Ubuntu Manpage: munge_ctx_create, munge_ctx_copy, munge_ctx_destroy, munge_ctx_strerror, munge_ctx

Provided by: libmunge-dev_0.5.14-6_amd64

NAME

       munge_ctx_create,  munge_ctx_copy,  munge_ctx_destroy,  munge_ctx_strerror, munge_ctx_get,
       munge_ctx_set - MUNGE context functions

SYNOPSIS

       #include <munge.h>

       munge_ctx_t munge_ctx_create (void);

       munge_ctx_t munge_ctx_copy (munge_ctx_t ctx);

       void munge_ctx_destroy (munge_ctx_t ctx);

       const char * munge_ctx_strerror (munge_ctx_t ctx);

       munge_err_t munge_ctx_get (munge_ctx_t ctx, munge_opt_t opt, ...);

       munge_err_t munge_ctx_set (munge_ctx_t ctx, munge_opt_t opt, ...);

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

DESCRIPTION

       The munge_ctx_create() function creates and returns a new MUNGE context, or NULL on error.

       The munge_ctx_copy() function copies the context ctx and returns a new MUNGE  context,  or
       NULL on error.

       The munge_ctx_destroy() function destroys the context ctx.

       The  munge_ctx_strerror()  function returns a descriptive text string describing the MUNGE
       error number according to the context ctx, or NULL if no error condition exists.  This may
       provide a more detailed error message than that returned by munge_strerror().

       The  munge_ctx_get()  function gets the value for the option opt associated with the MUNGE
       context ctx, storing the result in the subsequent pointer argument.  If the  result  is  a
       string, that string should not be freed or modified by the caller.

       The  munge_ctx_set()  function sets the value for the option opt associated with the MUNGE
       context ctx, using the value of the subsequent argument.

RETURN VALUE

       The munge_ctx_create() and munge_ctx_copy()  functions  return  a  newly  allocated  MUNGE
       context, or NULL on error.

       The  munge_ctx_strerror()  function  returns  a  pointer to a NUL-terminated constant text
       string, or NULL if no error condition exists.  This string should not be freed or modified
       by the caller.

       The  munge_ctx_get()  and munge_ctx_set() functions return EMUNGE_SUCCESS on success, or a
       MUNGE error number otherwise.

CONTEXT OPTIONS

The following context options can be queried via munge_ctx_get() or specified via
munge_ctx_set(). The type following each enumeration is the variable type used for the
subsequent argument in munge_ctx_set(), or the variable type of a pointer used for the
subsequent argument in munge_ctx_get().

MUNGE_OPT_CIPHER_TYPE , int
Get or set the cipher type (see CIPHER TYPES).

MUNGE_OPT_MAC_TYPE , int
Get or set the MAC type (see MAC TYPES).

MUNGE_OPT_ZIP_TYPE , int
Get or set the compression type (see COMPRESSION TYPES).

MUNGE_OPT_REALM , char *
Get or set the security realm, where the char * type is a NUL-terminated character
string. The string returned by munge_ctx_get() should not be freed or modified by
the caller. NOT CURRENTLY SUPPORTED.

MUNGE_OPT_TTL , int
Get or set the time-to-live (in seconds) (see TTL TYPES). This value controls how
long the credential is valid once it has been encoded.

MUNGE_OPT_ADDR4 , struct in_addr
Get the IPv4 address of the host where the credential was encoded. This option
cannot be explicitly set.

MUNGE_OPT_ENCODE_TIME , time_t
Get the time (in seconds since the epoch) at which the credential was encoded.
This option cannot be explicitly set.

MUNGE_OPT_DECODE_TIME , time_t
Get the time (in seconds since the epoch) at which the credential was decoded.
This option cannot be explicitly set.

MUNGE_OPT_SOCKET , char *
Get or set the local domain socket for connecting with munged, where the char *
type is a NUL-terminated character string. The string returned by munge_ctx_get()
should not be freed or modified by the caller.

MUNGE_OPT_UID_RESTRICTION , uid_t
Get or set the UID allowed to decode the credential (see UID & GID TYPES). This
value will be matched against the effective user ID of the process requesting the
credential decode.

MUNGE_OPT_GID_RESTRICTION , gid_t
Get or set the GID allowed to decode the credential (see UID & GID TYPES). This
value will be matched against the effective group ID of the process requesting the
credential decode, as well as each supplementary group of which the effective user
ID of that process is a member.

CIPHER TYPES

Credentials can be encrypted using the secret key shared by all munged daemons within a
security realm. Anyone having access to this key can use it to decrypt a credential,
thereby bypassing any restrictions being imposed by munged.

MUNGE_CIPHER_NONE
Specify that encryption is to be disabled.

MUNGE_CIPHER_DEFAULT
Specify the default according to the munged configuration.

MUNGE_CIPHER_BLOWFISH
Specify the Blowfish cipher designed by Bruce Schneier. This cipher has a 64-bit
block-size and a variable key length. MUNGE uses it with a 128-bit key in CBC
mode. It is a fast block cipher but suffers from a slow key setup time.
Consequently, it underperforms when generating small credentials.

MUNGE_CIPHER_CAST5
Specify the CAST5 cipher designed by Carlisle Adams and Stafford Tavares. This
cipher has a 64-bit block-size and a variable key length. MUNGE uses it with a
128-bit key in CBC mode.

MUNGE_CIPHER_AES128
Specify the AES (Advanced Encryption Standard) cipher, also known as Rijndael. It
was designed by Joan Daemen and Vincent Rijmen. This cipher has a 128-bit block-
size and a key length of 128, 192, or 256 bits. MUNGE uses it here with a 128-bit
key in CBC mode.

MUNGE_CIPHER_AES256
Specify the AES (Advanced Encryption Standard) cipher, also known as Rijndael. It
was designed by Joan Daemen and Vincent Rijmen. This cipher has a 128-bit block-
size and a key length of 128, 192, or 256 bits. MUNGE uses it here with a 256-bit
key in CBC mode. Currently, MUNGE_CIPHER_AES256 requires the use of
MUNGE_MAC_SHA256.

MAC TYPES

The message authentication code (MAC) is a required component of the credential;
consequently, it cannot be disabled.

MUNGE_MAC_DEFAULT
Specify the default according to the munged configuration.

MUNGE_MAC_MD5
Specify the MD5 algorithm designed by Ron Rivest and published in 1991. This
algorithm has a 128-bit message digest. In 2004, a successful collision attack
against MD5 was demonstrated. In 2009, a theoretical pre-image attack against MD5
was published. Consequently, use of MD5 is not recommended due to its lower
security margin.

MUNGE_MAC_SHA1
Specify the SHA-1 algorithm designed by the National Security Agency and published
in 1995; this is the successor to the original Secure Hash Algorithm (now called
SHA-0) published in 1993. This algorithm has a 160-bit message digest. In 2005,
successful collision attacks were demonstrated against SHA-1. In 2017, a
successful identical-prefix collision attack (SHAttered) was announced. In 2020, a
successful chosen-prefix collision attack (SHA-1 is a Shambles) was announced.
Since a pre-image attack has not yet been demonstrated, SHA-1 should still be safe
to use within MUNGE; however, use of a SHA-2 hash function (such as SHA-256 or
SHA-512) should be preferred.

MUNGE_MAC_RIPEMD160
Specify the RIPEMD-160 (RACE Integrity Primitives Evaluation Message Digest)
algorithm designed in Europe by Hans Dobbertin, Antoon Bosselaers, and Bart
Preneel, and published in 1996. This algorithm has a 160-bit message digest. It
is somewhat less popular than SHA-1 and correspondingly less well studied. While
slower than SHA-1, it is believed to have a slightly better security margin.

MUNGE_MAC_SHA256
Specify the SHA-256 algorithm designed by the National Security Agency and
published in 2002; this is one of the SHA-2 variants in the Secure Hash Algorithm
family. This algorithm has a 256-bit message digest. In 2006, NIST began
encouraging the use of the SHA-2 family of hash functions for all new applications
and protocols.

MUNGE_MAC_SHA512
Specify the SHA-512 algorithm designed by the National Security Agency and
published in 2002; this is one of the SHA-2 variants in the Secure Hash Algorithm
family. This algorithm has a 512-bit message digest. In 2006, NIST began
encouraging the use of the SHA-2 family of hash functions for all new applications
and protocols.

COMPRESSION TYPES

       If  a  compression  type  is  specified,  a  payload-bearing credential will be compressed
       accordingly.  However, if the resulting  compressed  data  is  larger  than  the  original
       uncompressed data, the uncompressed data will be restored and compression will be disabled
       for that credential.

       MUNGE_ZIP_NONE
              Specify that compression is to be disabled.  This is the recommended setting unless
              there is a payload of sufficient size to compress.

       MUNGE_ZIP_DEFAULT
              Specify the default according to the munged configuration.

       MUNGE_ZIP_BZLIB
              Specify the bzip2 library developed by Julian Seward.  This is slower and uses more
              memory, but generally gets better compression on larger payloads.

       MUNGE_ZIP_ZLIB
              Specify the zlib library developed by Jean-loup Gailly and  Mark  Adler.   This  is
              faster and uses less memory, but gets pretty good compression nonetheless.

TTL TYPES

       The  time-to-live  value  specifies  the  number of seconds after the encode-time that the
       credential is considered valid.  In addition to specifying an integer value, the following
       types are available.

       MUNGE_TTL_MAXIMUM
              Specify the maximum allowed by the munged configuration.

       MUNGE_TTL_DEFAULT
              Specify the default according to the munged configuration.

UID & GID TYPES

       The  UID and GID restrictions can be used to restrict the decoding of the credential based
       on the effective user and group ID of the requesting process.  In addition  to  specifying
       an integer value, the following types are available.

       MUNGE_UID_ANY
              Specify that no UID restriction is to take effect; this is the default behavior.

       MUNGE_GID_ANY
              Specify that no GID restriction is to take effect; this is the default behavior.

ERRORS

       Refer to munge(3) for a complete list of errors.

EXAMPLE

       The  following  example  program  illustrates  the  use  of the MUNGE context to query the
       location of the munged domain socket.

       #include <stdio.h>                      /* for printf() */
       #include <stdlib.h>                     /* for exit() */
       #include <munge.h>

       int
       main (int argc, char *argv[])
       {
           munge_ctx_t  ctx;
           munge_err_t  err;
           char        *str;

           if (!(ctx = munge_ctx_create ())) {
               fprintf (stderr, "ERROR: Unable to create MUNGE context\n");
               exit (1);
           }
           err = munge_ctx_get (ctx, MUNGE_OPT_SOCKET, &str);

           if (err != EMUNGE_SUCCESS) {
               fprintf (stderr, "ERROR: %s\n", munge_ctx_strerror (ctx));
               exit (1);
           }
           printf ("socket=%s\n", str);
           /*
            *  Note that 'str' is not to be free()d since
            *    it points to a string within the 'ctx'.
            */
           munge_ctx_destroy (ctx);
           exit (0);
       }

NOTES

       Abandoning a new or copied MUNGE context without destroying it will  result  in  a  memory
       leak.

       The  context  passed  to  munge_encode() is treated read-only except for the error message
       that is set when an error is returned.   The  context  passed  to  munge_decode()  is  set
       according  to  the  context used to encode the credential; however, on error, its settings
       may be in a state which is invalid for encoding.  Consequently, separate  contexts  should
       be used for encoding and decoding.

       A context should not be shared between threads unless it is protected by a mutex; however,
       a better alternative is to use a separate context (or two)  for  each  thread,  either  by
       creating a new one via munge_ctx_create() or copying an existing one via munge_ctx_copy().

AUTHOR

       Chris Dunlap <cdunlap@llnl.gov>

COPYRIGHT

       Copyright (C) 2007-2020 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.