zcertstore - Man Page

Class for work with CURVE security certificate stores


//  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 a new certificate store from a disk directory, loading and
//  indexing all certificates in that location. The directory itself may be
//  absent, and created later, or modified at any time. The certificate store
//  is automatically refreshed on any zcertstore_lookup() call. If the
//  location is specified as NULL, creates a pure-memory store, which you
//  can work with by inserting certificates at runtime.
CZMQ_EXPORT zcertstore_t *
    zcertstore_new (const char *location);

//  Destroy a certificate store object in memory. Does not affect anything
//  stored on disk.
    zcertstore_destroy (zcertstore_t **self_p);

//  Look up certificate by public key, returns zcert_t object if found,
//  else returns NULL. The public key is provided in Z85 text format.
CZMQ_EXPORT zcert_t *
    zcertstore_lookup (zcertstore_t *self, const char *public_key);

//  Insert certificate into certificate store in memory. Note that this
//  does not save the certificate to disk. To do that, use zcert_save()
//  directly on the certificate. Takes ownership of zcert_t object.
    zcertstore_insert (zcertstore_t *self, zcert_t **cert_p);

//  Print list of certificates in store to logging facility
    zcertstore_print (zcertstore_t *self);

//  Self test of this class
    zcertstore_test (bool verbose);

// Loaders retrieve certificates from an arbitrary source.
typedef void (zcertstore_loader) (
    zcertstore_t *self);

// Destructor for loader state.
typedef void (zcertstore_destructor) (
    void **self_p);

//  *** Draft method, for development use, may change without warning ***
//  Override the default disk loader with a custom loader fn.
    zcertstore_set_loader (zcertstore_t *self, zcertstore_loader loader, zcertstore_destructor destructor, void *state);

//  *** Draft method, for development use, may change without warning ***
//  Empty certificate hashtable. This wrapper exists to be friendly to bindings,
//  which don't usually have access to struct internals.
    zcertstore_empty (zcertstore_t *self);

//  *** Draft method, for development use, may change without warning ***
//  Return a list of all the certificates in the store.
//  The caller takes ownership of the zlistx_t object and is responsible
//  for destroying it.  The caller does not take ownership of the zcert_t
//  objects.
//  Caller owns return value and must destroy it when done.
CZMQ_EXPORT zlistx_t *
    zcertstore_certs (zcertstore_t *self);

//  *** Draft method, for development use, may change without warning ***
//  Return the state stored in certstore
    zcertstore_state (zcertstore_t *self);

Please add '@interface' section in './../src/zcertstore.c'.


To authenticate new clients using the ZeroMQ CURVE security mechanism, we have to check that the client’s public key matches a key we know and accept. There are numerous ways to store accepted client public keys. The mechanism CZMQ implements is "certificates" (plain text files) held in a "certificate store" (a disk directory). This class works with such certificate stores, and lets you easily load them from disk, and check if a given client public key is known or not. The zcert class does the work of managing a single certificate.

The certificate store can be memory-only, in which case you can load it yourself by inserting certificate objects one by one, or it can be loaded from disk, in which case you can add, modify, or remove certificates on disk at any time, and the store will detect such changes and refresh itself automatically. In most applications you won’t use this class directly but through the zauth class, which provides a high-level API for authentication (and manages certificate stores for you). To actually create certificates on disk, use the zcert class in code, or the tools/zmakecert.c command line tool, or any text editor. The format of a certificate file is defined in the zcert man page.


From zcertstore_test method.

const char *SELFTEST_DIR_RW = "src/selftest-rw";

const char *testbasedir  = ".test_zcertstore";
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

basedirpath = zsys_sprintf ("%s/%s", SELFTEST_DIR_RW, testbasedir);
assert (basedirpath);
filepath = zsys_sprintf ("%s/%s", basedirpath, testfile);
assert (filepath);

// 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);

//  Load certificate store from disk; it will be empty
zcertstore_t *certstore = zcertstore_new (basedirpath);
assert (certstore);

//  Create a single new certificate and save to disk
zcert_t *cert = zcert_new ();
assert (cert);
char *client_key = strdup (zcert_public_txt (cert));
assert (client_key);
zcert_set_meta (cert, "name", "John Doe");
zcert_save (cert, filepath);
zcert_destroy (&cert);

//  Check that certificate store refreshes as expected
cert = zcertstore_lookup (certstore, client_key);
assert (cert);
assert (streq (zcert_meta (cert, "name"), "John Doe"));

//  DRAFT-API: Security
// Iterate through certs
zlistx_t *certs = zcertstore_certs(certstore);
cert = (zcert_t *) zlistx_first(certs);
int cert_count = 0;
while (cert) {
    assert (streq (zcert_meta (cert, "name"), "John Doe"));
    cert = (zcert_t *) zlistx_next(certs);

//  Test custom loader
test_loader_state *state = (test_loader_state *) zmalloc (sizeof (test_loader_state));
state->index = 0;
zcertstore_set_loader (certstore, s_test_loader, s_test_destructor, (void *)state);
cert = zcertstore_lookup (certstore, client_key);
assert (cert == NULL);
cert = zcertstore_lookup (certstore, "abcdefghijklmnopqrstuvwxyzabcdefghijklmn");
assert (cert);

freen (client_key);

if (verbose)
    zcertstore_print (certstore);
zcertstore_destroy (&certstore);

//  Delete all test files
dir = zdir_new (basedirpath, NULL);
assert (dir);
zdir_remove (dir, true);
zdir_destroy (&dir);

zstr_free (&basedirpath);
zstr_free (&filepath);

#if defined (__WINDOWS__)


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07/19/2023 CZMQ 4.2.1 CZMQ Manual