Initial QSfera import

Server/vendor/github.com/Azure/go-ntlmssp/authheader.go

@@ -0,0 +1,65 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+package ntlmssp
+
+import (
+	"encoding/base64"
+	"net/http"
+	"strings"
+)
+
+var schemaPreference = [...]string{"NTLM", "Negotiate", "Basic"}
+
+type authheader struct {
+	schema string
+	data   string
+}
+
+// newAuthHeader extracts the authheader from the provided HTTP headers.
+// It selects the most preferred authentication scheme.
+// If no supported scheme is found, it returns an empty authheader.
+func newAuthHeader(req http.Header) authheader {
+	auth := req.Values("Www-Authenticate")
+	preferred, idx := -1, -1
+	for i, s := range auth {
+		for j, schema := range schemaPreference {
+			if s == schema || strings.HasPrefix(s, schema+" ") {
+				if preferred == -1 || j < preferred {
+					preferred = j
+					idx = i
+					break
+				}
+			}
+		}
+	}
+	if idx == -1 {
+		return authheader{}
+	}
+	schema, data, _ := strings.Cut(auth[idx], " ")
+	return authheader{
+		schema: schema,
+		data:   data,
+	}
+}
+
+// isNTLM returns true if the authheader schema is NTLM or Negotiate.
+func (h authheader) isNTLM() bool {
+	return h.schema == "NTLM" || h.schema == "Negotiate"
+}
+
+// isBasic returns true if the authheader schema is Basic.
+func (h authheader) isBasic() bool {
+	return h.schema == "Basic"
+}
+
+// token extracts and decodes the base64 token from the authheader.
+// It returns nil if the schema is not NTLM or Negotiate.
+func (h authheader) token() ([]byte, error) {
+	if !h.isNTLM() {
+		// Schema not supported for token extraction
+		return nil, nil
+	}
+	// RFC4559 4.2 - The token is a base64-encoded value
+	return base64.StdEncoding.DecodeString(h.data)
+}