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88 lines
3.8 KiB
Markdown
88 lines
3.8 KiB
Markdown
# SQL Injection (SQLi) Evasion Techniques
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### 1. **Obfuscation Techniques**
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#### **1.1 Comment Insertion**
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- **Definition:** Use SQL comments to break up or hide parts of the SQL query.
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- **Example:** `1' OR 1=1--` can be obfuscated as `1' OR 1=1 /* comment */--`.
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- **Purpose:** Hide the true intent of the injected SQL code from detection mechanisms.
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#### **1.2 Encoding**
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- **Definition:** Encode the payload using various encoding schemes to evade detection.
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- **Types:**
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- **URL Encoding:** Convert characters to their URL-encoded equivalents (e.g., `%27` for `'`).
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- **Hex Encoding:** Use hexadecimal values (e.g., `0x27` for `'`).
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- **Base64 Encoding:** Encode payloads in Base64 (e.g., `JTIxPTElM0El` for `1=1`).
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- **Example:** `1' OR 1=1--` can be encoded as `1%27%20OR%201%3D1--`.
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#### **1.3 Case Manipulation**
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- **Definition:** Alter the case of SQL keywords and operators.
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- **Example:** `SELECT` can be written as `sElEcT` or `SeLeCt`.
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- **Purpose:** Bypass simple pattern-matching filters.
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#### **1.4 String Concatenation**
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- **Definition:** Break up SQL keywords or payloads using string concatenation functions.
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- **Example:** `SELECT` can be broken as `CONCAT('SE', 'LECT')`.
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- **Purpose:** Avoid detection by breaking up recognizable patterns.
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### 2. **Advanced Evasion Techniques**
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#### **2.1 Dynamic SQL Injection**
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- **Definition:** Exploit SQL queries that are dynamically constructed at runtime.
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- **Example:** Attacking a query that builds SQL commands using user input.
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- **Purpose:** Bypass static query detection and filtering.
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#### **2.2 Blind SQL Injection**
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- **Definition:** Use techniques that do not return error messages but still manipulate the database.
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- **Types:**
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- **Boolean-Based Blind SQLi:** Infer information based on changes in the response (e.g., `AND 1=1` vs. `AND 1=2`).
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- **Time-Based Blind SQLi:** Measure the time taken for responses to infer data (e.g., `SLEEP()` function).
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- **Purpose:** Extract information without visible data or errors.
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#### **2.3 Out-of-Band SQL Injection**
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- **Definition:** Use alternative channels (e.g., DNS or HTTP requests) to extract data.
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- **Example:** Using functions like `xp_cmdshell` to make the database server contact an attacker’s server.
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- **Purpose:** Bypass direct response-based filtering and detection.
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#### **2.4 Using Built-in Functions**
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- **Definition:** Exploit SQL built-in functions to gather information or manipulate queries.
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- **Example:** Using `UNION ALL SELECT` to combine results from multiple queries or `@@version` to get database version.
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- **Purpose:** Extract information without directly triggering detection mechanisms.
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### 3. **Other Evasion Techniques**
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#### **3.1 Character Substitution**
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- **Definition:** Replace SQL keywords or special characters with alternative representations.
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- **Example:** Replacing `AND` with `+AND+` or using `CHAR()` function for character substitution.
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- **Purpose:** Bypass keyword-based filters.
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#### **3.2 Using Alternative Syntax**
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- **Definition:** Exploit alternative SQL syntax or functions that achieve the same result.
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- **Example:** Using `SELECT * FROM INFORMATION_SCHEMA.TABLES` instead of `SELECT * FROM sysobjects`.
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- **Purpose:** Avoid detection by using less common SQL syntax or functions.
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#### **3.3 HTTP Parameter Pollution**
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- **Definition:** Inject malicious parameters into HTTP requests to alter the query.
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- **Example:** Adding extra parameters to a URL or POST request to manipulate the SQL query.
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- **Purpose:** Bypass input validation and filtering mechanisms.
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#### **3.4 Advanced Encoding Techniques**
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- **Definition:** Use more sophisticated encoding schemes to obscure payloads.
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- **Types:**
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- **Double Encoding:** Encode the payload twice (e.g., `%2527` for `'`).
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- **Unicode Encoding:** Use Unicode representations to obfuscate SQL keywords.
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- **Purpose:** Evade detection by making the payload less recognizable.
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