kvm/internal/utils/ssh.go

72 lines
1.5 KiB
Go

package utils
import (
"fmt"
"slices"
"strings"
"golang.org/x/crypto/ssh"
)
// ValidSSHKeyTypes is a list of valid SSH key types
//
// Please make sure that all the types in this list are supported by dropbear
// https://github.com/mkj/dropbear/blob/003c5fcaabc114430d5d14142e95ffdbbd2d19b6/src/signkey.c#L37
//
// ssh-dss is not allowed here as it's insecure
var ValidSSHKeyTypes = []string{
ssh.KeyAlgoRSA,
ssh.KeyAlgoED25519,
ssh.KeyAlgoECDSA256,
ssh.KeyAlgoECDSA384,
ssh.KeyAlgoECDSA521,
}
// ValidateSSHKey validates authorized_keys file content
func ValidateSSHKey(sshKey string) error {
// validate SSH key
var (
hasValidPublicKey = false
lastError = fmt.Errorf("no valid SSH key found")
)
for _, key := range strings.Split(sshKey, "\n") {
key = strings.TrimSpace(key)
// skip empty lines and comments
if key == "" || strings.HasPrefix(key, "#") {
continue
}
parsedPublicKey, _, _, _, err := ssh.ParseAuthorizedKey([]byte(key))
if err != nil {
lastError = err
continue
}
if parsedPublicKey == nil {
continue
}
parsedType := parsedPublicKey.Type()
textType := strings.Fields(key)[0]
if parsedType != textType {
lastError = fmt.Errorf("parsed SSH key type %s does not match type in text %s", parsedType, textType)
continue
}
if !slices.Contains(ValidSSHKeyTypes, parsedType) {
lastError = fmt.Errorf("invalid SSH key type: %s", parsedType)
continue
}
hasValidPublicKey = true
}
if !hasValidPublicKey {
return lastError
}
return nil
}