specify extended key usage attributes via x509.ExtraExtensions (#292)

* specify extended key usage attributes via x509.ExtraExtensions

Directly specifying extended key usage attributes means Critical flag
is always set to false. But as seen with timestamping - https://www.ietf.org/rfc/rfc3161.txt ,
there may be a need to set Critical flag for certain EKUs. Using x509.ExtraExtensions field
provides this flexibility. Currently all EKUs except timestamping one have Critical flag set
to false, but we can revise other EKUs or make them configurable if deemed necessary later.

.github/workflows/golangci-lint.yml

@@ -26,7 +26,7 @@ jobs:
     steps:
       - uses: actions/setup-go@v4
         with:
-          go-version: 1.19
+          go-version: 1.20.6
       - uses: actions/[email protected]
       - name: golangci-lint
         uses: golangci/[email protected]

.github/workflows/license.yml

@@ -27,7 +27,7 @@ jobs:
     - name: Setup Go
       uses: actions/setup-go@v4
       with:
-        go-version: 1.19
+        go-version: 1.20.6
     - name: checkout
       uses: actions/[email protected]
     - name: Install addlicense

.github/workflows/linux.yml

@@ -25,7 +25,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        go: [ '1.18.x', '1.19', '1.20' ]
+        go: [ '1.18.x', '1.19.x', '1.20.6' ]
     name: Go ${{ matrix.go }} build
     steps:
       - name: checkout

.github/workflows/release.yml

@@ -29,7 +29,7 @@ jobs:
     - name: install go
       uses: actions/setup-go@v4
       with:
-        go-version: 1.19
+        go-version: 1.20.6
 
     - name: get version
       id: v

.github/workflows/reuse.yml

@@ -43,13 +43,13 @@ jobs:
     steps:
       - name: Checkout release
         if: ${{ inputs.tag == 'release'}}
-        uses: actions/[email protected] # v2.4.0
+        uses: actions/[email protected] # v3.5.3
         with:
           fetch-depth: 0
 
       - name: Checkout image
         if: ${{ inputs.tag == 'image'}}
-        uses: actions/[email protected] # v2.4.0
+        uses: actions/[email protected] # v3.5.3
 
       - name: Unshallow
         if: ${{ inputs.tag == 'image'}}
@@ -58,7 +58,7 @@ jobs:
       - name: Set up Go
         uses: actions/setup-go@v4 # v2.1.5
         with:
-          go-version: ~1.18.6
+          go-version: ~1.20.6
 
       - name: Install Cosign
         uses: sigstore/cosign-installer@6e04d228eb30da1757ee4e1dd75a0ec73a653e06 # v3.1.1

.github/workflows/scorecards.yml

@@ -24,7 +24,7 @@ jobs:
 
     steps:
       - name: "Checkout code"
-        uses: actions/[email protected] # v2.4.0
+        uses: actions/[email protected] # v3.5.3
         with:
           persist-credentials: false
 

docker-softhsm/Dockerfile

@@ -19,7 +19,7 @@ WORKDIR ${CRYPKI_DIR}
 RUN go get -v ./... && go test ./... && go build -o crypki-bin ${CRYPKI_DIR}/cmd/crypki && \
     go build -o gen-cacert ${CRYPKI_DIR}/cmd/gen-cacert
 
-FROM debian:sid-slim
+FROM debian:bookworm-slim
 ENV CRYPKI_DIR /go/src/github.com/theparanoids/crypki
 WORKDIR /opt/crypki
 
@@ -29,8 +29,8 @@ COPY ./docker-softhsm/init_hsm.sh /opt/crypki
 COPY ./docker-softhsm/crypki.conf.sample /opt/crypki
 
 RUN mkdir -p /var/log/crypki /opt/crypki /opt/crypki/slot_pubkeys \
-&& apt-get update \
-&& apt-get install -y softhsm opensc openssl \
+&& apt update \
+&& apt install -y softhsm2 opensc openssl \
 && /bin/bash -x /opt/crypki/init_hsm.sh
 
 CMD ["/usr/bin/crypki-bin", "-config", "/opt/crypki/crypki-softhsm.json"]

docker-softhsm/crypki.conf.sample

@@ -62,7 +62,7 @@
             "UserPinPath": "/dev/shm/slot_pwd.txt"
         }
     ],
-    "ModulePath": "/usr/lib/x86_64-linux-gnu/softhsm/libsofthsm2.so",
+    "ModulePath": "/usr/lib/softhsm/libsofthsm2.so",
     "TLSCACertPath": "/opt/crypki/tls-crt/ca.crt",
     "TLSClientAuthMode": 4,
     "TLSServerCertPath": "/opt/crypki/tls-crt/server.crt",

docker-softhsm/init_hsm.sh

@@ -31,8 +31,8 @@ user_ssh_label="user_ssh"
 host_x509_label="host_x509"
 host_ssh_label="host_ssh"
 sign_blob_label="sign_blob"
-user_ssh_keytype="EC:prime384v1"
-host_x509_keytype="EC:prime384v1"
+user_ssh_keytype="EC:secp256r1"
+host_x509_keytype="EC:secp256r1"
 host_ssh_keytype="rsa:4096"
 sign_blob_keytype="rsa:4096"
 user_ssh_cipher_cmd="ec"

docker-softhsm/x509_csr_eku.json

@@ -0,0 +1 @@
+{"validity": 432000,"csr": "-----BEGIN CERTIFICATE REQUEST-----\nMIICZjCCAU4CAQAwITELMAkGA1UEBhMCVVMxEjAQBgNVBAMMCWxvY2FsaG9zdDCC\nASIwDQYJKoZIhvcNAQEBBQADggEPADCCAQoCggEBANycK6JNgdOromSB6Ym90+Ss\nr+k5to+os0sshmpgXRf/4/rbq5IYafulyrKPZ4Ymj9kuvqkpp99d7gbzndee8vQi\nxv7hEvfkCHzPbLjHkf7pNYHSFVJSpBn3ySxfq0/Ie9A6XHkFeLD3J/exFJ4Vlv4K\nQl4xher7ie5sFSYw47b0IhCzcnTaGUwbLnnhnRga7Ly4NC4zSk3KjEQYGg8QFOY0\nPlQ5Zvq3d7zldAs8MypGgxlyurz/UyorFdTQ2cF+c8o2SvpvBD9EbbmUSVh7KTZi\nduLIefRhV+VsHG8EIcM7fhLrTRUdO9KESL76GvUG77f96cU3ZeoRlMF/+jgwRoEC\nAwEAAaAAMA0GCSqGSIb3DQEBCwUAA4IBAQBY6Ff3Eb6H0AEjaz8+aum7H5MkGNeF\n8et2zVSRErPEQ5hkjB6nI9qBQ9TAyI99RdltJE5IP443bPmNLjZvRCdihC2EgDvf\n3TYEAAlHh4ihtIn7vKi9Rw9M09uAi3yJRs3zhBmN2rZvV3JmwqSdd/4dmiCaa+Y0\nTAESbwGv7fURGlsJJ6xa3/6osxb6DmbaGFOK7a1+2onHi4Xmlmmc3GawzW8Q/mXJ\nayRjLZGdwbOa5fMfWWlLtlSBaPKo/zTYuRl0idYIUFIuInJDx1ydQQQQ/opl4Qpo\nynt0uhRtvugQ+TYN0Yjp5ONK8oinmT6AEVckIfJ4aKIOCf3snUkPfQBi\n-----END CERTIFICATE REQUEST-----", "ext_key_usage": [1,2,3,4,8]}

x509cert/encode.go

@@ -5,6 +5,8 @@ package x509cert
 
 import (
 	"crypto/x509"
+	"crypto/x509/pkix"
+	"encoding/asn1"
 	"encoding/pem"
 	"errors"
 	"fmt"
@@ -43,25 +45,139 @@ func DecodeRequest(req *proto.X509CertificateSigningRequest) (*x509.Certificate,
 		EmailAddresses:        csr.EmailAddresses,
 		URIs:                  csr.URIs,
 		KeyUsage:              x509.KeyUsageKeyEncipherment | x509.KeyUsageDigitalSignature,
-		ExtKeyUsage:           x509ExtKeyUsage,
+		ExtraExtensions:       x509ExtKeyUsage,
 		BasicConstraintsValid: true,
 	}, nil
 }
 
-// getX509ExtKeyUsage returns []x509.ExtKeyUsage from []int32
-func getX509ExtKeyUsage(x509ExtKeyUsages []int32) ([]x509.ExtKeyUsage, error) {
+// extKeyUsageToExtension returns []pkix.Extension from []x509.ExtKeyUsage.
+// This allows us to add EKU with a specific Critical bit instead of the default false value.
+
+func extKeyUsageToExtension(extKeyUsage []x509.ExtKeyUsage) ([]pkix.Extension, error) {
+
+	var critMap = map[x509.ExtKeyUsage]bool{
+		x509.ExtKeyUsageAny:             false,
+		x509.ExtKeyUsageServerAuth:      false,
+		x509.ExtKeyUsageClientAuth:      false,
+		x509.ExtKeyUsageCodeSigning:     false,
+		x509.ExtKeyUsageEmailProtection: false,
+		x509.ExtKeyUsageIPSECEndSystem:  false,
+		x509.ExtKeyUsageIPSECTunnel:     false,
+		x509.ExtKeyUsageIPSECUser:       false,
+		// https://www.ietf.org/rfc/rfc3161.txt "id-kp-timeStamping.  This extension MUST be critical."
+		x509.ExtKeyUsageTimeStamping:                   true,
+		x509.ExtKeyUsageOCSPSigning:                    false,
+		x509.ExtKeyUsageMicrosoftServerGatedCrypto:     false,
+		x509.ExtKeyUsageNetscapeServerGatedCrypto:      false,
+		x509.ExtKeyUsageMicrosoftCommercialCodeSigning: false,
+		x509.ExtKeyUsageMicrosoftKernelCodeSigning:     false,
+	}
+
+	// values copied from Go crypto/x509 library - https://cs.opensource.google/go/go/+/refs/tags/go1.20.6:src/crypto/x509/x509.go;l=599
+	var (
+		oidExtensionExtendedKeyUsage                 = asn1.ObjectIdentifier{2, 5, 29, 37}
+		oidExtKeyUsageAny                            = asn1.ObjectIdentifier{2, 5, 29, 37, 0}
+		oidExtKeyUsageServerAuth                     = asn1.ObjectIdentifier{1, 3, 6, 1, 5, 5, 7, 3, 1}
+		oidExtKeyUsageClientAuth                     = asn1.ObjectIdentifier{1, 3, 6, 1, 5, 5, 7, 3, 2}
+		oidExtKeyUsageCodeSigning                    = asn1.ObjectIdentifier{1, 3, 6, 1, 5, 5, 7, 3, 3}
+		oidExtKeyUsageEmailProtection                = asn1.ObjectIdentifier{1, 3, 6, 1, 5, 5, 7, 3, 4}
+		oidExtKeyUsageIPSECEndSystem                 = asn1.ObjectIdentifier{1, 3, 6, 1, 5, 5, 7, 3, 5}
+		oidExtKeyUsageIPSECTunnel                    = asn1.ObjectIdentifier{1, 3, 6, 1, 5, 5, 7, 3, 6}
+		oidExtKeyUsageIPSECUser                      = asn1.ObjectIdentifier{1, 3, 6, 1, 5, 5, 7, 3, 7}
+		oidExtKeyUsageTimeStamping                   = asn1.ObjectIdentifier{1, 3, 6, 1, 5, 5, 7, 3, 8}
+		oidExtKeyUsageOCSPSigning                    = asn1.ObjectIdentifier{1, 3, 6, 1, 5, 5, 7, 3, 9}
+		oidExtKeyUsageMicrosoftServerGatedCrypto     = asn1.ObjectIdentifier{1, 3, 6, 1, 4, 1, 311, 10, 3, 3}
+		oidExtKeyUsageNetscapeServerGatedCrypto      = asn1.ObjectIdentifier{2, 16, 840, 1, 113730, 4, 1}
+		oidExtKeyUsageMicrosoftCommercialCodeSigning = asn1.ObjectIdentifier{1, 3, 6, 1, 4, 1, 311, 2, 1, 22}
+		oidExtKeyUsageMicrosoftKernelCodeSigning     = asn1.ObjectIdentifier{1, 3, 6, 1, 4, 1, 311, 61, 1, 1}
+	)
+	var extCritTrue, extCritFalse []asn1.ObjectIdentifier
+	var extensions []pkix.Extension
+	for _, eku := range extKeyUsage {
+		var oid asn1.ObjectIdentifier
+		switch eku {
+		case x509.ExtKeyUsageAny:
+			oid = oidExtKeyUsageAny
+		case x509.ExtKeyUsageServerAuth:
+			oid = oidExtKeyUsageServerAuth
+		case x509.ExtKeyUsageClientAuth:
+			oid = oidExtKeyUsageClientAuth
+		case x509.ExtKeyUsageCodeSigning:
+			oid = oidExtKeyUsageCodeSigning
+		case x509.ExtKeyUsageEmailProtection:
+			oid = oidExtKeyUsageEmailProtection
+		case x509.ExtKeyUsageIPSECEndSystem:
+			oid = oidExtKeyUsageIPSECEndSystem
+		case x509.ExtKeyUsageIPSECTunnel:
+			oid = oidExtKeyUsageIPSECTunnel
+		case x509.ExtKeyUsageIPSECUser:
+			oid = oidExtKeyUsageIPSECUser
+		case x509.ExtKeyUsageTimeStamping:
+			oid = oidExtKeyUsageTimeStamping
+		case x509.ExtKeyUsageOCSPSigning:
+			oid = oidExtKeyUsageOCSPSigning
+		case x509.ExtKeyUsageMicrosoftServerGatedCrypto:
+			oid = oidExtKeyUsageMicrosoftServerGatedCrypto
+		case x509.ExtKeyUsageNetscapeServerGatedCrypto:
+			oid = oidExtKeyUsageNetscapeServerGatedCrypto
+		case x509.ExtKeyUsageMicrosoftCommercialCodeSigning:
+			oid = oidExtKeyUsageMicrosoftCommercialCodeSigning
+		case x509.ExtKeyUsageMicrosoftKernelCodeSigning:
+			oid = oidExtKeyUsageMicrosoftKernelCodeSigning
+		}
+		// Group all EKUs based on whether Critical flag is set.
+		// Each set forms a separate pkix.Extension.
+		if critMap[eku] {
+			extCritTrue = append(extCritTrue, oid)
+		} else {
+			extCritFalse = append(extCritFalse, oid)
+		}
+	}
+	if len(extCritTrue) != 0 {
+		oidM, err := asn1.Marshal(extCritTrue)
+		if err != nil {
+			return nil, err
+		}
+		extension := pkix.Extension{
+			Id:       oidExtensionExtendedKeyUsage,
+			Critical: true,
+			Value:    oidM,
+		}
+		extensions = append(extensions, extension)
+	}
+	if len(extCritFalse) != 0 {
+		oidM, err := asn1.Marshal(extCritFalse)
+		if err != nil {
+			return nil, err
+		}
+		extension := pkix.Extension{
+			Id:       oidExtensionExtendedKeyUsage,
+			Critical: false,
+			Value:    oidM,
+		}
+		extensions = append(extensions, extension)
+	}
+	return extensions, nil
+
+}
+
+// getX509ExtKeyUsage returns []pkix.Extension from []int32
+func getX509ExtKeyUsage(x509ExtKeyUsages []int32) ([]pkix.Extension, error) {
+	// value of last EKU x509.ExtKeyUsageMicrosoftKernelCodeSigning
+	// per https://go.dev/src/crypto/x509/x509.go?s=18153:18173#L634
+	const maxValidEKU = 13
 	if len(x509ExtKeyUsages) == 0 {
-		return []x509.ExtKeyUsage{x509.ExtKeyUsageClientAuth, x509.ExtKeyUsageServerAuth}, nil
+		return extKeyUsageToExtension([]x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth, x509.ExtKeyUsageClientAuth})
 	}
-	var x509ExtKeyUsagesRet []x509.ExtKeyUsage
-	for _, x509ExtKeyUsage := range x509ExtKeyUsages {
-		// validate if extUsage falls under https://golang.org/src/crypto/x509/x509.go?s=18153:18173#L558
-		if x509ExtKeyUsage < 0 || x509ExtKeyUsage > 11 {
-			return nil, fmt.Errorf("invalid x509 ExtKeyUsage value: %d, valid values are [0,1,...11]", x509ExtKeyUsage)
+	ekuRet := make([]x509.ExtKeyUsage, len(x509ExtKeyUsages))
+	for i, eku := range x509ExtKeyUsages {
+		// extKeyUsage valid values - https://golang.org/src/crypto/x509/x509.go?s=18153:18173#L621
+		if eku < 0 || eku > maxValidEKU {
+			return nil, fmt.Errorf("invalid x509 ExtKeyUsage value: %d, valid values are [0,1,...13]", eku)
 		}
-		x509ExtKeyUsagesRet = append(x509ExtKeyUsagesRet, x509.ExtKeyUsage(x509ExtKeyUsage))
+		ekuRet[i] = x509.ExtKeyUsage(eku)
 	}
-	return x509ExtKeyUsagesRet, nil
+	return extKeyUsageToExtension(ekuRet)
 }
 
 // decodeCSR decodes CSR and returns x509 CertificateRequest struct.