified assertion.
//
// This function handles verifying the digital signature, and verifying
// that the specified conditions and properties are met.
//
// If the function fails it will return an InvalidResponseError whose
// properties are useful in describing which part of the parsing process
// failed. However, to discourage inadvertent disclosure the diagnostic
// information, the Error() method returns a static string.
func (sp *ServiceProvider) ParseXMLArtifactResponse(soapResponseXML []byte, possibleRequestIDs []string, artifactRequestID string) (*Assertion, error) {
now := TimeNow()
retErr := &InvalidResponseError{
Response: string(soapResponseXML),
Now: now,
}
// ensure that the response XML is well-formed before we parse it
if err := xrv.Validate(bytes.NewReader(soapResponseXML)); err != nil {
retErr.PrivateErr = fmt.Errorf("invalid xml: %s", err)
return nil, retErr
}
doc := etree.NewDocument()
if err := doc.ReadFromBytes(soapResponseXML); err != nil {
retErr.PrivateErr = fmt.Errorf("cannot unmarshal response: %s", err)
return nil, retErr
}
if doc.Root() == nil {
retErr.PrivateErr = errors.New("invalid xml: no root")
return nil, retErr
}
if doc.Root().NamespaceURI() != "http://schemas.xmlsoap.org/soap/envelope/" ||
doc.Root().Tag != "Envelope" {
retErr.PrivateErr = fmt.Errorf("expected a SOAP Envelope")
return nil, retErr
}
soapBodyEl, err := findOneChild(doc.Root(), "http://schemas.xmlsoap.org/soap/envelope/", "Body")
if err != nil {
retErr.PrivateErr = err
return nil, retErr
}
artifactResponseEl, err := findOneChild(soapBodyEl, "urn:oasis:names:tc:SAML:2.0:protocol", "ArtifactResponse")
if err != nil {
retErr.PrivateErr = err
return nil, retErr
}
return sp.parseArtifactResponse(artifactResponseEl, possibleRequestIDs, artifactRequestID, now)
}
func (sp *ServiceProvider) parseArtifactResponse(artifactResponseEl *etree.Element, possibleRequestIDs []string, artifactRequestID string, now time.Time) (*Assertion, error) {
retErr := &InvalidResponseError{
Now: now,
Response: elementToString(artifactResponseEl),
}
{
var artifactResponse ArtifactResponse
if err := unmarshalElement(artifactResponseEl, &artifactResponse); err != nil {
retErr.PrivateErr = err
return nil, retErr
}
if artifactResponse.InResponseTo != artifactRequestID {
retErr.PrivateErr = fmt.Errorf("`InResponseTo` does not match the artifact request ID (expected %s)", artifactRequestID)
return nil, retErr
}
if artifactResponse.IssueInstant.Add(MaxIssueDelay).Before(now) {
retErr.PrivateErr = fmt.Errorf("response IssueInstant expired at %s", artifactResponse.IssueInstant.Add(MaxIssueDelay))
return nil, retErr
}
if artifactResponse.Issuer != nil && artifactResponse.Issuer.Value != sp.IDPMetadata.EntityID {
retErr.PrivateErr = fmt.Errorf("response Issuer does not match the IDP metadata (expected %q)", sp.IDPMetadata.EntityID)
return nil, retErr
}
if artifactResponse.Status.StatusCode.Value != StatusSuccess {
retErr.PrivateErr = ErrBadStatus{Status: artifactResponse.Status.StatusCode.Value}
return nil, retErr
}
}
var signatureRequirement signatureRequirement
sigErr := sp.validateSignature(artifactResponseEl)
switch sigErr {
case nil:
signatureRequirement = signatureNotRequired
case errSignatureElementNotPresent:
signatureRequirement = signatureRequired
default:
retErr.PrivateErr = sigErr
return nil, retErr
}
responseEl, err := findOneChild(artifactResponseEl, "urn:oasis:names:tc:SAML:2.0:protocol", "Response")
if err != nil {
retErr.PrivateErr = err
return nil, retErr
}
assertion, err := sp.parseResponse(responseEl, possibleRequestIDs, now, signatureRequirement)
if err != nil {
retErr.PrivateErr = err
return nil, retErr
}
return assertion, nil
}
// ParseXMLResponse parses and validates the SAML IDP response and
// returns the verified assertion.
//
// This function handles decrypting the message, verifying the digital
// signature on the assertion, and verifying that the specified conditions
// and properties are met.
//
// If the function fails it will return an InvalidResponseError whose
// properties are useful in describing which part of the parsing process
// failed. However, to discourage inadvertent disclosure the diagnostic
// information, the Error() method returns a static string.
func (sp *ServiceProvider) ParseXMLResponse(decodedResponseXML []byte, possibleRequestIDs []string) (*Assertion, error) {
now := TimeNow()
var err error
retErr := &InvalidResponseError{
Now: now,
Response: string(decodedResponseXML),
}
// ensure that the response XML is well-formed before we parse it
if err := xrv.Validate(bytes.NewReader(decodedResponseXML)); err != nil {
retErr.PrivateErr = fmt.Errorf("invalid xml: %s", err)
return nil, retErr
}
doc := etree.NewDocument()
if err := doc.ReadFromBytes(decodedResponseXML); err != nil {
retErr.PrivateErr = err
return nil, retErr
}
if doc.Root() == nil {
retErr.PrivateErr = errors.New("invalid xml: no root")
return nil, retErr
}
assertion, err := sp.parseResponse(doc.Root(), possibleRequestIDs, now, signatureRequired)
if err != nil {
retErr.PrivateErr = err
return nil, retErr
}
return assertion, nil
}
type signatureRequirement int
const (
signatureRequired signatureRequirement = iota
signatureNotRequired
)
// validateXMLResponse validates the SAML IDP response and returns
// the verified assertion.
//
// This function handles decrypting the message, verifying the digital
// signature on the assertion, and verifying that the specified conditions
// and properties are met.
func (sp *ServiceProvider) parseResponse(responseEl *etree.Element, possibleRequestIDs []string, now time.Time, signatureRequirement signatureRequirement) (*Assertion, error) {
var responseSignatureErr error
var responseHasSignature bool
if signatureRequirement == signatureRequired {
responseSignatureErr = sp.validateSignature(responseEl)
if responseSignatureErr != errSignatureElementNotPresent {
responseHasSignature = true
}
// Note: we're deferring taking action on the signature validation until after we've
// processed the request attributes, because certain test cases seem to require this mis-feature.
// TODO(ross): adjust the test cases so that we can abort here if the Response signature is invalid.
}
// validate request attributes
{
var response Response
if err := unmarshalElement(responseEl, &response); err != nil {
return nil, fmt.Errorf("cannot unmarshal response: %v", err)
}
// If the response is *not* signed, the Destination may be omitted.
if responseHasSignature || response.Destination != "" {
if response.Destination != sp.AcsURL.String() {
return nil, fmt.Errorf("`Destination` does not match AcsURL (expected %q, actual %q)", sp.AcsURL.String(), response.Destination)
}
}
requestIDvalid := false
if sp.AllowIDPInitiated {
requestIDvalid = true
} else {
for _, possibleRequestID := range possibleRequestIDs {
if response.InResponseTo == possibleRequestID {
requestIDvalid = true
}
}
}
if !requestIDvalid {
return nil, fmt.Errorf("`InResponseTo` does not match any of the possible request IDs (expected %v)", possibleRequestIDs)
}
if response.IssueInstant.Add(MaxIssueDelay).Before(now) {
return nil, fmt.Errorf("response IssueInstant expired at %s", response.IssueInstant.Add(MaxIssueDelay))
}
if response.Issuer != nil && response.Issuer.Value != sp.IDPMetadata.EntityID {
return nil, fmt.Errorf("response Issuer does not match the IDP metadata (expected %q)", sp.IDPMetadata.EntityID)
}
if response.Status.StatusCode.Value != StatusSuccess {
return nil, ErrBadStatus{Status: response.Status.StatusCode.Value}
}
}
if signatureRequirement == signatureRequired {
switch responseSignatureErr {
case nil:
// since the request has a signature, none of the Assertions need one
signatureRequirement = signatureNotRequired
case errSignatureElementNotPresent:
// the request has no signature, so assertions must be signed
signatureRequirement = signatureRequired // nop
default:
return nil, responseSignatureErr
}
}
var errs []error
var assertions []Assertion
// look for encrypted assertions
{
encryptedAssertionEls, err := findChildren(responseEl, "urn:oasis:names:tc:SAML:2.0:assertion", "EncryptedAssertion")
if err != nil {
return nil, err
}
for _, encryptedAssertionEl := range encryptedAssertionEls {
assertion, err := sp.parseEncryptedAssertion(encryptedAssertionEl, possibleRequestIDs, now, signatureRequirement)
if err != nil {
errs = append(errs, err)
continue
}
assertions = append(assertions, *assertion)
}
}
// look for plaintext assertions
{
assertionEls, err := findChildren(responseEl, "urn:oasis:names:tc:SAML:2.0:assertion", "Assertion")
if err != nil {
return nil, err
}
for _, assertionEl := range assertionEls {
assertion, err := sp.parseAssertion(assertionEl, possibleRequestIDs, now, signatureRequirement)
if err != nil {
errs = append(errs, err)
continue
}
assertions = append(assertions, *assertion)
}
}
if len(assertions) == 0 {
if len(errs) > 0 {
return nil, errs[0]
}
return nil, fmt.Errorf("expected at least one valid Assertion, none found")
}
// if we have at least one assertion, return the first one. It is almost universally true that valid responses
// contain only one assertion. This is less that fully correct, but we didn't realize that there could be more
// than one assertion at the time of establishing the public interface of ParseXMLResponse(), so for compatibility
// we return the first one.
return &assertions[0], nil
}
func (sp *ServiceProvider) parseEncryptedAssertion(encryptedAssertionEl *etree.Element, possibleRequestIDs []string, now time.Time, signatureRequirement signatureRequirement) (*Assertion, error) {
assertionEl, err := sp.decryptElement(encryptedAssertionEl)
if err != nil {
return nil, fmt.Errorf("failed to decrypt EncryptedAssertion: %v", err)
}
return sp.parseAssertion(assertionEl, possibleRequestIDs, now, signatureRequirement)
}
func (sp *ServiceProvider) decryptElement(encryptedEl *etree.Element) (*etree.Element, error) {
encryptedDataEl, err := findOneChild(encryptedEl, "http://www.w3.org/2001/04/xmlenc#", "EncryptedData")
if err != nil {
return nil, err
}
var key interface{} = sp.Key
keyEl := encryptedEl.FindElement("./EncryptedKey")
if keyEl != nil {
var err error
key, err = xmlenc.Decrypt(sp.Key, keyEl)
if err != nil {
return nil, fmt.Errorf("failed to decrypt key from response: %s", err)
}
}
plaintextEl, err := xmlenc.Decrypt(key, encryptedDataEl)
if err != nil {
return nil, err
}
if err := xrv.Validate(bytes.NewReader(plaintextEl)); err != nil {
return nil, fmt.Errorf("plaintext response contains invalid XML: %s", err)
}
doc := etree.NewDocument()
if err := doc.ReadFromBytes(plaintextEl); err != nil {
return nil, fmt.Errorf("cannot parse plaintext response %v", err)
}
return doc.Root(), nil
}