feat(M51): add SCEP server (RFC 8894) for MDM and network device enrollment

Implements Simple Certificate Enrollment Protocol with single-endpoint
operation-based dispatch (GetCACaps, GetCACert, PKIOperation), PKCS#7
SignedData CSR extraction with fallback for raw/base64 CSR, challenge
password authentication via CSR attributes, and shared internal/pkcs7
package extracted from EST handler to eliminate code duplication.

24 new tests (11 service + 13 handler) plus 5 shared pkcs7 package tests.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

README.md

@@ -70,7 +70,7 @@ For a detailed comparison with other competitors and enterprise platforms, see [
 
 - **Everything is auditable.** Immutable append-only audit trail records every lifecycle action, every API call, and every approval decision. Certificate digest emails deliver daily briefings. Prometheus metrics endpoint for Grafana dashboards.
 
-- **Standards-based protocol support.** EST server (RFC 7030) for device and WiFi certificate enrollment. ACME ARI (RFC 9773) for CA-directed renewal timing. S/MIME certificate issuance with email protection EKU for end-to-end encrypted email. DER-encoded X.509 CRL and embedded OCSP responder for revocation infrastructure.
+- **Standards-based protocol support.** EST server (RFC 7030) for device and WiFi certificate enrollment. SCEP server (RFC 8894) for MDM platforms and network device enrollment. ACME ARI (RFC 9773) for CA-directed renewal timing. S/MIME certificate issuance with email protection EKU for end-to-end encrypted email. DER-encoded X.509 CRL and embedded OCSP responder for revocation infrastructure.
 
 - **Multiple interfaces for different workflows.** REST API (107 routes) for automation, CLI for scripting, MCP server for AI assistants (Claude, Cursor, Windsurf), Helm chart for Kubernetes, and the web dashboard (24 pages) for day-to-day operations.
 

cmd/server/main.go

@@ -339,6 +339,26 @@ func main() {
 			"endpoints", "/.well-known/est/{cacerts,simpleenroll,simplereenroll,csrattrs}")
 	}
 
+	// Register SCEP (RFC 8894) handlers if enabled
+	if cfg.SCEP.Enabled {
+		issuerConn, ok := issuerRegistry.Get(cfg.SCEP.IssuerID)
+		if !ok {
+			logger.Error("SCEP issuer not found in registry", "issuer_id", cfg.SCEP.IssuerID)
+			os.Exit(1)
+		}
+		scepService := service.NewSCEPService(cfg.SCEP.IssuerID, issuerConn, auditService, logger, cfg.SCEP.ChallengePassword)
+		if cfg.SCEP.ProfileID != "" {
+			scepService.SetProfileID(cfg.SCEP.ProfileID)
+		}
+		scepHandler := handler.NewSCEPHandler(scepService)
+		apiRouter.RegisterSCEPHandlers(scepHandler)
+		logger.Info("SCEP server enabled",
+			"issuer_id", cfg.SCEP.IssuerID,
+			"profile_id", cfg.SCEP.ProfileID,
+			"challenge_password_set", cfg.SCEP.ChallengePassword != "",
+			"endpoints", "/scep?operation={GetCACaps,GetCACert,PKIOperation}")
+	}
+
 	logger.Info("registered all API handlers")
 
 	// Build middleware stack

docs/architecture.md

@@ -673,6 +673,46 @@ type ESTService interface {
 
 **Audit:** Every EST enrollment is recorded in the audit trail with `protocol: "EST"`, the CN, SANs, issuer ID, serial number, and optional profile ID.
 
+### SCEP Server (RFC 8894)
+
+The SCEP (Simple Certificate Enrollment Protocol) server provides certificate enrollment for MDM platforms and network devices. It runs at `/scep` with operation-based dispatch via query parameters per RFC 8894.
+
+**Architecture:** SCEP follows the exact same layering as EST — a handler-level protocol that delegates certificate issuance to an existing `IssuerConnector`. The `SCEPService` bridges the `SCEPHandler` to whichever issuer connector is configured via `CERTCTL_SCEP_ISSUER_ID`.
+
+```
+Client (MDM, network device, SCEP client)
+    │
+    ▼
+SCEPHandler (handler layer)
+    │  PKCS#7 envelope parsing, CSR extraction, challenge password extraction
+    ▼
+SCEPService (service layer)
+    │  Challenge password validation, CSR validation, CN/SAN extraction, audit recording
+    ▼
+IssuerConnector (connector layer via IssuerConnectorAdapter)
+    │  Certificate signing (Local CA, step-ca, etc.)
+    ▼
+Signed certificate returned as PKCS#7 certs-only
+```
+
+**Wire format:** SCEP clients wrap CSRs in PKCS#7 SignedData envelopes. The handler parses the outer ASN.1 ContentInfo → SignedData → EncapsulatedContentInfo to extract the CSR bytes. Fallback paths handle base64-encoded PKCS#7 and raw CSR submissions (for simpler clients). Responses use PKCS#7 certs-only via the shared `internal/pkcs7` package (same as EST). Single certs are returned as raw DER for `GetCACert`, chains as PKCS#7.
+
+**Authentication:** SCEP uses challenge passwords embedded in CSR attributes (OID 1.2.840.113549.1.9.7) rather than TLS client certificates. The server validates the challenge password against `CERTCTL_SCEP_CHALLENGE_PASSWORD`. When no challenge password is configured, any value is accepted.
+
+**Interface:** The `SCEPHandler` defines an `SCEPService` interface (dependency inversion):
+
+```go
+type SCEPService interface {
+    GetCACaps(ctx context.Context) string
+    GetCACert(ctx context.Context) (string, error)
+    PKCSReq(ctx context.Context, csrPEM string, challengePassword string, transactionID string) (*domain.SCEPEnrollResult, error)
+}
+```
+
+**Shared PKCS#7 package:** Both EST and SCEP handlers share a common `internal/pkcs7` package for building PKCS#7 certs-only responses and PEM-to-DER chain conversion, eliminating code duplication between the two enrollment protocols.
+
+**Audit:** Every SCEP enrollment is recorded in the audit trail with `protocol: "SCEP"`, the CN, SANs, issuer ID, serial number, transaction ID, and optional profile ID.
+
 ## Security Model
 
 ### Private Key Management

docs/connectors.md

@@ -314,16 +314,16 @@ Each issuer handles revocation differently:
 - **step-ca**: Calls step-ca's `/revoke` API endpoint. Clients should check step-ca's own CRL/OCSP for authoritative status.
 - **OpenSSL/Custom CA**: Invokes the configured revoke script (`CERTCTL_OPENSSL_REVOKE_SCRIPT`) with the serial number as an argument.
 
-### EST Integration (GetCACertPEM)
+### EST/SCEP Integration (GetCACertPEM)
 
-The `GetCACertPEM()` method returns the PEM-encoded CA certificate chain, used by the EST server's `/.well-known/est/cacerts` endpoint (RFC 7030) to distribute the CA chain to enrolling devices. Each issuer handles this differently:
+The `GetCACertPEM()` method returns the PEM-encoded CA certificate chain, used by both the EST server's `/.well-known/est/cacerts` endpoint (RFC 7030) and the SCEP server's `GetCACert` operation (RFC 8894) to distribute the CA chain to enrolling devices. Each issuer handles this differently:
 
-- **Local CA**: Returns the CA certificate PEM (self-signed or sub-CA cert). This is the primary EST issuer.
+- **Local CA**: Returns the CA certificate PEM (self-signed or sub-CA cert). This is the primary EST/SCEP issuer.
 - **ACME**: Returns error — ACME CAs provide chains per-issuance, not statically.
 - **step-ca**: Returns error — step-ca serves its own `/root` endpoint for CA distribution.
 - **OpenSSL/Custom CA**: Returns error — custom script-based CAs have no CA cert access through certctl.
 
-Note: EST (Enrollment over Secure Transport) is not a connector — it's a protocol handler (`internal/api/handler/est.go`) that delegates certificate issuance to whichever issuer connector is configured via `CERTCTL_EST_ISSUER_ID`. See the [Architecture Guide](architecture.md#est-server-rfc-7030) for details.
+Note: EST and SCEP are not connectors — they are protocol handlers (`internal/api/handler/est.go` and `internal/api/handler/scep.go`) that delegate certificate issuance to whichever issuer connector is configured via `CERTCTL_EST_ISSUER_ID` or `CERTCTL_SCEP_ISSUER_ID`. Both share a common `internal/pkcs7` package for PKCS#7 response encoding. See the [Architecture Guide](architecture.md#est-server-rfc-7030) for details.
 
 ### Built-in: Vault PKI
 

docs/features.md

@@ -444,6 +444,27 @@ Accepts both base64-encoded DER (EST standard) and PEM-encoded PKCS#10 CSR input
 | `CERTCTL_EST_ISSUER_ID` | `iss-local` | Issuer for EST enrollments |
 | `CERTCTL_EST_PROFILE_ID` | (none) | Optional profile constraint |
 
+### SCEP Server (RFC 8894)
+
+<!-- Source: internal/service/scep.go, internal/api/handler/scep.go -->
+
+Simple Certificate Enrollment Protocol for MDM platforms and network devices. Single endpoint with operation-based dispatch:
+
+| Operation | Method | Description |
+|---|---|---|
+| `GetCACaps` | GET | Server capabilities (plaintext, one per line) |
+| `GetCACert` | GET | CA certificate (DER for single cert, PKCS#7 for chain) |
+| `PKIOperation` | POST | Certificate enrollment (PKCS#7-wrapped or raw CSR) |
+
+SCEP uses a single URL (`/scep?operation=...`). The handler extracts PKCS#10 CSRs from PKCS#7 SignedData envelopes, with fallback support for base64-encoded and raw CSR submissions. Challenge password authentication via CSR attributes (OID 1.2.840.113549.1.9.7). Responses are PKCS#7 certs-only (same shared `internal/pkcs7` package as EST).
+
+| Env Var | Default | Description |
+|---|---|---|
+| `CERTCTL_SCEP_ENABLED` | `false` | Enable SCEP endpoint |
+| `CERTCTL_SCEP_ISSUER_ID` | `iss-local` | Issuer for SCEP enrollments |
+| `CERTCTL_SCEP_PROFILE_ID` | (none) | Optional profile constraint |
+| `CERTCTL_SCEP_CHALLENGE_PASSWORD` | (none) | Shared secret for enrollment authentication |
+
 ---
 
 ## ACME Renewal Information (RFC 9773)

internal/api/handler/est.go

@@ -12,6 +12,7 @@ import (
 
 	"github.com/shankar0123/certctl/internal/api/middleware"
 	"github.com/shankar0123/certctl/internal/domain"
+	"github.com/shankar0123/certctl/internal/pkcs7"
 )
 
 // ESTService defines the service interface for EST enrollment operations.
@@ -67,7 +68,7 @@ func (h ESTHandler) CACerts(w http.ResponseWriter, r *http.Request) {
 	}
 
 	// Parse PEM to DER for PKCS#7 encoding
-	derCerts, err := pemToDERChain(caCertPEM)
+	derCerts, err := pkcs7.PEMToDERChain(caCertPEM)
 	if err != nil {
 		requestID := middleware.GetRequestID(r.Context())
 		ErrorWithRequestID(w, http.StatusInternalServerError, "Failed to encode CA certificates", requestID)
@@ -75,7 +76,7 @@ func (h ESTHandler) CACerts(w http.ResponseWriter, r *http.Request) {
 	}
 
 	// Build a simple PKCS#7 SignedData (certs-only, degenerate) structure
-	pkcs7Data, err := buildCertsOnlyPKCS7(derCerts)
+	pkcs7Data, err := pkcs7.BuildCertsOnlyPKCS7(derCerts)
 	if err != nil {
 		requestID := middleware.GetRequestID(r.Context())
 		ErrorWithRequestID(w, http.StatusInternalServerError, "Failed to build PKCS#7 response", requestID)
@@ -237,7 +238,7 @@ func (h ESTHandler) writeCertResponse(w http.ResponseWriter, result *domain.ESTE
 	var derCerts [][]byte
 
 	// Add the issued certificate
-	certDER, err := pemToDERChain(result.CertPEM)
+	certDER, err := pkcs7.PEMToDERChain(result.CertPEM)
 	if err != nil || len(certDER) == 0 {
 		http.Error(w, "Failed to encode certificate", http.StatusInternalServerError)
 		return
@@ -246,14 +247,14 @@ func (h ESTHandler) writeCertResponse(w http.ResponseWriter, result *domain.ESTE
 
 	// Add the CA chain if present
 	if result.ChainPEM != "" {
-		chainDER, err := pemToDERChain(result.ChainPEM)
+		chainDER, err := pkcs7.PEMToDERChain(result.ChainPEM)
 		if err == nil {
 			derCerts = append(derCerts, chainDER...)
 		}
 	}
 
 	// Build PKCS#7 certs-only
-	pkcs7Data, err := buildCertsOnlyPKCS7(derCerts)
+	pkcs7Data, err := pkcs7.BuildCertsOnlyPKCS7(derCerts)
 	if err != nil {
 		http.Error(w, "Failed to build PKCS#7 response", http.StatusInternalServerError)
 		return
@@ -273,132 +274,5 @@ func (h ESTHandler) writeCertResponse(w http.ResponseWriter, result *domain.ESTE
 	}
 }
 
-// pemToDERChain converts PEM-encoded certificates to a slice of DER-encoded certificates.
+// NOTE: PKCS#7 helpers (BuildCertsOnlyPKCS7, PEMToDERChain, ASN.1 wrappers)
-func pemToDERChain(pemData string) ([][]byte, error) {
+// are in the shared internal/pkcs7 package, used by both EST and SCEP handlers.
-	var derCerts [][]byte
-	rest := []byte(pemData)
-	for {
-		var block *pem.Block
-		block, rest = pem.Decode(rest)
-		if block == nil {
-			break
-		}
-		if block.Type == "CERTIFICATE" {
-			derCerts = append(derCerts, block.Bytes)
-		}
-	}
-	if len(derCerts) == 0 {
-		return nil, fmt.Errorf("no certificates found in PEM data")
-	}
-	return derCerts, nil
-}
-
-// buildCertsOnlyPKCS7 creates a degenerate PKCS#7 SignedData structure containing only certificates.
-// This is the "certs-only" format specified in RFC 7030 Section 4.1.3 for /cacerts responses
-// and enrollment responses.
-//
-// ASN.1 structure (simplified):
-//
-//	ContentInfo {
-//	  contentType: signedData (1.2.840.113549.1.7.2)
-//	  content: SignedData {
-//	    version: 1
-//	    digestAlgorithms: {} (empty)
-//	    encapContentInfo: { contentType: data (1.2.840.113549.1.7.1) }
-//	    certificates: [cert1, cert2, ...]
-//	    signerInfos: {} (empty)
-//	  }
-//	}
-func buildCertsOnlyPKCS7(derCerts [][]byte) ([]byte, error) {
-	// We build the ASN.1 manually to avoid pulling in a PKCS#7 library.
-	// This is a well-defined, static structure — no signing needed.
-
-	// OID for signedData: 1.2.840.113549.1.7.2
-	oidSignedData := []byte{0x06, 0x09, 0x2a, 0x86, 0x48, 0x86, 0xf7, 0x0d, 0x01, 0x07, 0x02}
-	// OID for data: 1.2.840.113549.1.7.1
-	oidData := []byte{0x06, 0x09, 0x2a, 0x86, 0x48, 0x86, 0xf7, 0x0d, 0x01, 0x07, 0x01}
-
-	// Build certificates [0] IMPLICIT SET OF Certificate
-	var certsContent []byte
-	for _, cert := range derCerts {
-		certsContent = append(certsContent, cert...)
-	}
-	certsField := asn1WrapImplicit(0, certsContent)
-
-	// Build encapContentInfo: SEQUENCE { OID data }
-	encapContentInfo := asn1WrapSequence(oidData)
-
-	// Build digestAlgorithms: SET {} (empty)
-	digestAlgorithms := asn1WrapSet(nil)
-
-	// Build signerInfos: SET {} (empty)
-	signerInfos := asn1WrapSet(nil)
-
-	// Version: INTEGER 1
-	version := []byte{0x02, 0x01, 0x01}
-
-	// Build SignedData SEQUENCE
-	var signedDataContent []byte
-	signedDataContent = append(signedDataContent, version...)
-	signedDataContent = append(signedDataContent, digestAlgorithms...)
-	signedDataContent = append(signedDataContent, encapContentInfo...)
-	signedDataContent = append(signedDataContent, certsField...)
-	signedDataContent = append(signedDataContent, signerInfos...)
-	signedData := asn1WrapSequence(signedDataContent)
-
-	// Wrap in [0] EXPLICIT for ContentInfo.content
-	contentField := asn1WrapExplicit(0, signedData)
-
-	// Build ContentInfo SEQUENCE
-	var contentInfoContent []byte
-	contentInfoContent = append(contentInfoContent, oidSignedData...)
-	contentInfoContent = append(contentInfoContent, contentField...)
-	contentInfo := asn1WrapSequence(contentInfoContent)
-
-	return contentInfo, nil
-}
-
-// asn1WrapSequence wraps content in an ASN.1 SEQUENCE tag (0x30).
-func asn1WrapSequence(content []byte) []byte {
-	return asn1Wrap(0x30, content)
-}
-
-// asn1WrapSet wraps content in an ASN.1 SET tag (0x31).
-func asn1WrapSet(content []byte) []byte {
-	return asn1Wrap(0x31, content)
-}
-
-// asn1WrapExplicit wraps content in an ASN.1 context-specific EXPLICIT tag.
-func asn1WrapExplicit(tag int, content []byte) []byte {
-	return asn1Wrap(byte(0xa0|tag), content)
-}
-
-// asn1WrapImplicit wraps content in an ASN.1 context-specific IMPLICIT CONSTRUCTED tag.
-func asn1WrapImplicit(tag int, content []byte) []byte {
-	return asn1Wrap(byte(0xa0|tag), content)
-}
-
-// asn1Wrap wraps content with an ASN.1 tag and length.
-func asn1Wrap(tag byte, content []byte) []byte {
-	length := len(content)
-	var result []byte
-	result = append(result, tag)
-	result = append(result, asn1EncodeLength(length)...)
-	result = append(result, content...)
-	return result
-}
-
-// asn1EncodeLength encodes a length in ASN.1 DER format.
-func asn1EncodeLength(length int) []byte {
-	if length < 0x80 {
-		return []byte{byte(length)}
-	}
-	// Long form
-	var lengthBytes []byte
-	l := length
-	for l > 0 {
-		lengthBytes = append([]byte{byte(l & 0xff)}, lengthBytes...)
-		l >>= 8
-	}
-	return append([]byte{byte(0x80 | len(lengthBytes))}, lengthBytes...)
-}

internal/api/handler/est_handler_test.go

@@ -18,6 +18,7 @@ import (
 	"time"
 
 	"github.com/shankar0123/certctl/internal/domain"
+	"github.com/shankar0123/certctl/internal/pkcs7"
 )
 
 // mockESTService implements ESTService for testing.
@@ -338,12 +339,12 @@ func TestESTCSRAttrs_MethodNotAllowed(t *testing.T) {
 	}
 }
 
-func TestBuildCertsOnlyPKCS7(t *testing.T) {
+func TestBuildCertsOnlyPKCS7_ViaSharedPackage(t *testing.T) {
-	// Test with a dummy DER certificate
+	// Test with a dummy DER certificate via shared pkcs7 package
 	dummyCert := []byte{0x30, 0x82, 0x01, 0x00} // minimal ASN.1 SEQUENCE
-	result, err := buildCertsOnlyPKCS7([][]byte{dummyCert})
+	result, err := pkcs7.BuildCertsOnlyPKCS7([][]byte{dummyCert})
 	if err != nil {
-		t.Fatalf("buildCertsOnlyPKCS7 failed: %v", err)
+		t.Fatalf("BuildCertsOnlyPKCS7 failed: %v", err)
 	}
 	if len(result) == 0 {
 		t.Error("expected non-empty PKCS#7 output")
@@ -354,49 +355,24 @@ func TestBuildCertsOnlyPKCS7(t *testing.T) {
 	}
 }
 
-func TestPemToDERChain(t *testing.T) {
+func TestPemToDERChain_ViaSharedPackage(t *testing.T) {
 	pemData := generateTestCertPEM(t)
-	certs, err := pemToDERChain(pemData)
+	certs, err := pkcs7.PEMToDERChain(pemData)
 	if err != nil {
-		t.Fatalf("pemToDERChain failed: %v", err)
+		t.Fatalf("PEMToDERChain failed: %v", err)
 	}
 	if len(certs) != 1 {
 		t.Errorf("expected 1 cert, got %d", len(certs))
 	}
 }
 
-func TestPemToDERChain_NoCerts(t *testing.T) {
+func TestPemToDERChain_NoCerts_ViaSharedPackage(t *testing.T) {
-	_, err := pemToDERChain("not a PEM")
+	_, err := pkcs7.PEMToDERChain("not a PEM")
 	if err == nil {
 		t.Error("expected error for invalid PEM")
 	}
 }
 
-func TestASN1EncodeLength(t *testing.T) {
-	tests := []struct {
-		length   int
-		expected []byte
-	}{
-		{0, []byte{0x00}},
-		{1, []byte{0x01}},
-		{127, []byte{0x7f}},
-		{128, []byte{0x81, 0x80}},
-		{256, []byte{0x82, 0x01, 0x00}},
-	}
-	for _, tt := range tests {
-		result := asn1EncodeLength(tt.length)
-		if len(result) != len(tt.expected) {
-			t.Errorf("asn1EncodeLength(%d): expected %d bytes, got %d", tt.length, len(tt.expected), len(result))
-			continue
-		}
-		for i := range result {
-			if result[i] != tt.expected[i] {
-				t.Errorf("asn1EncodeLength(%d): byte %d: expected 0x%02x, got 0x%02x", tt.length, i, tt.expected[i], result[i])
-			}
-		}
-	}
-}
-
 func TestESTCSRAttrs_ServiceError(t *testing.T) {
 	svc := &mockESTService{
 		CSRAttrsErr: errors.New("service error"),

internal/api/handler/scep.go

@@ -0,0 +1,353 @@
+package handler
+
+import (
+	"context"
+	"crypto/x509"
+	"encoding/asn1"
+	"encoding/base64"
+	"encoding/pem"
+	"fmt"
+	"io"
+	"net/http"
+	"strings"
+
+	"github.com/shankar0123/certctl/internal/api/middleware"
+	"github.com/shankar0123/certctl/internal/domain"
+	"github.com/shankar0123/certctl/internal/pkcs7"
+)
+
+// SCEPService defines the service interface for SCEP enrollment operations.
+// SCEP (RFC 8894) is a protocol for certificate enrollment used by MDM platforms
+// and network devices.
+type SCEPService interface {
+	// GetCACaps returns the SCEP server capabilities as a newline-separated string.
+	GetCACaps(ctx context.Context) string
+
+	// GetCACert returns the PEM-encoded CA certificate chain.
+	GetCACert(ctx context.Context) (string, error)
+
+	// PKCSReq processes a PKCS#10 CSR and returns a signed certificate.
+	PKCSReq(ctx context.Context, csrPEM string, challengePassword string, transactionID string) (*domain.SCEPEnrollResult, error)
+}
+
+// SCEPHandler handles HTTP requests for the SCEP protocol (RFC 8894).
+//
+// SCEP uses a single endpoint with operation-based dispatch via query parameters.
+// All operations use GET or POST to the same path.
+//
+// Supported operations:
+//   - GET  ?operation=GetCACaps    — server capabilities
+//   - GET  ?operation=GetCACert    — CA certificate distribution
+//   - POST ?operation=PKIOperation — certificate enrollment (PKCSReq)
+type SCEPHandler struct {
+	svc SCEPService
+}
+
+// NewSCEPHandler creates a new SCEPHandler.
+func NewSCEPHandler(svc SCEPService) SCEPHandler {
+	return SCEPHandler{svc: svc}
+}
+
+// HandleSCEP is the single entry point for all SCEP operations.
+// It dispatches based on the "operation" query parameter.
+func (h SCEPHandler) HandleSCEP(w http.ResponseWriter, r *http.Request) {
+	operation := r.URL.Query().Get("operation")
+
+	switch operation {
+	case "GetCACaps":
+		h.getCACaps(w, r)
+	case "GetCACert":
+		h.getCACert(w, r)
+	case "PKIOperation":
+		h.pkiOperation(w, r)
+	default:
+		http.Error(w, fmt.Sprintf("Unknown SCEP operation: %s", operation), http.StatusBadRequest)
+	}
+}
+
+// getCACaps handles GET ?operation=GetCACaps
+// Returns the SCEP server capabilities as plaintext, one per line.
+func (h SCEPHandler) getCACaps(w http.ResponseWriter, r *http.Request) {
+	if r.Method != http.MethodGet {
+		http.Error(w, "Method not allowed", http.StatusMethodNotAllowed)
+		return
+	}
+
+	caps := h.svc.GetCACaps(r.Context())
+	w.Header().Set("Content-Type", "text/plain")
+	w.WriteHeader(http.StatusOK)
+	w.Write([]byte(caps))
+}
+
+// getCACert handles GET ?operation=GetCACert
+// Returns the CA certificate(s). Single cert as DER, chain as PKCS#7.
+func (h SCEPHandler) getCACert(w http.ResponseWriter, r *http.Request) {
+	if r.Method != http.MethodGet {
+		http.Error(w, "Method not allowed", http.StatusMethodNotAllowed)
+		return
+	}
+
+	caCertPEM, err := h.svc.GetCACert(r.Context())
+	if err != nil {
+		requestID := middleware.GetRequestID(r.Context())
+		ErrorWithRequestID(w, http.StatusInternalServerError, fmt.Sprintf("Failed to get CA certificate: %v", err), requestID)
+		return
+	}
+
+	// Parse PEM to DER chain
+	derCerts, err := pkcs7.PEMToDERChain(caCertPEM)
+	if err != nil {
+		requestID := middleware.GetRequestID(r.Context())
+		ErrorWithRequestID(w, http.StatusInternalServerError, "Failed to parse CA certificates", requestID)
+		return
+	}
+
+	if len(derCerts) == 1 {
+		// Single CA cert — return as raw DER
+		w.Header().Set("Content-Type", "application/x-x509-ca-cert")
+		w.WriteHeader(http.StatusOK)
+		w.Write(derCerts[0])
+		return
+	}
+
+	// Multiple certs (CA + RA or chain) — return as PKCS#7
+	pkcs7Data, err := pkcs7.BuildCertsOnlyPKCS7(derCerts)
+	if err != nil {
+		requestID := middleware.GetRequestID(r.Context())
+		ErrorWithRequestID(w, http.StatusInternalServerError, "Failed to build PKCS#7 response", requestID)
+		return
+	}
+
+	w.Header().Set("Content-Type", "application/x-x509-ca-ra-cert")
+	w.WriteHeader(http.StatusOK)
+	w.Write(pkcs7Data)
+}
+
+// pkiOperation handles POST ?operation=PKIOperation
+// Processes a SCEP enrollment request containing a PKCS#7-wrapped CSR.
+func (h SCEPHandler) pkiOperation(w http.ResponseWriter, r *http.Request) {
+	if r.Method != http.MethodPost {
+		http.Error(w, "Method not allowed", http.StatusMethodNotAllowed)
+		return
+	}
+
+	requestID := middleware.GetRequestID(r.Context())
+
+	body, err := io.ReadAll(io.LimitReader(r.Body, 1<<20)) // 1MB limit
+	if err != nil {
+		ErrorWithRequestID(w, http.StatusBadRequest, "Failed to read request body", requestID)
+		return
+	}
+	defer r.Body.Close()
+
+	if len(body) == 0 {
+		ErrorWithRequestID(w, http.StatusBadRequest, "Empty request body", requestID)
+		return
+	}
+
+	// Extract the PKCS#10 CSR from the PKCS#7 SignedData envelope
+	csrDER, challengePassword, transactionID, err := extractCSRFromPKCS7(body)
+	if err != nil {
+		ErrorWithRequestID(w, http.StatusBadRequest, fmt.Sprintf("Invalid SCEP message: %v", err), requestID)
+		return
+	}
+
+	// Validate the CSR
+	csr, err := x509.ParseCertificateRequest(csrDER)
+	if err != nil {
+		ErrorWithRequestID(w, http.StatusBadRequest, fmt.Sprintf("Invalid CSR: %v", err), requestID)
+		return
+	}
+	if err := csr.CheckSignature(); err != nil {
+		ErrorWithRequestID(w, http.StatusBadRequest, fmt.Sprintf("CSR signature invalid: %v", err), requestID)
+		return
+	}
+
+	// Convert DER CSR to PEM for the service layer
+	csrPEM := string(pem.EncodeToMemory(&pem.Block{
+		Type:  "CERTIFICATE REQUEST",
+		Bytes: csrDER,
+	}))
+
+	result, err := h.svc.PKCSReq(r.Context(), csrPEM, challengePassword, transactionID)
+	if err != nil {
+		if strings.Contains(err.Error(), "challenge password") {
+			ErrorWithRequestID(w, http.StatusForbidden, "Invalid challenge password", requestID)
+			return
+		}
+		ErrorWithRequestID(w, http.StatusInternalServerError, fmt.Sprintf("Enrollment failed: %v", err), requestID)
+		return
+	}
+
+	// Build response: issued cert wrapped in PKCS#7 certs-only
+	h.writeSCEPResponse(w, result)
+}
+
+// writeSCEPResponse writes a SCEP enrollment response as PKCS#7 certs-only (DER).
+func (h SCEPHandler) writeSCEPResponse(w http.ResponseWriter, result *domain.SCEPEnrollResult) {
+	var derCerts [][]byte
+
+	certDER, err := pkcs7.PEMToDERChain(result.CertPEM)
+	if err != nil || len(certDER) == 0 {
+		http.Error(w, "Failed to encode certificate", http.StatusInternalServerError)
+		return
+	}
+	derCerts = append(derCerts, certDER...)
+
+	if result.ChainPEM != "" {
+		chainDER, err := pkcs7.PEMToDERChain(result.ChainPEM)
+		if err == nil {
+			derCerts = append(derCerts, chainDER...)
+		}
+	}
+
+	pkcs7Data, err := pkcs7.BuildCertsOnlyPKCS7(derCerts)
+	if err != nil {
+		http.Error(w, "Failed to build PKCS#7 response", http.StatusInternalServerError)
+		return
+	}
+
+	w.Header().Set("Content-Type", "application/x-pki-message")
+	w.WriteHeader(http.StatusOK)
+	w.Write(pkcs7Data)
+}
+
+// extractCSRFromPKCS7 extracts a PKCS#10 CSR from a SCEP PKCS#7 SignedData envelope.
+//
+// SCEP clients wrap the CSR in a PKCS#7 SignedData structure. For the MVP, we parse
+// the outer ASN.1 structure to find the encapsulated content (the CSR bytes), and
+// extract the challenge password from the CSR attributes.
+//
+// Returns: csrDER, challengePassword, transactionID, error
+func extractCSRFromPKCS7(data []byte) ([]byte, string, string, error) {
+	// Try to decode as PKCS#7 SignedData
+	csrDER, err := parseSignedDataForCSR(data)
+	if err != nil {
+		// Fallback: some clients send the CSR directly (not wrapped in PKCS#7)
+		// or send base64-encoded data
+		decoded, decErr := base64.StdEncoding.DecodeString(strings.TrimSpace(string(data)))
+		if decErr == nil {
+			// Try the decoded data as PKCS#7
+			csrDER2, err2 := parseSignedDataForCSR(decoded)
+			if err2 == nil {
+				return extractCSRFields(csrDER2)
+			}
+			// Maybe the decoded data IS the CSR directly
+			if _, parseErr := x509.ParseCertificateRequest(decoded); parseErr == nil {
+				return extractCSRFields(decoded)
+			}
+		}
+		// Maybe the raw data IS the CSR directly (no PKCS#7 wrapping)
+		if _, parseErr := x509.ParseCertificateRequest(data); parseErr == nil {
+			return extractCSRFields(data)
+		}
+		return nil, "", "", fmt.Errorf("failed to extract CSR from PKCS#7: %w", err)
+	}
+	return extractCSRFields(csrDER)
+}
+
+// extractCSRFields extracts the challenge password and transaction ID from CSR attributes.
+func extractCSRFields(csrDER []byte) ([]byte, string, string, error) {
+	csr, err := x509.ParseCertificateRequest(csrDER)
+	if err != nil {
+		return nil, "", "", fmt.Errorf("invalid CSR: %w", err)
+	}
+
+	challengePassword := ""
+	transactionID := ""
+
+	// OID for challengePassword: 1.2.840.113549.1.9.7
+	oidChallengePassword := asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 9, 7}
+
+	// Extract challenge password from parsed CSR attributes.
+	// Attributes is []pkix.AttributeTypeAndValueSET where each has Type (OID)
+	// and Value ([][]pkix.AttributeTypeAndValue). The challenge password value
+	// is stored as a string in the inner AttributeTypeAndValue.Value field.
+	for _, attr := range csr.Attributes {
+		if attr.Type.Equal(oidChallengePassword) {
+			if len(attr.Value) > 0 && len(attr.Value[0]) > 0 {
+				if pwd, ok := attr.Value[0][0].Value.(string); ok {
+					challengePassword = pwd
+				}
+			}
+		}
+	}
+
+	// Use CN as fallback transaction ID if not found in attributes
+	if transactionID == "" && csr.Subject.CommonName != "" {
+		transactionID = csr.Subject.CommonName
+	}
+
+	return csrDER, challengePassword, transactionID, nil
+}
+
+// pkcs7ContentInfo represents the outer ContentInfo structure.
+type pkcs7ContentInfo struct {
+	ContentType asn1.ObjectIdentifier
+	Content     asn1.RawValue `asn1:"explicit,tag:0"`
+}
+
+// pkcs7SignedData represents a simplified SignedData structure for CSR extraction.
+type pkcs7SignedData struct {
+	Version          int
+	DigestAlgorithms asn1.RawValue
+	EncapContentInfo asn1.RawValue
+}
+
+// pkcs7EncapContent represents the EncapsulatedContentInfo.
+type pkcs7EncapContent struct {
+	ContentType asn1.ObjectIdentifier
+	Content     asn1.RawValue `asn1:"explicit,optional,tag:0"`
+}
+
+// parseSignedDataForCSR extracts the encapsulated content (CSR) from PKCS#7 SignedData.
+func parseSignedDataForCSR(data []byte) ([]byte, error) {
+	var contentInfo pkcs7ContentInfo
+	rest, err := asn1.Unmarshal(data, &contentInfo)
+	if err != nil {
+		return nil, fmt.Errorf("failed to parse ContentInfo: %w", err)
+	}
+	if len(rest) > 0 {
+		// Trailing data is OK for some implementations
+	}
+
+	// OID for signedData: 1.2.840.113549.1.7.2
+	oidSignedData := asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 7, 2}
+	if !contentInfo.ContentType.Equal(oidSignedData) {
+		return nil, fmt.Errorf("not SignedData: got OID %v", contentInfo.ContentType)
+	}
+
+	// Parse the SignedData
+	var signedData pkcs7SignedData
+	_, err = asn1.Unmarshal(contentInfo.Content.Bytes, &signedData)
+	if err != nil {
+		return nil, fmt.Errorf("failed to parse SignedData: %w", err)
+	}
+
+	// Parse the EncapsulatedContentInfo to get the CSR
+	var encapContent pkcs7EncapContent
+	_, err = asn1.Unmarshal(signedData.EncapContentInfo.FullBytes, &encapContent)
+	if err != nil {
+		return nil, fmt.Errorf("failed to parse EncapsulatedContentInfo: %w", err)
+	}
+
+	if len(encapContent.Content.Bytes) == 0 {
+		return nil, fmt.Errorf("empty encapsulated content")
+	}
+
+	// The content may be wrapped in an OCTET STRING
+	var csrBytes []byte
+	var octetString asn1.RawValue
+	if _, err := asn1.Unmarshal(encapContent.Content.Bytes, &octetString); err == nil && octetString.Tag == asn1.TagOctetString {
+		csrBytes = octetString.Bytes
+	} else {
+		csrBytes = encapContent.Content.Bytes
+	}
+
+	// Validate it's a parseable CSR
+	if _, err := x509.ParseCertificateRequest(csrBytes); err != nil {
+		return nil, fmt.Errorf("extracted content is not a valid CSR: %w", err)
+	}
+
+	return csrBytes, nil
+}

internal/api/handler/scep_handler_test.go

@@ -0,0 +1,262 @@
+package handler
+
+import (
+	"context"
+	"encoding/pem"
+	"errors"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+
+	"github.com/shankar0123/certctl/internal/domain"
+)
+
+// mockSCEPService implements SCEPService for testing.
+type mockSCEPService struct {
+	CACaps       string
+	CACertPEM    string
+	CACertErr    error
+	EnrollResult *domain.SCEPEnrollResult
+	EnrollErr    error
+}
+
+func (m *mockSCEPService) GetCACaps(ctx context.Context) string {
+	if m.CACaps != "" {
+		return m.CACaps
+	}
+	return "POSTPKIOperation\nSHA-256\nAES\nSCEPStandard\n"
+}
+
+func (m *mockSCEPService) GetCACert(ctx context.Context) (string, error) {
+	return m.CACertPEM, m.CACertErr
+}
+
+func (m *mockSCEPService) PKCSReq(ctx context.Context, csrPEM string, challengePassword string, transactionID string) (*domain.SCEPEnrollResult, error) {
+	return m.EnrollResult, m.EnrollErr
+}
+
+func TestSCEP_GetCACaps_Success(t *testing.T) {
+	svc := &mockSCEPService{}
+	h := NewSCEPHandler(svc)
+
+	req := httptest.NewRequest(http.MethodGet, "/scep?operation=GetCACaps", nil)
+	w := httptest.NewRecorder()
+	h.HandleSCEP(w, req)
+
+	if w.Code != http.StatusOK {
+		t.Errorf("expected 200, got %d: %s", w.Code, w.Body.String())
+	}
+	ct := w.Header().Get("Content-Type")
+	if ct != "text/plain" {
+		t.Errorf("expected text/plain, got %s", ct)
+	}
+	body := w.Body.String()
+	if !strings.Contains(body, "POSTPKIOperation") {
+		t.Errorf("expected POSTPKIOperation in response, got: %s", body)
+	}
+	if !strings.Contains(body, "SHA-256") {
+		t.Errorf("expected SHA-256 in response, got: %s", body)
+	}
+}
+
+func TestSCEP_GetCACaps_MethodNotAllowed(t *testing.T) {
+	svc := &mockSCEPService{}
+	h := NewSCEPHandler(svc)
+
+	req := httptest.NewRequest(http.MethodPost, "/scep?operation=GetCACaps", nil)
+	w := httptest.NewRecorder()
+	h.HandleSCEP(w, req)
+
+	if w.Code != http.StatusMethodNotAllowed {
+		t.Errorf("expected 405, got %d", w.Code)
+	}
+}
+
+func TestSCEP_GetCACert_Success_SingleCert(t *testing.T) {
+	certPEM := generateTestCertPEM(t)
+	svc := &mockSCEPService{
+		CACertPEM: certPEM,
+	}
+	h := NewSCEPHandler(svc)
+
+	req := httptest.NewRequest(http.MethodGet, "/scep?operation=GetCACert", nil)
+	w := httptest.NewRecorder()
+	h.HandleSCEP(w, req)
+
+	if w.Code != http.StatusOK {
+		t.Errorf("expected 200, got %d: %s", w.Code, w.Body.String())
+	}
+	ct := w.Header().Get("Content-Type")
+	if ct != "application/x-x509-ca-cert" {
+		t.Errorf("expected application/x-x509-ca-cert, got %s", ct)
+	}
+	if w.Body.Len() == 0 {
+		t.Error("expected non-empty body")
+	}
+}
+
+func TestSCEP_GetCACert_MethodNotAllowed(t *testing.T) {
+	svc := &mockSCEPService{}
+	h := NewSCEPHandler(svc)
+
+	req := httptest.NewRequest(http.MethodPost, "/scep?operation=GetCACert", nil)
+	w := httptest.NewRecorder()
+	h.HandleSCEP(w, req)
+
+	if w.Code != http.StatusMethodNotAllowed {
+		t.Errorf("expected 405, got %d", w.Code)
+	}
+}
+
+func TestSCEP_GetCACert_ServiceError(t *testing.T) {
+	svc := &mockSCEPService{
+		CACertErr: errors.New("CA unavailable"),
+	}
+	h := NewSCEPHandler(svc)
+
+	req := httptest.NewRequest(http.MethodGet, "/scep?operation=GetCACert", nil)
+	w := httptest.NewRecorder()
+	h.HandleSCEP(w, req)
+
+	if w.Code != http.StatusInternalServerError {
+		t.Errorf("expected 500, got %d", w.Code)
+	}
+}
+
+func TestSCEP_PKIOperation_MethodNotAllowed(t *testing.T) {
+	svc := &mockSCEPService{}
+	h := NewSCEPHandler(svc)
+
+	req := httptest.NewRequest(http.MethodGet, "/scep?operation=PKIOperation", nil)
+	w := httptest.NewRecorder()
+	h.HandleSCEP(w, req)
+
+	if w.Code != http.StatusMethodNotAllowed {
+		t.Errorf("expected 405, got %d", w.Code)
+	}
+}
+
+func TestSCEP_PKIOperation_EmptyBody(t *testing.T) {
+	svc := &mockSCEPService{}
+	h := NewSCEPHandler(svc)
+
+	req := httptest.NewRequest(http.MethodPost, "/scep?operation=PKIOperation", strings.NewReader(""))
+	w := httptest.NewRecorder()
+	h.HandleSCEP(w, req)
+
+	if w.Code != http.StatusBadRequest {
+		t.Errorf("expected 400, got %d", w.Code)
+	}
+}
+
+func TestSCEP_PKIOperation_InvalidBody(t *testing.T) {
+	svc := &mockSCEPService{}
+	h := NewSCEPHandler(svc)
+
+	req := httptest.NewRequest(http.MethodPost, "/scep?operation=PKIOperation", strings.NewReader("not-valid-asn1-or-csr"))
+	w := httptest.NewRecorder()
+	h.HandleSCEP(w, req)
+
+	if w.Code != http.StatusBadRequest {
+		t.Errorf("expected 400, got %d: %s", w.Code, w.Body.String())
+	}
+}
+
+func TestSCEP_PKIOperation_ServiceError(t *testing.T) {
+	svc := &mockSCEPService{
+		EnrollErr: errors.New("enrollment failed"),
+	}
+	h := NewSCEPHandler(svc)
+
+	// Generate a valid raw CSR DER to send as body (fallback path)
+	csrPEM := generateTestCSRPEM(t)
+	block, _ := pem.Decode([]byte(csrPEM))
+	if block == nil {
+		t.Fatal("failed to decode CSR PEM")
+	}
+
+	req := httptest.NewRequest(http.MethodPost, "/scep?operation=PKIOperation", strings.NewReader(string(block.Bytes)))
+	w := httptest.NewRecorder()
+	h.HandleSCEP(w, req)
+
+	if w.Code != http.StatusInternalServerError {
+		t.Errorf("expected 500, got %d: %s", w.Code, w.Body.String())
+	}
+}
+
+func TestSCEP_PKIOperation_Success_RawCSR(t *testing.T) {
+	certPEM := generateTestCertPEM(t)
+	svc := &mockSCEPService{
+		EnrollResult: &domain.SCEPEnrollResult{
+			CertPEM:  certPEM,
+			ChainPEM: "",
+		},
+	}
+	h := NewSCEPHandler(svc)
+
+	csrPEM := generateTestCSRPEM(t)
+	block, _ := pem.Decode([]byte(csrPEM))
+	if block == nil {
+		t.Fatal("failed to decode CSR PEM")
+	}
+
+	req := httptest.NewRequest(http.MethodPost, "/scep?operation=PKIOperation", strings.NewReader(string(block.Bytes)))
+	w := httptest.NewRecorder()
+	h.HandleSCEP(w, req)
+
+	if w.Code != http.StatusOK {
+		t.Errorf("expected 200, got %d: %s", w.Code, w.Body.String())
+	}
+	ct := w.Header().Get("Content-Type")
+	if ct != "application/x-pki-message" {
+		t.Errorf("expected application/x-pki-message, got %s", ct)
+	}
+}
+
+func TestSCEP_PKIOperation_ChallengePasswordRejected(t *testing.T) {
+	svc := &mockSCEPService{
+		EnrollErr: errors.New("invalid challenge password"),
+	}
+	h := NewSCEPHandler(svc)
+
+	csrPEM := generateTestCSRPEM(t)
+	block, _ := pem.Decode([]byte(csrPEM))
+	if block == nil {
+		t.Fatal("failed to decode CSR PEM")
+	}
+
+	req := httptest.NewRequest(http.MethodPost, "/scep?operation=PKIOperation", strings.NewReader(string(block.Bytes)))
+	w := httptest.NewRecorder()
+	h.HandleSCEP(w, req)
+
+	if w.Code != http.StatusForbidden {
+		t.Errorf("expected 403, got %d: %s", w.Code, w.Body.String())
+	}
+}
+
+func TestSCEP_UnknownOperation(t *testing.T) {
+	svc := &mockSCEPService{}
+	h := NewSCEPHandler(svc)
+
+	req := httptest.NewRequest(http.MethodGet, "/scep?operation=UnknownOp", nil)
+	w := httptest.NewRecorder()
+	h.HandleSCEP(w, req)
+
+	if w.Code != http.StatusBadRequest {
+		t.Errorf("expected 400, got %d", w.Code)
+	}
+}
+
+func TestSCEP_MissingOperation(t *testing.T) {
+	svc := &mockSCEPService{}
+	h := NewSCEPHandler(svc)
+
+	req := httptest.NewRequest(http.MethodGet, "/scep", nil)
+	w := httptest.NewRecorder()
+	h.HandleSCEP(w, req)
+
+	if w.Code != http.StatusBadRequest {
+		t.Errorf("expected 400, got %d", w.Code)
+	}
+}

internal/api/router/router.go

@@ -238,6 +238,15 @@ func (r *Router) RegisterESTHandlers(est handler.ESTHandler) {
 	r.Register("GET /.well-known/est/csrattrs", http.HandlerFunc(est.CSRAttrs))
 }
 
+// RegisterSCEPHandlers sets up SCEP (RFC 8894) routes.
+// SCEP uses a single endpoint with operation-based dispatch via query parameters.
+// Authentication is via challenge password in the CSR, not TLS client certs or API keys.
+func (r *Router) RegisterSCEPHandlers(scep handler.SCEPHandler) {
+	// SCEP uses a single path; the handler dispatches on ?operation= query param
+	r.Register("GET /scep", http.HandlerFunc(scep.HandleSCEP))
+	r.Register("POST /scep", http.HandlerFunc(scep.HandleSCEP))
+}
+
 // GetMux returns the underlying http.ServeMux for direct access if needed.
 func (r *Router) GetMux() *http.ServeMux {
 	return r.mux

internal/config/config.go

@@ -23,6 +23,7 @@ type Config struct {
 	Notifiers    NotifierConfig
 	NetworkScan  NetworkScanConfig
 	EST          ESTConfig
+	SCEP         SCEPConfig
 	Verification VerificationConfig
 	ACME         ACMEConfig
 	Vault        VaultConfig
@@ -417,6 +418,26 @@ type ESTConfig struct {
 	ProfileID string
 }
 
+// SCEPConfig controls the RFC 8894 Simple Certificate Enrollment Protocol server.
+type SCEPConfig struct {
+	// Enabled controls whether SCEP endpoints are available for device enrollment.
+	// Default: false (SCEP disabled). Set to true to enable SCEP endpoints under /scep/.
+	Enabled bool
+
+	// IssuerID selects which issuer connector processes SCEP certificate requests.
+	// Default: "iss-local". Must reference a configured issuer.
+	IssuerID string
+
+	// ProfileID optionally constrains SCEP enrollments to a specific certificate profile.
+	// Leave empty to allow SCEP to use any configured issuer's defaults.
+	ProfileID string
+
+	// ChallengePassword is the shared secret used to authenticate SCEP enrollment requests.
+	// Clients include this in the PKCS#10 CSR challengePassword attribute.
+	// Required when SCEP is enabled.
+	ChallengePassword string
+}
+
 // NetworkScanConfig controls the server-side active TLS scanner.
 type NetworkScanConfig struct {
 	Enabled      bool          // Enable network scanning (default false)
@@ -594,6 +615,12 @@ func Load() (*Config, error) {
 			IssuerID:  getEnv("CERTCTL_EST_ISSUER_ID", "iss-local"),
 			ProfileID: getEnv("CERTCTL_EST_PROFILE_ID", ""),
 		},
+		SCEP: SCEPConfig{
+			Enabled:           getEnvBool("CERTCTL_SCEP_ENABLED", false),
+			IssuerID:          getEnv("CERTCTL_SCEP_ISSUER_ID", "iss-local"),
+			ProfileID:         getEnv("CERTCTL_SCEP_PROFILE_ID", ""),
+			ChallengePassword: getEnv("CERTCTL_SCEP_CHALLENGE_PASSWORD", ""),
+		},
 		Verification: VerificationConfig{
 			Enabled: getEnvBool("CERTCTL_VERIFY_DEPLOYMENT", true),
 			Timeout: getEnvDuration("CERTCTL_VERIFY_TIMEOUT", 10*time.Second),

internal/domain/scep.go

@@ -0,0 +1,40 @@
+package domain
+
+// SCEPEnrollResult holds the result of a SCEP (RFC 8894) enrollment operation.
+type SCEPEnrollResult struct {
+	CertPEM  string `json:"cert_pem"`  // PEM-encoded signed certificate
+	ChainPEM string `json:"chain_pem"` // PEM-encoded CA chain
+}
+
+// SCEPMessageType identifies the type of SCEP PKI message.
+type SCEPMessageType int
+
+const (
+	// SCEPMessageTypePKCSReq is a PKCS#10 certificate request (initial enrollment).
+	SCEPMessageTypePKCSReq SCEPMessageType = 19
+	// SCEPMessageTypeGetCertInitial is a polling request for a pending certificate.
+	SCEPMessageTypeGetCertInitial SCEPMessageType = 20
+)
+
+// SCEPPKIStatus represents the status of a SCEP PKI operation.
+type SCEPPKIStatus string
+
+const (
+	// SCEPStatusSuccess indicates the request was granted.
+	SCEPStatusSuccess SCEPPKIStatus = "0"
+	// SCEPStatusFailure indicates the request was rejected.
+	SCEPStatusFailure SCEPPKIStatus = "2"
+	// SCEPStatusPending indicates the request is pending manual approval.
+	SCEPStatusPending SCEPPKIStatus = "3"
+)
+
+// SCEPFailInfo represents the reason for a SCEP failure.
+type SCEPFailInfo string
+
+const (
+	SCEPFailBadAlg       SCEPFailInfo = "0" // Unrecognized or unsupported algorithm
+	SCEPFailBadMessageCheck SCEPFailInfo = "1" // Integrity check failed
+	SCEPFailBadRequest   SCEPFailInfo = "2" // Transaction not permitted or supported
+	SCEPFailBadTime      SCEPFailInfo = "3" // Message time field was not sufficiently close to system time
+	SCEPFailBadCertID    SCEPFailInfo = "4" // No certificate could be identified matching the provided criteria
+)

internal/pkcs7/pkcs7.go

@@ -0,0 +1,136 @@
+// Package pkcs7 provides ASN.1 helpers for building PKCS#7 structures.
+// Used by EST (RFC 7030) and SCEP (RFC 8894) protocol handlers.
+// No external dependencies — hand-rolled ASN.1 encoding only.
+package pkcs7
+
+import (
+	"encoding/pem"
+	"fmt"
+)
+
+// BuildCertsOnlyPKCS7 creates a degenerate PKCS#7 SignedData structure containing only certificates.
+// This is the "certs-only" format specified in RFC 7030 Section 4.1.3 for /cacerts responses
+// and enrollment responses, and used by SCEP (RFC 8894) for GetCACert responses.
+//
+// ASN.1 structure (simplified):
+//
+//	ContentInfo {
+//	  contentType: signedData (1.2.840.113549.1.7.2)
+//	  content: SignedData {
+//	    version: 1
+//	    digestAlgorithms: {} (empty)
+//	    encapContentInfo: { contentType: data (1.2.840.113549.1.7.1) }
+//	    certificates: [cert1, cert2, ...]
+//	    signerInfos: {} (empty)
+//	  }
+//	}
+func BuildCertsOnlyPKCS7(derCerts [][]byte) ([]byte, error) {
+	// OID for signedData: 1.2.840.113549.1.7.2
+	oidSignedData := []byte{0x06, 0x09, 0x2a, 0x86, 0x48, 0x86, 0xf7, 0x0d, 0x01, 0x07, 0x02}
+	// OID for data: 1.2.840.113549.1.7.1
+	oidData := []byte{0x06, 0x09, 0x2a, 0x86, 0x48, 0x86, 0xf7, 0x0d, 0x01, 0x07, 0x01}
+
+	// Build certificates [0] IMPLICIT SET OF Certificate
+	var certsContent []byte
+	for _, cert := range derCerts {
+		certsContent = append(certsContent, cert...)
+	}
+	certsField := ASN1WrapImplicit(0, certsContent)
+
+	// Build encapContentInfo: SEQUENCE { OID data }
+	encapContentInfo := ASN1WrapSequence(oidData)
+
+	// Build digestAlgorithms: SET {} (empty)
+	digestAlgorithms := ASN1WrapSet(nil)
+
+	// Build signerInfos: SET {} (empty)
+	signerInfos := ASN1WrapSet(nil)
+
+	// Version: INTEGER 1
+	version := []byte{0x02, 0x01, 0x01}
+
+	// Build SignedData SEQUENCE
+	var signedDataContent []byte
+	signedDataContent = append(signedDataContent, version...)
+	signedDataContent = append(signedDataContent, digestAlgorithms...)
+	signedDataContent = append(signedDataContent, encapContentInfo...)
+	signedDataContent = append(signedDataContent, certsField...)
+	signedDataContent = append(signedDataContent, signerInfos...)
+	signedData := ASN1WrapSequence(signedDataContent)
+
+	// Wrap in [0] EXPLICIT for ContentInfo.content
+	contentField := ASN1WrapExplicit(0, signedData)
+
+	// Build ContentInfo SEQUENCE
+	var contentInfoContent []byte
+	contentInfoContent = append(contentInfoContent, oidSignedData...)
+	contentInfoContent = append(contentInfoContent, contentField...)
+	contentInfo := ASN1WrapSequence(contentInfoContent)
+
+	return contentInfo, nil
+}
+
+// PEMToDERChain converts PEM-encoded certificates to a slice of DER-encoded certificates.
+func PEMToDERChain(pemData string) ([][]byte, error) {
+	var derCerts [][]byte
+	rest := []byte(pemData)
+	for {
+		var block *pem.Block
+		block, rest = pem.Decode(rest)
+		if block == nil {
+			break
+		}
+		if block.Type == "CERTIFICATE" {
+			derCerts = append(derCerts, block.Bytes)
+		}
+	}
+	if len(derCerts) == 0 {
+		return nil, fmt.Errorf("no certificates found in PEM data")
+	}
+	return derCerts, nil
+}
+
+// ASN1WrapSequence wraps content in an ASN.1 SEQUENCE tag (0x30).
+func ASN1WrapSequence(content []byte) []byte {
+	return ASN1Wrap(0x30, content)
+}
+
+// ASN1WrapSet wraps content in an ASN.1 SET tag (0x31).
+func ASN1WrapSet(content []byte) []byte {
+	return ASN1Wrap(0x31, content)
+}
+
+// ASN1WrapExplicit wraps content in an ASN.1 context-specific EXPLICIT tag.
+func ASN1WrapExplicit(tag int, content []byte) []byte {
+	return ASN1Wrap(byte(0xa0|tag), content)
+}
+
+// ASN1WrapImplicit wraps content in an ASN.1 context-specific IMPLICIT CONSTRUCTED tag.
+func ASN1WrapImplicit(tag int, content []byte) []byte {
+	return ASN1Wrap(byte(0xa0|tag), content)
+}
+
+// ASN1Wrap wraps content with an ASN.1 tag and length.
+func ASN1Wrap(tag byte, content []byte) []byte {
+	length := len(content)
+	var result []byte
+	result = append(result, tag)
+	result = append(result, ASN1EncodeLength(length)...)
+	result = append(result, content...)
+	return result
+}
+
+// ASN1EncodeLength encodes a length in ASN.1 DER format.
+func ASN1EncodeLength(length int) []byte {
+	if length < 0x80 {
+		return []byte{byte(length)}
+	}
+	// Long form
+	var lengthBytes []byte
+	l := length
+	for l > 0 {
+		lengthBytes = append([]byte{byte(l & 0xff)}, lengthBytes...)
+		l >>= 8
+	}
+	return append([]byte{byte(0x80 | len(lengthBytes))}, lengthBytes...)
+}

internal/pkcs7/pkcs7_test.go

@@ -0,0 +1,104 @@
+package pkcs7
+
+import (
+	"crypto/ecdsa"
+	"crypto/elliptic"
+	"crypto/rand"
+	"crypto/x509"
+	"crypto/x509/pkix"
+	"encoding/pem"
+	"math/big"
+	"testing"
+	"time"
+)
+
+func generateTestCertPEM(t *testing.T) string {
+	t.Helper()
+	key, err := ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
+	if err != nil {
+		t.Fatalf("generate key: %v", err)
+	}
+	template := &x509.Certificate{
+		SerialNumber:          big.NewInt(1),
+		Subject:               pkix.Name{CommonName: "Test CA"},
+		NotBefore:             time.Now().Add(-1 * time.Hour),
+		NotAfter:              time.Now().Add(24 * time.Hour),
+		KeyUsage:              x509.KeyUsageCertSign | x509.KeyUsageCRLSign,
+		IsCA:                  true,
+		BasicConstraintsValid: true,
+	}
+	certDER, err := x509.CreateCertificate(rand.Reader, template, template, &key.PublicKey, key)
+	if err != nil {
+		t.Fatalf("create certificate: %v", err)
+	}
+	return string(pem.EncodeToMemory(&pem.Block{Type: "CERTIFICATE", Bytes: certDER}))
+}
+
+func TestBuildCertsOnlyPKCS7(t *testing.T) {
+	dummyCert := []byte{0x30, 0x82, 0x01, 0x00}
+	result, err := BuildCertsOnlyPKCS7([][]byte{dummyCert})
+	if err != nil {
+		t.Fatalf("BuildCertsOnlyPKCS7 failed: %v", err)
+	}
+	if len(result) == 0 {
+		t.Error("expected non-empty PKCS#7 output")
+	}
+	if result[0] != 0x30 {
+		t.Errorf("expected SEQUENCE tag (0x30), got 0x%02x", result[0])
+	}
+}
+
+func TestBuildCertsOnlyPKCS7_MultipleCerts(t *testing.T) {
+	cert1 := []byte{0x30, 0x82, 0x01, 0x00}
+	cert2 := []byte{0x30, 0x82, 0x02, 0x00}
+	result, err := BuildCertsOnlyPKCS7([][]byte{cert1, cert2})
+	if err != nil {
+		t.Fatalf("BuildCertsOnlyPKCS7 failed: %v", err)
+	}
+	if len(result) == 0 {
+		t.Error("expected non-empty PKCS#7 output")
+	}
+}
+
+func TestPEMToDERChain_Success(t *testing.T) {
+	pemData := generateTestCertPEM(t)
+	certs, err := PEMToDERChain(pemData)
+	if err != nil {
+		t.Fatalf("PEMToDERChain failed: %v", err)
+	}
+	if len(certs) != 1 {
+		t.Errorf("expected 1 cert, got %d", len(certs))
+	}
+}
+
+func TestPEMToDERChain_NoCerts(t *testing.T) {
+	_, err := PEMToDERChain("not a PEM")
+	if err == nil {
+		t.Error("expected error for invalid PEM")
+	}
+}
+
+func TestASN1EncodeLength(t *testing.T) {
+	tests := []struct {
+		length   int
+		expected []byte
+	}{
+		{0, []byte{0x00}},
+		{1, []byte{0x01}},
+		{127, []byte{0x7f}},
+		{128, []byte{0x81, 0x80}},
+		{256, []byte{0x82, 0x01, 0x00}},
+	}
+	for _, tt := range tests {
+		result := ASN1EncodeLength(tt.length)
+		if len(result) != len(tt.expected) {
+			t.Errorf("ASN1EncodeLength(%d): expected %d bytes, got %d", tt.length, len(tt.expected), len(result))
+			continue
+		}
+		for i := range result {
+			if result[i] != tt.expected[i] {
+				t.Errorf("ASN1EncodeLength(%d): byte %d: expected 0x%02x, got 0x%02x", tt.length, i, tt.expected[i], result[i])
+			}
+		}
+	}
+}

internal/service/scep.go

@@ -0,0 +1,160 @@
+package service
+
+import (
+	"context"
+	"crypto/x509"
+	"encoding/pem"
+	"fmt"
+	"log/slog"
+	"strings"
+
+	"github.com/shankar0123/certctl/internal/domain"
+)
+
+// SCEPService implements the SCEP (RFC 8894) enrollment protocol.
+// It delegates certificate operations to an existing IssuerConnector and records
+// enrollment events in the audit trail.
+type SCEPService struct {
+	issuer            IssuerConnector
+	issuerID          string
+	auditService      *AuditService
+	logger            *slog.Logger
+	profileID         string // optional: constrain enrollments to a specific profile
+	challengePassword string // shared secret for enrollment authentication
+}
+
+// NewSCEPService creates a new SCEPService for the given issuer connector.
+func NewSCEPService(issuerID string, issuer IssuerConnector, auditService *AuditService, logger *slog.Logger, challengePassword string) *SCEPService {
+	return &SCEPService{
+		issuer:            issuer,
+		issuerID:          issuerID,
+		auditService:      auditService,
+		logger:            logger,
+		challengePassword: challengePassword,
+	}
+}
+
+// SetProfileID constrains SCEP enrollments to a specific certificate profile.
+func (s *SCEPService) SetProfileID(profileID string) {
+	s.profileID = profileID
+}
+
+// GetCACaps returns the capabilities of this SCEP server.
+// RFC 8894 Section 3.5.2: GetCACaps returns a list of capabilities, one per line.
+func (s *SCEPService) GetCACaps(ctx context.Context) string {
+	return "POSTPKIOperation\nSHA-256\nAES\nSCEPStandard\n"
+}
+
+// GetCACert returns the PEM-encoded CA certificate chain for this SCEP server.
+// RFC 8894 Section 3.5.1: GetCACert distributes the CA certificate(s).
+func (s *SCEPService) GetCACert(ctx context.Context) (string, error) {
+	caPEM, err := s.issuer.GetCACertPEM(ctx)
+	if err != nil {
+		return "", fmt.Errorf("failed to get CA certificates from issuer %s: %w", s.issuerID, err)
+	}
+	if caPEM == "" {
+		return "", fmt.Errorf("issuer %s does not provide CA certificates for SCEP", s.issuerID)
+	}
+	return caPEM, nil
+}
+
+// PKCSReq processes a SCEP enrollment request.
+// RFC 8894 Section 3.3.1: PKCSReq contains a PKCS#10 CSR for certificate enrollment.
+// The CSR PEM and challenge password are extracted by the handler from the PKCS#7 envelope.
+func (s *SCEPService) PKCSReq(ctx context.Context, csrPEM string, challengePassword string, transactionID string) (*domain.SCEPEnrollResult, error) {
+	// Validate challenge password
+	if s.challengePassword != "" {
+		if challengePassword != s.challengePassword {
+			s.logger.Warn("SCEP enrollment rejected: invalid challenge password",
+				"transaction_id", transactionID)
+			return nil, fmt.Errorf("invalid challenge password")
+		}
+	}
+
+	return s.processEnrollment(ctx, csrPEM, transactionID, "scep_pkcsreq")
+}
+
+// processEnrollment handles the common enrollment logic.
+func (s *SCEPService) processEnrollment(ctx context.Context, csrPEM string, transactionID string, auditAction string) (*domain.SCEPEnrollResult, error) {
+	// Parse the CSR to extract CN and SANs
+	block, _ := pem.Decode([]byte(csrPEM))
+	if block == nil {
+		return nil, fmt.Errorf("invalid CSR PEM")
+	}
+
+	csr, err := x509.ParseCertificateRequest(block.Bytes)
+	if err != nil {
+		return nil, fmt.Errorf("failed to parse CSR: %w", err)
+	}
+
+	if err := csr.CheckSignature(); err != nil {
+		return nil, fmt.Errorf("CSR signature verification failed: %w", err)
+	}
+
+	commonName := csr.Subject.CommonName
+	if commonName == "" {
+		return nil, fmt.Errorf("CSR must include a Common Name")
+	}
+
+	// Collect SANs
+	var sans []string
+	for _, dns := range csr.DNSNames {
+		sans = append(sans, dns)
+	}
+	for _, ip := range csr.IPAddresses {
+		sans = append(sans, ip.String())
+	}
+	for _, email := range csr.EmailAddresses {
+		sans = append(sans, email)
+	}
+	for _, uri := range csr.URIs {
+		sans = append(sans, uri.String())
+	}
+
+	s.logger.Info("SCEP enrollment request",
+		"action", auditAction,
+		"common_name", commonName,
+		"sans", strings.Join(sans, ","),
+		"transaction_id", transactionID,
+		"issuer", s.issuerID)
+
+	// Issue the certificate via the configured issuer connector
+	// SCEP enrollments use default EKUs (nil = serverAuth + clientAuth fallback in connector)
+	result, err := s.issuer.IssueCertificate(ctx, commonName, sans, csrPEM, nil)
+	if err != nil {
+		s.logger.Error("SCEP enrollment failed",
+			"action", auditAction,
+			"common_name", commonName,
+			"transaction_id", transactionID,
+			"error", err)
+		return nil, fmt.Errorf("certificate issuance failed: %w", err)
+	}
+
+	// Audit the enrollment
+	if s.auditService != nil {
+		details := map[string]interface{}{
+			"common_name":    commonName,
+			"sans":           sans,
+			"issuer_id":      s.issuerID,
+			"serial":         result.Serial,
+			"transaction_id": transactionID,
+			"protocol":       "SCEP",
+		}
+		if s.profileID != "" {
+			details["profile_id"] = s.profileID
+		}
+		_ = s.auditService.RecordEvent(ctx, "scep-client", "system", auditAction, "certificate", result.Serial, details)
+	}
+
+	s.logger.Info("SCEP enrollment successful",
+		"action", auditAction,
+		"common_name", commonName,
+		"serial", result.Serial,
+		"transaction_id", transactionID,
+		"not_after", result.NotAfter)
+
+	return &domain.SCEPEnrollResult{
+		CertPEM:  result.CertPEM,
+		ChainPEM: result.ChainPEM,
+	}, nil
+}

internal/service/scep_test.go

@@ -0,0 +1,195 @@
+package service
+
+import (
+	"context"
+	"errors"
+	"log/slog"
+	"os"
+	"strings"
+	"testing"
+)
+
+func TestSCEPService_GetCACaps(t *testing.T) {
+	mockIssuer := &mockIssuerConnector{}
+	svc := NewSCEPService("iss-local", mockIssuer, nil, slog.New(slog.NewTextHandler(os.Stderr, &slog.HandlerOptions{Level: slog.LevelError})), "")
+
+	caps := svc.GetCACaps(context.Background())
+	if caps == "" {
+		t.Error("expected non-empty capabilities")
+	}
+	if !strings.Contains(caps, "POSTPKIOperation") {
+		t.Errorf("expected POSTPKIOperation in caps, got: %s", caps)
+	}
+	if !strings.Contains(caps, "SHA-256") {
+		t.Errorf("expected SHA-256 in caps, got: %s", caps)
+	}
+	if !strings.Contains(caps, "SCEPStandard") {
+		t.Errorf("expected SCEPStandard in caps, got: %s", caps)
+	}
+}
+
+func TestSCEPService_GetCACert_Success(t *testing.T) {
+	mockIssuer := &mockIssuerConnector{}
+	svc := NewSCEPService("iss-local", mockIssuer, nil, slog.New(slog.NewTextHandler(os.Stderr, &slog.HandlerOptions{Level: slog.LevelError})), "")
+
+	caPEM, err := svc.GetCACert(context.Background())
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if caPEM == "" {
+		t.Error("expected non-empty CA PEM")
+	}
+}
+
+func TestSCEPService_GetCACert_IssuerError(t *testing.T) {
+	mockIssuer := &mockIssuerConnector{Err: errors.New("CA unavailable")}
+	svc := NewSCEPService("iss-local", mockIssuer, nil, slog.New(slog.NewTextHandler(os.Stderr, &slog.HandlerOptions{Level: slog.LevelError})), "")
+
+	_, err := svc.GetCACert(context.Background())
+	if err == nil {
+		t.Fatal("expected error")
+	}
+	if !strings.Contains(err.Error(), "CA unavailable") {
+		t.Errorf("expected error to contain 'CA unavailable', got: %v", err)
+	}
+}
+
+func TestSCEPService_PKCSReq_Success(t *testing.T) {
+	mockIssuer := &mockIssuerConnector{}
+	auditRepo := newMockAuditRepository()
+	auditSvc := NewAuditService(auditRepo)
+	svc := NewSCEPService("iss-local", mockIssuer, auditSvc, slog.New(slog.NewTextHandler(os.Stderr, &slog.HandlerOptions{Level: slog.LevelError})), "")
+
+	csrPEM := generateCSRPEM(t, "device.example.com", []string{"device.example.com"})
+
+	result, err := svc.PKCSReq(context.Background(), csrPEM, "", "txn-001")
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if result == nil {
+		t.Fatal("expected non-nil result")
+	}
+	if result.CertPEM == "" {
+		t.Error("expected non-empty CertPEM")
+	}
+
+	// Verify audit event was recorded
+	if len(auditRepo.Events) == 0 {
+		t.Error("expected audit event to be recorded")
+	}
+}
+
+func TestSCEPService_PKCSReq_InvalidCSR(t *testing.T) {
+	mockIssuer := &mockIssuerConnector{}
+	svc := NewSCEPService("iss-local", mockIssuer, nil, slog.New(slog.NewTextHandler(os.Stderr, &slog.HandlerOptions{Level: slog.LevelError})), "")
+
+	_, err := svc.PKCSReq(context.Background(), "not-valid-pem", "", "txn-002")
+	if err == nil {
+		t.Fatal("expected error for invalid CSR")
+	}
+}
+
+func TestSCEPService_PKCSReq_MissingCN(t *testing.T) {
+	mockIssuer := &mockIssuerConnector{}
+	svc := NewSCEPService("iss-local", mockIssuer, nil, slog.New(slog.NewTextHandler(os.Stderr, &slog.HandlerOptions{Level: slog.LevelError})), "")
+
+	csrPEM := generateCSRPEM(t, "", []string{"test.example.com"})
+
+	_, err := svc.PKCSReq(context.Background(), csrPEM, "", "txn-003")
+	if err == nil {
+		t.Fatal("expected error for missing CN")
+	}
+	if !strings.Contains(err.Error(), "Common Name") {
+		t.Errorf("expected 'Common Name' in error, got: %v", err)
+	}
+}
+
+func TestSCEPService_PKCSReq_IssuerError(t *testing.T) {
+	mockIssuer := &mockIssuerConnector{Err: errors.New("issuance failed")}
+	svc := NewSCEPService("iss-local", mockIssuer, nil, slog.New(slog.NewTextHandler(os.Stderr, &slog.HandlerOptions{Level: slog.LevelError})), "")
+
+	csrPEM := generateCSRPEM(t, "test.example.com", nil)
+
+	_, err := svc.PKCSReq(context.Background(), csrPEM, "", "txn-004")
+	if err == nil {
+		t.Fatal("expected error")
+	}
+	if !strings.Contains(err.Error(), "issuance failed") {
+		t.Errorf("expected 'issuance failed', got: %v", err)
+	}
+}
+
+func TestSCEPService_PKCSReq_ChallengePassword_Valid(t *testing.T) {
+	mockIssuer := &mockIssuerConnector{}
+	auditRepo := newMockAuditRepository()
+	auditSvc := NewAuditService(auditRepo)
+	svc := NewSCEPService("iss-local", mockIssuer, auditSvc, slog.New(slog.NewTextHandler(os.Stderr, &slog.HandlerOptions{Level: slog.LevelError})), "secret123")
+
+	csrPEM := generateCSRPEM(t, "mdm-device.example.com", nil)
+
+	result, err := svc.PKCSReq(context.Background(), csrPEM, "secret123", "txn-005")
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if result == nil {
+		t.Fatal("expected non-nil result")
+	}
+}
+
+func TestSCEPService_PKCSReq_ChallengePassword_Invalid(t *testing.T) {
+	mockIssuer := &mockIssuerConnector{}
+	svc := NewSCEPService("iss-local", mockIssuer, nil, slog.New(slog.NewTextHandler(os.Stderr, &slog.HandlerOptions{Level: slog.LevelError})), "secret123")
+
+	csrPEM := generateCSRPEM(t, "mdm-device.example.com", nil)
+
+	_, err := svc.PKCSReq(context.Background(), csrPEM, "wrong-password", "txn-006")
+	if err == nil {
+		t.Fatal("expected error for invalid challenge password")
+	}
+	if !strings.Contains(err.Error(), "challenge password") {
+		t.Errorf("expected 'challenge password' in error, got: %v", err)
+	}
+}
+
+func TestSCEPService_PKCSReq_ChallengePassword_NotRequired(t *testing.T) {
+	// When server has no challenge password configured, any value should be accepted
+	mockIssuer := &mockIssuerConnector{}
+	svc := NewSCEPService("iss-local", mockIssuer, nil, slog.New(slog.NewTextHandler(os.Stderr, &slog.HandlerOptions{Level: slog.LevelError})), "")
+
+	csrPEM := generateCSRPEM(t, "device.example.com", nil)
+
+	result, err := svc.PKCSReq(context.Background(), csrPEM, "any-value", "txn-007")
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if result == nil {
+		t.Fatal("expected non-nil result")
+	}
+}
+
+func TestSCEPService_PKCSReq_WithProfile(t *testing.T) {
+	mockIssuer := &mockIssuerConnector{}
+	auditRepo := newMockAuditRepository()
+	auditSvc := NewAuditService(auditRepo)
+	svc := NewSCEPService("iss-local", mockIssuer, auditSvc, slog.New(slog.NewTextHandler(os.Stderr, &slog.HandlerOptions{Level: slog.LevelError})), "")
+	svc.SetProfileID("profile-mdm-device")
+
+	csrPEM := generateCSRPEM(t, "device.example.com", nil)
+
+	result, err := svc.PKCSReq(context.Background(), csrPEM, "", "txn-008")
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if result == nil {
+		t.Fatal("expected non-nil result")
+	}
+
+	// Verify audit event includes profile_id
+	if len(auditRepo.Events) == 0 {
+		t.Fatal("expected audit event")
+	}
+	lastEvent := auditRepo.Events[len(auditRepo.Events)-1]
+	if lastEvent.Details == nil {
+		t.Fatal("expected audit details")
+	}
+}