source: code/trunk/vendor/github.com/lib/pq/ssl.go@ 822

package pq

import (
        "crypto/tls"
        "crypto/x509"
        "io/ioutil"
        "net"
        "os"
        "os/user"
        "path/filepath"
        "strings"
)

// ssl generates a function to upgrade a net.Conn based on the "sslmode" and
// related settings. The function is nil when no upgrade should take place.
func ssl(o values) (func(net.Conn) (net.Conn, error), error) {
        verifyCaOnly := false
        tlsConf := tls.Config{}
        switch mode := o["sslmode"]; mode {
        // "require" is the default.
        case "", "require":
                // We must skip TLS's own verification since it requires full
                // verification since Go 1.3.
                tlsConf.InsecureSkipVerify = true

                // From http://www.postgresql.org/docs/current/static/libpq-ssl.html:
                //
                // Note: For backwards compatibility with earlier versions of
                // PostgreSQL, if a root CA file exists, the behavior of
                // sslmode=require will be the same as that of verify-ca, meaning the
                // server certificate is validated against the CA. Relying on this
                // behavior is discouraged, and applications that need certificate
                // validation should always use verify-ca or verify-full.
                if sslrootcert, ok := o["sslrootcert"]; ok {
                        if _, err := os.Stat(sslrootcert); err == nil {
                                verifyCaOnly = true
                        } else {
                                delete(o, "sslrootcert")
                        }
                }
        case "verify-ca":
                // We must skip TLS's own verification since it requires full
                // verification since Go 1.3.
                tlsConf.InsecureSkipVerify = true
                verifyCaOnly = true
        case "verify-full":
                tlsConf.ServerName = o["host"]
        case "disable":
                return nil, nil
        default:
                return nil, fmterrorf(`unsupported sslmode %q; only "require" (default), "verify-full", "verify-ca", and "disable" supported`, mode)
        }

        // Set Server Name Indication (SNI), if enabled by connection parameters.
        // By default SNI is on, any value which is not starting with "1" disables
        // SNI -- that is the same check vanilla libpq uses.
        if sslsni := o["sslsni"]; sslsni == "" || strings.HasPrefix(sslsni, "1") {
                // RFC 6066 asks to not set SNI if the host is a literal IP address (IPv4
                // or IPv6). This check is coded already crypto.tls.hostnameInSNI, so
                // just always set ServerName here and let crypto/tls do the filtering.
                tlsConf.ServerName = o["host"]
        }

        err := sslClientCertificates(&tlsConf, o)
        if err != nil {
                return nil, err
        }
        err = sslCertificateAuthority(&tlsConf, o)
        if err != nil {
                return nil, err
        }

        // Accept renegotiation requests initiated by the backend.
        //
        // Renegotiation was deprecated then removed from PostgreSQL 9.5, but
        // the default configuration of older versions has it enabled. Redshift
        // also initiates renegotiations and cannot be reconfigured.
        tlsConf.Renegotiation = tls.RenegotiateFreelyAsClient

        return func(conn net.Conn) (net.Conn, error) {
                client := tls.Client(conn, &tlsConf)
                if verifyCaOnly {
                        err := sslVerifyCertificateAuthority(client, &tlsConf)
                        if err != nil {
                                return nil, err
                        }
                }
                return client, nil
        }, nil
}

// sslClientCertificates adds the certificate specified in the "sslcert" and
// "sslkey" settings, or if they aren't set, from the .postgresql directory
// in the user's home directory. The configured files must exist and have
// the correct permissions.
func sslClientCertificates(tlsConf *tls.Config, o values) error {
        sslinline := o["sslinline"]
        if sslinline == "true" {
                cert, err := tls.X509KeyPair([]byte(o["sslcert"]), []byte(o["sslkey"]))
                if err != nil {
                        return err
                }
                tlsConf.Certificates = []tls.Certificate{cert}
                return nil
        }

        // user.Current() might fail when cross-compiling. We have to ignore the
        // error and continue without home directory defaults, since we wouldn't
        // know from where to load them.
        user, _ := user.Current()

        // In libpq, the client certificate is only loaded if the setting is not blank.
        //
        // https://github.com/postgres/postgres/blob/REL9_6_2/src/interfaces/libpq/fe-secure-openssl.c#L1036-L1037
        sslcert := o["sslcert"]
        if len(sslcert) == 0 && user != nil {
                sslcert = filepath.Join(user.HomeDir, ".postgresql", "postgresql.crt")
        }
        // https://github.com/postgres/postgres/blob/REL9_6_2/src/interfaces/libpq/fe-secure-openssl.c#L1045
        if len(sslcert) == 0 {
                return nil
        }
        // https://github.com/postgres/postgres/blob/REL9_6_2/src/interfaces/libpq/fe-secure-openssl.c#L1050:L1054
        if _, err := os.Stat(sslcert); os.IsNotExist(err) {
                return nil
        } else if err != nil {
                return err
        }

        // In libpq, the ssl key is only loaded if the setting is not blank.
        //
        // https://github.com/postgres/postgres/blob/REL9_6_2/src/interfaces/libpq/fe-secure-openssl.c#L1123-L1222
        sslkey := o["sslkey"]
        if len(sslkey) == 0 && user != nil {
                sslkey = filepath.Join(user.HomeDir, ".postgresql", "postgresql.key")
        }

        if len(sslkey) > 0 {
                if err := sslKeyPermissions(sslkey); err != nil {
                        return err
                }
        }

        cert, err := tls.LoadX509KeyPair(sslcert, sslkey)
        if err != nil {
                return err
        }

        tlsConf.Certificates = []tls.Certificate{cert}
        return nil
}

// sslCertificateAuthority adds the RootCA specified in the "sslrootcert" setting.
func sslCertificateAuthority(tlsConf *tls.Config, o values) error {
        // In libpq, the root certificate is only loaded if the setting is not blank.
        //
        // https://github.com/postgres/postgres/blob/REL9_6_2/src/interfaces/libpq/fe-secure-openssl.c#L950-L951
        if sslrootcert := o["sslrootcert"]; len(sslrootcert) > 0 {
                tlsConf.RootCAs = x509.NewCertPool()

                sslinline := o["sslinline"]

                var cert []byte
                if sslinline == "true" {
                        cert = []byte(sslrootcert)
                } else {
                        var err error
                        cert, err = ioutil.ReadFile(sslrootcert)
                        if err != nil {
                                return err
                        }
                }

                if !tlsConf.RootCAs.AppendCertsFromPEM(cert) {
                        return fmterrorf("couldn't parse pem in sslrootcert")
                }
        }

        return nil
}

// sslVerifyCertificateAuthority carries out a TLS handshake to the server and
// verifies the presented certificate against the CA, i.e. the one specified in
// sslrootcert or the system CA if sslrootcert was not specified.
func sslVerifyCertificateAuthority(client *tls.Conn, tlsConf *tls.Config) error {
        err := client.Handshake()
        if err != nil {
                return err
        }
        certs := client.ConnectionState().PeerCertificates
        opts := x509.VerifyOptions{
                DNSName:       client.ConnectionState().ServerName,
                Intermediates: x509.NewCertPool(),
                Roots:         tlsConf.RootCAs,
        }
        for i, cert := range certs {
                if i == 0 {
                        continue
                }
                opts.Intermediates.AddCert(cert)
        }
        _, err = certs[0].Verify(opts)
        return err
}