Add SAML support

Signed-off-by: Bryan Frimin <bryan@getprobo.com>

pkg/auth/saml_config_validator.go

@@ -0,0 +1,127 @@
+// Copyright (c) 2025 Probo Inc <hello@getprobo.com>.
+//
+// Permission to use, copy, modify, and/or distribute this software for any
+// purpose with or without fee is hereby granted, provided that the above
+// copyright notice and this permission notice appear in all copies.
+//
+// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
+// REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
+// AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
+// INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
+// LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
+// OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
+// PERFORMANCE OF THIS SOFTWARE.
+
+package auth
+
+import (
+	"crypto/x509"
+	"encoding/pem"
+	"fmt"
+	"net/url"
+)
+
+type ValidationError struct {
+	Field   string
+	Message string
+}
+
+func (e ValidationError) Error() string {
+	return fmt.Sprintf("%s: %s", e.Field, e.Message)
+}
+
+// ValidateIdPConfiguration validates only the IdP (Identity Provider) configuration.
+// This validates user-provided data from the IdP.
+// SP (Service Provider) configuration is generated by the application and doesn't need validation.
+func ValidateIdPConfiguration(
+	idpEntityID string,
+	idpSsoURL string,
+	idpCertificate string,
+) []ValidationError {
+	var errors []ValidationError
+
+	// Validate IdP Entity ID
+	if idpEntityID == "" {
+		errors = append(errors, ValidationError{
+			Field:   "idp_entity_id",
+			Message: "IdP Entity ID cannot be empty",
+		})
+	}
+
+	// Validate IdP SSO URL - accept both HTTP and HTTPS
+	if err := validateURL(idpSsoURL, "idp_sso_url"); err != nil {
+		errors = append(errors, *err)
+	}
+
+	// Validate IdP certificate
+	if err := validateCertificate(idpCertificate); err != nil {
+		errors = append(errors, ValidationError{
+			Field:   "idp_certificate",
+			Message: err.Error(),
+		})
+	}
+
+	return errors
+}
+
+func validateURL(urlStr string, fieldName string) *ValidationError {
+	if urlStr == "" {
+		return &ValidationError{
+			Field:   fieldName,
+			Message: "URL cannot be empty",
+		}
+	}
+
+	parsedURL, err := url.Parse(urlStr)
+	if err != nil {
+		return &ValidationError{
+			Field:   fieldName,
+			Message: fmt.Sprintf("invalid URL format: %v", err),
+		}
+	}
+
+	if parsedURL.Scheme == "" {
+		return &ValidationError{
+			Field:   fieldName,
+			Message: "URL must have a scheme (http or https)",
+		}
+	}
+
+	if parsedURL.Scheme != "http" && parsedURL.Scheme != "https" {
+		return &ValidationError{
+			Field:   fieldName,
+			Message: "URL scheme must be http or https (found: " + parsedURL.Scheme + ")",
+		}
+	}
+
+	if parsedURL.Host == "" {
+		return &ValidationError{
+			Field:   fieldName,
+			Message: "URL must have a host",
+		}
+	}
+
+	return nil
+}
+
+func validateCertificate(certPEM string) error {
+	if certPEM == "" {
+		return fmt.Errorf("certificate cannot be empty")
+	}
+
+	block, _ := pem.Decode([]byte(certPEM))
+	if block == nil {
+		return fmt.Errorf("failed to parse certificate PEM")
+	}
+
+	if block.Type != "CERTIFICATE" {
+		return fmt.Errorf("PEM block type must be CERTIFICATE (found: %s)", block.Type)
+	}
+
+	_, err := x509.ParseCertificate(block.Bytes)
+	if err != nil {
+		return fmt.Errorf("failed to parse X.509 certificate: %w", err)
+	}
+
+	return nil
+}