initial commit, xmldsig support

xmldsig/xmldsig.go

@@ -0,0 +1,163 @@
+package xmldsig
+
+import (
+	"errors"
+	"unsafe"
+)
+
+// Note: on mac you need: brew install libxmlsec1 libxml2
+
+// #cgo pkg-config: xmlsec1
+// #include <xmlsec/xmlsec.h>
+// #include <xmlsec/xmltree.h>
+// #include <xmlsec/xmldsig.h>
+// #include <xmlsec/crypto.h>
+import "C"
+
+// #cgo pkg-config: libxml-2.0
+// #include "libxml/parser.h"
+// #include "libxml/parserInternals.h"
+// #include "libxml/xmlmemory.h"
+import "C"
+
+func init() {
+	C.xmlInitParser()
+
+	if rv := C.xmlSecInit(); rv < 0 {
+		panic("xmlsec failed to initialize")
+	}
+	if rv := C.xmlSecCryptoAppInit(nil); rv < 0 {
+		panic("xmlsec crypto initialization failed.")
+	}
+	if rv := C.xmlSecCryptoInit(); rv < 0 {
+		panic("xmlsec crypto initialization failed.")
+	}
+}
+
+func newContext(pemFormatKey []byte) (*C.xmlSecDSigCtx, error) {
+	ctx := C.xmlSecDSigCtxCreate(nil)
+	if ctx == nil {
+		return nil, errors.New("failed to create signature context")
+	}
+
+	ctx.signKey = C.xmlSecCryptoAppKeyLoadMemory(
+		(*C.xmlSecByte)(unsafe.Pointer(&pemFormatKey[0])),
+		C.xmlSecSize(len(pemFormatKey)),
+		C.xmlSecKeyDataFormatPem,
+		nil, nil, nil)
+	if ctx.signKey == nil {
+		return nil, errors.New("failed to load pem key")
+	}
+	return ctx, nil
+}
+
+func closeContext(ctx *C.xmlSecDSigCtx) {
+	C.xmlSecDSigCtxDestroy(ctx)
+}
+
+func newDoc(s string) (*C.xmlDoc, error) {
+	ctx := C.xmlCreateMemoryParserCtxt(C.CString(s), C.int(len(s)))
+	if ctx == nil {
+		return nil, errors.New("error creating parser")
+	}
+	defer C.xmlFreeParserCtxt(ctx)
+
+	//C.xmlCtxtUseOptions(ctx, C.int(p.Options))
+	C.xmlParseDocument(ctx)
+
+	if ctx.wellFormed == C.int(0) {
+		return nil, errors.New("malformed XML")
+	}
+
+	doc := ctx.myDoc
+	if doc == nil {
+		return nil, errors.New("parse failed")
+	}
+	return doc, nil
+}
+
+func dumpDoc(doc *C.xmlDoc) string {
+	var buffer *C.xmlChar
+	var bufferSize C.int
+	C.xmlDocDumpMemory(doc, &buffer, &bufferSize)
+	rv := C.GoStringN((*C.char)(unsafe.Pointer(buffer)), bufferSize)
+	C.xmlMemFree(unsafe.Pointer(buffer))
+	return rv
+}
+
+func closeDoc(doc *C.xmlDoc) {
+	C.xmlFreeDoc(doc)
+}
+
+// Sign returns a version of docStr signed with key according to
+// the XML-DSIG standard. docStr is a template document meaning
+// that it contains a `Signature` element in the
+// http://www.w3.org/2000/09/xmldsig# namespace.
+func Sign(key []byte, docStr string) (string, error) {
+	ctx, err := newContext(key)
+	if err != nil {
+		return "", err
+	}
+	defer closeContext(ctx)
+
+	doc, err := newDoc(docStr)
+	if err != nil {
+		return "", err
+	}
+	defer closeDoc(doc)
+
+	node := C.xmlSecFindNode(C.xmlDocGetRootElement(doc),
+		(*C.xmlChar)(unsafe.Pointer(&C.xmlSecNodeSignature)),
+		(*C.xmlChar)(unsafe.Pointer(&C.xmlSecDSigNs)))
+	if node == nil {
+		return "", errors.New("cannot find start node")
+	}
+
+	if rv := C.xmlSecDSigCtxSign(ctx, node); rv < 0 {
+		return "", errors.New("failed to sign")
+	}
+
+	return dumpDoc(doc), nil
+}
+
+var ErrVerificationFailed = errors.New("signature verification failed")
+
+const (
+	xmlSecDSigStatusUnknown   = 0
+	xmlSecDSigStatusSucceeded = 1
+	xmlSecDSigStatusInvalid   = 2
+)
+
+// Verify checks that the signature in docStr is valid according
+// to the XML-DSIG specification. publicKey is the public part of
+// the key used to sign docStr. If the signature is not correct,
+// this function returns ErrVarificationFailed.
+func Verify(publicKey []byte, docStr string) error {
+	ctx, err := newContext(publicKey)
+	if err != nil {
+		return err
+	}
+	defer closeContext(ctx)
+
+	doc, err := newDoc(docStr)
+	if err != nil {
+		return err
+	}
+	defer closeDoc(doc)
+
+	node := C.xmlSecFindNode(C.xmlDocGetRootElement(doc),
+		(*C.xmlChar)(unsafe.Pointer(&C.xmlSecNodeSignature)),
+		(*C.xmlChar)(unsafe.Pointer(&C.xmlSecDSigNs)))
+	if node == nil {
+		return errors.New("cannot find start node")
+	}
+
+	if rv := C.xmlSecDSigCtxVerify(ctx, node); rv < 0 {
+		return errors.New("failed to verify")
+	}
+
+	if ctx.status != xmlSecDSigStatusSucceeded {
+		return ErrVerificationFailed
+	}
+	return nil
+}