Initial QSfera import

Server/vendor/github.com/crewjam/saml/xmlenc/decrypt.go

@@ -0,0 +1,116 @@
+package xmlenc
+
+import (
+
+	// nolint: gas
+	"crypto/rsa"
+	"crypto/x509"
+	"encoding/base64"
+	"encoding/pem"
+	"errors"
+	"fmt"
+
+	"strings"
+
+	"github.com/beevik/etree"
+)
+
+// ErrAlgorithmNotImplemented is returned when encryption used is not
+// supported.
+type ErrAlgorithmNotImplemented string
+
+func (e ErrAlgorithmNotImplemented) Error() string {
+	return "algorithm is not implemented: " + string(e)
+}
+
+// ErrCannotFindRequiredElement is returned by Decrypt when a required
+// element cannot be found.
+type ErrCannotFindRequiredElement string
+
+func (e ErrCannotFindRequiredElement) Error() string {
+	return "cannot find required element: " + string(e)
+}
+
+// ErrIncorrectTag is returned when Decrypt is passed an element which
+// is neither an EncryptedType nor an EncryptedKey
+var ErrIncorrectTag = fmt.Errorf("tag must be an EncryptedType or EncryptedKey")
+
+// ErrIncorrectKeyLength is returned when the fixed length key is not
+// of the required length.
+type ErrIncorrectKeyLength int
+
+func (e ErrIncorrectKeyLength) Error() string {
+	return fmt.Sprintf("expected key to be %d bytes", int(e))
+}
+
+// ErrIncorrectKeyType is returned when the key is not the correct type
+type ErrIncorrectKeyType string
+
+func (e ErrIncorrectKeyType) Error() string {
+	return fmt.Sprintf("expected key to be %s", string(e))
+}
+
+// Decrypt decrypts the encrypted data using the provided key. If the
+// data are encrypted using AES or 3DEC, then the key should be a []byte.
+// If the data are encrypted with PKCS1v15 or RSA-OAEP-MGF1P then key should
+// be a *rsa.PrivateKey.
+func Decrypt(key interface{}, ciphertextEl *etree.Element) ([]byte, error) {
+	encryptionMethodEl := ciphertextEl.FindElement("./EncryptionMethod")
+	if encryptionMethodEl == nil {
+		return nil, ErrCannotFindRequiredElement("EncryptionMethod")
+	}
+	algorithm := encryptionMethodEl.SelectAttrValue("Algorithm", "")
+	decrypter, ok := decrypters[algorithm]
+	if !ok {
+		return nil, ErrAlgorithmNotImplemented(algorithm)
+	}
+	return decrypter.Decrypt(key, ciphertextEl)
+}
+
+func getCiphertext(encryptedKey *etree.Element) ([]byte, error) {
+	ciphertextEl := encryptedKey.FindElement("./CipherData/CipherValue")
+	if ciphertextEl == nil {
+		return nil, fmt.Errorf("cannot find CipherData element containing a CipherValue element")
+	}
+	ciphertext, err := base64.StdEncoding.DecodeString(strings.TrimSpace(ciphertextEl.Text()))
+	if err != nil {
+		return nil, err
+	}
+	return ciphertext, nil
+}
+
+func validateRSAKeyIfPresent(key interface{}, encryptedKey *etree.Element) (*rsa.PrivateKey, error) {
+	rsaKey, ok := key.(*rsa.PrivateKey)
+	if !ok {
+		return nil, errors.New("expected key to be a *rsa.PrivateKey")
+	}
+
+	// extract and verify that the public key matches the certificate
+	// this section is included to either let the service know up front
+	// if the key will work, or let the service provider know which key
+	// to use to decrypt the message. Either way, verification is not
+	// security-critical.
+	//nolint:revive,staticcheck // Keep the later empty branch so that we know to address this at a later date.
+	if el := encryptedKey.FindElement("./KeyInfo/X509Data/X509Certificate"); el != nil {
+		certPEMbuf := el.Text()
+		certPEMbuf = "-----BEGIN CERTIFICATE-----\n" + certPEMbuf + "\n-----END CERTIFICATE-----\n"
+		certPEM, _ := pem.Decode([]byte(certPEMbuf))
+		if certPEM == nil {
+			return nil, fmt.Errorf("invalid certificate")
+		}
+		cert, err := x509.ParseCertificate(certPEM.Bytes)
+		if err != nil {
+			return nil, err
+		}
+		pubKey, ok := cert.PublicKey.(*rsa.PublicKey)
+		if !ok {
+			return nil, fmt.Errorf("expected certificate to be an *rsa.PublicKey")
+		}
+		if rsaKey.N.Cmp(pubKey.N) != 0 || rsaKey.E != pubKey.E {
+			return nil, fmt.Errorf("certificate does not match provided key")
+		}
+	} else if el = encryptedKey.FindElement("./KeyInfo/X509Data/X509IssuerSerial"); el != nil {
+		// TODO: determine how to validate the issuer serial information
+	}
+	return rsaKey, nil
+}