xmlsig

Documentation

Overview

Package xmlsig builds the WS-Security signed SOAP envelopes required by the SAT "Descarga Masiva" web service.

The SAT authentication endpoint expects a SOAP 1.1 envelope whose <Timestamp> element is signed with the FIEL using an enveloped XML-DSig: exclusive canonicalization (xml-exc-c14n), SHA-1 digests and an RSA-SHA1 signature, with the certificate carried in a <BinarySecurityToken>.

Rather than run a general-purpose C14N engine over parsed XML (fragile and error-prone), we emit the signed fragments (Timestamp and SignedInfo) directly in their canonical form and sign those exact bytes. Because we control the XML generation, the emitted form already matches exclusive-C14N output. This is the same strategy used by the reference phpcfdi implementation.

Index

• func AuthEnvelope(s Signer, created time.Time, ttl time.Duration, timestampID, tokenID string) (string, error)
• func NoSpaces(s string) string
• func SignEnveloped(s Signer, toDigest, uri, keyInfoXML string) (string, error)
• type Signer

Functions

func AuthEnvelope

func AuthEnvelope(s Signer, created time.Time, ttl time.Duration, timestampID, tokenID string) (string, error)

AuthEnvelope builds a signed SOAP envelope for the SAT Autenticacion operation. created is the moment the timestamp opens; the timestamp is valid for ttl (the SAT uses 5 minutes). tokenID and timestampID must be unique per request.

func NoSpaces

func NoSpaces(s string) string

NoSpaces removes insignificant whitespace between XML tags, matching the simplified canonicalization the SAT expects (phpcfdi's Helpers::nospaces).

func SignEnveloped

func SignEnveloped(s Signer, toDigest, uri, keyInfoXML string) (string, error)

SignEnveloped builds an enveloped <Signature> that signs toDigest (the element to be digested, in its canonical form) with the given Reference URI (empty for the SAT SolicitaDescarga signature). keyInfoXML is the <KeyInfo> block.

The digest is SHA-1 over NoSpaces(toDigest); the SignedInfo is signed with RSA-SHA1. The emitted SignedInfo omits its redundant xmlns (inherited from the enclosing Signature), while the signed bytes include it — exclusive C14N makes the two equivalent, which is what the SAT verifies.

Types

type Signer

type Signer interface {
	// SignSHA1 signs data with RSA PKCS#1 v1.5 / SHA-1 using the FIEL private key.
	SignSHA1(data []byte) ([]byte, error)
	// CertificateBase64 returns the base64 DER certificate for the token.
	CertificateBase64() string
}

Signer holds the material needed to produce a signature.