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How do you defend yourself from something you can’t see? 

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x.509 Certificates - Critical vs non-critical extensions

Extensions are used to associate additional information with the user or the key.  Each certificate extension has three attributes - extnID, critical, extnValue extnID - Extension ID - an OID that specifies the format and definitions of the extension critical - Critical flag - Boolean value extnValue - Extension value  Criticality flag specifies whether the information in an extension is important. If an application doesn't recognize the extension marked as critical, the certificate cannot be accepted. If an extension is not marked as critical (critical value False) it can be ignored by an application. In Windows, critical extensions are marked with a yellow exclamation mark,  View certificate extensions using OpenSSL: # openssl x509 -inform pem -in cert.pem -text -noout (output abbreviated)         X509v3 extensions:             X509v3 Key Usage: critical                 Digital Signature, Key Encipherment             X509v3 Subject Key Identifier

Cisco ASA Certificate Revocation Checking

ASA supports status verification using CRLs and OCSP. CRL can be retrieved using HTTP, LDAP or SCEP. Revocation checking using CRL: Over HTTP: ciscoasa(config)# crypto ca trustpoint ASDM_TrustPoint2 ciscoasa(config-ca-trustpoint)# revocation-check crl ciscoasa(config-ca-crl)# protocol http By default ASA will use address listed in CDP extension of the certificate that is being validated.  To override default behaviour we need to add the following in the CRL configuration context. ciscoasa(config-ca-crl)# policy static ciscoasa(config-ca-crl)# url 1 Over LDAP: Certificate I'm using for this lab, doesn't have LDAP address in its CDP extension. Therefore I'm using "policy static"  to specify LDAP URL where CRL can be retrieved.  ciscoasa(config)# crypto ca trustpoint ASDM_TrustPoint2 ciscoasa(config-ca-trustpoint)# revocation-check crl ciscoasa(config-ca-trustpoint)# crl configure ciscoasa

Count number of lines - 'findstr'

How do I count number of lines in a command output? findstr /r/n "^" | find /c ":" Above commands will display number of lines output by whatever command (well, nearly whatever) you specify in the front.  For example:  C:\>ping localhost | findstr /r/n "^" | find /c ":" FINDSTR: // ignored 12 This comes handy if you want to find out how many OUs you have in Active Directory: dsquery ou  -limit 0 | findstr /r/n "^" | find /c ":" How many user accounts there are: dsquery user -limit 0 | findstr /r/n "^" | find /c ":" Computers: dsquery computer -limit | findstr /r/n "^" | find /c ":"