Visual FoxPro

Verify an XML Signature with Multiple References

See more XML Digital Signatures Examples

Demonstrates how to verify an XML digital signature that contains multiple references. Visual FoxPro

LOCAL lnSuccess
LOCAL loHttp
LOCAL loSbXml
LOCAL loVerifier
LOCAL lnVerifyReferenceDigests
LOCAL lnVerified
LOCAL lnSignedInfoVerified
LOCAL lnNumRefs
LOCAL i
LOCAL lnRefDigestVerified

lnSuccess = 0

* This example requires the Chilkat API to have been previously unlocked.
* See Global Unlock Sample for sample code.

* An example of an enveloping XML signature with mulitple references is available at
* https://www.chilkatsoft.com/exampleData/envelopedMultipleRefs.xml

* This example will show how to verify the signature and all references, and also how
* to verify each reference individually.  This is useful to distinguish which part
* of the XML signature validation failed.  It could be that one or more of the references
* failed because of a hash computation mismatch.  Or it could be that the signature over
* the SignedInfo failed.  

* First, let's grab the sample XML signature.
loHttp = CreateObject('Chilkat.Http')
loSbXml = CreateObject('Chilkat.StringBuilder')
lnSuccess = loHttp.QuickGetSb("https://www.chilkatsoft.com/exampleData/envelopedMultipleRefs.xml",loSbXml)
IF (lnSuccess <> 1) THEN
    ? loHttp.LastErrorText
    RELEASE loHttp
    RELEASE loSbXml
    CANCEL
ENDIF

* Load the XML containing the signature to be verified.
loVerifier = CreateObject('Chilkat.XmlDSig')
lnSuccess = loVerifier.LoadSignatureSb(loSbXml)
IF (lnSuccess <> 1) THEN
    ? loVerifier.LastErrorText
    RELEASE loHttp
    RELEASE loSbXml
    RELEASE loVerifier
    CANCEL
ENDIF

lnVerifyReferenceDigests = 1

* The quick way to validate all references and the signature over the SignedInfo
* is to call VerifySignature with verifyReferenceDigests equal to 1.
lnVerified = loVerifier.VerifySignature(lnVerifyReferenceDigests)
? "Signature and all reference digests verified = " + STR(lnVerified)

* Let's pretend the call to VerifySignature returned 0.  Something did not validate.
* Was it one or more of the References that did not hash to the correct value?
* Or was it the signature over the SignedInfo that failed?
* We can check just the signature over the SignedInfo by passing 0 to VerifySignature.
* This allows us to skip the hashing and checking each Reference.  
lnVerifyReferenceDigests = 0
lnSignedInfoVerified = loVerifier.VerifySignature(lnVerifyReferenceDigests)
? "Neglecting the reference hashes, the SignedInfo validation result = " + STR(lnSignedInfoVerified)

* We can also verify each reference digest separately
lnNumRefs = loVerifier.NumReferences
i = 0
DO WHILE i < lnNumRefs
    lnRefDigestVerified = loVerifier.VerifyReferenceDigest(i)
    ? "Reference " + STR(i) + " digest verified = " + STR(lnRefDigestVerified)
    i = i + 1
ENDDO

* For this sample XML signature with 3 References, we get the following output:

* Signature and all reference digests verified = True
* Neglecting the reference hashes, the SignedInfo validation result = True
* Reference 0 digest verified = True
* Reference 1 digest verified = True
* Reference 2 digest verified = Tru

RELEASE loHttp
RELEASE loSbXml
RELEASE loVerifier