MUNGE_CTX(3) MUNGE Uid 'N' Gid Emporium MUNGE_CTX(3)NAME
munge_ctx_create, munge_ctx_copy, munge_ctx_destroy, munge_ctx_str‐
error, 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 con‐
text, 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 associ‐
ated 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 associ‐
ated 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 creden‐
tial 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 creden‐
tial 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 modi‐
fied 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 orig‐
inal Secure Hash Algorithm (now called SHA-0) published in 1993.
This algorithm has a 160-bit message digest. In 2005, success‐
ful 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 bet‐
ter 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 recom‐
mended 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 compres‐
sion 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 request‐
ing 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) 2007-2013 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 ALSOmunge(1), remunge(1), unmunge(1), munge(3), munge_enum(3), munge(7),
munged(8).
https://munge.googlecode.com/
munge-0.5.11 2013-08-27 MUNGE_CTX(3)
