Manual Reference Pages  - OPENSSL-VULNKEY (1)


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


Blacklist Sha1sum Format
See Also


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


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 | openssl-vulnkey -

will test the certificate used by 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.


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.




.An -nosplit
.An Jamie Strandboge Aq

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

$Mdocdate: May 12 2008 $ OPENSSL-VULNKEY (1)
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