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package server
import (
"fmt"
"io/ioutil"
"os"
osUser "os/user"
"github.com/mimecast/dtail/internal/config"
"github.com/mimecast/dtail/internal/io/logger"
user "github.com/mimecast/dtail/internal/user/server"
gossh "golang.org/x/crypto/ssh"
)
// PublicKeyCallback is for the server to check whether a public SSH key is authorized ot not.
func PublicKeyCallback(c gossh.ConnMetadata, offeredPubKey gossh.PublicKey) (*gossh.Permissions, error) {
user := user.New(c.User(), c.RemoteAddr().String())
logger.Info(user, "Incoming authorization")
cwd, err := os.Getwd()
if err != nil {
return nil, fmt.Errorf("Unable to get current working directory|%s|", err.Error())
}
authorizedKeysFile := fmt.Sprintf("%s/%s/%s.authorized_keys", cwd, config.Common.CacheDir, user.Name)
if _, err := os.Stat(authorizedKeysFile); os.IsNotExist(err) {
user, err := osUser.Lookup(user.Name)
if err != nil {
return nil, fmt.Errorf("Unable to authorize|%s|%s|", user, err.Error())
}
// Fallback to ~
authorizedKeysFile = user.HomeDir + "/.ssh/authorized_keys"
}
logger.Info(user, "Reading", authorizedKeysFile)
authorizedKeysBytes, err := ioutil.ReadFile(authorizedKeysFile)
if err != nil {
return nil, fmt.Errorf("Unable to read authorized keys file|%s|%s|%s", authorizedKeysFile, user, err.Error())
}
authorizedKeysMap := map[string]bool{}
for len(authorizedKeysBytes) > 0 {
authorizedPubKey, _, _, restBytes, err := gossh.ParseAuthorizedKey(authorizedKeysBytes)
if err != nil {
return nil, fmt.Errorf("Unable to parse authorized keys bytes|%s|%s", user, err.Error())
}
authorizedKeysMap[string(authorizedPubKey.Marshal())] = true
authorizedKeysBytes = restBytes
logger.Debug(user, "Authorized public key fingerprint", gossh.FingerprintSHA256(authorizedPubKey))
}
logger.Debug(user, "Offered public key fingerprint", gossh.FingerprintSHA256(offeredPubKey))
if authorizedKeysMap[string(offeredPubKey.Marshal())] {
return &gossh.Permissions{
Extensions: map[string]string{
"pubkey-fp": gossh.FingerprintSHA256(offeredPubKey),
},
}, nil
}
return nil, fmt.Errorf("%s|Public key of user not authorized", user)
}
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