SSL_CTX_load_verify_locations - Set default locations for
trusted CA certificates
const char *CAfile,
const char *CApath );
The SSL_CTX_load_verify_locations() function 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 the following sequences:
... (CA certificate in base64 encoding) ...
Text is allowed before, between, and after the certificates.
It can be used, for example, to describe 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 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
The certificates in CApath are only looked up when
required, such as 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
In server mode, when requesting a client certificate, the
server must send the list of CAs from which it will accept
client certificates. This listis not influenced by the
contents of CAfile or CApath and must explicitly be set
using the SSL_CTX_set_client_CA_list() 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()
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. Do no mix expired certificates with valid certificates.
The following return values can occur: 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. The operation succeeded.
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:
Functions: ssl(3), SSL_CTX_set_client_CA_list(3),
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