feat(M50): cloud secret manager discovery — AWS SM, Azure KV, GCP SM

Extend certificate discovery from filesystem + network to cloud secret managers. Three pluggable DiscoverySource connectors feed into the existing discovery pipeline via sentinel agent pattern, with a 9th scheduler loop for periodic cloud scanning. - AWS Secrets Manager: aws-sdk-go-v2, tag/prefix filtering, 10 tests - Azure Key Vault: stdlib HTTP + OAuth2, base64 DER/PEM, 16 tests - GCP Secret Manager: stdlib HTTP + JWT OAuth2, label filter, 14 tests - CloudDiscoveryService orchestrator with 9 tests - 9th scheduler loop (6h default, atomic.Bool idempotency) - Discovery page: color-coded source type badges - 14 new env vars across CloudDiscoveryConfig structs - Docs: connectors.md, architecture.md, features.md, README updated 49 new tests. All CI checks pass (go vet, race, lint, coverage). Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
2026-06-14 07:48:57 +00:00 · 2026-04-15 23:01:00 -04:00
parent 3f619bcaac
commit e1bcde4cf1
19 changed files with 3791 additions and 24 deletions
@@ -0,0 +1,515 @@
+// Package azurekv implements the domain.DiscoverySource interface for
+// Azure Key Vault certificate discovery.
+//
+// Azure Key Vault is a cloud-based secret and certificate management service.
+// This connector discovers certificates stored in an Azure Key Vault using the
+// Azure Key Vault REST API with OAuth2 client credentials authentication.
+//
+// No Azure SDK dependency — uses stdlib net/http + OAuth2 for authentication.
+//
+// API endpoints used:
+//
+//	GET /certificates?api-version=7.4         - List certificates
+//	GET /certificates/{name}/{version}?api-version=7.4  - Get certificate details
+//
+// Authentication: OAuth2 client credentials flow via Azure AD.
+// Token is cached with 5-minute refresh buffer.
+package azurekv
+
+import (
+	"bytes"
+	"context"
+	"crypto/ecdsa"
+	"crypto/rsa"
+	"crypto/sha256"
+	"crypto/x509"
+	"encoding/base64"
+	"encoding/json"
+	"encoding/pem"
+	"fmt"
+	"io"
+	"log/slog"
+	"net/http"
+	"net/url"
+	"regexp"
+	"strings"
+	"sync"
+	"time"
+
+	"github.com/shankar0123/certctl/internal/domain"
+)
+
+// Config represents the Azure Key Vault discovery configuration.
+type Config struct {
+	// VaultURL is the Azure Key Vault URL (e.g., "https://myvault.vault.azure.net").
+	// Required. Set via CERTCTL_AZURE_KV_VAULT_URL environment variable.
+	VaultURL string `json:"vault_url"`
+
+	// TenantID is the Azure AD tenant ID (e.g., "00000000-0000-0000-0000-000000000000").
+	// Required. Set via CERTCTL_AZURE_KV_TENANT_ID environment variable.
+	TenantID string `json:"tenant_id"`
+
+	// ClientID is the Azure AD application (client) ID.
+	// Required. Set via CERTCTL_AZURE_KV_CLIENT_ID environment variable.
+	ClientID string `json:"client_id"`
+
+	// ClientSecret is the Azure AD application secret or certificate.
+	// Required. Set via CERTCTL_AZURE_KV_CLIENT_SECRET environment variable.
+	ClientSecret string `json:"client_secret"`
+}
+
+// cachedToken holds an OAuth2 access token and its expiry time.
+type cachedToken struct {
+	token     string
+	expiresAt time.Time
+}
+
+// certificateListResponse represents the Azure Key Vault list certificates response.
+type certificateListResponse struct {
+	Value []struct {
+		ID         string `json:"id"`
+		Attributes struct {
+			Enabled int64  `json:"enabled"`
+			Created int64  `json:"created"`
+			Updated int64  `json:"updated"`
+			Exp     int64  `json:"exp"`
+		} `json:"attributes,omitempty"`
+		Tags map[string]string `json:"tags,omitempty"`
+	} `json:"value"`
+	NextLink string `json:"nextLink"`
+}
+
+// certificateBundle represents the Azure Key Vault certificate details response.
+type certificateBundle struct {
+	ID         string `json:"id"`
+	CER        string `json:"cer"`
+	Attributes struct {
+		Enabled int64  `json:"enabled"`
+		Created int64  `json:"created"`
+		Updated int64  `json:"updated"`
+		Exp     int64  `json:"exp"`
+	} `json:"attributes,omitempty"`
+}
+
+// KVClient is an interface for Azure Key Vault operations, allowing injection for testing.
+type KVClient interface {
+	// ListCertificates retrieves the list of certificates in the vault.
+	ListCertificates(ctx context.Context, vaultURL string) ([]struct {
+		ID         string
+		Attributes struct {
+			Exp int64
+		}
+	}, error)
+	// GetCertificate retrieves a specific certificate version.
+	GetCertificate(ctx context.Context, vaultURL, certName, version string) (*certificateBundle, error)
+}
+
+// Source implements domain.DiscoverySource for Azure Key Vault.
+type Source struct {
+	config Config
+	logger *slog.Logger
+	client KVClient
+}
+
+// New creates a new Azure Key Vault discovery source with real HTTP client.
+func New(cfg Config, logger *slog.Logger) *Source {
+	return &Source{
+		config: cfg,
+		logger: logger,
+		client: &httpKVClient{
+			config:     cfg,
+			httpClient: &http.Client{Timeout: 30 * time.Second},
+		},
+	}
+}
+
+// NewWithClient creates a new Azure Key Vault discovery source with injected client (for testing).
+func NewWithClient(cfg Config, client KVClient, logger *slog.Logger) *Source {
+	return &Source{
+		config: cfg,
+		logger: logger,
+		client: client,
+	}
+}
+
+// Name returns a human-readable name for this discovery source.
+func (s *Source) Name() string {
+	return "Azure Key Vault"
+}
+
+// Type returns the short type identifier for this discovery source.
+func (s *Source) Type() string {
+	return "azure-kv"
+}
+
+// ValidateConfig checks that the Azure Key Vault configuration is valid.
+func (s *Source) ValidateConfig() error {
+	if s.config.VaultURL == "" {
+		return fmt.Errorf("Azure Key Vault URL is required")
+	}
+	if s.config.TenantID == "" {
+		return fmt.Errorf("Azure Key Vault tenant ID is required")
+	}
+	if s.config.ClientID == "" {
+		return fmt.Errorf("Azure Key Vault client ID is required")
+	}
+	if s.config.ClientSecret == "" {
+		return fmt.Errorf("Azure Key Vault client secret is required")
+	}
+
+	// Basic URL validation
+	if !strings.HasPrefix(s.config.VaultURL, "https://") {
+		return fmt.Errorf("Azure Key Vault URL must use HTTPS")
+	}
+
+	return nil
+}
+
+// Discover scans the Azure Key Vault and returns a DiscoveryReport.
+func (s *Source) Discover(ctx context.Context) (*domain.DiscoveryReport, error) {
+	s.logger.Info("starting Azure Key Vault discovery", "vault_url", s.config.VaultURL)
+
+	report := &domain.DiscoveryReport{
+		AgentID:     "cloud-azure-kv",
+		Directories: []string{fmt.Sprintf("azure-kv://%s/", s.config.VaultURL)},
+		Certificates: []domain.DiscoveredCertEntry{},
+		Errors:      []string{},
+	}
+
+	startTime := time.Now()
+
+	// List certificates
+	certs, err := s.client.ListCertificates(ctx, s.config.VaultURL)
+	if err != nil {
+		s.logger.Error("failed to list Azure Key Vault certificates", "error", err)
+		report.Errors = append(report.Errors, fmt.Sprintf("list certificates failed: %v", err))
+		return report, nil
+	}
+
+	// Process each certificate
+	for _, cert := range certs {
+		// Extract certificate name and version from ID
+		// ID format: https://myvault.vault.azure.net/certificates/mycert/version123
+		certName, version, err := extractCertNameAndVersion(cert.ID)
+		if err != nil {
+			s.logger.Warn("failed to parse certificate ID", "id", cert.ID, "error", err)
+			report.Errors = append(report.Errors, fmt.Sprintf("parse cert ID failed: %v", err))
+			continue
+		}
+
+		// Get certificate details
+		certBundle, err := s.client.GetCertificate(ctx, s.config.VaultURL, certName, version)
+		if err != nil {
+			s.logger.Warn("failed to get certificate details", "name", certName, "version", version, "error", err)
+			report.Errors = append(report.Errors, fmt.Sprintf("get cert %s/%s failed: %v", certName, version, err))
+			continue
+		}
+
+		// Decode the base64-encoded DER certificate
+		if certBundle.CER == "" {
+			s.logger.Warn("empty certificate data", "name", certName, "version", version)
+			continue
+		}
+
+		derBytes, err := base64.StdEncoding.DecodeString(certBundle.CER)
+		if err != nil {
+			s.logger.Warn("failed to decode certificate", "name", certName, "version", version, "error", err)
+			report.Errors = append(report.Errors, fmt.Sprintf("decode cert %s/%s failed: %v", certName, version, err))
+			continue
+		}
+
+		// Parse certificate
+		x509Cert, err := x509.ParseCertificate(derBytes)
+		if err != nil {
+			s.logger.Warn("failed to parse certificate", "name", certName, "version", version, "error", err)
+			report.Errors = append(report.Errors, fmt.Sprintf("parse cert %s/%s failed: %v", certName, version, err))
+			continue
+		}
+
+		// Extract certificate metadata
+		entry := extractCertMetadata(x509Cert, certName, version)
+
+		// Encode as PEM for inclusion in report
+		certPEM := encodeCertPEM(derBytes)
+		entry.PEMData = certPEM
+
+		report.Certificates = append(report.Certificates, entry)
+		s.logger.Info("discovered certificate",
+			"name", certName,
+			"common_name", entry.CommonName,
+			"serial", entry.SerialNumber,
+			"not_after", entry.NotAfter)
+	}
+
+	report.ScanDurationMs = int(time.Since(startTime).Milliseconds())
+
+	s.logger.Info("Azure Key Vault discovery completed",
+		"certs_found", len(report.Certificates),
+		"errors", len(report.Errors),
+		"duration_ms", report.ScanDurationMs)
+
+	return report, nil
+}
+
+// httpKVClient implements KVClient using Azure Key Vault REST API.
+type httpKVClient struct {
+	config     Config
+	httpClient *http.Client
+
+	// OAuth2 token caching
+	mu         sync.Mutex
+	tokenCache *cachedToken
+}
+
+// ListCertificates retrieves the list of certificates in the vault.
+func (c *httpKVClient) ListCertificates(ctx context.Context, vaultURL string) ([]struct {
+	ID         string
+	Attributes struct {
+		Exp int64
+	}
+}, error) {
+	var results []struct {
+		ID         string
+		Attributes struct {
+			Exp int64
+		}
+	}
+
+	listURL := fmt.Sprintf("%s/certificates?api-version=7.4", strings.TrimSuffix(vaultURL, "/"))
+
+	for listURL != "" {
+		token, err := c.getAccessToken(ctx)
+		if err != nil {
+			return nil, fmt.Errorf("failed to get access token: %w", err)
+		}
+
+		req, err := http.NewRequestWithContext(ctx, http.MethodGet, listURL, nil)
+		if err != nil {
+			return nil, fmt.Errorf("failed to create request: %w", err)
+		}
+		req.Header.Set("Authorization", "Bearer "+token)
+
+		resp, err := c.httpClient.Do(req)
+		if err != nil {
+			return nil, fmt.Errorf("list request failed: %w", err)
+		}
+		defer resp.Body.Close()
+
+		body, err := io.ReadAll(resp.Body)
+		if err != nil {
+			return nil, fmt.Errorf("failed to read response: %w", err)
+		}
+
+		if resp.StatusCode != http.StatusOK {
+			return nil, fmt.Errorf("list certificates returned status %d: %s", resp.StatusCode, string(body))
+		}
+
+		var listResp certificateListResponse
+		if err := json.Unmarshal(body, &listResp); err != nil {
+			return nil, fmt.Errorf("failed to parse list response: %w", err)
+		}
+
+		for _, cert := range listResp.Value {
+			results = append(results, struct {
+				ID         string
+				Attributes struct {
+					Exp int64
+				}
+			}{
+				ID: cert.ID,
+				Attributes: struct {
+					Exp int64
+				}{Exp: cert.Attributes.Exp},
+			})
+		}
+
+		// Handle pagination
+		if listResp.NextLink == "" {
+			break
+		}
+		listURL = listResp.NextLink
+	}
+
+	return results, nil
+}
+
+// GetCertificate retrieves a specific certificate version from the vault.
+func (c *httpKVClient) GetCertificate(ctx context.Context, vaultURL, certName, version string) (*certificateBundle, error) {
+	token, err := c.getAccessToken(ctx)
+	if err != nil {
+		return nil, fmt.Errorf("failed to get access token: %w", err)
+	}
+
+	// Ensure vaultURL has no trailing slash
+	vaultURL = strings.TrimSuffix(vaultURL, "/")
+
+	// Build the certificate URL
+	// Format: https://myvault.vault.azure.net/certificates/mycert/version123?api-version=7.4
+	certURL := fmt.Sprintf("%s/certificates/%s/%s?api-version=7.4",
+		vaultURL, url.PathEscape(certName), url.PathEscape(version))
+
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, certURL, nil)
+	if err != nil {
+		return nil, fmt.Errorf("failed to create request: %w", err)
+	}
+	req.Header.Set("Authorization", "Bearer "+token)
+
+	resp, err := c.httpClient.Do(req)
+	if err != nil {
+		return nil, fmt.Errorf("get certificate request failed: %w", err)
+	}
+	defer resp.Body.Close()
+
+	body, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return nil, fmt.Errorf("failed to read response: %w", err)
+	}
+
+	if resp.StatusCode != http.StatusOK {
+		return nil, fmt.Errorf("get certificate returned status %d: %s", resp.StatusCode, string(body))
+	}
+
+	var certBundle certificateBundle
+	if err := json.Unmarshal(body, &certBundle); err != nil {
+		return nil, fmt.Errorf("failed to parse certificate response: %w", err)
+	}
+
+	return &certBundle, nil
+}
+
+// getAccessToken returns a valid OAuth2 access token, refreshing if needed.
+func (c *httpKVClient) getAccessToken(ctx context.Context) (string, error) {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+
+	// Return cached token if still valid (5 min buffer)
+	if c.tokenCache != nil && time.Now().Add(5*time.Minute).Before(c.tokenCache.expiresAt) {
+		return c.tokenCache.token, nil
+	}
+
+	// Exchange client credentials for access token
+	tokenURL := fmt.Sprintf("https://login.microsoftonline.com/%s/oauth2/v2.0/token",
+		url.PathEscape(c.config.TenantID))
+
+	form := url.Values{
+		"grant_type":    {"client_credentials"},
+		"client_id":     {c.config.ClientID},
+		"client_secret": {c.config.ClientSecret},
+		"scope":         {"https://vault.azure.net/.default"},
+	}
+
+	req, err := http.NewRequestWithContext(ctx, http.MethodPost, tokenURL,
+		strings.NewReader(form.Encode()))
+	if err != nil {
+		return "", fmt.Errorf("failed to create token request: %w", err)
+	}
+	req.Header.Set("Content-Type", "application/x-www-form-urlencoded")
+
+	resp, err := c.httpClient.Do(req)
+	if err != nil {
+		return "", fmt.Errorf("token request failed: %w", err)
+	}
+	defer resp.Body.Close()
+
+	body, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return "", fmt.Errorf("failed to read token response: %w", err)
+	}
+
+	if resp.StatusCode != http.StatusOK {
+		return "", fmt.Errorf("token request returned status %d: %s", resp.StatusCode, string(body))
+	}
+
+	var tokenResp struct {
+		AccessToken string `json:"access_token"`
+		ExpiresIn   int    `json:"expires_in"`
+		TokenType   string `json:"token_type"`
+	}
+	if err := json.Unmarshal(body, &tokenResp); err != nil {
+		return "", fmt.Errorf("failed to parse token response: %w", err)
+	}
+
+	if tokenResp.AccessToken == "" {
+		return "", fmt.Errorf("empty access token in response")
+	}
+
+	// Cache token
+	c.tokenCache = &cachedToken{
+		token:     tokenResp.AccessToken,
+		expiresAt: time.Now().Add(time.Duration(tokenResp.ExpiresIn) * time.Second),
+	}
+
+	return tokenResp.AccessToken, nil
+}
+
+// extractCertNameAndVersion extracts the certificate name and version from the Azure ID.
+// ID format: https://myvault.vault.azure.net/certificates/mycert/version123
+func extractCertNameAndVersion(id string) (name, version string, err error) {
+	// Use regex to extract name and version from the ID URL
+	// Pattern: /certificates/{name}/{version}
+	re := regexp.MustCompile(`/certificates/([^/]+)/([^/]+)$`)
+	matches := re.FindStringSubmatch(id)
+
+	if len(matches) != 3 {
+		return "", "", fmt.Errorf("cannot parse certificate ID: %s", id)
+	}
+
+	return matches[1], matches[2], nil
+}
+
+// extractCertMetadata extracts metadata from a parsed X.509 certificate.
+func extractCertMetadata(cert *x509.Certificate, certName, version string) domain.DiscoveredCertEntry {
+	// Extract Subject Alternative Names (DNS names and email addresses)
+	sans := []string{}
+	sans = append(sans, cert.DNSNames...)
+
+	// Extract key algorithm
+	keyAlgo := "unknown"
+	keySize := 0
+
+	switch pub := cert.PublicKey.(type) {
+	case *rsa.PublicKey:
+		keyAlgo = "RSA"
+		keySize = pub.N.BitLen()
+	case *ecdsa.PublicKey:
+		keyAlgo = "ECDSA"
+		keySize = pub.Curve.Params().BitSize
+	}
+
+	// Compute SHA-256 fingerprint
+	fp := sha256.Sum256(cert.Raw)
+	fingerprint := fmt.Sprintf("%X", fp)
+
+	// Format times as RFC3339
+	notBefore := cert.NotBefore.UTC().Format(time.RFC3339)
+	notAfter := cert.NotAfter.UTC().Format(time.RFC3339)
+
+	return domain.DiscoveredCertEntry{
+		FingerprintSHA256: fingerprint,
+		CommonName:        cert.Subject.CommonName,
+		SANs:              sans,
+		SerialNumber:      fmt.Sprintf("%x", cert.SerialNumber),
+		IssuerDN:          cert.Issuer.String(),
+		SubjectDN:         cert.Subject.String(),
+		NotBefore:         notBefore,
+		NotAfter:          notAfter,
+		KeyAlgorithm:      keyAlgo,
+		KeySize:           keySize,
+		IsCA:              cert.IsCA,
+		SourcePath:        fmt.Sprintf("azure-kv://%s/%s", certName, version),
+		SourceFormat:      "DER",
+	}
+}
+
+// encodeCertPEM encodes a DER certificate as PEM.
+func encodeCertPEM(derBytes []byte) string {
+	var buf bytes.Buffer
+	pem.Encode(&buf, &pem.Block{
+		Type:  "CERTIFICATE",
+		Bytes: derBytes,
+	})
+	return buf.String()
+}
+
+// Ensure Source implements domain.DiscoverySource.
+var _ domain.DiscoverySource = (*Source)(nil)
@@ -0,0 +1,597 @@
+package azurekv
+
+import (
+	"context"
+	"crypto/ecdsa"
+	"crypto/elliptic"
+	"crypto/rand"
+	"crypto/sha256"
+	"crypto/x509"
+	"crypto/x509/pkix"
+	"encoding/base64"
+	"encoding/pem"
+	"fmt"
+	"log/slog"
+	"math/big"
+	"testing"
+	"time"
+
+	"github.com/shankar0123/certctl/internal/domain"
+)
+
+// TestValidateConfig_Success validates a correct configuration.
+func TestValidateConfig_Success(t *testing.T) {
+	cfg := Config{
+		VaultURL:     "https://myvault.vault.azure.net",
+		TenantID:     "00000000-0000-0000-0000-000000000000",
+		ClientID:     "11111111-1111-1111-1111-111111111111",
+		ClientSecret: "mysecret123",
+	}
+
+	src := &Source{config: cfg, logger: slog.Default()}
+
+	if err := src.ValidateConfig(); err != nil {
+		t.Fatalf("ValidateConfig failed: %v", err)
+	}
+}
+
+// TestValidateConfig_MissingVaultURL validates error when VaultURL is empty.
+func TestValidateConfig_MissingVaultURL(t *testing.T) {
+	cfg := Config{
+		VaultURL:     "",
+		TenantID:     "tenant-id",
+		ClientID:     "client-id",
+		ClientSecret: "secret",
+	}
+
+	src := &Source{config: cfg, logger: slog.Default()}
+
+	if err := src.ValidateConfig(); err == nil {
+		t.Fatal("expected error for missing VaultURL")
+	}
+}
+
+// TestValidateConfig_MissingTenantID validates error when TenantID is empty.
+func TestValidateConfig_MissingTenantID(t *testing.T) {
+	cfg := Config{
+		VaultURL:     "https://myvault.vault.azure.net",
+		TenantID:     "",
+		ClientID:     "client-id",
+		ClientSecret: "secret",
+	}
+
+	src := &Source{config: cfg, logger: slog.Default()}
+
+	if err := src.ValidateConfig(); err == nil {
+		t.Fatal("expected error for missing TenantID")
+	}
+}
+
+// TestValidateConfig_MissingClientID validates error when ClientID is empty.
+func TestValidateConfig_MissingClientID(t *testing.T) {
+	cfg := Config{
+		VaultURL:     "https://myvault.vault.azure.net",
+		TenantID:     "tenant-id",
+		ClientID:     "",
+		ClientSecret: "secret",
+	}
+
+	src := &Source{config: cfg, logger: slog.Default()}
+
+	if err := src.ValidateConfig(); err == nil {
+		t.Fatal("expected error for missing ClientID")
+	}
+}
+
+// TestValidateConfig_MissingClientSecret validates error when ClientSecret is empty.
+func TestValidateConfig_MissingClientSecret(t *testing.T) {
+	cfg := Config{
+		VaultURL:     "https://myvault.vault.azure.net",
+		TenantID:     "tenant-id",
+		ClientID:     "client-id",
+		ClientSecret: "",
+	}
+
+	src := &Source{config: cfg, logger: slog.Default()}
+
+	if err := src.ValidateConfig(); err == nil {
+		t.Fatal("expected error for missing ClientSecret")
+	}
+}
+
+// TestValidateConfig_InvalidURL validates error when VaultURL is not HTTPS.
+func TestValidateConfig_InvalidURL(t *testing.T) {
+	cfg := Config{
+		VaultURL:     "http://myvault.vault.azure.net",
+		TenantID:     "tenant-id",
+		ClientID:     "client-id",
+		ClientSecret: "secret",
+	}
+
+	src := &Source{config: cfg, logger: slog.Default()}
+
+	if err := src.ValidateConfig(); err == nil {
+		t.Fatal("expected error for non-HTTPS URL")
+	}
+}
+
+// mockKVClient implements KVClient for testing.
+type mockKVClient struct {
+	certs map[string]*certificateBundle
+	err   error
+}
+
+func (m *mockKVClient) ListCertificates(ctx context.Context, vaultURL string) ([]struct {
+	ID         string
+	Attributes struct {
+		Exp int64
+	}
+}, error) {
+	if m.err != nil {
+		return nil, m.err
+	}
+
+	var results []struct {
+		ID         string
+		Attributes struct {
+			Exp int64
+		}
+	}
+
+	for id := range m.certs {
+		results = append(results, struct {
+			ID         string
+			Attributes struct {
+				Exp int64
+			}
+		}{ID: id})
+	}
+
+	return results, nil
+}
+
+func (m *mockKVClient) GetCertificate(ctx context.Context, vaultURL, certName, version string) (*certificateBundle, error) {
+	if m.err != nil {
+		return nil, m.err
+	}
+
+	id := fmt.Sprintf("https://myvault.vault.azure.net/certificates/%s/%s", certName, version)
+	cert, ok := m.certs[id]
+	if !ok {
+		return nil, fmt.Errorf("certificate not found")
+	}
+
+	return cert, nil
+}
+
+// generateTestCert generates a test X.509 certificate.
+func generateTestCert(cn string, sans []string) ([]byte, error) {
+	privKey, err := ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
+	if err != nil {
+		return nil, err
+	}
+
+	serialNumber, err := rand.Int(rand.Reader, big.NewInt(0).Exp(big.NewInt(2), big.NewInt(64), nil))
+	if err != nil {
+		return nil, err
+	}
+
+	template := x509.Certificate{
+		SerialNumber: serialNumber,
+		Subject: pkix.Name{
+			CommonName: cn,
+		},
+		NotBefore:             time.Now(),
+		NotAfter:              time.Now().Add(365 * 24 * time.Hour),
+		KeyUsage:              x509.KeyUsageDigitalSignature,
+		ExtKeyUsage:           []x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth},
+		BasicConstraintsValid: true,
+		IsCA:                  false,
+		DNSNames:              sans,
+	}
+
+	derBytes, err := x509.CreateCertificate(rand.Reader, &template, &template, &privKey.PublicKey, privKey)
+	if err != nil {
+		return nil, err
+	}
+
+	return derBytes, nil
+}
+
+// TestDiscover_Success validates successful certificate discovery.
+func TestDiscover_Success(t *testing.T) {
+	// Generate test certificates
+	cert1DER, err := generateTestCert("example.com", []string{"www.example.com", "api.example.com"})
+	if err != nil {
+		t.Fatalf("failed to generate test cert: %v", err)
+	}
+
+	cert2DER, err := generateTestCert("test.example.com", []string{})
+	if err != nil {
+		t.Fatalf("failed to generate test cert: %v", err)
+	}
+
+	// Create mock client
+	mockClient := &mockKVClient{
+		certs: map[string]*certificateBundle{
+			"https://myvault.vault.azure.net/certificates/example/v1": {
+				ID:  "https://myvault.vault.azure.net/certificates/example/v1",
+				CER: base64.StdEncoding.EncodeToString(cert1DER),
+			},
+			"https://myvault.vault.azure.net/certificates/test/v2": {
+				ID:  "https://myvault.vault.azure.net/certificates/test/v2",
+				CER: base64.StdEncoding.EncodeToString(cert2DER),
+			},
+		},
+	}
+
+	cfg := Config{
+		VaultURL:     "https://myvault.vault.azure.net",
+		TenantID:     "tenant-id",
+		ClientID:     "client-id",
+		ClientSecret: "secret",
+	}
+
+	src := NewWithClient(cfg, mockClient, slog.Default())
+
+	ctx := context.Background()
+	report, err := src.Discover(ctx)
+	if err != nil {
+		t.Fatalf("Discover failed: %v", err)
+	}
+
+	if report == nil {
+		t.Fatal("expected non-nil report")
+	}
+
+	if len(report.Certificates) != 2 {
+		t.Fatalf("expected 2 certificates, got %d", len(report.Certificates))
+	}
+
+	// Verify first cert metadata
+	if report.Certificates[0].CommonName == "" {
+		t.Fatal("expected common name in first cert")
+	}
+
+	// Verify PEM encoding
+	if report.Certificates[0].PEMData == "" {
+		t.Fatal("expected PEM data in first cert")
+	}
+
+	// Verify PEM is valid
+	block, _ := pem.Decode([]byte(report.Certificates[0].PEMData))
+	if block == nil {
+		t.Fatal("failed to decode PEM data")
+	}
+}
+
+// TestDiscover_ListError validates error handling when listing fails.
+func TestDiscover_ListError(t *testing.T) {
+	mockClient := &mockKVClient{
+		err: fmt.Errorf("connection error"),
+	}
+
+	cfg := Config{
+		VaultURL:     "https://myvault.vault.azure.net",
+		TenantID:     "tenant-id",
+		ClientID:     "client-id",
+		ClientSecret: "secret",
+	}
+
+	src := NewWithClient(cfg, mockClient, slog.Default())
+
+	ctx := context.Background()
+	report, err := src.Discover(ctx)
+
+	// Should return partial report with error
+	if err != nil {
+		t.Fatalf("expected no error, got %v", err)
+	}
+
+	if len(report.Errors) == 0 {
+		t.Fatal("expected errors in report")
+	}
+}
+
+// TestDiscover_EmptyResults validates handling of empty certificate list.
+func TestDiscover_EmptyResults(t *testing.T) {
+	mockClient := &mockKVClient{
+		certs: map[string]*certificateBundle{},
+	}
+
+	cfg := Config{
+		VaultURL:     "https://myvault.vault.azure.net",
+		TenantID:     "tenant-id",
+		ClientID:     "client-id",
+		ClientSecret: "secret",
+	}
+
+	src := NewWithClient(cfg, mockClient, slog.Default())
+
+	ctx := context.Background()
+	report, err := src.Discover(ctx)
+
+	if err != nil {
+		t.Fatalf("Discover failed: %v", err)
+	}
+
+	if len(report.Certificates) != 0 {
+		t.Fatalf("expected 0 certificates, got %d", len(report.Certificates))
+	}
+
+	if len(report.Errors) != 0 {
+		t.Fatalf("expected 0 errors, got %d", len(report.Errors))
+	}
+}
+
+// TestDiscover_InvalidCertData validates handling of invalid certificate data.
+func TestDiscover_InvalidCertData(t *testing.T) {
+	// Generate one valid cert and one invalid
+	validDER, err := generateTestCert("valid.example.com", []string{})
+	if err != nil {
+		t.Fatalf("failed to generate test cert: %v", err)
+	}
+
+	mockClient := &mockKVClient{
+		certs: map[string]*certificateBundle{
+			"https://myvault.vault.azure.net/certificates/valid/v1": {
+				ID:  "https://myvault.vault.azure.net/certificates/valid/v1",
+				CER: base64.StdEncoding.EncodeToString(validDER),
+			},
+			"https://myvault.vault.azure.net/certificates/invalid/v1": {
+				ID:  "https://myvault.vault.azure.net/certificates/invalid/v1",
+				CER: "not-valid-base64!@#$%",
+			},
+		},
+	}
+
+	cfg := Config{
+		VaultURL:     "https://myvault.vault.azure.net",
+		TenantID:     "tenant-id",
+		ClientID:     "client-id",
+		ClientSecret: "secret",
+	}
+
+	src := NewWithClient(cfg, mockClient, slog.Default())
+
+	ctx := context.Background()
+	report, err := src.Discover(ctx)
+
+	if err != nil {
+		t.Fatalf("Discover failed: %v", err)
+	}
+
+	// Should have 1 valid cert
+	if len(report.Certificates) != 1 {
+		t.Fatalf("expected 1 valid certificate, got %d", len(report.Certificates))
+	}
+
+	// Should have 1 error
+	if len(report.Errors) != 1 {
+		t.Fatalf("expected 1 error, got %d", len(report.Errors))
+	}
+}
+
+// TestDiscover_AgentIDAndSourcePath validates correct agent ID and source paths.
+func TestDiscover_AgentIDAndSourcePath(t *testing.T) {
+	certDER, err := generateTestCert("test.example.com", []string{})
+	if err != nil {
+		t.Fatalf("failed to generate test cert: %v", err)
+	}
+
+	mockClient := &mockKVClient{
+		certs: map[string]*certificateBundle{
+			"https://myvault.vault.azure.net/certificates/mycert/v1": {
+				ID:  "https://myvault.vault.azure.net/certificates/mycert/v1",
+				CER: base64.StdEncoding.EncodeToString(certDER),
+			},
+		},
+	}
+
+	cfg := Config{
+		VaultURL:     "https://myvault.vault.azure.net",
+		TenantID:     "tenant-id",
+		ClientID:     "client-id",
+		ClientSecret: "secret",
+	}
+
+	src := NewWithClient(cfg, mockClient, slog.Default())
+
+	ctx := context.Background()
+	report, err := src.Discover(ctx)
+
+	if err != nil {
+		t.Fatalf("Discover failed: %v", err)
+	}
+
+	if report.AgentID != "cloud-azure-kv" {
+		t.Fatalf("expected agent_id 'cloud-azure-kv', got %s", report.AgentID)
+	}
+
+	if len(report.Directories) == 0 {
+		t.Fatal("expected directories in report")
+	}
+
+	if len(report.Certificates) > 0 {
+		cert := report.Certificates[0]
+		if !domain.IsValidDiscoveryStatus(cert.SourcePath) == false {
+			// SourcePath should follow azure-kv://certname/version format
+			if !contains(cert.SourcePath, "azure-kv://") {
+				t.Fatalf("expected source path to start with 'azure-kv://', got %s", cert.SourcePath)
+			}
+		}
+	}
+}
+
+// TestName validates the Name method.
+func TestName(t *testing.T) {
+	src := &Source{
+		config: Config{},
+		logger: slog.Default(),
+	}
+
+	expected := "Azure Key Vault"
+	if src.Name() != expected {
+		t.Fatalf("expected Name '%s', got '%s'", expected, src.Name())
+	}
+}
+
+// TestType validates the Type method.
+func TestType(t *testing.T) {
+	src := &Source{
+		config: Config{},
+		logger: slog.Default(),
+	}
+
+	expected := "azure-kv"
+	if src.Type() != expected {
+		t.Fatalf("expected Type '%s', got '%s'", expected, src.Type())
+	}
+}
+
+// TestExtractCertNameAndVersion validates certificate ID parsing.
+func TestExtractCertNameAndVersion(t *testing.T) {
+	tests := []struct {
+		id       string
+		wantName string
+		wantVer  string
+		wantErr  bool
+	}{
+		{
+			id:       "https://myvault.vault.azure.net/certificates/example/v1",
+			wantName: "example",
+			wantVer:  "v1",
+			wantErr:  false,
+		},
+		{
+			id:       "https://myvault.vault.azure.net/certificates/my-cert/version123",
+			wantName: "my-cert",
+			wantVer:  "version123",
+			wantErr:  false,
+		},
+		{
+			id:      "invalid-id",
+			wantErr: true,
+		},
+	}
+
+	for _, tt := range tests {
+		name, ver, err := extractCertNameAndVersion(tt.id)
+		if (err != nil) != tt.wantErr {
+			t.Fatalf("extractCertNameAndVersion(%s) error = %v, wantErr %v", tt.id, err, tt.wantErr)
+		}
+		if !tt.wantErr {
+			if name != tt.wantName || ver != tt.wantVer {
+				t.Fatalf("extractCertNameAndVersion(%s) = (%s, %s), want (%s, %s)",
+					tt.id, name, ver, tt.wantName, tt.wantVer)
+			}
+		}
+	}
+}
+
+// TestExtractCertMetadata validates certificate metadata extraction.
+func TestExtractCertMetadata(t *testing.T) {
+	// Generate a test certificate
+	privKey, err := ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
+	if err != nil {
+		t.Fatalf("failed to generate key: %v", err)
+	}
+
+	serialNumber := big.NewInt(123456)
+	template := x509.Certificate{
+		SerialNumber: serialNumber,
+		Subject: pkix.Name{
+			CommonName: "test.example.com",
+		},
+		NotBefore:             time.Now(),
+		NotAfter:              time.Now().Add(365 * 24 * time.Hour),
+		KeyUsage:              x509.KeyUsageDigitalSignature,
+		ExtKeyUsage:           []x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth},
+		BasicConstraintsValid: true,
+		IsCA:                  false,
+		DNSNames:              []string{"test.example.com", "www.test.example.com"},
+	}
+
+	derBytes, err := x509.CreateCertificate(rand.Reader, &template, &template, &privKey.PublicKey, privKey)
+	if err != nil {
+		t.Fatalf("failed to create cert: %v", err)
+	}
+
+	cert, err := x509.ParseCertificate(derBytes)
+	if err != nil {
+		t.Fatalf("failed to parse cert: %v", err)
+	}
+
+	entry := extractCertMetadata(cert, "testcert", "v1")
+
+	if entry.CommonName != "test.example.com" {
+		t.Fatalf("expected CN 'test.example.com', got %s", entry.CommonName)
+	}
+
+	if len(entry.SANs) != 2 {
+		t.Fatalf("expected 2 SANs, got %d", len(entry.SANs))
+	}
+
+	if entry.KeyAlgorithm != "ECDSA" {
+		t.Fatalf("expected key algorithm ECDSA, got %s", entry.KeyAlgorithm)
+	}
+
+	if entry.KeySize != 256 {
+		t.Fatalf("expected key size 256, got %d", entry.KeySize)
+	}
+
+	if entry.SerialNumber == "" {
+		t.Fatal("expected serial number, got empty")
+	}
+
+	if entry.SourceFormat != "DER" {
+		t.Fatalf("expected source format DER, got %s", entry.SourceFormat)
+	}
+
+	// Verify fingerprint is valid hex
+	if len(entry.FingerprintSHA256) != 64 {
+		t.Fatalf("expected 64-char fingerprint, got %d chars", len(entry.FingerprintSHA256))
+	}
+
+	// Verify manually calculated fingerprint
+	fp := sha256.Sum256(derBytes)
+	expectedFP := fmt.Sprintf("%X", fp)
+	if entry.FingerprintSHA256 != expectedFP {
+		t.Fatalf("fingerprint mismatch: got %s, want %s", entry.FingerprintSHA256, expectedFP)
+	}
+}
+
+// TestEncodeCertPEM validates PEM encoding.
+func TestEncodeCertPEM(t *testing.T) {
+	derBytes, err := generateTestCert("test.example.com", []string{})
+	if err != nil {
+		t.Fatalf("failed to generate test cert: %v", err)
+	}
+
+	pemStr := encodeCertPEM(derBytes)
+
+	// Verify PEM format
+	if !contains(pemStr, "-----BEGIN CERTIFICATE-----") {
+		t.Fatal("expected PEM header")
+	}
+
+	if !contains(pemStr, "-----END CERTIFICATE-----") {
+		t.Fatal("expected PEM footer")
+	}
+
+	// Verify we can decode it back
+	block, _ := pem.Decode([]byte(pemStr))
+	if block == nil {
+		t.Fatal("failed to decode PEM")
+	}
+
+	if len(block.Bytes) != len(derBytes) {
+		t.Fatal("decoded PEM does not match original DER")
+	}
+}
+
+// Helper function to check if string contains substring
+func contains(s, substr string) bool {
+	return len(s) > 0 && len(substr) > 0 && s != substr &&
+		(s == substr || len(s) > len(substr))
+}