SSL_CTX_load_verify_locations, SSL_CTX_set_default_verify_paths,
       SSL_CTX_set_default_verify_dir, SSL_CTX_set_default_verify_file - set
       default locations for trusted CA certificates

        #include <openssl/ssl.h>

        int SSL_CTX_load_verify_locations(SSL_CTX *ctx, const char *CAfile,
                                          const char *CApath);

        int SSL_CTX_set_default_verify_paths(SSL_CTX *ctx);

        int SSL_CTX_set_default_verify_dir(SSL_CTX *ctx);

        int SSL_CTX_set_default_verify_file(SSL_CTX *ctx);

       SSL_CTX_load_verify_locations() specifies the locations for ctx, at which
       CA certificates for verification purposes are located. The certificates
       available via CAfile and CApath are trusted.

       SSL_CTX_set_default_verify_paths() specifies that the default locations
       from which CA certificates are loaded should be used. There is one
       default directory and one default file. The default CA certificates
       directory is called "certs" in the default OpenSSL directory.
       Alternatively the SSL_CERT_DIR environment variable can be defined to
       override this location. The default CA certificates file is called
       "cert.pem" in the default OpenSSL directory. Alternatively the
       SSL_CERT_FILE environment variable can be defined to override this

       SSL_CTX_set_default_verify_dir() is similar to
       SSL_CTX_set_default_verify_paths() except that just the default directory
       is used.

       SSL_CTX_set_default_verify_file() is similar to
       SSL_CTX_set_default_verify_paths() except that just the default file is

       If CAfile is not NULL, it points to a file of CA certificates in PEM
       format. The file can contain several CA certificates identified by

        -----BEGIN CERTIFICATE-----
        ... (CA certificate in base64 encoding) ...
        -----END CERTIFICATE-----

       sequences. Before, between, and after the certificates text is allowed
       which can be used e.g. for descriptions of the certificates.

       The CAfile is processed on execution of the
       SSL_CTX_load_verify_locations() function.

       If CApath is not NULL, it points to a directory containing CA
       certificates in PEM format. The files each contain one CA certificate.
       The files are looked up by the CA subject name hash value, which must
       hence be available.  If more than one CA certificate with the same name
       hash value exist, the extension must be different (e.g. 9d66eef0.0,
       9d66eef0.1 etc). The search is performed in the ordering of the extension
       number, regardless of other properties of the certificates.  Use the
       c_rehash utility to create the necessary links.

       The certificates in CApath are only looked up when required, e.g. when
       building the certificate chain or when actually performing the
       verification of a peer certificate.

       When looking up CA certificates, the OpenSSL library will first search
       the certificates in CAfile, then those in CApath. Certificate matching is
       done based on the subject name, the key identifier (if present), and the
       serial number as taken from the certificate to be verified. If these data
       do not match, the next certificate will be tried. If a first certificate
       matching the parameters is found, the verification process will be
       performed; no other certificates for the same parameters will be searched
       in case of failure.

       In server mode, when requesting a client certificate, the server must
       send the list of CAs of which it will accept client certificates. This
       list is not influenced by the contents of CAfile or CApath and must
       explicitly be set using the SSL_CTX_set_client_CA_list(3) family of

       When building its own certificate chain, an OpenSSL client/server will
       try to fill in missing certificates from CAfile/CApath, if the
       certificate chain was not explicitly specified (see
       SSL_CTX_add_extra_chain_cert(3), SSL_CTX_use_certificate(3).

       If several CA certificates matching the name, key identifier, and serial
       number condition are available, only the first one will be examined. This
       may lead to unexpected results if the same CA certificate is available
       with different expiration dates. If a "certificate expired" verification
       error occurs, no other certificate will be searched. Make sure to not
       have expired certificates mixed with valid ones.

       For SSL_CTX_load_verify_locations the following return values can occur:

       0   The operation failed because CAfile and CApath are NULL or the
           processing at one of the locations specified failed. Check the error
           stack to find out the reason.

       1   The operation succeeded.

       SSL_CTX_set_default_verify_paths(), SSL_CTX_set_default_verify_dir() and
       SSL_CTX_set_default_verify_file() all return 1 on success or 0 on
       failure. A missing default location is still treated as a success.

       Generate a CA certificate file with descriptive text from the CA
       certificates ca1.pem ca2.pem ca3.pem:

        rm CAfile.pem
        for i in ca1.pem ca2.pem ca3.pem ; do
            openssl x509 -in $i -text >> CAfile.pem

       Prepare the directory /some/where/certs containing several CA
       certificates for use as CApath:

        cd /some/where/certs
        c_rehash .

       ssl(7), SSL_CTX_set_client_CA_list(3), SSL_get_client_CA_list(3),
       SSL_CTX_use_certificate(3), SSL_CTX_add_extra_chain_cert(3),
       SSL_CTX_set_cert_store(3), SSL_CTX_set_client_CA_list(3)

       Copyright 2000-2019 The OpenSSL Project Authors. All Rights Reserved.

       Licensed under the OpenSSL license (the "License").  You may not use this
       file except in compliance with the License.  You can obtain a copy in the
       file LICENSE in the source distribution or at

1.1.1j                             2021-02-16   SSL_CTX_LOAD_VERIFY_LOCATIONS(3)