Ubuntu Manpage: SSL_CTX_load_verify_locations - set default locations for trusted CA certificates

Provided by: libssl-doc_1.0.1f-1ubuntu2.27_all

NAME

       SSL_CTX_load_verify_locations - set default locations for trusted CA certificates

SYNOPSIS

        #include <openssl/ssl.h>

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

DESCRIPTION

       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.

NOTES

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 functions.

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).

WARNINGS

       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.

EXAMPLES

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

        #!/bin/sh
        rm CAfile.pem
        for i in ca1.pem ca2.pem ca3.pem ; do
          openssl x509 -in $i -text >> CAfile.pem
        done

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

        cd /some/where/certs
        c_rehash .

RETURN VALUES

       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.