112 lines
3.5 KiB
Go
112 lines
3.5 KiB
Go
package tlsutil
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import (
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"crypto/ecdsa"
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"crypto/elliptic"
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"crypto/rand"
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"crypto/tls"
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"crypto/x509"
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"crypto/x509/pkix"
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"encoding/pem"
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"math/big"
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"net"
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"time"
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"codeberg.org/VARASYS/ZDDC/zddc/internal/config"
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)
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// TLSConfig returns a *tls.Config and a flag indicating whether to use TLS.
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// If cfg.TLSMode is "none", returns (nil, false, nil) for plain HTTP.
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// If cfg.TLSMode is "selfsigned" or "provided", returns a TLS config and true.
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func TLSConfig(cfg config.Config) (*tls.Config, bool, error) {
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if cfg.TLSMode == "none" {
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return nil, false, nil
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}
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var cert tls.Certificate
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var err error
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if cfg.TLSCert != "" && cfg.TLSKey != "" {
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cert, err = tls.LoadX509KeyPair(cfg.TLSCert, cfg.TLSKey)
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} else {
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cert, err = selfSigned()
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}
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if err != nil {
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return nil, false, err
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}
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return &tls.Config{
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Certificates: []tls.Certificate{cert},
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MinVersion: tls.VersionTLS12,
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// NIST SP 800-52 Rev. 2 conformant cipher allowlist for TLS 1.2.
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// (TLS 1.3 ciphers are not operator-selectable in Go's stdlib —
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// the runtime picks from a fixed set of AEAD suites; that's fine
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// because all of them meet the federal bar.) Order matters when
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// preferServerCipherSuites was respected by clients; modern Go
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// uses the runtime's own preference, but the explicit list still
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// drops every weak suite a client might offer.
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// AES-128-GCM is listed before AES-256-GCM because hardware
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// AES-NI makes the 128-bit suite measurably faster with no
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// security-margin compromise (NIST allows both).
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CipherSuites: []uint16{
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tls.TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256,
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tls.TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384,
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tls.TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256,
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tls.TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384,
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tls.TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305,
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tls.TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305,
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},
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// NIST SP 800-52 Rev. 2 § 3.3.2: X25519, P-256, P-384.
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// X25519 first — fastest modern curve, no known weaknesses;
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// the NIST P-curves follow for clients that don't support it.
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CurvePreferences: []tls.CurveID{
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tls.X25519,
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tls.CurveP256,
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tls.CurveP384,
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},
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}, true, nil
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}
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// selfSigned generates an in-memory ECDSA P-256 self-signed certificate
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// valid for 10 years. The certificate is never written to disk.
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func selfSigned() (tls.Certificate, error) {
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priv, err := ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
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if err != nil {
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return tls.Certificate{}, err
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}
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serial, err := rand.Int(rand.Reader, new(big.Int).Lsh(big.NewInt(1), 128))
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if err != nil {
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return tls.Certificate{}, err
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}
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template := &x509.Certificate{
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SerialNumber: serial,
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Subject: pkix.Name{
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CommonName: "zddc-server",
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Organization: []string{"ZDDC"},
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},
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NotBefore: time.Now().Add(-time.Minute),
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NotAfter: time.Now().Add(10 * 365 * 24 * time.Hour),
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KeyUsage: x509.KeyUsageDigitalSignature | x509.KeyUsageKeyEncipherment,
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ExtKeyUsage: []x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth},
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BasicConstraintsValid: true,
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IPAddresses: []net.IP{net.ParseIP("127.0.0.1"), net.IPv6loopback},
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DNSNames: []string{"localhost"},
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}
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certDER, err := x509.CreateCertificate(rand.Reader, template, template, &priv.PublicKey, priv)
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if err != nil {
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return tls.Certificate{}, err
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}
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privDER, err := x509.MarshalECPrivateKey(priv)
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if err != nil {
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return tls.Certificate{}, err
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}
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certPEM := pem.EncodeToMemory(&pem.Block{Type: "CERTIFICATE", Bytes: certDER})
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keyPEM := pem.EncodeToMemory(&pem.Block{Type: "EC PRIVATE KEY", Bytes: privDER})
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return tls.X509KeyPair(certPEM, keyPEM)
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}
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