1 files changed, 61 insertions, 0 deletions
diff --git a/ssh/server/publickeycallback.go b/ssh/server/publickeycallback.go
new file mode 100644
index 0000000..867f639
--- /dev/null
+++ b/ssh/server/publickeycallback.go
@@ -0,0 +1,61 @@
+package server
+
+import (
+	"dtail/config"
+	"dtail/logger"
+	"dtail/server/user"
+	"fmt"
+	"io/ioutil"
+	"os"
+	osUser "os/user"
+
+	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, pubKey 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 {
+		pubKey, _, _, rest, err := gossh.ParseAuthorizedKey(authorizedKeysBytes)
+		if err != nil {
+			return nil, fmt.Errorf("Unable to parse authorized keys bytes|%s|%s", user, err.Error())
+		}
+		authorizedKeysMap[string(pubKey.Marshal())] = true
+		authorizedKeysBytes = rest
+	}
+
+	if authorizedKeysMap[string(pubKey.Marshal())] {
+		logger.Debug("Public key fingerprint", gossh.FingerprintSHA256(pubKey), user)
+		return &gossh.Permissions{
+			Extensions: map[string]string{
+				"pubkey-fp": gossh.FingerprintSHA256(pubKey),
+			},
+		}, nil
+	}
+
+	return nil, fmt.Errorf("Unknown public key|%s", user)
+}