c_rehash, rehash - Create symbolic links to files named by the hash values
openssl rehash [-h] [-help] [-old]
On some platforms, the OpenSSL rehash
command is available as an external
script called c_rehash
. They are functionally equivalent, except for
minor differences noted below.
scans directories and calculates a hash value of each
".pem", ".crt", ".cer", or ".crl" file
in the specified directory list and creates symbolic links for each file,
where the name of the link is the hash value. (If the platform does not
support symbolic links, a copy is made.) This utility is useful as many
programs that use OpenSSL require directories to be set up like this in order
to find certificates.
If any directories are named on the command line, then those are processed in
turn. If not, then the SSL_CERT_DIR
environment variable is consulted;
this should be a colon-separated list of directories, like the Unix
variable. If that is not set then the default directory
(installation-specific but often /usr/local/ssl/certs
) is processed.
In order for a directory to be processed, the user must have write permissions
on that directory, otherwise an error will be generated.
The links created are of the form "HHHHHHHH.D", where each H
a hexadecimal character and D
is a single decimal digit. When
processing a directory, rehash
will first remove all links that have a
name in that syntax, even if they are being used for some other purpose. To
skip the removal step, use the -n
flag. Hashes for CRL's look similar
except the letter r
appears after the period, like this:
Multiple objects may have the same hash; they will be indicated by incrementing
value. Duplicates are found by comparing the full SHA-1
fingerprint. A warning will be displayed if a duplicate is found.
A warning will also be displayed if there are files that cannot be parsed as
either a certificate or a CRL or if more than one such object appears in the
script uses the openssl
program to compute the hashes
and fingerprints. If not found in the user's PATH
, then set the
environment variable to the full pathname. Any program can be
used, it will be invoked as follows for either a certificate or CRL:
$OPENSSL x509 -hash -fingerprint -noout -in FILENAME
$OPENSSL crl -hash -fingerprint -noout -in FILENAME
is the filename. It must output the hash of the file on
the first line, and the fingerprint on the second, optionally prefixed with
some text and an equals sign.
- -help -h
- Display a brief usage message.
- Use old-style hashing (MD5, as opposed to SHA-1) for
generating links to be used for releases before 1.0.0. Note that current
versions will not use the old style.
- Do not remove existing links. This is needed when keeping
new and old-style links in the same directory.
- Print messages about old links removed and new links
created. By default, rehash only lists each directory as it is
- The path to an executable to use to generate hashes and
fingerprints (see above).
- Colon separated list of directories to operate on. Ignored
if directories are listed on the command line.
Copyright 2015-2016 The OpenSSL Project Authors. All Rights Reserved.
Licensed under the OpenSSL license (the "License"). You may not use
this file except in compliance with the License. You can obtain a copy in the
file LICENSE in the source distribution or at