crypto/tls: add CipherSuites, InsecureCipherSuites and CipherSuiteName

Fixes #30325

Change-Id: I497110224bb73ecfcc4655698a794e7aa4a66925
Reviewed-on: https://go-review.googlesource.com/c/go/+/175517
Run-TryBot: Filippo Valsorda <filippo@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Adam Langley <agl@golang.org>

src/crypto/tls/cipher_suites.go

@@ -14,10 +14,100 @@ import (
 	"crypto/sha1"
 	"crypto/sha256"
 	"crypto/x509"
-	"golang.org/x/crypto/chacha20poly1305"
+	"fmt"
 	"hash"
+
+	"golang.org/x/crypto/chacha20poly1305"
+)
+
+// CipherSuite is a TLS cipher suite. Note that most functions in this package
+// accept and expose cipher suite IDs instead of this type.
+type CipherSuite struct {
+	ID   uint16
+	Name string
+
+	// Supported versions is the list of TLS protocol versions that can
+	// negotiate this cipher suite.
+	SupportedVersions []uint16
+
+	// Insecure is true if the cipher suite has known security issues
+	// due to its primitives, design, or implementation.
+	Insecure bool
+}
+
+var (
+	supportedUpToTLS12 = []uint16{VersionTLS10, VersionTLS11, VersionTLS12}
+	supportedOnlyTLS12 = []uint16{VersionTLS12}
+	supportedOnlyTLS13 = []uint16{VersionTLS13}
 )
 
+// CipherSuites returns a list of cipher suites currently implemented by this
+// package, excluding those with security issues, which are returned by
+// InsecureCipherSuites.
+//
+// The list is sorted by ID. Note that the default cipher suites selected by
+// this package might depend on logic that can't be captured by a static list.
+func CipherSuites() []*CipherSuite {
+	return []*CipherSuite{
+		{TLS_RSA_WITH_3DES_EDE_CBC_SHA, "TLS_RSA_WITH_3DES_EDE_CBC_SHA", supportedUpToTLS12, false},
+		{TLS_RSA_WITH_AES_128_CBC_SHA, "TLS_RSA_WITH_AES_128_CBC_SHA", supportedUpToTLS12, false},
+		{TLS_RSA_WITH_AES_256_CBC_SHA, "TLS_RSA_WITH_AES_256_CBC_SHA", supportedUpToTLS12, false},
+		{TLS_RSA_WITH_AES_128_GCM_SHA256, "TLS_RSA_WITH_AES_128_GCM_SHA256", supportedOnlyTLS12, false},
+		{TLS_RSA_WITH_AES_256_GCM_SHA384, "TLS_RSA_WITH_AES_256_GCM_SHA384", supportedOnlyTLS12, false},
+
+		{TLS_AES_128_GCM_SHA256, "TLS_AES_128_GCM_SHA256", supportedOnlyTLS13, false},
+		{TLS_AES_256_GCM_SHA384, "TLS_AES_256_GCM_SHA384", supportedOnlyTLS13, false},
+		{TLS_CHACHA20_POLY1305_SHA256, "TLS_CHACHA20_POLY1305_SHA256", supportedOnlyTLS13, false},
+
+		{TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA, "TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA", supportedUpToTLS12, false},
+		{TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA, "TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA", supportedUpToTLS12, false},
+		{TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA, "TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA", supportedUpToTLS12, false},
+		{TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA, "TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA", supportedUpToTLS12, false},
+		{TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA, "TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA", supportedUpToTLS12, false},
+		{TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256, "TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256", supportedOnlyTLS12, false},
+		{TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384, "TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384", supportedOnlyTLS12, false},
+		{TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256, "TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256", supportedOnlyTLS12, false},
+		{TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384, "TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384", supportedOnlyTLS12, false},
+		{TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305_SHA256, "TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305_SHA256", supportedOnlyTLS12, false},
+		{TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305_SHA256, "TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305_SHA256", supportedOnlyTLS12, false},
+	}
+}
+
+// InsecureCipherSuites returns a list of cipher suites currently implemented by
+// this package and which have security issues.
+//
+// Most applications should not use the cipher suites in this list, and should
+// only use those returned by CipherSuites.
+func InsecureCipherSuites() []*CipherSuite {
+	// RC4 suites are broken because RC4 is.
+	// CBC-SHA256 suites have no Lucky13 countermeasures.
+	return []*CipherSuite{
+		{TLS_RSA_WITH_RC4_128_SHA, "TLS_RSA_WITH_RC4_128_SHA", supportedUpToTLS12, true},
+		{TLS_RSA_WITH_AES_128_CBC_SHA256, "TLS_RSA_WITH_AES_128_CBC_SHA256", supportedOnlyTLS12, true},
+		{TLS_ECDHE_ECDSA_WITH_RC4_128_SHA, "TLS_ECDHE_ECDSA_WITH_RC4_128_SHA", supportedUpToTLS12, true},
+		{TLS_ECDHE_RSA_WITH_RC4_128_SHA, "TLS_ECDHE_RSA_WITH_RC4_128_SHA", supportedUpToTLS12, true},
+		{TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256, "TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256", supportedOnlyTLS12, true},
+		{TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256, "TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256", supportedOnlyTLS12, true},
+	}
+}
+
+// CipherSuiteName returns the standard name for the passed cipher suite ID
+// (e.g. "TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256"), or a fallback representation
+// of the ID value if the cipher suite is not implemented by this package.
+func CipherSuiteName(id uint16) string {
+	for _, c := range CipherSuites() {
+		if c.ID == id {
+			return c.Name
+		}
+	}
+	for _, c := range InsecureCipherSuites() {
+		if c.ID == id {
+			return c.Name
+		}
+	}
+	return fmt.Sprintf("0x%04X", id)
+}
+
 // a keyAgreement implements the client and server side of a TLS key agreement
 // protocol by generating and processing key exchange messages.
 type keyAgreement interface {

src/crypto/tls/tls_test.go

@@ -1215,6 +1215,90 @@ func TestClientHelloInfo_SupportsCertificate(t *testing.T) {
 	}
 }
 
+func TestCipherSuites(t *testing.T) {
+	var lastID uint16
+	for _, c := range CipherSuites() {
+		if lastID > c.ID {
+			t.Errorf("CipherSuites are not ordered by ID: got %#04x after %#04x", c.ID, lastID)
+		} else {
+			lastID = c.ID
+		}
+
+		if c.Insecure {
+			t.Errorf("%#04x: Insecure CipherSuite returned by CipherSuites()", c.ID)
+		}
+	}
+	lastID = 0
+	for _, c := range InsecureCipherSuites() {
+		if lastID > c.ID {
+			t.Errorf("InsecureCipherSuites are not ordered by ID: got %#04x after %#04x", c.ID, lastID)
+		} else {
+			lastID = c.ID
+		}
+
+		if !c.Insecure {
+			t.Errorf("%#04x: not Insecure CipherSuite returned by InsecureCipherSuites()", c.ID)
+		}
+	}
+
+	cipherSuiteByID := func(id uint16) *CipherSuite {
+		for _, c := range CipherSuites() {
+			if c.ID == id {
+				return c
+			}
+		}
+		for _, c := range InsecureCipherSuites() {
+			if c.ID == id {
+				return c
+			}
+		}
+		return nil
+	}
+
+	for _, c := range cipherSuites {
+		cc := cipherSuiteByID(c.id)
+		if cc == nil {
+			t.Errorf("%#04x: no CipherSuite entry", c.id)
+			continue
+		}
+
+		if defaultOff := c.flags&suiteDefaultOff != 0; defaultOff != cc.Insecure {
+			t.Errorf("%#04x: Insecure %v, expected %v", c.id, cc.Insecure, defaultOff)
+		}
+		if tls12Only := c.flags&suiteTLS12 != 0; tls12Only && len(cc.SupportedVersions) != 1 {
+			t.Errorf("%#04x: suite is TLS 1.2 only, but SupportedVersions is %v", c.id, cc.SupportedVersions)
+		} else if !tls12Only && len(cc.SupportedVersions) != 3 {
+			t.Errorf("%#04x: suite TLS 1.0-1.2, but SupportedVersions is %v", c.id, cc.SupportedVersions)
+		}
+
+		if got := CipherSuiteName(c.id); got != cc.Name {
+			t.Errorf("%#04x: unexpected CipherSuiteName: got %q, expected %q", c.id, got, cc.Name)
+		}
+	}
+	for _, c := range cipherSuitesTLS13 {
+		cc := cipherSuiteByID(c.id)
+		if cc == nil {
+			t.Errorf("%#04x: no CipherSuite entry", c.id)
+			continue
+		}
+
+		if cc.Insecure {
+			t.Errorf("%#04x: Insecure %v, expected false", c.id, cc.Insecure)
+		}
+		if len(cc.SupportedVersions) != 1 || cc.SupportedVersions[0] != VersionTLS13 {
+			t.Errorf("%#04x: suite is TLS 1.3 only, but SupportedVersions is %v", c.id, cc.SupportedVersions)
+		}
+
+		if got := CipherSuiteName(c.id); got != cc.Name {
+			t.Errorf("%#04x: unexpected CipherSuiteName: got %q, expected %q", c.id, got, cc.Name)
+		}
+	}
+
+	if got := CipherSuiteName(0xabc); got != "0x0ABC" {
+		t.Errorf("unexpected fallback CipherSuiteName: got %q, expected 0x0ABC", got)
+	}
+}
+
 type brokenSigner struct{ crypto.Signer }
 
 func (s brokenSigner) Sign(rand io.Reader, digest []byte, opts crypto.SignerOpts) (signature []byte, err error) {