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SignatureValidationFilter

The Shibboleth IdP V4 software has reached its End of Life and is no longer supported. This documentation is available for historical purposes only. See the IDP5 wiki space for current documentation on the supported version.

SignatureValidationFilter

Owned by Scott Cantor
Last updated: Sept 22, 2021 by Rod Widdowson

Namespace: urn:mace:shibboleth:2.0:metadata
Schema: http://shibboleth.net/schema/idp/shibboleth-metadata.xsd

Overview

The SignatureValidation filter verifies that a metadata instance is signed correctly with a trusted key, and is the linchpin of the security of most Shibboleth deployments.

The "Sign and Expire" distribution model

In practice, a SignatureValidation filter and a RequiredValidUntilFilter filter are often used together to securely obtain remote metadata via HTTP. See the FileBackedHTTPMetadataProvider and DynamicHTTPMetadataProvider topics for explicit configuration examples. Other distribution models are discussed in the TrustManagement topic.

There are four approaches to supplying a trust policy to the SignatureValidation filter:

  • A pointer to a certificate file

  • A reference to an externally defined TrustEngine bean

  • An inline <PublicKey> element

  • An inline <security:TrustEngine> element

Filter order is important!

In the overall sequence of filters, a filter of type SignatureValidation must appear before any filter that alters the metadata instance. Examples of the latter include EntityAttributesFilter, EntityRoleFilter, NameIDFormatFilter, and PredicateMetadataFilter .

Reference

Name / Type / Default

Description

Name / Type / Default

Description

requireSignedRoot

Boolean

true

If true, this fails to load metadata with no signature on the root XML element.

alwaysVerifyTrustedSource

Boolean

false

If true, the root signature of the metadata currently being processed will always be verified.

If false, then the root signature will be verified unless the metadata source is "trusted", defined as:

  • The backup file of a FileBackedHTTPMetadataProvider

certificateFile

File pathname

Path to a certificate file whose key is used to verify the signature.

Conflicts with trustEngineRef and both allowable child elements.

trustEngineRef

Bean ID

Bean ID of a <security:TrustEngine> defined somewhere else in the configuration.

Conflicts with certificateFile and both allowable child elements.

defaultCriteriaRef

Bean ID

shibboleth.MetadataSignatureValidationStaticCriteria

(ADVANCED, not generally needed)

Bean ID of an externally defined CriteriaSet used as input the to the trust engine

signaturePrevalidatorRef

Bean ID

SAMLSignatureProfileValidator

(ADVANCED, not generally needed)

Bean ID of an externally defined SignaturePrevalidator. Used to perform pre-validation of an XML Signature, for example to validate that the signature conforms to a particular profile of XML Signature.

dynamicTrustedNamesStrategyRef

Bean ID

BasicDynamicTrustedNamesStrategy

(ADVANCED, not generally needed)

Bean ID of an externally defined Function<XMLObject, Set<String>>. This will be used to extract dynamic trusted names from signed metadata elements.

One of the following two child elements may be configured. Their use conflicts with the certificateFile and trustEngineRef XML attributes.

Name

Description

Name

Description

<PublicKey>

A PEM-format public key.

You can obtain a public key from a certificate using a command such as:

$ openssl x509 -pubkey -in cert.pem -noout

<security:TrustEngine>

A trust engine plugin that defines how the signature is to be checked

Examples

Externally specified certificate file
<MetadataFilter xsi:type="SignatureValidation" requireSignedRoot="true" certificateFile="${idp.home}/credentials/signer.pem"/>
Inline key
<MetadataFilter xsi:type="SignatureValidation" requireSignedRoot="true"> <PublicKey> MIIBI..... </PublicKey> </MetadataFilter>
Metadata Provider with inline trust engine
<MetadataFilter xsi:type="SignatureValidation" requireSignedRoot="true"> <security:TrustEngine id="SignerTrustEngine" xsi:type="security:StaticExplicitKeySignature"> <security:Credential id="SignerCredential" xsi:type="security:X509ResourceBacked"> <security:Certificate>${idp.home}/credentials/signer.pem</security:Certificate> </security:Credential> </security:TrustEngine> </MetadataFilter>
Metadata Provider with inline trust engine with multiple validation credentials
<MetadataFilter xsi:type="SignatureValidation" requireSignedRoot="true"> <security:TrustEngine id="SignerTrustEngine" xsi:type="security:StaticExplicitKeySignature"> <security:Credential id="SignerCredential_1" xsi:type="security:X509ResourceBacked"> <security:Certificate>${idp.home}/credentials/signer1.pem</security:Certificate> </security:Credential> <security:Credential id="SignerCredential_2" xsi:type="security:X509ResourceBacked"> <security:Certificate>${idp.home}/credentials/signer2.pem</security:Certificate> </security:Credential> </security:TrustEngine> </MetadataFilter>
PKIX signature validation with static trust anchors
<MetadataFilter xsi:type="SignatureValidation" requireSignedRoot="true"> <security:TrustEngine id="VTSignerTrustEngine" xsi:type="security:StaticPKIXSignature"> <security:TrustedName>shib</security:TrustedName> <security:ValidationInfo id="VTPKIXValidationInfo" xsi:type="security:PKIXResourceBacked"> <security:Certificate>${idp.home}/credentials/vtmwca.pem</security:Certificate> </security:ValidationInfo> </security:TrustEngine> </MetadataFilter>

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