libssl/man/SSL_CTX_load_verify_locations.3

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.Dd $Mdocdate: March 27 2018 $
.Dt SSL_CTX_LOAD_VERIFY_LOCATIONS 3
.Os
.Sh NAME
.Nm SSL_CTX_load_verify_locations ,
.Nm SSL_CTX_set_default_verify_paths
.Nd set default locations for trusted CA certificates
.Sh SYNOPSIS
.In openssl/ssl.h
.Ft int
.Fo SSL_CTX_load_verify_locations
.Fa "SSL_CTX *ctx" "const char *CAfile" "const char *CApath"
.Fc
.Ft int
.Fo SSL_CTX_set_default_verify_paths
.Fa "SSL_CTX *ctx"
.Fc
.Sh DESCRIPTION
.Fn SSL_CTX_load_verify_locations
specifies the locations for
.Fa ctx ,
at which CA certificates for verification purposes are located.
The certificates available via
.Fa CAfile
and
.Fa CApath
are trusted.
.Pp
.Fn SSL_CTX_set_default_verify_paths
specifies that the default locations from which CA certificates are
loaded should be used.
There is one default directory and one default file.
The default CA certificates directory is called
.Pa certs
in the default OpenSSL directory.
The default CA certificates file is called
.Pa cert.pem
in the default OpenSSL directory.
.Pp
If
.Fa CAfile
is not
.Dv NULL ,
it points to a file of CA certificates in PEM format.
The file can contain several CA certificates identified by sequences of:
.Bd -literal
 -----BEGIN CERTIFICATE-----
 ... (CA certificate in base64 encoding) ...
 -----END CERTIFICATE-----
.Ed
.Pp
Before, between, and after the certificates arbitrary text is allowed which can
be used, e.g., for descriptions of the certificates.
.Pp
The
.Fa CAfile
is processed on execution of the
.Fn SSL_CTX_load_verify_locations
function.
.Pp
If
.Fa 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.,
.Pa 9d66eef0.0 ,
.Pa 9d66eef0.1 ,
etc.).
The search is performed in the ordering of the extension number,
regardless of other properties of the certificates.
.Pp
The certificates in
.Fa CApath
are only looked up when required, e.g., when building the certificate chain or
when actually performing the verification of a peer certificate.
.Pp
When looking up CA certificates, the OpenSSL library will first search the
certificates in
.Fa CAfile ,
then those in
.Fa 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.
.Pp
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
.Fa CAfile
or
.Fa CApath
and must explicitly be set using the
.Xr SSL_CTX_set_client_CA_list 3
family of functions.
.Pp
When building its own certificate chain, an OpenSSL client/server will try to
fill in missing certificates from
.Fa CAfile Ns / Fa CApath ,
if the
certificate chain was not explicitly specified (see
.Xr SSL_CTX_add_extra_chain_cert 3
and
.Xr SSL_CTX_use_certificate 3 ) .
.Sh RETURN VALUES
For
.Fn SSL_CTX_load_verify_locations ,
the following return values can occur:
.Bl -tag -width Ds
.It 0
The operation failed because
.Fa CAfile
and
.Fa CApath
are
.Dv NULL
or the processing at one of the locations specified failed.
Check the error stack to find out the reason.
.It 1
The operation succeeded.
.El
.Pp
.Fn SSL_CTX_set_default_verify_paths
returns 1 on success or 0 on failure.
A missing default location is still treated as a success.
.Sh EXAMPLES
Generate a CA certificate file with descriptive text from the CA certificates
.Pa ca1.pem
.Pa ca2.pem
.Pa ca3.pem :
.Bd -literal
#!/bin/sh
rm CAfile.pem
for i in ca1.pem ca2.pem ca3.pem; do
	openssl x509 -in $i -text >> CAfile.pem
done
.Ed
.Pp
Prepare the directory /some/where/certs containing several CA certificates
for use as
.Fa CApath :
.Bd -literal
$ 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
.Ed
.Sh SEE ALSO
.Xr ssl 3 ,
.Xr SSL_CTX_add_extra_chain_cert 3 ,
.Xr SSL_CTX_set_cert_store 3 ,
.Xr SSL_CTX_set_client_CA_list 3 ,
.Xr SSL_CTX_use_certificate 3 ,
.Xr SSL_get_client_CA_list 3
.Sh HISTORY
.Fn SSL_CTX_load_verify_locations
and
.Fn SSL_CTX_set_default_verify_paths
first appeared in SSLeay 0.8.0 and have been available since
.Ox 2.4 .
.Sh CAVEATS
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
.Dq certificate expired
verification error occurs, no other certificate will be searched.
Make sure to not have expired certificates mixed with valid ones.