feat(M46): Windows Certificate Store + Java Keystore target connectors, shared certutil package

Extract shared certutil helpers (CreatePFX, ParsePrivateKey, ComputeThumbprint,
GenerateRandomPassword, ParseCertificatePEM) from IIS connector for reuse.
Add WinCertStore connector (PowerShell Import-PfxCertificate, dual local/WinRM
mode, configurable store/location, expired cert cleanup) and JavaKeystore
connector (PEM→PKCS#12→keytool pipeline, JKS/PKCS12 support, shell injection
prevention, path traversal protection). 53 new tests, all passing.

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

internal/connector/target/certutil/certutil.go

@@ -0,0 +1,125 @@
+// Package certutil provides shared certificate utility functions for target connectors.
+// These functions handle PEM/PFX conversion, key parsing, thumbprint computation,
+// and random password generation. Extracted from the IIS connector (M39) to enable
+// reuse by Windows Certificate Store (M46) and Java Keystore (M46) connectors.
+package certutil
+
+import (
+	"crypto/rand"
+	"crypto/sha1"
+	"crypto/x509"
+	"encoding/hex"
+	"encoding/pem"
+	"fmt"
+	"strings"
+
+	pkcs12 "software.sslmate.com/src/go-pkcs12"
+)
+
+// CreatePFX converts PEM-encoded cert, key, and chain into PKCS#12 (PFX) format.
+// Uses go-pkcs12 Modern encoder with strong encryption.
+func CreatePFX(certPEM, keyPEM, chainPEM string, password string) ([]byte, error) {
+	// Parse leaf certificate
+	certBlock, _ := pem.Decode([]byte(certPEM))
+	if certBlock == nil || certBlock.Type != "CERTIFICATE" {
+		return nil, fmt.Errorf("failed to decode certificate PEM")
+	}
+	leafCert, err := x509.ParseCertificate(certBlock.Bytes)
+	if err != nil {
+		return nil, fmt.Errorf("failed to parse leaf certificate: %w", err)
+	}
+
+	// Parse private key (supports PKCS#8, PKCS#1 RSA, and EC)
+	keyBlock, _ := pem.Decode([]byte(keyPEM))
+	if keyBlock == nil {
+		return nil, fmt.Errorf("failed to decode private key PEM")
+	}
+	privateKey, err := ParsePrivateKey(keyBlock.Bytes)
+	if err != nil {
+		return nil, fmt.Errorf("failed to parse private key: %w", err)
+	}
+
+	// Parse CA chain certificates (optional)
+	var caCerts []*x509.Certificate
+	if chainPEM != "" {
+		rest := []byte(chainPEM)
+		for {
+			var block *pem.Block
+			block, rest = pem.Decode(rest)
+			if block == nil {
+				break
+			}
+			if block.Type != "CERTIFICATE" {
+				continue
+			}
+			caCert, err := x509.ParseCertificate(block.Bytes)
+			if err != nil {
+				return nil, fmt.Errorf("failed to parse CA certificate: %w", err)
+			}
+			caCerts = append(caCerts, caCert)
+		}
+	}
+
+	// Encode as PKCS#12 with Modern encryption
+	pfxData, err := pkcs12.Modern.Encode(privateKey, leafCert, caCerts, password)
+	if err != nil {
+		return nil, fmt.Errorf("failed to encode PKCS#12: %w", err)
+	}
+
+	return pfxData, nil
+}
+
+// ParsePrivateKey attempts to parse a DER-encoded private key.
+// Tries PKCS#8, PKCS#1 RSA, and EC formats in order.
+func ParsePrivateKey(der []byte) (interface{}, error) {
+	if key, err := x509.ParsePKCS8PrivateKey(der); err == nil {
+		return key, nil
+	}
+	if key, err := x509.ParsePKCS1PrivateKey(der); err == nil {
+		return key, nil
+	}
+	if key, err := x509.ParseECPrivateKey(der); err == nil {
+		return key, nil
+	}
+	return nil, fmt.Errorf("unsupported private key format")
+}
+
+// ComputeThumbprint calculates the SHA-1 thumbprint of a PEM-encoded certificate.
+// Windows uses SHA-1 thumbprints as the primary certificate identifier.
+// Returns uppercase hex string matching Windows certutil output.
+func ComputeThumbprint(certPEM string) (string, error) {
+	block, _ := pem.Decode([]byte(certPEM))
+	if block == nil || block.Type != "CERTIFICATE" {
+		return "", fmt.Errorf("failed to decode certificate PEM for thumbprint")
+	}
+	hash := sha1.Sum(block.Bytes)
+	return strings.ToUpper(hex.EncodeToString(hash[:])), nil
+}
+
+// GenerateRandomPassword creates a random alphanumeric password.
+// Typically used for transient PFX encryption — the password is only used
+// between PFX creation and import, it never persists.
+func GenerateRandomPassword(length int) (string, error) {
+	const charset = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"
+	b := make([]byte, length)
+	if _, err := rand.Read(b); err != nil {
+		return "", fmt.Errorf("failed to read random bytes: %w", err)
+	}
+	for i := range b {
+		b[i] = charset[int(b[i])%len(charset)]
+	}
+	return string(b), nil
+}
+
+// ParseCertificatePEM parses a PEM-encoded certificate and returns the x509.Certificate.
+func ParseCertificatePEM(certPEM string) (*x509.Certificate, error) {
+	block, _ := pem.Decode([]byte(certPEM))
+	if block == nil || block.Type != "CERTIFICATE" {
+		return nil, fmt.Errorf("failed to decode certificate PEM")
+	}
+	cert, err := x509.ParseCertificate(block.Bytes)
+	if err != nil {
+		return nil, fmt.Errorf("failed to parse certificate: %w", err)
+	}
+	return cert, nil
+}