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package dtls
import (
"crypto/tls"
"crypto/x509"
"strings"
)
func (c *handshakeConfig) getCertificate(serverName string) (*tls.Certificate, error) {
c.mu.Lock()
defer c.mu.Unlock()
if c.nameToCertificate == nil {
nameToCertificate := make(map[string]*tls.Certificate)
for i := range c.localCertificates {
cert := &c.localCertificates[i]
x509Cert := cert.Leaf
if x509Cert == nil {
var parseErr error
x509Cert, parseErr = x509.ParseCertificate(cert.Certificate[0])
if parseErr != nil {
continue
}
}
if len(x509Cert.Subject.CommonName) > 0 {
nameToCertificate[strings.ToLower(x509Cert.Subject.CommonName)] = cert
}
for _, san := range x509Cert.DNSNames {
nameToCertificate[strings.ToLower(san)] = cert
}
}
c.nameToCertificate = nameToCertificate
}
if len(c.localCertificates) == 0 {
return nil, errNoCertificates
}
if len(c.localCertificates) == 1 {
// There's only one choice, so no point doing any work.
return &c.localCertificates[0], nil
}
if len(serverName) == 0 {
return &c.localCertificates[0], nil
}
name := strings.TrimRight(strings.ToLower(serverName), ".")
if cert, ok := c.nameToCertificate[name]; ok {
return cert, nil
}
// 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, nil
}
}
// If nothing matches, return the first certificate.
return &c.localCertificates[0], nil
}
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