---

sidebar_position: 2 sidebar_label: Embedded Go Library

Embedded Go Library

For Go applications, you can embed the PolicyEngine directly using the github.com/manetu/policyengine package. This approach offers the lowest latency since policy evaluation happens in-process, but is only available in the Community Edition and does not offer an upgrade path to the Premium offering. See Choosing Your Integration Method for a detailed comparison of integration options.

:::warning The embedded Go library is only available in the Community Edition — it cannot connect to Premium services. If you decide later to upgrade to Premium, you will need to port your PEPs to the HTTP-API :::

Installation

go get github.com/manetu/policyengine

Basic Usage

The simplest way to create a PolicyEngine is with NewLocalPolicyEngine, which loads policy domains from YAML files:

package main

import (
    "context"
    "log"

    "github.com/manetu/policyengine/pkg/core"
)

func main() {
    // Create a PolicyEngine from local policy domain files
    pe, err := core.NewLocalPolicyEngine([]string{
        "./policies/policydomain.yaml",
    })
    if err != nil {
        log.Fatalf("Failed to create PolicyEngine: %v", err)
    }

    // Create a PORC expression as a JSON string
    porc := `{
        "principal": {
            "sub": "user@example.com",
            "mroles": ["mrn:iam:example.com:role:developer"],
            "mclearance": "MODERATE"
        },
        "operation": "api:documents:read",
        "resource": "mrn:app:example:document:12345",
        "context": {
            "source_ip": "192.168.1.100"
        }
    }`

    // Authorize the request
    ctx := context.Background()
    allowed, err := pe.Authorize(ctx, porc)
    if err != nil {
        log.Fatalf("Authorization error: %v", err)
    }

    if allowed {
        log.Println("Access GRANTED")
    } else {
        log.Println("Access DENIED")
    }
}

Loading Multiple Domains

You can load multiple policy domain files. Domains are loaded in order, with later domains taking precedence for name collisions:

pe, err := core.NewLocalPolicyEngine([]string{
    "./policies/base-domain.yaml",      // Common policies
    "./policies/app-domain.yaml",       // Application-specific policies
})

Using Maps for Efficiency

The Authorize method accepts either a JSON string or a map[string]interface{}. Using a map directly avoids JSON parsing overhead:

porc := map[string]interface{}{
    "principal": map[string]interface{}{
        "sub":        "user@example.com",
        "mroles":     []string{"mrn:iam:example.com:role:developer"},
        "mclearance": "MODERATE",
    },
    "operation": "api:documents:read",
    "resource":  "mrn:app:example:document:12345",
    "context": map[string]interface{}{
        "source_ip": "192.168.1.100",
    },
}

allowed, err := pe.Authorize(ctx, porc)

:::tip Array Type Flexibility When constructing PORC maps directly in Go, you can use either []string or []interface{} for array fields like mroles, mgroups, and scopes. Both formats work correctly:

// Both formats work:
"mroles": []string{"mrn:iam:example.com:role:admin", "mrn:iam:example.com:role:user"},
"mroles": []interface{}{"mrn:iam:example.com:role:admin", "mrn:iam:example.com:role:user"},

Using []string is more idiomatic Go, while []interface{} matches the format produced by json.Unmarshal(). :::

Configuration Options

The PolicyEngine can be configured with various options:

import (
    "github.com/manetu/policyengine/pkg/core"
    "github.com/manetu/policyengine/pkg/core/options"
    "github.com/manetu/policyengine/pkg/core/accesslog"
)

pe, err := core.NewLocalPolicyEngine(
    []string{"./policies/policydomain.yaml"},
    options.WithAccessLog(accesslog.NewStdoutFactory()),
    // Add additional options as needed
)

Available Options

Option	Description
WithAccessLog(factory)	Configure access logging
WithCompilerOptions(opts...)	Configure OPA compiler options

Probe Mode

Use probe mode to check permissions without generating audit logs. This is useful for UI capability checks—for example, determining whether to show an "Edit" button:

allowed, err := pe.Authorize(ctx, porc, options.SetProbeMode(true))

When probe mode is enabled:

• Policies are evaluated normally
• No audit records are generated
• Useful for pre-flight permission checks

:::warning Only use probe mode for UI capability checks. Actual access control decisions should always be audited (omit the probe option or set it to false). See Audit for more information. :::

Complete Middleware Example

Here's a complete HTTP middleware PEP implementation:

package main

import (
    "context"
    "encoding/json"
    "fmt"
    "log"
    "net/http"
    "strings"

    "github.com/manetu/policyengine/pkg/core"
)

type AuthMiddleware struct {
    pe core.PolicyEngine
}

func NewAuthMiddleware(policyDomains []string) (*AuthMiddleware, error) {
    pe, err := core.NewLocalPolicyEngine(policyDomains)
    if err != nil {
        return nil, err
    }
    return &AuthMiddleware{pe: pe}, nil
}

func (m *AuthMiddleware) Handler(next http.Handler) http.Handler {
    return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
        // Extract claims from JWT (use proper JWT validation in production)
        claims := extractClaims(r)
        if claims == nil {
            http.Error(w, "Unauthorized", http.StatusUnauthorized)
            return
        }

        // Build PORC expression
        porc := map[string]interface{}{
            "principal": map[string]interface{}{
                "sub":          claims["sub"],
                "mroles":       claims["mroles"],
                "mgroups":      claims["mgroups"],
                "scopes":       claims["scope"],
                "mclearance":   claims["mclearance"],
                "mannotations": claims["mannotations"],
            },
            "operation": fmt.Sprintf("api:%s:%s",
                extractResourceType(r.URL.Path),
                strings.ToLower(r.Method)),
            "resource": extractResourceMRN(r.URL.Path),
            "context": map[string]interface{}{
                "source_ip":  r.RemoteAddr,
                "user_agent": r.UserAgent(),
                "method":     r.Method,
                "path":       r.URL.Path,
            },
        }

        // Call PDP
        allowed, err := m.pe.Authorize(r.Context(), porc)
        if err != nil {
            log.Printf("PDP error: %v", err)
            http.Error(w, "Internal Server Error", http.StatusInternalServerError)
            return
        }

        if !allowed {
            log.Printf("Access denied: sub=%s operation=%s resource=%s",
                claims["sub"], porc["operation"], porc["resource"])
            http.Error(w, "Forbidden", http.StatusForbidden)
            return
        }

        // Access granted - proceed
        next.ServeHTTP(w, r)
    })
}

func extractClaims(r *http.Request) map[string]interface{} {
    // Implementation: Parse and validate JWT from Authorization header
    return nil // placeholder
}

func extractResourceType(path string) string {
    // Implementation: Extract resource type from URL path
    return "resource" // placeholder
}

func extractResourceMRN(path string) string {
    // Implementation: Build MRN from URL path
    return "mrn:app:example:resource:id" // placeholder
}

func main() {
    // Load policy domains from YAML files
    policyDomains := []string{"./policies/policydomain.yaml"}

    middleware, err := NewAuthMiddleware(policyDomains)
    if err != nil {
        log.Fatalf("Failed to create auth middleware: %v", err)
    }

    mux := http.NewServeMux()
    mux.HandleFunc("/api/", func(w http.ResponseWriter, r *http.Request) {
        json.NewEncoder(w).Encode(map[string]string{"status": "ok"})
    })

    handler := middleware.Handler(mux)
    log.Println("Server starting on :8080")
    log.Fatal(http.ListenAndServe(":8080", handler))
}