[dev.boringcrypto] all: merge master into dev.boringcrypto

[gostls13.git] / src / crypto / tls / common.go

diff --git a/src/crypto/tls/common.go b/src/crypto/tls/common.go
index 0da93677b52a6d2aec3386995e2eb7569e708810..d17cac30eb49cd48007410c875c6bc4d81978baa 100644 (file)
--- a/src/crypto/tls/common.go
+++ b/src/crypto/tls/common.go
@@ -18,6 +18,7 @@ import (
        "crypto/x509"
        "errors"
        "fmt"
+       "internal/godebug"
        "io"
        "net"
        "strings"
@@ -682,11 +683,20 @@ type Config struct {
        ClientSessionCache ClientSessionCache
 
        // MinVersion contains the minimum TLS version that is acceptable.
-       // If zero, TLS 1.0 is currently taken as the minimum.
+       //
+       // By default, TLS 1.2 is currently used as the minimum when acting as a
+       // client, and TLS 1.0 when acting as a server. TLS 1.0 is the minimum
+       // supported by this package, both as a client and as a server.
+       //
+       // The client-side default can temporarily be reverted to TLS 1.0 by
+       // including the value "x509sha1=1" in the GODEBUG environment variable.
+       // Note that this option will be removed in Go 1.19 (but it will still be
+       // possible to set this field to VersionTLS10 explicitly).
        MinVersion uint16
 
        // MaxVersion contains the maximum TLS version that is acceptable.
-       // If zero, the maximum version supported by this package is used,
+       //
+       // By default, the maximum version supported by this package is used,
        // which is currently TLS 1.3.
        MaxVersion uint16
 
@@ -967,12 +977,24 @@ var supportedVersions = []uint16{
        VersionTLS10,
 }
 
-func (c *Config) supportedVersions() []uint16 {
+// debugEnableTLS10 enables TLS 1.0. See issue 45428.
+var debugEnableTLS10 = godebug.Get("tls10default") == "1"
+
+// roleClient and roleServer are meant to call supportedVersions and parents
+// with more readability at the callsite.
+const roleClient = true
+const roleServer = false
+
+func (c *Config) supportedVersions(isClient bool) []uint16 {
        versions := make([]uint16, 0, len(supportedVersions))
        for _, v := range supportedVersions {
                if needFIPS() && (v < fipsMinVersion(c) || v > fipsMaxVersion(c)) {
                        continue
                }
+               if (c == nil || c.MinVersion == 0) && !debugEnableTLS10 &&
+                       isClient && v < VersionTLS12 {
+                       continue
+               }
                if c != nil && c.MinVersion != 0 && v < c.MinVersion {
                        continue
                }
@@ -984,8 +1006,8 @@ func (c *Config) supportedVersions() []uint16 {
        return versions
 }
 
-func (c *Config) maxSupportedVersion() uint16 {
-       supportedVersions := c.supportedVersions()
+func (c *Config) maxSupportedVersion(isClient bool) uint16 {
+       supportedVersions := c.supportedVersions(isClient)
        if len(supportedVersions) == 0 {
                return 0
        }
@@ -1029,8 +1051,8 @@ func (c *Config) supportsCurve(curve CurveID) bool {
 
 // mutualVersion returns the protocol version to use given the advertised
 // versions of the peer. Priority is given to the peer preference order.
-func (c *Config) mutualVersion(peerVersions []uint16) (uint16, bool) {
-       supportedVersions := c.supportedVersions()
+func (c *Config) mutualVersion(isClient bool, peerVersions []uint16) (uint16, bool) {
+       supportedVersions := c.supportedVersions(isClient)
        for _, peerVersion := range peerVersions {
                for _, v := range supportedVersions {
                        if v == peerVersion {
@@ -1109,7 +1131,7 @@ func (chi *ClientHelloInfo) SupportsCertificate(c *Certificate) error {
        if config == nil {
                config = &Config{}
        }
-       vers, ok := config.mutualVersion(chi.SupportedVersions)
+       vers, ok := config.mutualVersion(roleServer, chi.SupportedVersions)
        if !ok {
                return errors.New("no mutually supported protocol versions")
        }