Signed URLs for temporary access in GCP - Mini Project: Build & Apply

Signed URLs for temporary access

📖 Scenario: You work for a company that stores private files in Google Cloud Storage. You want to share a file temporarily with a client without making it public. To do this, you will create a signed URL that allows access to the file for a limited time.

🎯 Goal: Create a signed URL for a Google Cloud Storage object that grants temporary access to the file.

📋 What You'll Learn

Create a variable with the bucket name and object name

Set an expiration time for the signed URL

Generate the signed URL using Google Cloud Storage client

Output the signed URL for sharing

💡 Why This Matters

🌍 Real World

Signed URLs let you share private files securely for a limited time without making them public.

💼 Career

Cloud engineers and developers often use signed URLs to control access to storage resources in real projects.

1

Set up bucket and object names

Create two variables called bucket_name and object_name with the exact values "my-private-bucket" and "documents/report.pdf" respectively.

GCP

# Create variables for bucket and object names
# Your code here

Hint

Think of bucket_name as the folder and object_name as the file path inside it.

2

Set the expiration time for the signed URL

Create a variable called expiration_time and set it to 3600 seconds (which is 1 hour).

GCP

bucket_name = "my-private-bucket"
object_name = "documents/report.pdf"
# Set expiration time in seconds
# Your code here

Hint

The expiration time controls how long the signed URL will work.

3

Generate the signed URL

Import storage from google.cloud and datetime, timedelta from datetime. Create a storage.Client() instance called client. Use client.bucket(bucket_name) to get the bucket and bucket.blob(object_name) to get the blob. Compute expiration = datetime.utcnow() + timedelta(seconds=expiration_time). Then call blob.generate_signed_url(expiration=expiration) and save the result in a variable called signed_url.

GCP

bucket_name = "my-private-bucket"
object_name = "documents/report.pdf"
expiration_time = 3600
# Import modules
# Compute expiration datetime
# Create client, get bucket/blob, generate signed URL
# Your code here

Hint

Use the Google Cloud Storage client library to create the signed URL.

4

Complete the code to output the signed URL

Add a line that assigns the signed_url variable to a variable called temporary_access_link.

GCP

from google.cloud import storage
from datetime import datetime, timedelta

bucket_name = "my-private-bucket"
object_name = "documents/report.pdf"
expiration_time = 3600

expiration = datetime.utcnow() + timedelta(seconds=expiration_time)
client = storage.Client()
bucket = client.bucket(bucket_name)
blob = bucket.blob(object_name)
signed_url = blob.generate_signed_url(expiration=expiration)
# Assign signed_url to temporary_access_link
# Your code here

Hint

This variable will hold the URL you can share with others.

Practice

1. What is the main purpose of a signed URL in Google Cloud Storage?

easy

A. To permanently make a file public to everyone

B. To encrypt a file stored in the bucket

C. To provide temporary, secure access to a file without making it public

D. To delete a file from the bucket automatically

Solution

1. Step 1: Understand what signed URLs do

   Signed URLs allow access to a file for a limited time without changing its public status.

2. Step 2: Compare options

   Only To provide temporary, secure access to a file without making it public describes temporary, secure access without making the file public.

3. Final Answer:

   To provide temporary, secure access to a file without making it public -> Option C

4. Quick Check:

   Signed URL = Temporary secure access [OK]

Hint: Signed URLs = temporary access without public exposure [OK]

Common Mistakes:

• Thinking signed URLs make files permanently public
• Confusing signed URLs with encryption
• Assuming signed URLs delete files

2. Which gcloud command correctly creates a signed URL valid for 1 hour to download a file named photo.jpg from bucket my-bucket?

easy

A. gcloud storage signed-urls create gs://my-bucket/photo.jpg --duration=1h

B. gcloud storage signed-url create gs://my-bucket/photo.jpg --valid-for=1h

C. gcloud storage signed-url generate gs://my-bucket/photo.jpg --duration=60m

D. gcloud storage url-sign create gs://my-bucket/photo.jpg --time=1h

Solution

1. Step 1: Identify correct command syntax

   The correct command uses 'gcloud storage signed-urls create' with '--duration' to specify time.

2. Step 2: Check options for correct flags and command

   gcloud storage signed-urls create gs://my-bucket/photo.jpg --duration=1h matches the correct syntax and flag '--duration=1h'. Others use wrong flags or commands.

3. Final Answer:

   gcloud storage signed-urls create gs://my-bucket/photo.jpg --duration=1h -> Option A

4. Quick Check:

   Correct command + --duration flag = gcloud storage signed-urls create gs://my-bucket/photo.jpg --duration=1h [OK]

Hint: Use 'signed-urls create' with '--duration' for time [OK]

Common Mistakes:

• Using incorrect flags like --valid-for or --time
• Using 'generate' instead of 'create'
• Mixing command order or bucket syntax

3. What will happen if you try to use a signed URL after its expiration time?

medium

A. The signed URL will return an error indicating access denied

B. The file will be accessible without restrictions

C. The signed URL will automatically renew for another period

D. The file will be deleted from the bucket

Solution

1. Step 1: Understand signed URL expiration

   Signed URLs only allow access during their valid time window.

2. Step 2: Identify behavior after expiration

   After expiration, access is denied and an error is returned.

3. Final Answer:

   The signed URL will return an error indicating access denied -> Option A

4. Quick Check:

   Expired signed URL = Access denied error [OK]

Hint: Expired signed URLs deny access with error [OK]

Common Mistakes:

• Assuming URLs auto-renew after expiration
• Thinking files become public after expiration
• Believing files get deleted automatically

4. You created a signed URL with the command gcloud storage signed-urls create gs://my-bucket/file.txt --duration=30m, but users report they cannot access the file. What is the most likely cause?

medium

A. The bucket name is incorrect or does not exist

B. The file file.txt is missing or misspelled in the bucket

C. The signed URL duration is too long

D. Signed URLs do not work for text files

Solution

1. Step 1: Check bucket and file existence

   If the file name is wrong or missing, access via signed URL fails.

2. Step 2: Evaluate other options

   Bucket name error would cause different error; duration too long is allowed; file type does not restrict signed URLs.

3. Final Answer:

   The file file.txt is missing or misspelled in the bucket -> Option B

4. Quick Check:

   Missing file = Access failure [OK]

Hint: Check file name and existence if signed URL fails [OK]

Common Mistakes:

• Assuming duration too long blocks access
• Believing signed URLs depend on file type
• Ignoring typos in file or bucket names

5. You want to share a file securely with a partner for exactly 2 hours, but only allow them to upload a new version, not download the existing one. Which approach using signed URLs is best?

hard

A. Create a signed URL with DELETE method and 2-hour duration

B. Create a signed URL with GET method and 2-hour duration for downloading

C. Make the file public and send the link

D. Create a signed URL with PUT method and 2-hour duration for uploading

Solution

1. Step 1: Understand HTTP methods for signed URLs

   PUT allows uploading or replacing a file; GET allows downloading; DELETE removes the file.

2. Step 2: Match requirement to method

   To allow upload but not download, use a signed URL with PUT method and set duration to 2 hours.

3. Final Answer:

   Create a signed URL with PUT method and 2-hour duration for uploading -> Option D

4. Quick Check:

   Upload access = PUT method signed URL [OK]

Hint: Use PUT signed URL to allow upload only [OK]

Common Mistakes:

• Using GET method which allows download
• Making file public exposes it permanently
• Using DELETE method deletes the file