nbdkit_read_password(3)

Usage

 #include <nbdkit-plugin.h>
 int nbdkit_read_password (const char *value, char **password);

Overview

The "nbdkit_read_password" utility function can be used to read passwords from config parameters.

The "password" result string is allocated by malloc, and so you may need to free it.

Example

 char *password = NULL;
 static int
 myplugin_config (const char *key, const char *value)
 {
   ..
   if (strcmp (key, "password") == 0) {
     free (password);
     if (nbdkit_read_password (value, &password) == -1)
       return -1;
   }
   ..
 }

Password formats

This function recognizes several password formats. A password may be used directly on the command line, eg:

 nbdkit myplugin password=mostsecret

But more securely this function can also read a password interactively:

 nbdkit myplugin password=-

or from a file:

 nbdkit myplugin password=+/tmp/secret

or from a file descriptor inherited by nbdkit:

 nbdkit myplugin password=-99

Notes on reading passwords

If the password begins with a "-" or "+" character then it must be passed in a file.

"password=-" can only be used when stdin is a terminal.

"password=-FD" cannot be used with stdin, stdout or stderr (ie. -0, -1 or -2). The reason is that after reading the password the file descriptor is closed, which causes bad stuff to happen.

Return value

The function returns 0 on success.

If there is an error it calls nbdkit_error(3) and returns -1.

Language bindings

In nbdkit-ocaml-plugin(3):

 NBDKit.read_password : string -> string

In nbdkit-python-plugin(3):

 import nbdkit
 password = nbdkit.parse_size(value)

Referred to by

nbdkit-plugin(3) how to write nbdkit plugins nbdkit_stdio_safe(3) is it safe to interact with stdin and stdout nbdkit-python-plugin(3) nbdkit python plugin