xmldsig.pl -- XML Digital signature

This library deals with XMLDSIG, RSA signed XML documents.

See also

- http://www.di-mgt.com.au/xmldsig.html

- https://www.bmt-online.org/geekisms/RSA_verify

- http://stackoverflow.com/questions/5576777/whats-the-difference-between-nid-sha-and-nid-sha1-in-openssl

 xmld_signed_DOM(+DOM, -SignedDOM, +Options) is det

Translate an XML DOM structure in a signed version. Options:

key_file(+File)

File holding the private key needed to sign

key_password(+Password)

String holding the password to op the private key.

The SignedDOM must be emitted using xml_write/3 or xml_write_canonical/3. If xml_write/3 is used, the option layout(false) is needed to avoid changing the layout of the SignedInfo element and the signed DOM, which will cause the signature to be invalid.

 dom_hash(+DOM, -ODOM, -Hash, +Options) is det[private]

Compute the digest for DOM.

Arguments:

Hash	- is the base64 encoded version of the selected SHA algorithm.

 signed_info(+Hash, -Signature, -SDOM, -KeyDOM, +Options)[private]

 signed_info_dom(+Hash, -SDOM, +Options) is det[private]

True when SDOM is the xmldsign:Signature DOM for an object with the given Hash.

 rsa_signature(+SignedInfo:string, -Signature, -KeyDOM, +Options)[private]

 rsa_key_dom(+Key, -DOM) is det[private]

Produce the KeyInfo node from the private key.

 key_info(+Key, -Info) is det[private]

Extract the RSA modulus and exponent from a private key. These are the first end second field of the rsa term. They are represented as hexadecimal encoded bytes. We must recode this to base64.

To be done

- Provide better support from library(ssl).

 xmld_verify_signature(+DOM, +SignatureDOM, -Certificate, +Options) is det

Confirm that an ds:Signature element contains a valid signature. Certificate is bound to the certificate that appears in the element if the signature is valid. It is up to the caller to determine if the certificate is trusted or not.

Note: The DOM and SignatureDOM must have been obtained using the load_structure/3 option keep_prefix(true) otherwise it is impossible to generate an identical document for checking the signature. See also xml_write_canonical/3.