/
utils.go
242 lines (199 loc) · 6.02 KB
/
utils.go
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package ssh
import (
"crypto/rand"
"crypto/rsa"
"crypto/sha256"
"crypto/x509"
"encoding/base64"
"encoding/pem"
"fmt"
mathrand "math/rand"
"reflect"
"strings"
"sync"
"time"
"github.com/notion/bastion/config"
"golang.org/x/crypto/ssh"
)
var sshPermissions = map[string]string{
"permit-X11-forwarding": "",
"permit-agent-forwarding": "",
"permit-port-forwarding": "",
"permit-pty": "",
"permit-user-rc": "",
}
// CASigner is the main CASigner object
type CASigner struct {
CA ssh.Signer
Validity time.Duration
Principals []string
Permissions []string
}
// Sign creates a certificate that has been signed by the CASigner
func (s *CASigner) Sign(env *config.Env, user string, pubKey ssh.PublicKey) (*ssh.Certificate, []byte, error) {
var privateKey []byte
if pubKey == nil {
privateKey = createPrivateKey(env, false, "")
pk, err := ssh.ParsePrivateKey(privateKey)
if err != nil {
env.Red.Println("Unable to parse created private key:", err)
return nil, privateKey, err
}
pubKey = pk.PublicKey()
}
expires := time.Now().UTC().Add(s.Validity)
cert := &ssh.Certificate{
CertType: ssh.UserCert,
Key: pubKey,
KeyId: fmt.Sprintf("%s_%d", user, time.Now().UTC().Unix()),
ValidAfter: uint64(time.Now().UTC().Unix()),
ValidBefore: uint64(expires.Unix()),
ValidPrincipals: []string{user},
}
cert.ValidPrincipals = append(cert.ValidPrincipals, s.Principals...)
cert.CriticalOptions = make(map[string]string)
cert.Extensions = make(map[string]string)
for _, perm := range s.Permissions {
if strings.Contains(perm, "=") {
opt := strings.Split(perm, "=")
cert.CriticalOptions[strings.TrimSpace(opt[0])] = strings.TrimSpace(opt[1])
} else {
cert.Extensions[perm] = ""
}
}
if len(cert.Extensions) == 0 {
cert.Extensions = sshPermissions
}
if err := cert.SignCert(rand.Reader, s.CA); err != nil {
return nil, privateKey, err
}
return cert, privateKey, nil
}
// NewCASigner creates a CASigner from different certificate settings
func NewCASigner(sshsigner ssh.Signer, expireIn time.Duration, principals []string, permissions []string) *CASigner {
signer := &CASigner{
CA: sshsigner,
Validity: expireIn,
Principals: principals,
Permissions: permissions,
}
return signer
}
func createPrivateKey(env *config.Env, addToEnv bool, passphrase string) []byte {
pk, err := rsa.GenerateKey(rand.Reader, 2048)
if err != nil {
env.Red.Fatal(err)
}
env.Blue.Println("Generated RSA Keypair")
pemBlock := &pem.Block{
Type: "RSA PRIVATE KEY",
Bytes: x509.MarshalPKCS1PrivateKey(pk),
}
var pemData []byte
if passphrase != "" {
encBlock, err := x509.EncryptPEMBlock(rand.Reader, pemBlock.Type, pemBlock.Bytes, []byte(passphrase), x509.PEMCipherAES256)
if err != nil {
env.Red.Fatal("Unable to encrypt Private Key:", err)
}
pemData = pem.EncodeToMemory(encBlock)
} else {
pemData = pem.EncodeToMemory(pemBlock)
}
if addToEnv {
env.Config.PrivateKey = pemData
}
return pemData
}
// ParsePrivateKey pareses the PrivateKey into a ssh.Signer and let's it be used by CASigner
func ParsePrivateKey(pk []byte, passphrase string, env *config.Env) ssh.Signer {
var signer ssh.Signer
var err error
if passphrase != "" {
signer, err = ssh.ParsePrivateKeyWithPassphrase(pk, []byte(passphrase))
if err != nil {
env.Red.Fatal("Unable to parse private key:", err)
}
} else {
signer, err = ssh.ParsePrivateKey(pk)
if err != nil {
env.Red.Fatal("Unable to parse private key:", err)
}
}
return signer
}
func initializeCerts(env *config.Env, force bool) {
for _, v := range []string{"PrivateKey", "ServerPrivateKey", "UserPrivateKey"} {
var pkBytes []byte
r := reflect.ValueOf(env.Config)
f := reflect.Indirect(r).FieldByName(v)
pkBytes = f.Bytes()
if len(pkBytes) == 0 || force {
pkBytes = createPrivateKey(env, false, env.PKPassphrase)
}
signer := ParsePrivateKey(pkBytes, env.PKPassphrase, env)
shaHash := sha256.Sum256(signer.PublicKey().Marshal())
env.Yellow.Println(fmt.Sprintf("Private key information for %s: \nPublic Key: %sSHA256: %s", v, string(ssh.MarshalAuthorizedKey(signer.PublicKey())), base64.StdEncoding.EncodeToString(shaHash[:])))
if len(f.Bytes()) > 0 && !force {
continue
}
switch v {
case "PrivateKey":
env.Config.PrivateKey = pkBytes
break
case "ServerPrivateKey":
env.Config.ServerPrivateKey = pkBytes
break
case "UserPrivateKey":
env.Config.UserPrivateKey = pkBytes
break
}
}
return
}
// RandStringBytesMaskImprSrc creates a random string of n length
// https://stackoverflow.com/questions/22892120/how-to-generate-a-random-string-of-a-fixed-length-in-go/31832326
func RandStringBytesMaskImprSrc(n int) string {
const letterBytes = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"
const (
letterIdxBits = 6 // 6 bits to represent a letter index
letterIdxMask = 1<<letterIdxBits - 1 // All 1-bits, as many as letterIdxBits
letterIdxMax = 63 / letterIdxBits // # of letter indices fitting in 63 bits
)
var src = mathrand.NewSource(time.Now().UnixNano())
b := make([]byte, n)
// A src.Int63() generates 63 random bits, enough for letterIdxMax characters!
for i, cache, remain := n-1, src.Int63(), letterIdxMax; i >= 0; {
if remain == 0 {
cache, remain = src.Int63(), letterIdxMax
}
if idx := int(cache & letterIdxMask); idx < len(letterBytes) {
b[i] = letterBytes[idx]
i--
}
cache >>= letterIdxBits
remain--
}
return string(b)
}
// GetRegexMatches will return a slice of all of the matching regexes for a user
func GetRegexMatches(user *config.User) []string {
matchers := []string{user.AuthorizedHosts}
for _, v := range user.AuthRules {
matchers = append(matchers, v.AuthorizedHosts)
}
return matchers
}
// WaitTimeout waits for a waitgroup
func WaitTimeout(group *sync.WaitGroup, timeout time.Duration) bool {
stop := make(chan struct{})
go func() {
defer close(stop)
group.Wait()
}()
select {
case <-stop:
return false
case <-time.After(timeout):
return true
}
}