HTTPS (SSL) connection fails with an application running in a Linux virtual machine

Products

• VMware vSphere ESXi

Issue/Introduction

Symptoms:

With an application running in a Linux virtual machine:

• An HTTPS connection cannot be established
• An HTTPS connection times out or works intermittently
• Application logs show timeouts on /dev/random
• Necessary entropy is not available to meet required application needs
  

Environment

VMware ESXi 4.1.x Embedded
VMware ESXi 4.1.x Installable
VMware ESX 4.1.x

Cause

In Unix and Linux operating systems, /dev/random and /dev/urandom are special files that serve as random number generators. They allow access to environmental noise collected from device drivers and other sources. Inside a virtual machine environment, these devices exhaust their pool of random bits much more quickly than in a physical environment because hardware events are less common in a virtual machine.

Resolution

To resolve this issue, either:

• Configure your application to use /dev/urandom instead of /dev/random
  
  OR
  
  
• Replace /dev/random with a symbolic link to /dev/urandom

To replace /dev/random with a symbolic link to /dev/urandom:

1. Log in to the console of the Linux virtual machine as root.
2. Back up the current contents of /dev/random with this command:
   
   mv /dev/random /dev/random.orig
   
   
3. Create the symbolic link from /dev/random to /dev/urandom with this command:
   
   ln -s /dev/urandom /dev/random