Arrays & Strings: Advanced Concepts in Code Coverage and Security Testing Quiz

Explore advanced topics in arrays and strings as they relate to code coverage analysis and security testing. This quiz covers common pitfalls, mutation testing, and vulnerability detection techniques essential for ensuring software quality and resilience.

1. Boundary Testing in Arrays

   When performing code coverage analysis, which type of array input is most effective for revealing off-by-one errors in security-sensitive functions (e.g., copying user data into an array)?

   1. An array exactly at maximum allowed length
   2. An array with all identical elements
   3. An empty array
   4. An array with sorted elements

   Explanation: Testing with an array at the maximum allowed length effectively exposes off-by-one errors, which are common vulnerabilities in security-related code. Arrays with identical or sorted elements may not stress the bounds, and an empty array only checks lower bound handling. Off-by-one mistakes typically surface when just reaching the allowed capacity, making this input essential.

2. String Mutation for Security Testing

   Which string mutation is most likely to uncover missing input validation that could lead to injection vulnerabilities during automated security testing?

   1. A string containing special characters such as quotes and semicolons
   2. A string with repeating word patterns
   3. A string of only numeric digits
   4. A string in reversed order

   Explanation: Special characters like quotes and semicolons are commonly used in injection attacks and can reveal weaknesses in input validation when used during testing. Repeating patterns, numeric-only, or reversed strings do not typically exercise the code paths vulnerable to injection. This is why mutation with special characters is crucial for security testing.

3. Array Out-of-Bounds Detection

   During code quality evaluation, what is a reliable symptom that a function is susceptible to array out-of-bounds vulnerabilities?

   1. Accessing indexes based on unchecked user input
   2. Using arrays of constant size only
   3. Iterating from zero up to the array’s length
   4. Copying arrays element by element

   Explanation: Accessing indexes determined by unchecked user input can lead to out-of-bounds access, a major security flaw. Using arrays of constant size does not inherently introduce this risk, and proper iteration from zero to the array’s length is safe. Copying elements does not cause issues unless bounds are mishandled, making unchecked user input the real danger.

4. Coverage Tools and String Path Exploration

   How can automated code coverage tools improve the detection of security-relevant bugs in complex string parsing routines?

   1. By generating and executing diverse input strings that cover rare conditional branches
   2. By focusing exclusively on testing the main function with sample input
   3. By running only successful parse cases
   4. By tracking array element values during runtime

   Explanation: Automated tools that generate input strings to trigger rare parsing branches in code can uncover subtle security bugs. Only testing the main function or running successful parsing cases limits coverage. Tracking array values does not directly target string path exploration. Exploring diverse branches ensures thorough security testing.

5. Invalid String Termination Vulnerabilities

   Which scenario is most likely to lead to a security issue related to strings during quality assessment?

   1. Failure to ensure proper null termination after copying a string into a fixed-size buffer
   2. Using dynamic arrays without initialization
   3. Sorting an array of strings alphabetically
   4. Reading strings with only alphanumeric characters

   Explanation: Omitting null termination after copying can result in buffer over-reads and is a well-known security risk in string handling. Using uninitialized dynamic arrays may cause bugs, but not specifically string vulnerabilities. Sorting or using alphanumeric-only inputs does not inherently cause string termination issues.