NAME

     openssl-vulnkey — check blacklist of compromised certificates, requests and keys

SYNOPSIS

     openssl-vulnkey [-q] file ...
     openssl-vulnkey [-q] -b BITS -m MODULUS

DESCRIPTION

     openssl-vulnkey checks a certificate, request or key against a blacklist of compromised
     moduli.

     A substantial number of certificates, requests and keys are known to have been generated
     using a broken version of OpenSSL distributed by Debian which failed to seed its random
     number generator correctly.  x509 certificates, certificate requests and RSA keys generated
     using these OpenSSL versions should be assumed to be compromised.  This tool may be useful
     in checking for such OpenSSL x509 certificates, certificate requests and RSA keys.

     Certificates, requests and keys that are compromised cannot be repaired; replacements must
     be generated using openssl(8).

     If “-” is given as an argument, openssl-vulnkey will read from standard input.  This can be
     used to process certificate output from s_client(1ssl), for example:

           $ echo | openssl s_client -connect remote.example.org:https | openssl-vulnkey -

     will test the certificate used by remote.example.org for HTTPS.

     The options are as follows:

     -q      Quiet mode.  Normally, openssl-vulnkey outputs the fingerprint of each file scanned,
             with a description of its status.  This option suppresses that output.

     -b      Number of bits for the modulus specified.  Requires -m.

     -m      Check modulus.  Requires -b.

BLACKLIST SHA1SUM FORMAT

     The blacklist file may start with comments, on lines starting with “#”.  After these initial
     comments, it must follow a strict format:

           •   Each line must consist of the lower-case hexadecimal SHA1 fingerprint of the
               certificate or key's modulus, and with the first 20 characters removed (that is,
               the least significant 80 bits of the fingerprint).

     The fingerprint of the modulus may be generated using

           $ openssl x509 -noout -modulus -in file | sha1sum | cut -d ' ' -f 1
           $ openssl rsa -noout -modulus -in file | sha1sum | cut -d ' ' -f 1
           $ openssl req -noout -modulus -in file | sha1sum | cut -d ' ' -f 1

     This strict format is necessary to allow the blacklist file to be checked quickly.

SEE ALSO

     openssl(1)

AUTHORS

     Jamie Strandboge <jamie@ubuntu.com>

     Much of this manpage is based on Colin Watson's ssh-vulnkey(1)