myshell | Simple shell program for HKU COMP3230 Principles

The ng new command will create a new workspace. So you can't use it inside a folder alread containing an angular.json file.

You can create a new angular project inside an existing workspace with the command ng g application

For exemple :

First, there are a number of mitigations that might be deployed to prevent this attack. You need to disable each one:

• ASLR: You have already disabled with sudo sysctl -w kernel.randomize_va_space=0. But a better option is to disable it only for one shell and its children: setarch $(uname -m) -R /bin/bash.
• Stack protector: The compiler can place stack canaries between the buffer and the return address on the stack, write a value into it before the buffer write operation is executed, and then just before returning, verify that it has not been changed by the buffer write operation. This can be disabled with -fno-stack-protector.
• Shadow stack: Newer processors might have a shadow stack feature (Intel CET) that when calling a function, stashes a copy of the return address away from the writable memory, which is checked against the return address when returning from the current function. This (and some other CET protections) can disabled with -fcf-protection=none.

The question does not mention it, but the addresses used in the code (along with use of long) indicate that a 32-bit system is targeted. If the system used is 64-bit, -m32 needs to be added to the compiler flags:

You should use -c option to have GCC do compilation only (create object file, no linking to build an executable) and -o option to specify the output file, not one of the input files.

parse() returns a pointer to the local array args. Since the lifetime of args ends when parse() returns, any attempt to use the return value of parse() is undefined behavior. You should allocate that array with malloc() instead (and free it later!).

What happens in my test is that the compiler notices that the return value of parse() can't legally be used (and it gives a warning!! which you should read and pay attention to!!), so it just returns NULL instead. When the child dereferences this pointer as *args to get the first argument for execvp, it segfaults and dies without calling execvp(). You could detect this if you checked the status returned by wait(), but you don't. So it just looks as if the child didn't do anything.

Oh, bonus bug: when end-of-file occurs on stdin (e.g. if you hit Ctrl-D), the string returned by fgets() will be empty and strIn[strlen(strIn)-1]='\0'; will store a null byte out of bounds. You need to test the return value of fgets().

This problem is more complex than it appears due to the interplay of the shell, the terminal, and your program.

Given that the requirements are:

1. Custom shell prompt
2. Custom commands
3. Have the shell work normally
4. Intercept the program output

My suggestion is:

1. Do the customizations from the shell side
2. Create a pty to fool programs into thinking they're writing to a terminal. In Java on Linux/Mac, a simple way to do this is via the script tool.

Here's an example shell configuration file myrc:

You need to allow egress on port 53 for DNS resolution

Error occurred because you have CC = gcc in makefile which points to compiler in host. This overrides CROSS_COMPILER set by yocto. so the binary you built hello_shell is for host (ELF 64-bit LSB executable, x86-64), which throws error while using aarch64-poky-linux-objcopy

Try removing CC = gcc from makefile