From 6f1dcf99bebccf96cf065916b800b10f464bb612 Mon Sep 17 00:00:00 2001 From: Adam Langley Date: Sat, 8 Oct 2011 10:06:53 -0400 Subject: [PATCH] crypto/tls: add server side SNI support. With this in place, a TLS server is capable of selecting the correct certificate based on the client's ServerNameIndication extension. The need to call Config.BuildNameToCertificate is unfortunate, but adding a sync.Once to the Config structure made it uncopyable and I felt that was too high a price to pay. Parsing the leaf certificates in each handshake was too inefficient to consider. R=bradfitz, rsc CC=golang-dev https://golang.org/cl/5151048 --- common.go | 66 +++++++++++++++++++++++++++++++++++++++++++++ conn_test.go | 54 +++++++++++++++++++++++++++++++++++++ handshake_server.go | 7 ++++- 3 files changed, 126 insertions(+), 1 deletion(-) diff --git a/common.go b/common.go index 8fb1a88..8b4dafb 100644 --- a/common.go +++ b/common.go @@ -10,6 +10,7 @@ import ( "crypto/x509" "io" "io/ioutil" + "strings" "sync" "time" ) @@ -101,6 +102,10 @@ type ConnectionState struct { NegotiatedProtocol string NegotiatedProtocolIsMutual bool + // ServerName contains the server name indicated by the client, if any. + // (Only valid for server connections.) + ServerName string + // the certificate chain that was presented by the other side PeerCertificates []*x509.Certificate // the verified certificate chains built from PeerCertificates. @@ -124,6 +129,14 @@ type Config struct { // Server configurations must include at least one certificate. Certificates []Certificate + // NameToCertificate maps from a certificate name to an element of + // Certificates. Note that a certificate name can be of the form + // '*.example.com' and so doesn't have to be a domain name as such. + // See Config.BuildNameToCertificate + // The nil value causes the first element of Certificates to be used + // for all connections. + NameToCertificate map[string]*Certificate + // RootCAs defines the set of root certificate authorities // that clients use when verifying server certificates. // If RootCAs is nil, TLS uses the host's root CA set. @@ -179,6 +192,59 @@ func (c *Config) cipherSuites() []uint16 { return s } +// getCertificateForName returns the best certificate for the given name, +// defaulting to the first element of c.Certificates if there are no good +// options. +func (c *Config) getCertificateForName(name string) *Certificate { + if len(c.Certificates) == 1 || c.NameToCertificate == nil { + // There's only one choice, so no point doing any work. + return &c.Certificates[0] + } + + name = strings.ToLower(name) + for len(name) > 0 && name[len(name)-1] == '.' { + name = name[:len(name)-1] + } + + if cert, ok := c.NameToCertificate[name]; ok { + return cert + } + + // try replacing labels in the name with wildcards until we get a + // match. + labels := strings.Split(name, ".") + for i := range labels { + labels[i] = "*" + candidate := strings.Join(labels, ".") + if cert, ok := c.NameToCertificate[candidate]; ok { + return cert + } + } + + // If nothing matches, return the first certificate. + return &c.Certificates[0] +} + +// BuildNameToCertificate parses c.Certificates and builds c.NameToCertificate +// from the CommonName and SubjectAlternateName fields of each of the leaf +// certificates. +func (c *Config) BuildNameToCertificate() { + c.NameToCertificate = make(map[string]*Certificate) + for i := range c.Certificates { + cert := &c.Certificates[i] + x509Cert, err := x509.ParseCertificate(cert.Certificate[0]) + if err != nil { + continue + } + if len(x509Cert.Subject.CommonName) > 0 { + c.NameToCertificate[x509Cert.Subject.CommonName] = cert + } + for _, san := range x509Cert.DNSNames { + c.NameToCertificate[san] = cert + } + } +} + // A Certificate is a chain of one or more certificates, leaf first. type Certificate struct { Certificate [][]byte diff --git a/conn_test.go b/conn_test.go index f44a50b..5c55514 100644 --- a/conn_test.go +++ b/conn_test.go @@ -50,3 +50,57 @@ func TestRemovePadding(t *testing.T) { } } } + +var certExampleCom = `308201403081eda003020102020101300b06092a864886f70d010105301e311c301a060355040a131354657374696e67204365727469666963617465301e170d3131313030313138353835325a170d3132303933303138353835325a301e311c301a060355040a131354657374696e67204365727469666963617465305a300b06092a864886f70d010101034b003048024100bced6e32368599eeddf18796bfd03958a154f87e5b084f96e85136a56b886733592f493f0fc68b0d6b3551781cb95e13c5de458b28d6fb60d20a9129313261410203010001a31a301830160603551d11040f300d820b6578616d706c652e636f6d300b06092a864886f70d0101050341001a0b419d2c74474c6450654e5f10b32bf426ffdf55cad1c52602e7a9151513a3424c70f5960dcd682db0c33769cc1daa3fcdd3db10809d2392ed4a1bf50ced18` + +var certWildcardExampleCom = `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` + +var certFooExampleCom = `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` + +var certDoubleWildcardExampleCom = `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` + +func TestCertificateSelection(t *testing.T) { + config := Config{ + Certificates: []Certificate{ + { + Certificate: [][]byte{fromHex(certExampleCom)}, + }, + { + Certificate: [][]byte{fromHex(certWildcardExampleCom)}, + }, + { + Certificate: [][]byte{fromHex(certFooExampleCom)}, + }, + { + Certificate: [][]byte{fromHex(certDoubleWildcardExampleCom)}, + }, + }, + } + + config.BuildNameToCertificate() + + pointerToIndex := func(c *Certificate) int { + for i := range config.Certificates { + if c == &config.Certificates[i] { + return i + } + } + return -1 + } + + if n := pointerToIndex(config.getCertificateForName("example.com")); n != 0 { + t.Errorf("example.com returned certificate %d, not 0", n) + } + if n := pointerToIndex(config.getCertificateForName("bar.example.com")); n != 1 { + t.Errorf("bar.example.com returned certificate %d, not 1", n) + } + if n := pointerToIndex(config.getCertificateForName("foo.example.com")); n != 2 { + t.Errorf("foo.example.com returned certificate %d, not 2", n) + } + if n := pointerToIndex(config.getCertificateForName("foo.bar.example.com")); n != 3 { + t.Errorf("foo.bar.example.com returned certificate %d, not 3", n) + } + if n := pointerToIndex(config.getCertificateForName("foo.bar.baz.example.com")); n != 0 { + t.Errorf("foo.bar.baz.example.com returned certificate %d, not 0", n) + } +} diff --git a/handshake_server.go b/handshake_server.go index f083a87..ed9a2e6 100644 --- a/handshake_server.go +++ b/handshake_server.go @@ -115,7 +115,12 @@ FindCipherSuite: } certMsg := new(certificateMsg) - certMsg.certificates = config.Certificates[0].Certificate + if len(clientHello.serverName) > 0 { + c.serverName = clientHello.serverName + certMsg.certificates = config.getCertificateForName(clientHello.serverName).Certificate + } else { + certMsg.certificates = config.Certificates[0].Certificate + } finishedHash.Write(certMsg.marshal()) c.writeRecord(recordTypeHandshake, certMsg.marshal())