This PR improves the handling of error responses when checking status using OCSP. It can handle a few types of errors:
* When the responder just returns an error (e.g., "Responder error: unauthorized").
* When the response cannot be verified (e.g., invalid signature, expired certificate).
* When the response is valid ("Response verify OK"), but there is a problem with the response for the individual certificate (e.g., information is too old, or status is "unknown").
This PR fixes two issues with OCSP checking. First, the syntax for specifying a host header changed in OpenSSL between versions 1.0.2 and 1.1.0. With OpenSSL 1.0.2-chacha, 1.0.2o, and LibreSSL the syntax needs to be "-header HOST <hostname>". With OpenSSL 1.1.0h and 1.1.1 the syntax needs to be "-header HOST=<hostname>". I have not been able to test other versions of OpenSSL 1.0.2 or 1.1.0, but am assuming that all versions of OpenSSL 1.1.0 use the same syntax as 1.1.0h.
This PR also fixes a typo in the case of an error, which was causing $code to be set to "empty ocsp response" if the response was not empty rather than if it was empty.
The current code for extracting the validity dates for certificates assumes that the strings "Not Before" and "Not After" will appear exactly once in the pretty-print of the certificate. In most cases that works. However, there are a few server certificates that include the private key usage period extension, which also includes "Not Before" and "Not After" times. The result is that the current code does not correctly extract the start date and end date from any certificates that have private key usage period extensions.
This PR fixes the problem and also speeds up extraction of the dates by only using Bash internal functions.
The pretty-print of a certificate begins as follows:
Certificate:
Data:
Version: 3 (0x2)
Serial Number: ...
Signature Algorithm: ...
Issuer: ...
Validity
Not Before: ... GMT
Not After : ... GMT
...
The code in this PR extracts the start date by first removing from the certificate everything that comes before "Not Before: ". It looks for the shortest string that includes ""Not Before: " in order to ensure it is not getting the date from the private key usage period extension. After that, the longest string that begins with "GMT" is removed so that only the notBefore date remains.
The part that removes the string up to "Not Before: " actually looks for the first instance of "Not Before: " that comes after the "Validity". This is to protect against the unlikely possibility that the string "Not Before: " appears somewhere in the issuer's name.
The extraction of the notAfter date works similarly. It first looks for the first instance of "Not After :" that appears after both "Validity" and "Not Before: " and then takes the date string that appears immediately afterwards, with the assumption that the date string ends in "GMT".
In some cases the OCSP URI contains multiple components in the path (e.g., http://www.example.com/OCSP/myOCSPresponder).
This PR changes check_revocation_ocsp() to remove all components in the path, rather than just the final component, when extracting the host name from the URI for the host header.
