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package crypto
import (
"bytes"
"crypto/rand"
"crypto/rsa"
"crypto/x509"
"encoding/pem"
"fmt"
"strings"
)
// RSAEncrypt - use the given public key to encrypt the given plaintext. The key
// should be a PEM-encoded RSA public key in PKIX, ASN.1 DER form, typically
// beginning with "PUBLIC KEY". PKCS#1 format is also supported as a fallback.
// The output will not be encoded, so consider base64-encoding it for display.
func RSAEncrypt(key string, in []byte) ([]byte, error) {
block, _ := pem.Decode([]byte(key))
if block == nil {
return nil, fmt.Errorf("failed to read key %q: no key found", key)
}
pub, err := x509.ParsePKIXPublicKey(block.Bytes)
if err != nil {
if strings.Contains(err.Error(), "use ParsePKCS1PublicKey instead") {
pub, err = x509.ParsePKCS1PublicKey(block.Bytes)
}
if err != nil {
return nil, fmt.Errorf("failed to parse public key: %w", err)
}
}
pubKey, ok := pub.(*rsa.PublicKey)
if !ok {
return nil, fmt.Errorf("public key in wrong format, was %T", pub)
}
out, err := rsa.EncryptPKCS1v15(rand.Reader, pubKey, in)
return out, err
}
// RSADecrypt - decrypt the ciphertext with the given private key. The key
// must be a PEM-encoded RSA private key in PKCS#1, ASN.1 DER form, typically
// beginning with "RSA PRIVATE KEY". The input text must be plain ciphertext,
// not base64-encoded.
func RSADecrypt(key string, in []byte) ([]byte, error) {
block, _ := pem.Decode([]byte(key))
if block == nil {
return nil, fmt.Errorf("failed to read key %q: no key found", key)
}
priv, err := x509.ParsePKCS1PrivateKey(block.Bytes)
if err != nil {
return nil, fmt.Errorf("invalid private key: %w", err)
}
out, err := priv.Decrypt(nil, in, nil)
if err != nil {
return nil, fmt.Errorf("failed to decrypt: %w", err)
}
return out, nil
}
// RSAGenerateKey -
func RSAGenerateKey(bits int) ([]byte, error) {
// Protect against CWE-326: Inadequate Encryption Strength
// https://cwe.mitre.org/data/definitions/326.html
if bits < 2048 {
return nil, fmt.Errorf("RSA key size must be at least 2048 bits")
}
priv, err := rsa.GenerateKey(rand.Reader, bits)
if err != nil {
return nil, fmt.Errorf("failed to generate RSA private key: %w", err)
}
block := &pem.Block{
Type: "RSA PRIVATE KEY",
Bytes: x509.MarshalPKCS1PrivateKey(priv),
}
buf := &bytes.Buffer{}
err = pem.Encode(buf, block)
if err != nil {
return nil, fmt.Errorf("failed to encode generated RSA private key: pem encoding failed: %w", err)
}
return buf.Bytes(), nil
}
// RSADerivePublicKey -
func RSADerivePublicKey(privateKey []byte) ([]byte, error) {
block, _ := pem.Decode(privateKey)
if block == nil {
return nil, fmt.Errorf("failed to read key: no key found")
}
priv, err := x509.ParsePKCS1PrivateKey(block.Bytes)
if err != nil {
return nil, fmt.Errorf("invalid private key: %w", err)
}
b, err := x509.MarshalPKIXPublicKey(&priv.PublicKey)
if err != nil {
return nil, fmt.Errorf("failed to marshal PKIX public key: %w", err)
}
block = &pem.Block{
Type: "PUBLIC KEY",
Bytes: b,
}
return pem.EncodeToMemory(block), nil
}
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