Doc fixes suggested by Claus Assmann

B<X509_LOOKUP_hash_dir> and B<X509_LOOKUP_file> are two certificate

lookup methods to use with B<X509_STORE>, provided by OpenSSL library.

Users of the library typically do not need to create instanses of these

Users of the library typically do not need to create instances of these

methods manually, they would be created automatically by

L<X509_STORE_load_locations(3)> or

L<SSL_CTX_load_verify_locations(3)>

=head2  FILE METHOD

B<X509_LOOKUP_file> method loads entire set of certificates and CRLs

into memory immediately when file name is passed to it. 

The B<X509_LOOKUP_file> method loads all the certificates or CRLs

present in a file into memory at the time the file is added as a

lookup source.

File format is ASCII text which contains concatenated PEM certificates

and CRLs.

This method should be used by applications which work with limited set

of CAs.

This method should be used by applications which work with a small

set of CAs.

=head2 HASHED DIR METHOD

B<X509_LOOKUP_hash_dir> is more sophisticated method, which loads

certificates and CRLs on demand, but caches them in the memory once they

are loaded. However, since OpenSSL 1.0.0beta1 it checks for newer CRLs

upon each lookup, so if newer CRL would appear in the directory, it

would be loaded.

Directory should contain each certificate and CRL in the separate file

in the PEM format, with file name derived from certificate subject (or CRL

issuer) hash, as returned by L<X509_NAME_hash(3)>

function of with option B<-hash> of L<x509(1)> or

L<crl(1)> command.

This hash value is appended by suffix .I<N> for certificates and

B<.r>I<N> for CRLs where I<N> is sequentual

number among certificates with same hash value, so it is possible to

have in the store several certificates with same subject or several CRLs

with same issuer (and, for example, different validity period).

When checking for new CRLs once one CRL for given hash value is loaded, 

hash_dir lookup method checks only for certificates with sequentual

number greater than one of already cached CRL.

Note that hash algorithm used for subject hashing is changed in OpenSSL

1.0, so all certificate stores have to be rehashed upon transitopn from

B<X509_LOOKUP_hash_dir> is a more advanced method, which loads

certificates and CRLs on demand, and caches them in memory once

they are loaded. As of OpenSSL 1.0.0, it also checks for newer CRLs

upon each lookup, so that newer CRLs are as soon as they appear in

the directory.

The directory should contain one certificate or CRL per file in PEM format,

with a file name of the form I<hash>.I<N> for a certificate, or

I<hash>.B<r>I<N> for a CRL.

The I<hash> is the value returned by the L<X509_NAME_hash(3)> function applied

to the subject name for certificates or issuer name for CRLs.

The hash can also be obtained via the B<-hash> option of the L<x509(1)> or

L<crl(1)> commands.

The .I<N> or .B<r>I<N> suffix is a sequence number that starts at zero, and is

incremented consecutively for each certificate or CRL with the same I<hash>

value.

Gaps in the sequence numbers are not supported, it is assumed that there are no

more objects with the same hash beyond the first missing number in the

sequence.

Sequence numbers make it possible for the directory to contain multiple

certificates with same subject name hash value.

For example, it is possible to have in the store several certificates with same

subject or several CRLs with same issuer (and, for example, different validity

period).

When checking for new CRLs once one CRL for given hash value is

loaded, hash_dir lookup method checks only for certificates with

sequence number greater than that of the already cached CRL.

Note that the hash algorithm used for subject name hashing changed in OpenSSL

1.0.0, and all certificate stores have to be rehashed when moving from OpenSSL

0.9.8 to 1.0.0.

OpenSSL includes utility L<c_rehash(1)> which creates

symlinks with correct hashed names for all files with .pem suffix in the

given directory.

OpenSSL includes a L<c_rehash(1)> utility which creates symlinks with correct

hashed names for all files with .pem suffix in a given directory.

=head1 SEE ALSO

There is no session available in B<ssl>.

=item Pointer to an SSL

=item Pointer to an SSL_SESSION

The return value points to the data of an SSL session.