Creating Secure Passwords with Linux Shell Scripting
Hello, everyone! Today, let’s delve into an essential skill for any Linux enthusiast or system administrator: creating secure, random passwords using shell scripting. This skill is crucial for automating account setups, enhancing security, and just making life a bit easier. Here’s a step-by-step guide to creating a script that generates strong, random passwords.
Starting Simple: Generating a Random Number
First, let’s start with the basics. The simplest form of a random password can be a random number. In bash, you can generate a random number using the $RANDOM
variable.
bash
PASSWORD=$RANDOM echo $PASSWORD
This script will output a random number each time you run it. However, this isn’t very secure, so let’s improve it.
Improving Security: Combining Random Numbers
To create a longer password, concatenate multiple $RANDOM
values:
bash
PASSWORD="${RANDOM}${RANDOM}${RANDOM}" echo $PASSWORD
This approach provides a longer string of numbers, but we can do better in terms of complexity.
Using Date and Time: A More Complex Approach
A more complex password can be generated using the current date and time. This ensures that the password changes every second, making it more secure.
bash
PASSWORD=$(date +%s) echo $PASSWORD
Here, %s
outputs the number of seconds since the Unix Epoch, providing a unique value.
Adding Nanoseconds: For Extra Complexity
For even more complexity, add nanoseconds to the mix:
bash
PASSWORD=$(date +%s%N) echo $PASSWORD
This script uses both the seconds and the nanoseconds, creating a very complex password.
Hash for Complexity: Using SHA256
For a highly secure password, you can hash the date and time using SHA256:
bash
PASSWORD=$(date +%s%N | sha256sum | head -c32) echo $PASSWORD
This command generates a SHA256 hash of the current date and time, then uses head
to truncate the hash to the first 32 characters, creating a strong password.
Final Touch: Adding Special Characters
Adding special characters further enhances security. Let’s generate a random special character and append it to our password:
bash
SPECIAL_CHAR=$(echo '!@#$%^&*()_-+=' | fold -w1 | shuf | head -c1) PASSWORD="${PASSWORD}${SPECIAL_CHAR}" echo $PASSWORD
This command picks a random special character from the provided list and appends it to our password.
Putting It All Together: The Complete Script
Here’s the a script combining the above elements:
bash
#!/bin/bash # Generate a password using a random number, date, time, and a special character PASSWORD="${RANDOM}${RANDOM}${RANDOM}$(date +%s%N | sha256sum | head -c32)" SPECIAL_CHAR=$(echo '!@#$%^&*()_-+=' | fold -w1 | shuf | head -c1) PASSWORD="${PASSWORD}${SPECIAL_CHAR}" echo "Your new secure password is: $PASSWORD"
Let’s next elevate our script with even more robust and unpredictable password generation techniques. I’ll introduce you to a more advanced method for creating highly secure passwords that include a mix of alphanumeric and special characters.
An Even Better Password Creation Method
We’ll start by creating a base password using a combination of the current time (in seconds and nanoseconds), random numbers, and a SHA256 hash. We’ll then append a special character to it:
bash
# Base password generation using date, time, and random numbers SPECIAL_CHARS='£$%^&*()~#<>-_+=' SPECIAL=$(echo "$SPECIAL_CHARS" | fold -w1 | shuf | head -c1) PASSWORD=$(date +%s%N${RANDOM}${RANDOM}${RANDOM} | sha256sum | cut -d ' ' -f 1 | head -c48) echo "${PASSWORD}${SPECIAL}"
In this script, SPECIAL_CHARS
holds a string of potential special characters. We use fold
, shuf
, and head
to pick one random special character from this string. The PASSWORD
is a combination of the current date and time, random numbers, and a SHA256 hash, truncated to 48 characters.
Adding a Random Number of Special Characters
Next, we enhance our password by adding a random number of special characters (between 1 and 5) to it:
bash
# Decide on a random number of special characters to add NUM_SPECIAL_CHARS=$(( RANDOM % 5 + 1 )) # Generate a string of random special characters RANDOM_SPECIALS=$(echo "$SPECIAL_CHARS" | fold -w1 | shuf | head -c$NUM_SPECIAL_CHARS) # Combine the base password and the random special characters NEWPASSWORD="${PASSWORD}${RANDOM_SPECIALS}"
Here, NUM_SPECIAL_CHARS
determines how many special characters to add. We then generate a string of random special characters of that length and append it to our base password.
Shuffling for Unpredictability
Finally, we shuffle this combined password to mix the special characters throughout, ensuring even more unpredictability:
bash
# Shuffle the combined string to mix special characters within FINAL_PASSWORD=$(echo "$NEWPASSWORD" | fold -w1 | shuf | tr -d '\n') # Output the final password echo "$FINAL_PASSWORD"
The FINAL_PASSWORD
is a shuffled version of NEWPASSWORD
, ensuring that the special characters are not just appended at the end but distributed throughout the password.
Conclusion
This advanced script showcases the true power and flexibility of Linux shell scripting. By combining various commands and techniques, we’ve created a script that generates highly secure, complex, and unpredictable passwords. This level of scripting not only enhances security but also demonstrates how shell scripting can be an invaluable tool in your Linux toolkit.
Remember, in the realm of cybersecurity, the strength of your password can make all the difference. Happy scripting and stay secure!