How to Read Password in Bash [3 Practical Cases]

Taking a user password in Bash is an important task. One can utilize the read command to read passwords securely. Moreover, the openssl command provides the opportunity to encrypt passwords in an irreversible way. This article discusses three different cases of how to read a user password in Bash considering its security concern.

Key Takeaways

• Reading password from user prompt.
• Reading passwords securely using -s.
• Securing passwords using hash encryption.

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3 Cases of Reading Password in Bash

The read command is commonly used to gather user input. Similarly, it’s handy for reading passwords while keeping them hidden with the -s option. Moreover one can read passwords from files. Let’s explore different scenarios of reading passwords in Bash.

Case 1: Reading Password from Prompt

The common approach to reading a password is by prompting the requirement of the password to the user. In the following script, I will show you how to read user password from the prompt using the read command.

Steps to Follow >

❶ At first, launch an Ubuntu Terminal.

❷ Write the following command to open a file named prompt.sh in the build-in nano editor:

nano prompt.sh

❸ Copy the following scripts and paste them into nano. Press CTRL+O and ENTER to save the file; CTRL+X to exit. Alternatively, copy the following script. Paste the script in a text editor and save it as .sh file.

Script (prompt.sh) >

#!/bin/bash

# Prompt the user for a password
read -p "Enter your password: " password
echo  # Move to a new line after reading the password

# Read the new username
read -p "Enter the username to add: " new_username
# Use sudo to add a new user
echo "$password" | sudo -S useradd "$new_username"

# Check if the user was added successfully
if [ $? -eq 0 ]; then
echo "User $new_username added successfully"
else
echo "Failed to add user $new_username"
fi

❹ Use the following two commands to make both file executable:

chmod u+x prompt.sh

❺ Run the prompt.sh script by the following command:

./prompt.sh

The image shows that the program first seeks the password of the user which is given as Ubuntu. Then it executes commands for adding a new user using the given password.

Case 2: Reading Password Without Displaying It to the User in Bash

The read command can be employed to capture a user’s password without displaying it on the screen. This approach adds an extra layer of protection and keeps passwords hidden from others’ sight. -s option of the read command is used for this purpose.

Script (hiddenpass.sh) >

#!/bin/bash
# Prompt the user for a password
read -p -s "Enter your password: " password
echo  # Move to a new line after reading the password

# Read the new username
read -p "Enter the username to add: " new_username

# Use sudo to add a new user
echo "$password" | sudo -S useradd "$new_username"

# Check if the user was added successfully
if [ $? -eq 0 ]; then
  echo "User $new_username added successfully"
else
  echo "Failed to add user $new_username"
fi

Run the hiddenpass.sh script by the following command:

./hiddenpass.sh

You can see user Bin is created successfully after reading the system password from the current user. However, the given password is not displayed while reading it from the user. The  -s option of read command successfully hides the password.

Case 3: Reading Password from a Password File

Imagine having a password file where you’ve stored all your passwords. Instead of inputting the password manually through a prompt, a program can retrieve it directly from the saved file. Let’s see how it works.

Script (filepass.sh) >

#!/bin/bash

file="password.txt"
# Use 'grep' to find the password
password=$(grep "Linux :" "$file" | awk -F ': ' '{print $2}')

# Check if the password was found
if [ -z "$password" ]; then
echo "Password not found."
exit 1
else
echo "System successfully finds the password."
fi

# Read the new username
read -p "Enter the username to add: " new_username
# Use sudo to add a new user with the extracted password
echo "$password" | sudo -S useradd "$new_username"

# Check if the user was added successfully
if [ $? -eq 0 ]; then
echo "User $new_username added successfully"
else
echo "Failed to add user $new_username"
fi

Now see the password.txt file first using the command below:

cat password.txt

As you can see there are passwords for various applications stored in the password.txt file. The password for Linux is in the third line of the file.

This time run the filepass.sh script by the following command:

./filepass.sh

As you can see the program reads the password of Linux from the file. Using this password it successfully added a new user Jemmy to the system.

Echoing * (Asterisk) for Each Character while Reading Password

Someone may be confused whether a program takes password or not if nothing is displayed on the terminal. So, instead of displaying nothing one can use the following script to display an asterisk for each inputted character of the password.

Script (asterisk.sh) >

#!/bin/bash

password=""
prompt="Enter your password: "

while IFS= read -p "$prompt" -r -s -n 1 letter; do
if [[ $letter == $'\0' ]]; then
break
fi
password="$password$letter"
prompt="*"
done

echo -e "\nPassword entered: $password"

Run the asterisk.sh script by the following command:

./asterisk.sh

As evident, the script displays asterisks to validate each user input. In this instance, the user entered Ubuntu as the password, resulting in the display of six asterisks. This pattern confirms to the user that their input has been accurately captured.

How to Encrypt Password Using Hash Algorithm in Bash

One can encrypt password using openssl command for public servers. It uses various hash algorithms such as SHA-256 algorithm and a randomly generated salt to encrypt a password. Hashing is a one-way function. It means that once a password is hashed, it isn’t easy to convert it back to the original.

Script (encryption.sh) >

#!/bin/bash

# Generate a random salt
salt=$(openssl rand -base64 8)

# Get the password from the user
read -p "Enter your password: " password

# Combine the password and salt, then hash using SHA-256
hashed_password=$(echo -n "$password$salt" | openssl dgst -sha256 -binary | base64)

echo "Salt: $salt"
echo "Hashed Password: $hashed_password"

Run the encryption.sh script by the following command:

./encryption.sh

Here the password Ubuntu is hashed using openssl command. The encrypted password is displayed in the image above.

Conclusion

In conclusion, one can read a user password in Bash in various ways with different layers of protection. Moreover, one can store encrypted passwords using hash-based algorithms. I believe from now on you can take user password securely as well as encrypt password where necessary.

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