SSL_CTX_load_verify_locations - set default locations for trusted CA
int SSL_CTX_load_verify_locations(SSL_CTX *ctx, const char *CAfile,
const char *CApath);
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.
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
... (CA certificate in base64 encoding) ...
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
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
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
Generate a CA certificate file with descriptive text from the CA
certificates ca1.pem ca2.pem ca3.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:
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(3), SSL_CTX_set_client_CA_list(3), SSL_get_client_CA_list(3),