Provided by: libmunge-dev_0.5.10-1_amd64 bug

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 ... -lmunge

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 (cf., CIPHER TYPES).

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

       MUNGE_OPT_ZIP_TYPE , int
              Get or set the compression type (cf., 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) (cf., 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 (cf., 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 (cf., 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.   But  since  a  pre-
              image  attack  has  not  yet  been  demonstrated, SHA-1 should still be safe to use
              within MUNGE.

       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) 2007-2011 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.

SEE ALSO

       munge(1), remunge(1), unmunge(1), munge(3), munge_enum(3), munge(7), munged(8).

       http://munge.googlecode.com/