Ethical Hacker Tip: Extracting Cookies into Bash Variables for Web Requests

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When working with web applications, cookies play a crucial role in authentication and session management. Instead of manually copying and pasting cookies into your `curl` commands, you can efficiently load them from a file into a Bash variable.

Step-by-Step Implementation

1. Prepare Your Cookie File (`cookie.txt`)

Ensure your cookies are stored in a semicolon-separated format:

_utmz=utmcsr=storage.googleapis.com|utmcmd=referral|utmccn=(referral)|utmcct=/;__Secure-Cookie=whatever;

2. Load Cookies into a Bash Variable

Use the following command to read the file content into a variable:

cookie=$(<cookie.txt)

3. Verify the Variable Content

echo $cookie

Expected Output:

_utmz=utmcsr=storage.googleapis.com|utmcmd=referral|utmccn=(referral)|utmcct=/;__Secure-Cookie=whatever;

4. Use the Variable in a `curl` Request

curl -v --user-agent "googleBot" "https://voice.google.com" --cookie "$cookie"

5. Enable Verbose Debugging with `–trace-ascii`

For detailed request/response logging:

curl -v --user-agent "googleBot" "https://voice.google.com" --cookie "$cookie" --trace-ascii voicetrace.txt

View the trace file:

cat voicetrace.txt

You Should Know: Advanced curl and Bash Techniques

1. Automating Cookie Extraction from Browser

  • Chrome/Edge:
    Use DevTools (F12 → `Application` → Cookies) and export cookies via extensions like EditThisCookie.
  • Firefox:
    Use Cookie-Editor extension to export cookies in JSON/text format.

2. Modifying Cookies Dynamically

Use `sed` or `awk` to modify cookies before sending:

modified_cookie=$(echo $cookie | sed 's/old_cookie=new_cookie/g')
curl --cookie "$modified_cookie" "https://example.com"

3. Handling Multiple Cookies

If cookies are stored in separate files:

cookie1=$(<cookie1.txt) 
cookie2=$(<cookie2.txt) 
combined_cookie="$cookie1;$cookie2" 
curl --cookie "$combined_cookie" "https://example.com"

4. Using Cookies in Python (Requests Library)

import requests 
cookies = {"_utmz": "value", "__Secure-Cookie": "value"} 
response = requests.get("https://example.com", cookies=cookies) 
print(response.text)

5. Debugging HTTP Requests Further

– `–trace-time` (Logs with timestamps)
– `–proxy` (Route traffic through Burp/Proxy)

curl --trace-time --proxy http://127.0.0.1:8080 "https://example.com"

6. Extracting Cookies from curl Responses

curl -v "https://example.com" --cookie-jar saved_cookies.txt

Reuse cookies:

curl --cookie saved_cookies.txt "https://example.com"

What Undercode Say

Managing cookies efficiently is critical in penetration testing, web scraping, and automation. Using Bash variables simplifies repetitive tasks, while `curl` debugging flags (--trace-ascii, --verbose) enhance visibility into HTTP transactions.

Additional Linux/Windows Commands for Web Testing

  • Linux:
    Extract specific cookie using grep 
grep -oP 'session_id=\K[^;]+' cookie.txt

Monitor HTTP traffic in real-time 
tcpdump -i eth0 -s 0 -A 'tcp port 80'

Check SSL/TLS handshake 
openssl s_client -connect example.com:443

  • Windows (PowerShell):

    Extract cookies from a web request 
$response = Invoke-WebRequest -Uri "https://example.com" -SessionVariable session 
$session.Cookies.GetCookies("https://example.com")

Send a request with cookies 
Invoke-WebRequest -Uri "https://example.com" -WebSession $session

Expected Output:

A structured, reusable method for handling cookies in security testing and automation workflows.

Prediction

As web applications grow more complex, automated cookie management will become essential in cybersecurity, particularly in red-team operations and API testing. Expect more tools integrating cookie manipulation features.

References:

Reported By: Activity 7325622348886249474 – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅

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