Update README.md

buffer_overflow_example/README.md

@@ -42,3 +42,81 @@ For 64 bit systems
 gcc vuln.c -o vuln -fno-stack-protector -m32
 ```
 `-fno-stack-protector` disabled the stack protection. Smashing the stack is now allowed. `-m32` made sure that the compiled binary is 32 bit. You may need to install some additional libraries to compile 32 bit binaries on 64 bit machines.
+
+## Additional Examples and References
+
+A buffer overflow is a type of software vulnerability that occurs when a program attempts to store more data in a buffer (a temporary storage area) than it can hold. This can cause the extra data to overflow into adjacent memory locations, potentially overwriting important data or instructions.
+
+Here is another example of a buffer overflow in C:
+
+```
+#include <stdio.h>
+#include <string.h>
+
+int main(int argc, char* argv[]) {
+    char buffer[5]; // Declare a buffer with a size of 5 bytes
+    strcpy(buffer, argv[1]); // Copy the first command line argument into the buffer
+    printf("%s\n", buffer); // Print the contents of the buffer
+    return 0;
+}
+```
+In this example, the program declares a `buffer` of size 5 bytes and uses the `strcpy` function to copy the first command line argument into the buffer. However, if the command line argument is longer than 5 bytes, the `strcpy` function will copy all the characters of the argument into the buffer, causing the extra characters to overflow into adjacent memory locations.
+
+A malicious attacker could exploit this vulnerability by providing a long string as an argument to the program, which can cause the program to crash or execute arbitrary code.
+
+Another example:
+
+```
+#include <stdio.h>
+
+void vulnerable_function(char* user_input) {
+    char buffer[10];
+    strcpy(buffer, user_input); // copy user input into the buffer
+    printf("Input: %s\n", buffer);
+}
+
+int main(int argc, char* argv[]) {
+    vulnerable_function(argv[1]);
+    return 0;
+}
+```
+In this example, the program has a function called `vulnerable_function` which takes a single argument, a string of user input. The function then declares a buffer of size 10 bytes and uses the `strcpy` function to copy the user input into the buffer.
+
+However, if the user input is longer than 10 bytes, the `strcpy` function will copy all the characters of the input into the buffer, causing the extra characters to overflow into adjacent memory locations.
+
+A malicious attacker could exploit this vulnerability by providing a long string as an argument to the program when it is executed, which can cause the program to crash or execute arbitrary code.
+
+There are several ways to fix a buffer overflow vulnerability. Here are a few examples:
+
+- Using a different function: Instead of using the `strcpy` function, which does not check for buffer overflow, you can use a function like `strncpy` which takes an additional argument specifying the maximum number of bytes to be copied. This can prevent overflowing the buffer.
+
+```
+strncpy(buffer, user_input, sizeof(buffer) - 1);
+buffer[sizeof(buffer) - 1] = '\0';
+```
+
+- Using a library function: You can use a library function like `snprintf` which can be used to write a limited number of characters to a buffer, making sure that the buffer is not overflown.
+
+```
+snprintf(buffer, sizeof(buffer), "%s", user_input);
+```
+
+- Input validation: You can validate the user input before it is copied into the buffer, checking if the length of the input is less than the size of the buffer.
+
+```
+if (strlen(user_input) < sizeof(buffer)) {
+    strcpy(buffer, user_input);
+} else {
+    printf("Error: input too long\n");
+    exit(1);
+}
+```
+
+- Using a safer data type: You can use a safer data type like std::string in C++, which automatically handles buffer overflow and other security issues.
+
+```
+std::string buffer;
+buffer = user_input;
+```
+
+It is important to remember that buffer overflow vulnerabilities can have serious security implications, so it is essential to ensure that your code is free of such vulnerabilities.