Add functionality to check the group membership of a user to decide t…

…he upstream

If a username is not given in the yaml config file it parses the groupname and
checks if user is part of that group and routes them accordinly to the
associated host defined in the config file for the yaml plugin

plugin/yaml/yaml.go

@@ -10,6 +10,8 @@ import (
 	"path/filepath"
 	"regexp"
 	"time"
+	"slices"
+	"os/user"
 
 	"github.com/patrickmn/go-cache"
 	"github.com/tg123/sshpiper/libplugin"
@@ -18,7 +20,8 @@ import (
 )
 
 type pipeConfigFrom struct {
-	Username           string `yaml:"username"`
+	Username           string `yaml:"username,omitempty"`
+	Groupname	   string `yaml:"groupname,omitempty"`
 	UsernameRegexMatch bool   `yaml:"username_regex_match,omitempty"`
 	AuthorizedKeys     string `yaml:"authorized_keys,omitempty"`
 	AuthorizedKeysData string `yaml:"authorized_keys_data,omitempty"`
@@ -220,20 +223,30 @@ func (p *plugin) createUpstream(conn libplugin.ConnMetadata, to pipeConfigTo, or
 
 func (p *plugin) findAndCreateUpstream(conn libplugin.ConnMetadata, password string, publicKey []byte) (*libplugin.Upstream, error) {
 	user := conn.User()
+	userGroups, err := getUserGroups(user)
+
+	if err != nil {
+		return nil, err
+	}
 
 	config, err := p.loadConfig()
+
 	if err != nil {
 		return nil, err
 	}
 
 	for _, pipe := range config.Pipes {
 		for _, from := range pipe.From {
-			matched := from.Username == user
-
-			if from.UsernameRegexMatch {
-				matched, _ = regexp.MatchString(from.Username, user)
+			var matched bool
+			if from.Username != "" {
+				matched = from.Username == user
+				if from.UsernameRegexMatch {
+					matched, _ = regexp.MatchString(from.Username, user)
+				}
+			} else {
+				fromPipeGroup := from.Groupname
+				matched = slices.Contains(userGroups, fromPipeGroup)
 			}
-
 			if !matched {
 				continue
 			}
@@ -265,3 +278,27 @@ func (p *plugin) findAndCreateUpstream(conn libplugin.ConnMetadata, password str
 
 	return nil, fmt.Errorf("no matching pipe for username [%v] found", user)
 }
+
+func getUserGroups(userName string) ([]string, error) {
+    usr, err := user.Lookup(userName)
+    if err != nil {
+        return nil, err
+    }
+
+    groupIds, err := usr.GroupIds()
+    if err != nil {
+        return nil, err
+    }
+
+    var groups []string
+    for _, groupId := range groupIds {
+        grp, err := user.LookupGroupId(groupId)
+        if err != nil {
+            return nil, err
+        }
+        groups = append(groups, grp.Name)
+    }
+
+    return groups, nil
+}
+