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 SSL_CTX_load_verify_locations()
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
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
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
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: