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|
package pq
import (
"crypto/tls"
"crypto/x509"
"io/ioutil"
"net"
"os"
"os/user"
"path/filepath"
)
// 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)
}
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 {
// 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()
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
}
|
