Merge #16: CryptoAPI TLS certificate injection

271a0c7 tlshook: Fix linter warning about shadowed variable. (JeremyRand)
978116d Travis: Disable gometalinter warnings on the portion of x509 that is copied verbatim from the Go standard library. (JeremyRand)
05afcd4 tlshook: Remove unused imports. (JeremyRand)
81fb477 tlshook: Removed commented-out code for non-dehydrated certificates; I plan to re-add that code once it's properly tested. (JeremyRand)
e16ad6f TLS dehydrated certificate injection for CryptoAPI trust store (triggered by hooking DNS lookups). (JeremyRand)

Pull request description:

  Add the ability to inject TLS certs into CryptoAPI's trust store before replying to DNS queries.

  Please review but do not merge yet.

  TODO before merging:

  - [x] Make the x509 build script use `go generate`.
  - [x] Make the x509 build script source `go env` and use `$GOROOT` from it.
  - [x] Update the `d/` spec to match the current dehydrated certificate format.  (It's changed slightly since I submitted the spec.)
  - [x] Look into using Errore instead of Fatal.
  - [x] Fix `.gitignore`.
  - [x] Squash commits.

Tree-SHA512: 1ce4e650e142aa1630f51b09497d85ad0626ae46ccc63c2e72fafa97d99bf340b3583db5ac76b5cc339228e56be8e9db673348d2d8f1f6173f1bca5306971629

.travis.yml

@@ -14,6 +14,7 @@ addons:
 sudo: false
 
 install:
+  - go generate -v ./...
   - go get -v -t ./...
   - env GOOS=windows GOARCH=amd64 go get -d -v -t ./...
 script:

.travis/script

@@ -14,6 +14,8 @@ fi
 
 gometalinter.v1 --install
 
+# The --exclude line disables warnings on the portion of x509 that is copied
+# verbatim from the Go standard library.
 echo ""
 echo "gometalinter critical (should be no warnings):"
 gometalinter.v1 --enable-all \
@@ -37,6 +39,7 @@ gometalinter.v1 --enable-all \
 --disable=unused \
 --concurrency=3 \
 --deadline=10m \
+--exclude='^x509/([a-wy-z]|x509.go|x509_[a-rt-z])' \
 ./...
 STATICRESULT1=$?
 
@@ -45,6 +48,7 @@ echo "gometalinter non-critical (warnings expected):"
 gometalinter.v1 --enable-all \
 --concurrency=3 \
 --deadline=10m \
+--exclude='^x509/([a-wy-z]|x509.go|x509_[a-rt-z])' \
 ./...
 STATICRESULT2=$?
 

backend/backend.go

@@ -6,6 +6,7 @@ import "gopkg.in/hlandau/madns.v1/merr"
 import "github.com/namecoin/ncdns/namecoin"
 import "github.com/namecoin/ncdns/util"
 import "github.com/namecoin/ncdns/ncdomain"
+import "github.com/namecoin/ncdns/tlshook"
 import "github.com/hlandau/xlog"
 import "sync"
 import "fmt"
@@ -421,6 +422,12 @@ func (tx *btx) _findNCValue(ncv *ncdomain.Value, isubname, subname string, depth
 
 func (tx *btx) addAnswersUnderNCValueActual(ncv *ncdomain.Value, sn string) (rrs []dns.RR, err error) {
 	rrs, err = ncv.RRs(nil, dns.Fqdn(tx.qname), dns.Fqdn(tx.basename+"."+tx.rootname))
+
+	// TODO: add callback variable "OnValueReferencedFunc" to backend options so that we don't pollute this function with every hook that we want
+	//       might need to add the other attributes of tx, and sn, to the callback variable for flexibility's sake
+	// This doesn't normally return errors, but any errors during execution will be logged.
+	tlshook.DomainValueHookTLS(tx.qname, ncv)
+
 	return
 }
 

certdehydrate/certdehydrate.go

@@ -0,0 +1,236 @@
+package certdehydrate
+
+import (
+	"bytes"
+	"crypto/sha256"
+	"crypto/x509/pkix"
+	"encoding/base64"
+	"encoding/binary"
+	"encoding/json"
+	"fmt"
+	"math/big"
+	"time"
+)
+
+import "github.com/namecoin/ncdns/x509"
+
+// TODO: add a version field
+type DehydratedCertificate struct {
+	PubkeyB64 string
+	NotBeforeScaled int64
+	NotAfterScaled int64
+	SignatureAlgorithm int64
+	SignatureB64 string
+}
+
+func (dehydrated DehydratedCertificate) SerialNumber(name string) ([]byte, error){
+
+	nameHash := sha256.Sum256([]byte(name))
+
+	pubkeyBytes, err := base64.StdEncoding.DecodeString(dehydrated.PubkeyB64)
+	if err != nil {
+		return nil, fmt.Errorf("Dehydrated cert pubkey is not valid base64: %s", err)
+	}
+	pubkeyHash := sha256.Sum256(pubkeyBytes)
+
+	notBeforeScaledBuf := new(bytes.Buffer)
+	err = binary.Write(notBeforeScaledBuf, binary.BigEndian, dehydrated.NotBeforeScaled)
+	if err != nil {
+		return nil, fmt.Errorf("binary.Write of notBefore failed: %s", err)
+	}
+	notBeforeHash := sha256.Sum256(notBeforeScaledBuf.Bytes())
+
+	notAfterScaledBuf := new(bytes.Buffer)
+	err = binary.Write(notAfterScaledBuf, binary.BigEndian, dehydrated.NotAfterScaled)
+	if err != nil {
+		return nil, fmt.Errorf("binary.Write of notAfter failed: %s", err)
+	}
+	notAfterHash := sha256.Sum256(notAfterScaledBuf.Bytes())
+
+	serialHash := sha256.New()
+	serialHash.Write(nameHash[:])
+	serialHash.Write(pubkeyHash[:])
+	serialHash.Write(notBeforeHash[:])
+	serialHash.Write(notAfterHash[:])
+
+	// 19 bytes will be less than 2^159, see https://crypto.stackexchange.com/a/260
+	return serialHash.Sum(nil)[0:19], nil
+}
+
+func (dehydrated DehydratedCertificate) String() string {
+	output := []interface{}{1, dehydrated.PubkeyB64, dehydrated.NotBeforeScaled, dehydrated.NotAfterScaled, dehydrated.SignatureAlgorithm, dehydrated.SignatureB64}
+	binOutput, _ := json.Marshal(output)
+	return string(binOutput)
+}
+
+func ParseDehydratedCert(data interface{}) (*DehydratedCertificate, error) {
+	dehydrated, ok := data.([]interface{})
+	if !ok {
+		return nil, fmt.Errorf("Dehydrated cert is not a list")
+	}
+
+	if len(dehydrated) < 1 {
+		return nil, fmt.Errorf("Dehydrated cert must have a version field")
+	}
+
+	version, ok := dehydrated[0].(float64)
+	if !ok {
+		return nil, fmt.Errorf("Dehydrated cert version must be an integer")
+	}
+
+	if version != 1 {
+		return nil, fmt.Errorf("Dehydrated cert has an unrecognized version")
+	}
+
+	if len(dehydrated) < 6 {
+		return nil, fmt.Errorf("Dehydrated cert must have 6 items")
+	}
+
+	pubkeyB64, ok := dehydrated[1].(string)
+	if !ok {
+		return nil, fmt.Errorf("Dehydrated cert pubkey must be a string")
+	}
+
+	notBeforeScaled, ok := dehydrated[2].(float64)
+	if !ok {
+		return nil, fmt.Errorf("Dehydrated cert notBefore must be an integer")
+	}
+
+	notAfterScaled, ok := dehydrated[3].(float64)
+	if !ok {
+		return nil, fmt.Errorf("Dehydrated cert notAfter must be an integer")
+	}
+
+	signatureAlgorithm, ok := dehydrated[4].(float64)
+	if !ok {
+		return nil, fmt.Errorf("Dehydrated cert signature algorithm must be an integer")
+	}
+
+	signatureB64, ok := dehydrated[5].(string)
+	if !ok {
+		return nil, fmt.Errorf("Dehydrated cert signature must be a string")
+	}
+
+	result := DehydratedCertificate {
+		PubkeyB64:             pubkeyB64,
+		NotBeforeScaled:       int64(notBeforeScaled),
+		NotAfterScaled:        int64(notAfterScaled),
+		SignatureAlgorithm:    int64(signatureAlgorithm),
+		SignatureB64:          signatureB64,
+	}
+
+	return &result, nil
+}
+
+func DehydrateCert(cert *x509.Certificate) (*DehydratedCertificate, error) {
+
+	pubkeyBytes, err := x509.MarshalPKIXPublicKey(cert.PublicKey)
+	if err != nil {
+		return nil, fmt.Errorf("failed to marshal parsed public key: %s", err)
+	}
+
+	pubkeyB64 := base64.StdEncoding.EncodeToString(pubkeyBytes)
+
+	notBeforeInt := cert.NotBefore.Unix()
+	notAfterInt := cert.NotAfter.Unix()
+
+	timestampPrecision := int64(5 * 60) // 5 minute precision
+
+	notBeforeScaled := notBeforeInt / timestampPrecision
+	notAfterScaled := notAfterInt / timestampPrecision
+
+	signatureAlgorithm := int64(cert.SignatureAlgorithm)
+	signatureBytes := cert.Signature
+	signatureB64 := base64.StdEncoding.EncodeToString(signatureBytes)
+
+	result := DehydratedCertificate{
+		PubkeyB64:             pubkeyB64,
+		NotBeforeScaled:       notBeforeScaled,
+		NotAfterScaled:        notAfterScaled,
+		SignatureAlgorithm:    signatureAlgorithm,
+		SignatureB64:          signatureB64,
+	}
+
+	return &result, nil
+}
+
+// Accepts as input the bare minimum data needed to produce a valid cert.
+// The input is untrusted.
+// The output is safe.
+// The timestamps are in 5-minute increments.
+func RehydrateCert(dehydrated *DehydratedCertificate) (*x509.Certificate, error) {
+
+	pubkeyBin, err := base64.StdEncoding.DecodeString(dehydrated.PubkeyB64)
+	if err != nil {
+		return nil, fmt.Errorf("Dehydrated cert pubkey must be valid base64: %s", err)
+	}
+
+	pubkey, err := x509.ParsePKIXPublicKey(pubkeyBin)
+	if err != nil {
+		return nil, fmt.Errorf("Dehydrated cert pubkey is invalid: %s", err)
+	}
+
+	timestampPrecision := int64(5 * 60) // 5 minute precision
+
+	notBeforeInt := dehydrated.NotBeforeScaled * timestampPrecision
+	notAfterInt := dehydrated.NotAfterScaled * timestampPrecision
+
+	notBefore := time.Unix(int64(notBeforeInt), 0)
+	notAfter := time.Unix(int64(notAfterInt), 0)
+
+	signatureAlgorithm := x509.SignatureAlgorithm(dehydrated.SignatureAlgorithm)
+
+	signature, err := base64.StdEncoding.DecodeString(dehydrated.SignatureB64)
+	if err != nil {
+		return nil, fmt.Errorf("Dehydrated cert signature must be valid base64: %s", err)
+	}
+
+	template := x509.Certificate{
+		SerialNumber: big.NewInt(1),
+		NotBefore: notBefore,
+		NotAfter: notAfter,
+
+		// x509.KeyUsageKeyEncipherment is used for RSA key exchange, but not DHE/ECDHE key exchange.  Since everyone should be using ECDHE (due to forward secrecy), we disallow x509.KeyUsageKeyEncipherment in our template.
+		//KeyUsage:              x509.KeyUsageKeyEncipherment | x509.KeyUsageDigitalSignature,
+		KeyUsage:              x509.KeyUsageDigitalSignature, 
+
+		ExtKeyUsage:           []x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth},
+		BasicConstraintsValid: true,
+
+		SignatureAlgorithm: signatureAlgorithm,
+		PublicKey: pubkey,
+		Signature: signature,
+	}
+
+	return &template, nil
+}
+
+func FillRehydratedCertTemplate(template x509.Certificate, name string) ([]byte, error) {
+
+	template.Subject = pkix.Name{
+		CommonName: name,
+		SerialNumber: "Namecoin TLS Certificate",
+	}
+
+	// DNS name
+	template.DNSNames = append(template.DNSNames, name)
+
+	// Serial number
+	dehydrated, err := DehydrateCert(&template)
+	if err != nil {
+		return nil, fmt.Errorf("Error dehydrating filled cert template: %s", err)
+	}
+	serialNumberBytes, err := dehydrated.SerialNumber(name)
+	if err != nil {
+		return nil, fmt.Errorf("Error calculating serial number: %s", err)
+	}
+	template.SerialNumber.SetBytes(serialNumberBytes)
+
+	derBytes, err := x509.CreateCertificateWithSplicedSignature(&template, &template)
+	if err != nil {
+		return nil, fmt.Errorf("Error splicing signature: %s", err)
+	}
+
+	return derBytes, nil
+
+}

certdehydrate/certdehydrate_test.go

@@ -0,0 +1,39 @@
+package certdehydrate_test
+
+import (
+	"testing"
+	"encoding/json"
+	"reflect"
+	"github.com/namecoin/ncdns/certdehydrate"
+)
+
+func TestDehydratedCertIdentityOperation(t *testing.T) {
+	bytesJson := []byte(`[1, "MFkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAE/hy1t4jB14ronx6n1m8VQh02jblRfu2cV3/LcyomfVljypUQMGjmuxWNbPI0a3cF6miNOijSCutqTZdb7TLvig==",4944096,5049216,10,"MEQCIGXXk6gYx95vQoknRwiQ4e27I+DXUWkE8L6dmLwAiGncAiBbtEX1nnZINx1YGzT5Fx8SxpjLwNDTUBkq22NpazHLIA=="]`)
+
+	var parsedJson []interface{}
+
+	if err := json.Unmarshal(bytesJson, &parsedJson); err != nil {
+		t.Error("Error parsing JSON:", err)
+	}
+
+	dehydrated, err := certdehydrate.ParseDehydratedCert(parsedJson)
+	if err != nil {
+		t.Error("Error parsing dehydrated certificate:", err)
+	}
+
+	template, err := certdehydrate.RehydrateCert(dehydrated)
+	if err != nil {
+		t.Error("Error rehydrating certificate:", err)
+	}
+
+	dehydrated2, err := certdehydrate.DehydrateCert(template)
+	if err != nil {
+		t.Error("Error dehydrating certificate:", err)
+	}
+
+	// Test to make sure that rehydrating and then dehydrating a cert doesn't change it.
+	if !reflect.DeepEqual(dehydrated, dehydrated2) {
+		t.Error(dehydrated, "!=", dehydrated2)
+	}
+}
+

certinject/certinject_misc.go

@@ -0,0 +1,15 @@
+// +build !windows
+
+package certinject
+
+import "github.com/hlandau/xlog"
+
+var log, Log = xlog.New("ncdns.certinject")
+
+func InjectCert(derBytes []byte) {
+
+}
+
+func CleanCerts() {
+
+}

certinject/certinject_windows.go

@@ -0,0 +1,36 @@
+package certinject
+
+import (
+	"gopkg.in/hlandau/easyconfig.v1/cflag"
+	"github.com/hlandau/xlog"
+)
+
+
+// This package is used to add and remove certificates to the system trust 
+// store.
+// Currently only supports Windows CryptoAPI.
+
+var log, Log = xlog.New("ncdns.certinject")
+
+var (
+	flagGroup          = cflag.NewGroup(nil, "certstore")
+	cryptoApiFlag      = cflag.Bool(flagGroup, "cryptoapi", false, "Synchronize TLS certs to the CryptoAPI trust store?  This enables HTTPS to work with Chromium/Chrome.  Only use if you've set up null HPKP in Chromium/Chrome as per documentation.  If you haven't set up null HPKP, or if you access ncdns from browsers not based on Chromium or Firefox, this is unsafe and should not be used.")
+	certExpirePeriod   = cflag.Int(flagGroup, "expire", 60 * 30, "Duration (in seconds) after which TLS certs will be removed from the trust store.  Making this smaller than the DNS TTL (default 600) may cause TLS errors.")
+)
+
+// Injects the given cert into all configured trust stores.
+func InjectCert(derBytes []byte) {
+
+	if cryptoApiFlag.Value() {
+		injectCertCryptoApi(derBytes)
+	}
+}
+
+// Cleans expired certs from all configured trust stores.
+func CleanCerts() {
+
+	if cryptoApiFlag.Value() {
+		cleanCertsCryptoApi()
+	}
+
+}