Use memfd for hybrid QR code #179
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -1,3 +1,4 @@ | ||
| pub mod client; | ||
| pub mod memfd; | ||
| pub mod model; | ||
| pub mod server; |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,118 @@ | ||
| use std::{ | ||
| io::{self, ErrorKind}, | ||
| mem::MaybeUninit, | ||
| os::{ | ||
| fd::{AsRawFd, FromRawFd, OwnedFd}, | ||
| raw::c_void, | ||
| }, | ||
| }; | ||
|
|
||
| use libc::{ | ||
| ftruncate, mmap, off_t, SYS_memfd_secret, MAP_SHARED, O_CLOEXEC, PROT_READ, PROT_WRITE, | ||
| }; | ||
| use zeroize::Zeroize; | ||
|
|
||
| pub fn read_secret(pin_fd: std::os::fd::OwnedFd) -> Result<String, std::io::Error> { | ||
| // Get pin length | ||
| let len = { | ||
| let mut stat_buf = MaybeUninit::<libc::stat>::uninit(); | ||
| let res = unsafe { libc::fstat(pin_fd.as_raw_fd(), stat_buf.as_mut_ptr()) }; | ||
| if res == -1 { | ||
| return Err(io::Error::last_os_error()); | ||
| } | ||
| let stat_buf = unsafe { stat_buf.assume_init() }; | ||
| usize::try_from(stat_buf.st_size) | ||
| .map_err(|_| io::Error::new(ErrorKind::FileTooLarge, "pin is too large"))? | ||
| }; | ||
|
|
||
| // map the memory from the file descriptor | ||
| let ptr = unsafe { | ||
| let ptr = libc::mmap( | ||
| std::ptr::null_mut(), | ||
| 4096, | ||
| PROT_READ | PROT_WRITE, | ||
| MAP_SHARED, | ||
| pin_fd.as_raw_fd(), | ||
| 0, | ||
| ); | ||
| if ptr == usize::MAX as *mut c_void { | ||
| return Err(std::io::Error::last_os_error()); | ||
| } | ||
| ptr as *const u8 | ||
| }; | ||
|
|
||
| // Copy the bytes. | ||
| let buf = unsafe { | ||
| let mut buf: Vec<u8> = Vec::with_capacity(len); | ||
| ptr.copy_to_nonoverlapping(buf.as_mut_ptr().cast(), len); | ||
| buf.set_len(len); | ||
| buf | ||
| }; | ||
|
|
||
| // Clean up mapping | ||
| unsafe { | ||
| if libc::munmap(ptr as *mut c_void, 4096) == -1 { | ||
| return Err(std::io::Error::last_os_error()); | ||
| } | ||
| } | ||
| drop(pin_fd); | ||
|
|
||
| String::from_utf8(buf).map_err(|_| { | ||
| std::io::Error::new( | ||
| std::io::ErrorKind::InvalidData, | ||
| "invalid UTF-8 data found in buffer", | ||
| ) | ||
| }) | ||
| } | ||
|
|
||
| pub fn write_secret(mut secret: Vec<u8>, max_len: usize) -> Result<OwnedFd, std::io::Error> { | ||
| let bytes_len = if secret.len() <= max_len { | ||
| secret.len() as u8 | ||
| } else { | ||
| return Err(io::Error::new( | ||
| ErrorKind::FileTooLarge, | ||
| "value is too large", | ||
| )); | ||
| }; | ||
|
|
||
| // Open memfd_secret | ||
| let ret: i64 = unsafe { libc::syscall(SYS_memfd_secret, O_CLOEXEC) }; | ||
| if ret == -1 { | ||
| return Err(std::io::Error::last_os_error()); | ||
| } | ||
| let fd = i32::try_from(ret).map_err(|_| std::io::Error::other("invalid file descriptor"))?; | ||
| if unsafe { ftruncate(fd, bytes_len as off_t) } == -1 { | ||
| return Err(std::io::Error::last_os_error()); | ||
|
Member
There was a problem hiding this comment. Leaks
Member
There was a problem hiding this comment. You can still use |
||
| } | ||
|
|
||
| let ptr = unsafe { | ||
| let ptr = mmap( | ||
|
Member
There was a problem hiding this comment. Nit: Ideally wrap in a struct with |
||
| std::ptr::null_mut(), | ||
| 4096, | ||
| PROT_READ | PROT_WRITE, | ||
| MAP_SHARED, | ||
| fd, | ||
| 0, | ||
| ); | ||
| if ptr == usize::MAX as *mut c_void { | ||
| return Err(std::io::Error::last_os_error()); | ||
| } | ||
| // ptr as *mut u8 | ||
| ptr | ||
| }; | ||
|
|
||
| // Copy the data | ||
| unsafe { | ||
| ptr.copy_from_nonoverlapping(secret.as_ptr().cast(), secret.len()); | ||
| } | ||
|
|
||
| // Cleanup | ||
| if unsafe { libc::munmap(ptr, 4096) } == -1 { | ||
| return Err(std::io::Error::last_os_error()); | ||
| } | ||
| secret.zeroize(); | ||
| drop(secret); | ||
|
|
||
| let owned_fd = unsafe { OwnedFd::from_raw_fd(fd) }; | ||
| Ok(owned_fd) | ||
| } | ||
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max_len here is CTAP_HYBRID_QR_CODE_MAX_LEN (4k). Won't fit in u8.
usize?
Alternatively we could reduce CTAP_HYBRID_QR_CODE_MAX_LEN until PQ, I think we're comfortably below 255 right now.