Information Technology & Cybersecurity

In this write up, we will focus mainly on the ARMv8-A exceptions, the role of ARM Trusted Firmware (that provides Secure Monitor functionality) and how the World Switch happens between Secure and Normal. If we look on the the architectural diagram of ARM Trustzone w.r.t ARMv8-A, the Execution Level is divided into four levels namely: EL0 (Secure & Non-Secure) - User Application EL1 (Secure & Non-Secure) - Kernel EL2 - Hypervisor for running different OS's simuntaneously EL3 - Security Monitor Now, whenever a normal world User Application calls for some Secure Operation, the calls goes via IOCTL call to the Linux Driver, which ultimately calls the smc instruction. To understand what the smc instruction, we have to look on the Exceptions in ARMv8 ARMv8 Exceptions In ARMv8 the exceptions are divided into two categories: Synchronous & Asynchronous.  An exception is described as synchronous if it is generated as a result of execution or attempted executi...

What if you write some piece of code that consist of VULNERABILITIES , that could lead to undesirable behavior of the flow of execution, if exploited by the hacker. One of the most common attack or exploit that is used today is a Stack Overflow type attack. Stack Overflow is an undesirable situation when the program tends to use more memory space then the call stack available. If we take a simple C program, that copies the memory from source to destination using memcpy function: #define STRING "I LOVE HACKING" char buffer[10]; memcpy(buffer, STRING, strlen(STRING)); In the above program, the actual size of buffer is 10, while memcpy will tend to copy 14 bytes of data to buffer. This will lead to overwrite some stack area that don't belong to the  buffer . In simple word, this is a vulnerability in the program, that can be exploited and which might lead to change the actual behavior of the program. Now let's see how the stacks are organized in an actual p...