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MUNGE(3) MUNGE Uid 'N' Gid Emporium MUNGE(3) 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 null- 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 null-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 (up to 1 MB), buf will be set to point to this data, and len will be set to its length. An additional null byte will be appended to this payload data but not in- cluded 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_EX- PIRED, 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 de- scribing 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 null-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 possibil- ity is that the credential has been altered since it was en- coded. EMUNGE_CRED_EXPIRED The credential was successfully decoded, but its decode time is later than its encode time by more than its TTL. The clocks on the encoding and decoding hosts could be out of sync. EMUNGE_CRED_REWOUND The credential was successfully decoded, but its decode time is earlier than its encode time by more than its TTL. The clocks on the encoding and decoding hosts are out of sync. EMUNGE_CRED_REPLAYED The credential was successfully decoded, but it has been previ- ously decoded on this host within its TTL skew. 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> #include <stdlib.h> #include <unistd.h> #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: Failed to encode credential: %s\n", munge_strerror (err)); exit (EXIT_FAILURE); } err = munge_decode (cred, NULL, NULL, NULL, &uid, &gid); if (err != EMUNGE_SUCCESS) { fprintf (stderr, "Error: Failed to decode credential: %s\n", munge_strerror (err)); exit (EXIT_FAILURE); } printf ("uid=%d gid=%d\n", uid, gid); free (cred); exit (EXIT_SUCCESS); } 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) 2007-2025 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 op- tion) 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 Li- cense 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_ctx(3), munge_enum(3), munge(7), munged(8), mungekey(8). https://github.com/dun/munge munge-0.5.17 2025-11-12 MUNGE(3)
NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | EXAMPLE | NOTES | AUTHOR | COPYRIGHT | SEE ALSO
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