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zcert - Class for work with CURVE security certificates


//  This is a stable class, and may not change except for emergencies. It
//  is provided in stable builds.
//  This class has draft methods, which may change over time. They are not
//  in stable releases, by default. Use --enable-drafts to enable.
//  Create and initialize a new certificate in memory
CZMQ_EXPORT zcert_t *

zcert_new (void); // Accepts public/secret key pair from caller CZMQ_EXPORT zcert_t *
zcert_new_from (const byte *public_key, const byte *secret_key); // Load certificate from file CZMQ_EXPORT zcert_t *
zcert_load (const char *filename); // Destroy a certificate in memory CZMQ_EXPORT void
zcert_destroy (zcert_t **self_p); // Return public part of key pair as 32-byte binary string CZMQ_EXPORT const byte *
zcert_public_key (zcert_t *self); // Return secret part of key pair as 32-byte binary string CZMQ_EXPORT const byte *
zcert_secret_key (zcert_t *self); // Return public part of key pair as Z85 armored string CZMQ_EXPORT const char *
zcert_public_txt (zcert_t *self); // Return secret part of key pair as Z85 armored string CZMQ_EXPORT const char *
zcert_secret_txt (zcert_t *self); // Set certificate metadata from formatted string. CZMQ_EXPORT void
zcert_set_meta (zcert_t *self, const char *name, const char *format, ...) CHECK_PRINTF (3); // Get metadata value from certificate; if the metadata value doesn't // exist, returns NULL. CZMQ_EXPORT const char *
zcert_meta (zcert_t *self, const char *name); // Get list of metadata fields from certificate. Caller is responsible for // destroying list. Caller should not modify the values of list items. CZMQ_EXPORT zlist_t *
zcert_meta_keys (zcert_t *self); // Save full certificate (public + secret) to file for persistent storage // This creates one public file and one secret file (filename + "_secret"). CZMQ_EXPORT int
zcert_save (zcert_t *self, const char *filename); // Save public certificate only to file for persistent storage CZMQ_EXPORT int
zcert_save_public (zcert_t *self, const char *filename); // Save secret certificate only to file for persistent storage CZMQ_EXPORT int
zcert_save_secret (zcert_t *self, const char *filename); // Apply certificate to socket, i.e. use for CURVE security on socket. // If certificate was loaded from public file, the secret key will be // undefined, and this certificate will not work successfully. CZMQ_EXPORT void
zcert_apply (zcert_t *self, void *socket); // Return copy of certificate; if certificate is NULL or we exhausted // heap memory, returns NULL. // Caller owns return value and must destroy it when done. CZMQ_EXPORT zcert_t *
zcert_dup (zcert_t *self); // Return true if two certificates have the same keys CZMQ_EXPORT bool
zcert_eq (zcert_t *self, zcert_t *compare); // Print certificate contents to stdout CZMQ_EXPORT void
zcert_print (zcert_t *self); // Self test of this class CZMQ_EXPORT void
zcert_test (bool verbose); #ifdef CZMQ_BUILD_DRAFT_API // *** Draft method, for development use, may change without warning *** // Accepts public/secret key text pair from caller CZMQ_EXPORT zcert_t *
zcert_new_from_txt (const char *public_txt, const char *secret_txt); // *** Draft method, for development use, may change without warning *** // Unset certificate metadata. CZMQ_EXPORT void
zcert_unset_meta (zcert_t *self, const char *name); #endif // CZMQ_BUILD_DRAFT_API Please add '@interface' section in './../src/zcert.c'.


The zcert class provides a way to create and work with security certificates for the ZMQ CURVE mechanism. A certificate contains a public + secret key pair, plus metadata. It can be used as a temporary object in memory, or persisted to disk. On disk, a certificate is stored as two files. One is public and contains only the public key. The second is secret and contains both keys. The two have the same filename, with the secret file adding "_secret". To exchange certificates, send the public file via some secure route. Certificates are not signed but are text files that can be verified by eye.

Certificates are stored in the ZPL (ZMQ RFC 4) format. They have two sections, "metadata" and "curve". The first contains a list of name = value pairs, one per line. Values may be enclosed in quotes. The curve section has a public-key = keyvalue and, for secret certificates, a secret-key = keyvalue line. The keyvalue is a Z85-encoded CURVE key.


From zcert_test method.

const char *SELFTEST_DIR_RW = "src/selftest-rw";
const char *testbasedir  = ".test_zcert";
const char *testfile = "mycert.txt";
char *basedirpath = NULL;   // subdir in a test, under SELFTEST_DIR_RW
char *filepath = NULL;      // pathname to testfile in a test, in dirpath
char *filepath_s = NULL;    // pathname to testfile+secret in a test, in dirpath
basedirpath = zsys_sprintf ("%s/%s", SELFTEST_DIR_RW, testbasedir);
assert (basedirpath);
filepath = zsys_sprintf ("%s/%s", basedirpath, testfile);
assert (filepath);
filepath_s = zsys_sprintf ("%s_secret", filepath);
assert (filepath_s);
// Make sure old aborted tests do not hinder us
zdir_t *dir = zdir_new (basedirpath, NULL);
if (dir) {

zdir_remove (dir, true);
zdir_destroy (&dir); } zsys_file_delete (filepath); zsys_dir_delete (basedirpath); // Create temporary directory for test files zsys_dir_create (basedirpath); // Create a simple certificate with metadata zcert_t *cert = zcert_new (); assert (cert); zcert_set_meta (cert, "email", ""); zcert_set_meta (cert, "name", "Pieter Hintjens"); zcert_set_meta (cert, "organization", "iMatix Corporation"); zcert_set_meta (cert, "version", "%d", 1); zcert_set_meta (cert, "delete_me", "now"); zcert_unset_meta (cert, "delete_me"); assert (streq (zcert_meta (cert, "email"), "")); zlist_t *keys = zcert_meta_keys (cert); assert (zlist_size (keys) == 4); zlist_destroy (&keys); // Check the dup and eq methods zcert_t *shadow = zcert_dup (cert); assert (zcert_eq (cert, shadow)); zcert_destroy (&shadow); // Check we can save and load certificate zcert_save (cert, filepath); assert (zsys_file_exists (filepath)); assert (zsys_file_exists (filepath_s)); // Load certificate, will in fact load secret one shadow = zcert_load (filepath); assert (shadow); assert (zcert_eq (cert, shadow)); zcert_destroy (&shadow); // Delete secret certificate, load public one int rc = zsys_file_delete (filepath_s); assert (rc == 0); shadow = zcert_load (filepath); // 32-byte null key encodes as 40 '0' characters assert (streq (zcert_secret_txt (shadow), FORTY_ZEROES)); #ifdef CZMQ_BUILD_DRAFT_API // test zcert_from_txt zcert_t *cert2 = zcert_new_from_txt(cert->public_txt, cert->secret_txt); assert (cert2); assert (zcert_eq (cert, cert2)); zcert_destroy(&cert2); #endif zcert_destroy (&shadow); zcert_destroy (&cert); // Delete all test files dir = zdir_new (basedirpath, NULL); assert (dir); zdir_remove (dir, true); zdir_destroy (&dir); zstr_free (&basedirpath); zstr_free (&filepath); zstr_free (&filepath_s); #if defined (__WINDOWS__) zsys_shutdown(); #endif


The czmq manual was written by the authors in the AUTHORS file.


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Copyright (c) the Contributors as noted in the AUTHORS file. This file is part of CZMQ, the high-level C binding for 0MQ: This Source Code Form is subject to the terms of the Mozilla Public License, v. 2.0. If a copy of the MPL was not distributed with this file, You can obtain one at LICENSE included with the czmq distribution.


01/17/2021 CZMQ 4.2.1