Ubuntu Manpage: munge_encode, munge_decode, munge_strerror

Provided by: libmunge-dev_0.5.13-1_amd64

NAME

       munge_encode, munge_decode, munge_strerror - MUNGE core functions

SYNOPSIS

       #include <munge.h>

       munge_err_t munge_encode (char **cred, munge_ctx_t ctx,
                                 const void *buf, int len);

       munge_err_t munge_decode (const char *cred, munge_ctx_t ctx,
                                 void **buf, int *len, uid_t *uid, gid_t *gid);

       const char * munge_strerror (munge_err_t e);

       cc `pkg-config --cflags --libs munge` -o foo foo.c

DESCRIPTION

       The  munge_encode()  function  creates  a  credential contained in a NUL-terminated base64
       string.  A payload specified by a buffer buf of length len can be encapsulated in as well.
       If  the  MUNGE  context  ctx  is NULL, the default context will be used.  A pointer to the
       resulting credential is returned via cred; on error, it is set to  NULL.   The  caller  is
       responsible for freeing the memory referenced by cred.

       The  munge_decode()  function  validates the NUL-terminated credential cred.  If the MUNGE
       context ctx is not NULL, it will be set to that used to encode the credential.  If buf and
       len  are  not NULL, memory will be allocated for the encapsulated payload, buf will be set
       to point to this data, and len will be set to its length.   An  additional  NUL  character
       will  be  appended  to  this  payload  data but not included in its length.  If no payload
       exists, buf will be set to NULL and len will be set  to  0.   For  certain  errors  (i.e.,
       EMUNGE_CRED_EXPIRED, EMUNGE_CRED_REWOUND, EMUNGE_CRED_REPLAYED), payload memory will still
       be allocated if necessary.  The caller is responsible for freeing the memory referenced by
       buf.   If  uid  or  gid  is  not NULL, they will be set to the UID/GID of the process that
       created the credential.

       The munge_strerror() function returns a descriptive text string describing the MUNGE error
       number e.

RETURN VALUE

       The  munge_encode()  and  munge_decode()  functions return EMUNGE_SUCCESS on success, or a
       MUNGE error otherwise.  If a MUNGE context was used, it may contain a more detailed  error
       message accessible via munge_ctx_strerror().

       The  munge_strerror() function returns a pointer to a NUL-terminated constant text string;
       this string should not be freed or modified by the caller.

ERRORS

EMUNGE_SUCCESS
Success.

EMUNGE_SNAFU
Internal error.

EMUNGE_BAD_ARG
Invalid argument.

EMUNGE_BAD_LENGTH
Exceeded the maximum message length as specified by the munged configuration.

EMUNGE_OVERFLOW
Exceeded the maximum length of a buffer.

EMUNGE_NO_MEMORY
Unable to allocate the requisite memory.

EMUNGE_SOCKET
Unable to communicate with the daemon on the domain socket.

EMUNGE_BAD_CRED
The credential does not match the specified format.

EMUNGE_BAD_VERSION
The credential contains an unsupported version number.

EMUNGE_BAD_CIPHER
The credential contains an unsupported cipher type.

EMUNGE_BAD_MAC
The credential contains an unsupported MAC type.

EMUNGE_BAD_ZIP
The credential contains an unsupported compression type.

EMUNGE_BAD_REALM
The credential contains an unrecognized security realm.

EMUNGE_CRED_INVALID
The credential is invalid. This means the credential could not be successfully
decoded. More than likely, the secret keys on the encoding and decoding hosts do
not match. Another possibility is that the credential has been altered since it
was encoded.

EMUNGE_CRED_EXPIRED
The credential has expired. This means more than TTL seconds have elapsed since
the credential was encoded. Another possibility is that the clocks on the encoding
and decoding hosts are out of sync.

EMUNGE_CRED_REWOUND
The credential appears to have been encoded at some point in the future. This
means the clock on the decoding host is slower than that of the encoding host by
more than the allowable clock skew. More than likely, the clocks on the encoding
and decoding hosts are out of sync.

EMUNGE_CRED_REPLAYED
The credential has been previously decoded on this host.

EMUNGE_CRED_UNAUTHORIZED
The client is not authorized to decode the credential based upon the effective user
and/or group ID of the process.

EXAMPLE

       The  following  example program illustrates the use of a MUNGE credential to ascertain the
       effective user and group ID of the encoding process.

       #include <stdio.h>                      /* for printf() */
       #include <stdlib.h>                     /* for exit() & free() */
       #include <unistd.h>                     /* for uid_t & gid_t */
       #include <munge.h>

       int
       main (int argc, char *argv[])
       {
           char        *cred;
           munge_err_t  err;
           uid_t        uid;
           gid_t        gid;

           err = munge_encode (&cred, NULL, NULL, 0);

           if (err != EMUNGE_SUCCESS) {
               fprintf (stderr, "ERROR: %s\n", munge_strerror (err));
               exit (1);
           }
           err = munge_decode (cred, NULL, NULL, NULL, &uid, &gid);

           if (err != EMUNGE_SUCCESS) {
               fprintf (stderr, "ERROR: %s\n", munge_strerror (err));
               exit (1);
           }
           printf ("uid=%d gid=%d\n", uid, gid);
           free (cred);
           exit (0);
       }

NOTES

       Both munge_encode() and munge_decode() may allocate memory that the caller is  responsible
       for freeing.  Failure to do so will result in a memory leak.

AUTHOR

       Chris Dunlap <cdunlap@llnl.gov>

COPYRIGHT

       Copyright (C) 2007-2017 Lawrence Livermore National Security, LLC.
       Copyright (C) 2002-2007 The Regents of the University of California.

       MUNGE  is  free  software: you can redistribute it and/or modify it under the terms of the
       GNU General Public License as published by the Free Software Foundation, either version  3
       of the License, or (at your option) any later version.

       Additionally  for  the  MUNGE library (libmunge), you can redistribute it and/or modify it
       under the terms of the GNU Lesser General Public License as published by the Free Software
       Foundation, either version 3 of the License, or (at your option) any later version.