SSL_CTX_LOAD_VERIFY_L... BSD Library Functions Manual SSL_CTX_LOAD_VERIFY_L...NAMESSL_CTX_load_verify_locations — set default locations for trusted CA cer‐
tificates
SYNOPSIS
#include <openssl/ssl.h>
int
SSL_CTX_load_verify_locations(SSL_CTX *ctx, const char *CAfile,
const char *CApath);
DESCRIPTIONSSL_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 for‐
mat. The file can contain several CA certificates identified by
sequences of:
-----BEGIN CERTIFICATE-----
... (CA certificate in base64 encoding) ...
-----END CERTIFICATE-----
Before, between, and after the certificates arbitrary 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 certifi‐
cates 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 exten‐
sion number, regardless of other properties of the certificates.
The certificates in CApath are only looked up when required, e.g., when
building the certificate chain or when actually performing the verifica‐
tion 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 cer‐
tificate 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 func‐
tions.
When building its own certificate chain, an OpenSSL client/server will
try to fill in missing certificates from CAfile/ CApath, if the certifi‐
cate chain was not explicitly specified (see
SSL_CTX_add_extra_chain_cert(3) and 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 avail‐
able with different expiration dates. If a “certificate expired” verifi‐
cation error occurs, no other certificate will be searched. Make sure to
not have expired certificates mixed with valid ones.
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.
EXAMPLES
Generate a CA certificate file with descriptive text from the CA certifi‐
cates 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 certifi‐
cates for use as CApath:
$ cd /some/where/certs
$ rm -f *.[0-9]* *.r[0-9]*
$ for c in *.pem; do
> [ "$c" = "*.pem" ] && continue
> hash=$(openssl x509 -noout -hash -in "$c")
> if egrep -q -- '-BEGIN( X509 | TRUSTED | )CERTIFICATE-' "$c"; then
> suf=0
> while [ -e $hash.$suf ]; do suf=$(( $suf + 1 )); done
> ln -s "$c" $hash.$suf
> fi
> if egrep -q -- '-BEGIN X509 CRL-' "$c"; then
> suf=0
> while [ -e $hash.r$suf ]; do suf=$(( $suf + 1 )); done
> ln -s "$c" $hash.r$suf
> fi
> done
SEE ALSOssl(3), SSL_CTX_add_extra_chain_cert(3), SSL_CTX_set_cert_store(3),
SSL_CTX_set_client_CA_list(3), SSL_CTX_use_certificate(3),
SSL_get_client_CA_list(3)BSD March 29, 2024 BSD