Skip to main content

Linux certificate storage

As opposed to Windows, Linux doesn't have crypto APIs that would be usable by user-mode applications. Linux does have Kernel level CryptoAPI (crypto.h) which is accessible to kernel mode processes. As such applications store certificates in application specific locations. That way we end up with multiple copies of the same certificate. One way to workaroud is to designate a directory for certificate storage and create symbolic links in required directories. 

The Linux Kernel Cryptographic API overview:

Generate CSR using a new key pair:

openssl req -nodes -newkey rsa:1024 -keyout serverName.key -out serverName.csr

Generate CSR using an existing key pair:

openssl req -new -key serverName.key -out serverName.csr

Once the request is signed, certs and keypair must be copied to relevant location. Most Linux applications require Base64 encoded certificate with .PEM extension. This however may vary. Apache for example requires Base64 encoded .CRT certificate. 

Sample storage locations:

Cisco AnyConnect:

User certs:

~/.cisco/certificates/ca                  Root CA
~/.cisco/certificates/client               User certificate 
~/.cisco/certificates/client/private       PrivateKeys

Computer certs:

/opt/.cisco/certificates/ca                    Root CA
/opt/.cisco/certificates/client                Client certificates 
/opt/.cisco/certificates/client/private    PrivateKeys




Locations of cert and private key are specified in the config file (sample config below) per virtual host. Sample location:


Enabling SSL in Apache. 

Enable mod_ssl:

# e2enmod ssl

Configure Virtual Host:

This is configured in an httpd.conf or apache2.conf (which by default includes httpd.conf)

DocumentRoot /var/www/
SSLEngine on
SSLCertificateFile /etc/apache2/conf/ssl.crt/
SSLCertificateKeyFile /etc/apache2/conf/ssl.key/

Restart  service:

# service httpd restart


# apachectl -restart


Popular posts from this blog

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

DNS response and error types

In this post we explore common DNS response codes. We will cover the following responses: NOERROR SERVFAIL NXDOMAIN NODATA REFUSED Throughout article we’ll refer to the following RFCs: RFC 1034 - DOMAIN NAMES - CONCEPTS AND FACILITIES RFC 2308 - Negative Caching of DNS Queries (DNS NCACHE) RFC 2136 - Dynamic Updates in the Domain Name System (DNS UPDATE) RFC 8914 - Extended DNS Errors Response Codes - RCODEs The DNS RCODES are best defined in RFC2316 .  They signify what type of response was sent by the server. “RCODE   Response code - this four bit field is undefined in requests and set in responses.”   The table below shows the summary of the currently defined RCODEs. Mnemonic Val Description NOERROR 0 No error condition.

DNS blocking in Indonesia

DNS based censorship and domain blocking in Indonesia is very inconsistent among ISPs. There’s a government mandated black list which the ISPs operating in the country should enforce. However, Indonesia lacks centralised internet infrastructure and has many separate ISPs. In addition, the Indonesian government granted ISPs the authority to block content at their own discretion. All of this leads to a very inconsistent DNS blocking in Indonesia. Official DNS domain blacklist in Indonesia The Government mandated DNS blacklist is published in a redacted form and can be downloaded here: . This is where the blocked domains get redirected to. We can search the database and check if a domain is blocked. In the screenshot below we can see that a popular cryptocurrency exchange is blocked (Ada) and that is not (Tidak Ada) - thanks to Google Translate. Examples of blocked DNS queries dig @ ;; global options: +cmd ;; Got