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|
use aya_ebpf::{
cty::{c_char, c_int, c_long},
helpers::{
bpf_get_current_task_btf, bpf_probe_read_kernel, bpf_probe_read_kernel_str_bytes,
bpf_probe_read_user_str_bytes, bpf_tail_call,
},
maps::PerCpuArray,
};
use fs_tracer_common::OpenSyscallBPF;
use crate::{
vmlinux::{task_struct, umode_t},
*,
};
const AT_FDCWD: c_int = -100;
const MAX_PATH: usize = 96; //TODO: 4096
#[repr(C)]
pub struct Buffer {
pub buf: [u8; MAX_PATH],
}
#[map]
static mut PATH_BUF: PerCpuArray<Buffer> = PerCpuArray::with_max_entries(1, 0);
#[map]
static mut TMP_BUF: PerCpuArray<Buffer> = PerCpuArray::with_max_entries(1, 0);
pub fn handle_sys_open(
ctx: TracePointContext,
syscall_type: SyscallType,
) -> Result<c_long, c_long> {
//info!(&ctx, "called");
match syscall_type {
SyscallType::Enter => unsafe { handle_sys_open_enter(ctx) },
SyscallType::Exit => unsafe { handle_sys_open_exit(ctx) },
}
}
unsafe fn handle_sys_open_enter(ctx: TracePointContext) -> Result<c_long, c_long> {
//info!(&ctx, "handle_sys_open_enter start");
#[repr(C)]
#[derive(Clone, Copy)]
struct OpenAtSyscallArgs {
dfd: c_int,
filename: *const c_char,
flags: c_int,
mode: umode_t,
}
let args = ctx.read_at::<OpenAtSyscallArgs>(16)?;
if args.dfd != AT_FDCWD {
return Err(1);
}
// TODO: If the path isnt relative, we already know the full path
let buf = get_buf(&PATH_BUF)?;
let filename: &str = unsafe {
core::str::from_utf8_unchecked(
bpf_probe_read_user_str_bytes(args.filename as *const u8, &mut buf.buf)
.unwrap_unchecked(),
)
};
info!(&ctx, "filename: {} dfd: {}", filename, args.dfd);
if filename.len() < 3 {
return Ok(0);
}
//let kbuf = get_buf(&PATH_BUF)?;
//info!(&ctx, "count: {}", kbuf.buf.len());
let (s, s1) = filename.split_at(0); //tODO this doesnt work
if s == "/" {
info!(&ctx, "SHIITT AINT RELATIVE BOIIIIIIIIIIIIIIIIIIIIIIII");
return Ok(0);
} else {
info!(&ctx, "relative call! {} {}", s, s1);
}
//TODO
// if filename.get(0).unwrap_unchecked() == '/' {
// return Ok(0);
//}
let mut task = bpf_get_current_task_btf() as *mut task_struct;
let pwd = get_task_pwd(&ctx, task)?;
info!(&ctx, "PWD: {}", pwd);
let tgid: u32 = ctx.tgid();
let _ = SYSCALL_ENTERS.insert(
&tgid,
&SyscallInfo::Open(OpenSyscallBPF {
pid: ctx.pid(),
dfd: args.dfd,
filename: buf.buf,
mode: args.mode,
flags: args.flags,
ret: -9999,
}),
0,
);
Ok(0)
}
unsafe fn handle_sys_open_exit(ctx: TracePointContext) -> Result<c_long, c_long> {
//info!(&ctx, "handle_sys_open_exit start");
let ret = ctx.read_at::<c_long>(16)?; //TODO: We cant use unwrap, thats why we couldnt use the aya helper fns
let tgid = ctx.tgid();
if let Some(syscall) = SYSCALL_ENTERS.get(&tgid)
&& let SyscallInfo::Open(mut syscall_open) = syscall
{
syscall_open.ret = ret;
EVENTS.output(&ctx, &SyscallInfo::Open(syscall_open), 0);
let _ = SYSCALL_ENTERS.remove(&tgid);
return Ok(0);
}
//bpf_tail_call(ctx, prog_array_map, index) //what is this
Err(0)
}
unsafe fn get_task_pwd<'a>(
ctx: &TracePointContext,
task: *const task_struct,
) -> Result<&'a str, c_long> {
let result = get_buf(&PATH_BUF)?;
let tmp_buf: &mut Buffer = get_buf(&TMP_BUF)?;
let fs = bpf_probe_read_kernel(&(*task).fs)?;
let pwd: vmlinux::path = bpf_probe_read_kernel(&(*fs).pwd)?;
let mut prev_dentry = bpf_probe_read_kernel(&pwd.dentry)?;
let mut dentry = prev_dentry;
let mut iters: usize = 0;
let mut num_chars: usize = 0;
loop {
info!(ctx, "num_chars: {}", num_chars);
let iname =
bpf_probe_read_kernel_str_bytes(&(*dentry).d_iname as *const u8, &mut tmp_buf.buf)?;
if iname.len() > 40 {
break;
}
*result.buf.as_mut_ptr().add(num_chars) = '/' as u8; //TODO: Look at this to get char
num_chars += 1;
for i in 0..iname.len() {
*result.buf.as_mut_ptr().add(num_chars) = iname[i]; //we shouldnt append but prepend
num_chars += 1;
}
iters += 1;
prev_dentry = dentry;
dentry = bpf_probe_read_kernel(&(*dentry).d_parent)?;
if dentry == prev_dentry || iters >= 2 {
//TODO: we are running out of instrs
break;
}
}
*result.buf.as_mut_ptr().add(num_chars) = 0; //idk why we have to index like this
Ok(str_from_u8_nul_utf8_unchecked(&result.buf))
}
unsafe fn get_buf<'a>(buf: &PerCpuArray<Buffer>) -> Result<&'a mut Buffer, i64> {
let ptr = buf.get_ptr_mut(0).ok_or(1)?;
Ok(&mut *ptr)
}
unsafe fn str_from_u8_nul_utf8_unchecked(utf8_src: &[u8]) -> &str {
let mut nul_range_end = utf8_src.len();
for i in 0..utf8_src.len() {
if i > 200 {
//satisfy the verifier
break;
}
if utf8_src[i] == b'\0' {
nul_range_end = i;
break;
}
}
str::from_utf8_unchecked(&utf8_src[0..nul_range_end])
}
|
