How to use the command 'systemd-creds' (with examples)

The systemd-creds command is a versatile tool designed for handling service credentials securely within a Linux environment. As part of the broader systemd ecosystem, it provides functionality to list, show, encrypt, and decrypt credentials. These capabilities are essential for managing sensitive information within system services, allowing for a more secure and controlled environment. Through the following examples, you will gain a deeper understanding of how to effectively use ‘systemd-creds’ for various use cases, from encrypting files to managing text-based credentials.

Use case 1: Encrypt a file and set a specific name

Code:

systemd-creds encrypt --name=name path/to/input_file path/to/output

Motivation:

In scenarios where you need to securely transfer a file containing sensitive information, encryption becomes necessary. This ensures that even if the file is intercepted, unauthorized parties cannot access its contents. By assigning a specific name, you can easily reference and manage the credentials later without having to recall the complex file paths.

Explanation:

• encrypt: This specifies that the action you want to perform is encryption.
• --name=name: The --name option allows you to assign a specific identifier to this set of credentials. This is useful for categorizing or referencing multiple encrypted items.
• path/to/input_file: This is the path to the original, unencrypted file that you wish to protect.
• path/to/output: This is the destination path where the encrypted result will be saved.

Example Output:

Upon running the command, you won’t see a direct output unless there’s an error. Instead, the encrypted file will be written to the specified output location, ready for secure storage or transfer.

Use case 2: Decrypt the file again

Code:

systemd-creds decrypt path/to/input_file path/to/output_file

Motivation:

Once you have received an encrypted file, you’ll need to decrypt it to access its contents. Decryption is a critical step to retrieve the original data in a readable format. This process must be handled carefully to maintain the security and integrity of the data.

Explanation:

• decrypt: Indicates that the operation to perform is decryption.
• path/to/input_file: Refers to the encrypted file that needs to be converted back to its original form.
• path/to/output_file: Designates where the decrypted file should be stored.

Example Output:

Decryption does not produce a visible output upon successful completion. The decrypted content will be available in the specified output file, mirroring the original data prior to encryption.

Use case 3: Encrypt text from stdin

Code:

echo -n text | systemd-creds encrypt --name=name - path/to/output

Motivation:

Encrypting text input directly via standard input (stdin) can be particularly useful for scripting or automated processes, where input data is generated dynamically. This method allows you to handle sensitive data programmatically without storing it first in a physical file.

Explanation:

• echo -n text: Uses the echo command to send text data directly to systemd-creds, with -n suppressing the new line.
• |: The pipe symbol directs the output of echo into the systemd-creds command.
• encrypt: Specifies that the operation is encryption.
• --name=name: Assigns a reference name to the credentials.
• -: Indicates that the input is being read from stdin.
• path/to/output: Location for storing the encrypted data.

Example Output:

The output is contained in the specified file, with no visible output on the terminal. The encrypted text is safely stored at the output path.

Use case 4: Encrypt the text and append it to the service file

Code:

echo -n text | systemd-creds encrypt --name=name --pretty - - >> service

Motivation:

When administering system services, credentials can be appended directly to service configuration files, streamlining the process of service management and deployment. This is particularly beneficial in managing services that require credentials to function securely but efficiently.

Explanation:

• echo -n text: The echo command outputs the text data for encryption.
• |: Pipes the data into systemd-creds.
• encrypt: Signifies encryption of the data.
• --name=name: Provides a name tag for organizational tracking.
• --pretty: Formats the output with a human-readable structure.
• - -: States that input is from stdin and output should append to the existing stream respectively.
• >> service: Appends the encrypted content to a service file.

Example Output:

The command appends the encrypted text to a specified service file (typically located in $CREDENTIALS_DIRECTORY). The text is securely integrated within the service’s credentials configuration.

Use case 5: Create a credential that is only valid until the given timestamp

Code:

systemd-creds encrypt --not-after="timestamp" path/to/input_file path/to/output_file

Motivation:

Time-bound credentials are crucial for enhancing security by limiting the lifespan of sensitive information. They ensure that even if credentials are compromised, they cannot be misused indefinitely. This practice is particularly helpful in temporary access scenarios or as part of a larger security strategy.

Explanation:

• encrypt: Specifies the desire to encrypt data.
• --not-after="timestamp": Sets an expiration date for the credentials. The timestamp dictates when the credentials will become invalid.
• path/to/input_file: Denotes the original file containing sensitive data.
• path/to/output_file: Marks the destination for the time-bound encrypted data.

Example Output:

The file at the output path contains encrypted credentials which are set to expire at the given timestamp, ensuring that they can only be used up until that specified date and time.

Conclusion:

Mastering the systemd-creds command allows system administrators and developers to enhance the security of their applications and services. By encrypting sensitive files and text, handling them securely within services, and implementing time-sensitive credentialing, users can manage their systems with greater confidence and efficiency. The examples provided demonstrate practical use cases essential for robust security management.