use stdin to provide authentication token to authenticator rather than command line option

doc/authentication.md

@@ -19,12 +19,7 @@ operation, the credentials are queried via `getcreds`request.
 ## Authenticator
 
 An authenticator is an executable or script used for token-based
-authentication. During HTTP handshake, webfuse will scan for the
-configured HTTP header and invoke the authenticator.
-
-    authenticator TOKEN
-
-The provided `token` contains the contents of the HTTP header.
+authentication. Credentials are passed to the authenticator via `stdin`.
 
 ## Header restrictions
 

example/authenticator/pam/src/main.cpp

@@ -133,54 +133,47 @@ bool authenticate(std::string const & username, std::string const & password)
 int main(int argc, char* argv[])
 {
     int exit_code = EXIT_FAILURE;
-    bool print_usage = true;
 
-    if (argc == 2)
+    if (argc == 1)
     {
-        std::string const token = argv[1];
-        if (("-h" != token) && ("--help" != token))
-        {
-            print_usage = false;
+        std::string token;
+        std::getline(std::cin, token);
 
-            openlog("webfuse_pam_auth", 0, LOG_AUTH);
+        openlog("webfuse_pam_auth", 0, LOG_AUTH);
 
-            std::string username;
-            std::string password;
-            auto const decode_valid = decode(token, username, password);
-            if (decode_valid)
+        std::string username;
+        std::string password;
+        auto const decode_valid = decode(token, username, password);
+        if (decode_valid)
+        {
+            auto const is_authenticated = authenticate(username, password);
+            if (is_authenticated)
             {
-                auto const is_authenticated = authenticate(username, password);
-                if (is_authenticated)
-                {
-                    syslog(LOG_AUTH, "authenticate user \"%s\"", username.c_str());
-                    exit_code = EXIT_SUCCESS;
-                }
-                else
-                {
-                    syslog(LOG_AUTH, "failed to authenticate user \"%s\"", username.c_str());
-                }
+                syslog(LOG_AUTH, "authenticate user \"%s\"", username.c_str());
+                exit_code = EXIT_SUCCESS;
             }
             else
             {
-                syslog(LOG_AUTH, "failed to decode authentication token");
+                syslog(LOG_AUTH, "failed to authenticate user \"%s\"", username.c_str());
             }
-
-            closelog();
         }
-    }
 
-
-    if (print_usage)
+        closelog();
+    }
+    else
     {
         std::cout << R"(webfuse_pam_authenticator, (c) 2023 Falk Werner
 webfuse PAM authenticator
 
 Usage:
-    webfuse_pam_authenticator <token>
+    webfuse_pam_authenticator [-h]
+
+Options:
+    --help, -h      print this message and exit
 
-Arguments:
-    <token> token used for authentication
-            token := base64(<username> ":" <password>)
+Credentials:
+    Credentials are passed as based64-encoded token via stdin:
+        token := base64(<username> ":" <password>)
 )";
     }
 

example/authenticator/simple/authenticator.sh

@@ -1,6 +1,6 @@
 #!/usr/bin/bash
 
-AUTH_TOKEN="$1"
+read AUTH_TOKEN
 
 if [[ "$AUTH_TOKEN" == "simple_token" ]]
 then

example/provider/python/webfuse_provider.py

@@ -577,7 +577,7 @@ class FilesystemProvider:
         writer.write_u64(buffer.f_namemax)
 
     def getcreds(self, _, writer):
-        credentials = self.token if self.token != "" else getpass.getpass(prompt="credentials: ")
+        credentials = self.token if self.token != None and self.token != "" else getpass.getpass(prompt="credentials: ")
         writer.write_str(credentials)
 
 def main():

src/webfuse/util/authenticator.cpp

@@ -17,23 +17,35 @@ bool authenticator::authenticate(std::string const & token)
 {
     bool result = false;
 
+    int fds[2];
+    int const rc = pipe(fds);
+    if (0 != rc)
+    {
+        return false;
+    }
+
     pid_t const pid = fork();
 
     if (pid == 0)
     {
         // child
 
+        close(STDIN_FILENO);
+        dup2(fds[0], STDIN_FILENO);
+
         // prepare file descriptors
-        closefrom(0);
-        open("/dev/null", O_RDONLY);
+        closefrom(1);
         open("/dev/null", O_WRONLY);
         dup2(STDOUT_FILENO, STDERR_FILENO);
 
-        execl(app_.c_str(), app_.c_str(), token.c_str(), nullptr);
+        execl(app_.c_str(), app_.c_str(), nullptr);
         exit(EXIT_FAILURE);
     }
     else if (pid > 0)
     {
+        write(fds[1], reinterpret_cast<void const*>(token.c_str()), token.size());
+        close(fds[1]);
+
         // parent
         int exit_status = EXIT_FAILURE;
 
@@ -44,7 +56,8 @@ bool authenticator::authenticate(std::string const & token)
             exit_status = WEXITSTATUS(status);
         }
 
-        result = (exit_status == EXIT_SUCCESS);
+        close(fds[0]);
+        result = (exit_status == EXIT_SUCCESS);        
     }
 
     return result;