openssl-vulnkey(1) check blacklist of compromised certificates, requests and keys


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


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, will read from standard input. This can be used to process certificate output from s_client1ssl, for example:

$ echo | openssl s_client -connect | openssl-vulnkey

will test the certificate used by for HTTPS.

The options are as follows:

Quiet mode. Normally, outputs the fingerprint of each file scanned, with a description of its status. This option suppresses that output.
Number of bits for the modulus specified. Requires -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 [email protected]

Much of this manpage is based on Colin Watson's ssh-vulnkey1