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Merge remote-tracking branch 'isis/bug25185'

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This commit is contained in:
Nick Mathewson 2018-02-15 20:35:30 -05:00
commit bda1dfb9e0
4 changed files with 170 additions and 132 deletions
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34
src/rust/protover/ffi.rs
View File

@ -12,9 +12,6 @@ use std::ffi::CString;
use protover::*;
use smartlist::*;
use tor_allocate::allocate_and_copy_string;
use tor_util::strings::byte_slice_is_c_like;
use tor_util::strings::empty_static_cstr;
/// Translate C enums to Rust Proto enums, using the integer value of the C
/// enum to map to its associated Rust enum
@ -143,18 +140,7 @@ pub extern "C" fn protocol_list_supports_protocol_or_later(
pub extern "C" fn protover_get_supported_protocols() -> *const c_char {
let supported: &'static CStr;
// If we're going to pass it to C, there cannot be any intermediate NUL
// bytes. An assert is okay here, since changing the const byte slice
// in protover.rs to contain a NUL byte somewhere in the middle would be a
// programming error.
assert!(byte_slice_is_c_like(SUPPORTED_PROTOCOLS));
// It's okay to unwrap the result of this function because
// we can see that the bytes we're passing into it 1) are valid UTF-8,
// 2) have no intermediate NUL bytes, and 3) are terminated with a NUL
// byte.
supported = CStr::from_bytes_with_nul(SUPPORTED_PROTOCOLS).unwrap();
supported = get_supported_protocols_cstr();
supported.as_ptr()
}
@ -202,10 +188,9 @@ pub extern "C" fn protover_is_supported_here(
#[no_mangle]
pub extern "C" fn protover_compute_for_old_tor(version: *const c_char) -> *const c_char {
let supported: &'static CStr;
let elder_protocols: &'static [u8];
let empty: &'static CStr;
empty = empty_static_cstr();
empty = cstr!("");
if version.is_null() {
return empty.as_ptr();
@ -220,19 +205,6 @@ pub extern "C" fn protover_compute_for_old_tor(version: *const c_char) -> *const
Err(_) => return empty.as_ptr(),
};
elder_protocols = compute_for_old_tor(&version);
// If we're going to pass it to C, there cannot be any intermediate NUL
// bytes. An assert is okay here, since changing the const byte slice
// in protover.rs to contain a NUL byte somewhere in the middle would be a
// programming error.
assert!(byte_slice_is_c_like(elder_protocols));
// It's okay to unwrap the result of this function because
// we can see that the bytes we're passing into it 1) are valid UTF-8,
// 2) have no intermediate NUL bytes, and 3) are terminated with a NUL
// byte.
supported = CStr::from_bytes_with_nul(elder_protocols).unwrap_or(empty);
supported = compute_for_old_tor(&version);
supported.as_ptr()
}

1
src/rust/protover/lib.rs
View File

@ -26,6 +26,7 @@ extern crate libc;
extern crate smartlist;
extern crate external;
extern crate tor_allocate;
#[macro_use]
extern crate tor_util;
mod protover;

95
src/rust/protover/protover.rs
View File

@ -5,14 +5,13 @@ use external::c_tor_version_as_new_as;
use std::str;
use std::str::FromStr;
use std::ffi::CStr;
use std::fmt;
use std::collections::{HashMap, HashSet};
use std::ops::Range;
use std::string::String;
use std::u32;
use tor_util::strings::NUL_BYTE;
/// The first version of Tor that included "proto" entries in its descriptors.
/// Authorities should use this to decide whether to guess proto lines.
///
@ -26,30 +25,6 @@ const FIRST_TOR_VERSION_TO_ADVERTISE_PROTOCOLS: &'static str = "0.2.9.3-alpha";
/// C_RUST_COUPLED: src/or/protover.c `MAX_PROTOCOLS_TO_EXPAND`
const MAX_PROTOCOLS_TO_EXPAND: usize = (1<<16);
/// Currently supported protocols and their versions, as a byte-slice.
///
/// # Warning
///
/// This byte-slice ends in a NUL byte. This is so that we can directly convert
/// it to an `&'static CStr` in the FFI code, in order to hand the static string
/// to C in a way that is compatible with C static strings.
///
/// Rust code which wishes to accesses this string should use
/// `protover::get_supported_protocols()` instead.
///
/// C_RUST_COUPLED: src/or/protover.c `protover_get_supported_protocols`
pub(crate) const SUPPORTED_PROTOCOLS: &'static [u8] =
b"Cons=1-2 \
Desc=1-2 \
DirCache=1-2 \
HSDir=1-2 \
HSIntro=3-4 \
HSRend=1-2 \
Link=1-5 \
LinkAuth=1,3 \
Microdesc=1-2 \
Relay=1-2\0";
/// Known subprotocols in Tor. Indicates which subprotocol a relay supports.
///
/// C_RUST_COUPLED: src/or/protover.h `protocol_type_t`
@ -97,21 +72,51 @@ impl FromStr for Proto {
}
}
/// Get the string representation of current supported protocols
/// Get a CStr representation of current supported protocols, for
/// passing to C, or for converting to a `&str` for Rust.
///
/// # Returns
///
/// A `String` whose value is the existing protocols supported by tor.
/// An `&'static CStr` whose value is the existing protocols supported by tor.
/// Returned data is in the format as follows:
///
/// "HSDir=1-1 LinkAuth=1"
///
pub fn get_supported_protocols() -> &'static str {
// The `len() - 1` is to remove the NUL byte.
// The `unwrap` is safe becauase we SUPPORTED_PROTOCOLS is under
// our control.
str::from_utf8(&SUPPORTED_PROTOCOLS[..SUPPORTED_PROTOCOLS.len() - 1])
.unwrap_or("")
/// # Note
///
/// Rust code can use the `&'static CStr` as a normal `&'a str` by
/// calling `protover::get_supported_protocols`.
///
// C_RUST_COUPLED: src/or/protover.c `protover_get_supported_protocols`
pub(crate) fn get_supported_protocols_cstr() -> &'static CStr {
cstr!("Cons=1-2 \
Desc=1-2 \
DirCache=1-2 \
HSDir=1-2 \
HSIntro=3-4 \
HSRend=1-2 \
Link=1-5 \
LinkAuth=1,3 \
Microdesc=1-2 \
Relay=1-2")
}
/// Get a string representation of current supported protocols.
///
/// # Returns
///
/// An `&'a str` whose value is the existing protocols supported by tor.
/// Returned data is in the format as follows:
///
/// "HSDir=1-1 LinkAuth=1"
pub fn get_supported_protocols<'a>() -> &'a str {
let supported_cstr: &'static CStr = get_supported_protocols_cstr();
let supported: &str = match supported_cstr.to_str() {
Ok(x) => x,
Err(_) => "",
};
supported
}
pub struct SupportedProtocols(HashMap<Proto, Versions>);
@ -754,7 +759,7 @@ pub fn is_supported_here(proto: Proto, vers: Version) -> bool {
///
/// # Returns
///
/// A `&'static [u8]` encoding a list of protocol names and supported
/// A `&'static CStr` encoding a list of protocol names and supported
/// versions. The string takes the following format:
///
/// "HSDir=1-1 LinkAuth=1"
@ -763,27 +768,29 @@ pub fn is_supported_here(proto: Proto, vers: Version) -> bool {
/// only for tor versions older than FIRST_TOR_VERSION_TO_ADVERTISE_PROTOCOLS.
///
/// C_RUST_COUPLED: src/rust/protover.c `compute_for_old_tor`
pub fn compute_for_old_tor(version: &str) -> &'static [u8] {
pub fn compute_for_old_tor(version: &str) -> &'static CStr {
let empty: &'static CStr = cstr!("");
if c_tor_version_as_new_as(version, FIRST_TOR_VERSION_TO_ADVERTISE_PROTOCOLS) {
return NUL_BYTE;
return empty;
}
if c_tor_version_as_new_as(version, "0.2.9.1-alpha") {
return b"Cons=1-2 Desc=1-2 DirCache=1 HSDir=1 HSIntro=3 HSRend=1-2 \
Link=1-4 LinkAuth=1 Microdesc=1-2 Relay=1-2\0";
return cstr!("Cons=1-2 Desc=1-2 DirCache=1 HSDir=1 HSIntro=3 HSRend=1-2 \
Link=1-4 LinkAuth=1 Microdesc=1-2 Relay=1-2");
}
if c_tor_version_as_new_as(version, "0.2.7.5") {
return b"Cons=1-2 Desc=1-2 DirCache=1 HSDir=1 HSIntro=3 HSRend=1 \
Link=1-4 LinkAuth=1 Microdesc=1-2 Relay=1-2\0";
return cstr!("Cons=1-2 Desc=1-2 DirCache=1 HSDir=1 HSIntro=3 HSRend=1 \
Link=1-4 LinkAuth=1 Microdesc=1-2 Relay=1-2");
}
if c_tor_version_as_new_as(version, "0.2.4.19") {
return b"Cons=1 Desc=1 DirCache=1 HSDir=1 HSIntro=3 HSRend=1 \
Link=1-4 LinkAuth=1 Microdesc=1 Relay=1-2\0";
return cstr!("Cons=1 Desc=1 DirCache=1 HSDir=1 HSIntro=3 HSRend=1 \
Link=1-4 LinkAuth=1 Microdesc=1 Relay=1-2");
}
NUL_BYTE
empty
}
#[cfg(test)]

172
src/rust/tor_util/strings.rs
View File

@ -3,80 +3,138 @@
//! Utilities for working with static strings.
use std::ffi::CStr;
/// A byte-array containing a single NUL byte (`b"\0"`).
pub const NUL_BYTE: &'static [u8] = b"\0";
/// Determine if a byte slice is a C-like string.
///
/// These checks guarantee that:
///
/// 1. there are no intermediate NUL bytes
/// 2. the last byte *is* a NUL byte
/// Create a `CStr` from a literal byte slice, appending a NUL byte to it first.
///
/// # Warning
///
/// This function does _not_ guarantee that the bytes represent any valid
/// encoding such as ASCII or UTF-8.
/// The literal byte slice which is taken as an argument *MUST NOT* have any NUL
/// bytes (`b"\0"`) in it, anywhere, or else an empty string will be returned
/// (`CStr::from_bytes_with_nul_unchecked(b"\0")`) so as to avoid `panic!()`ing.
///
/// # Examples
///
/// ```
/// # use tor_util::strings::byte_slice_is_c_like;
/// #
/// let bytes: &[u8] = b"foo bar baz";
/// #[macro_use]
/// extern crate tor_util;
///
/// assert!(byte_slice_is_c_like(&bytes) == false);
///
/// let bytes: &[u8] = b"foo\0bar baz";
///
/// assert!(byte_slice_is_c_like(&bytes) == false);
///
/// let bytes: &[u8] = b"foo bar baz\0";
///
/// assert!(byte_slice_is_c_like(&bytes) == true);
/// ```
pub fn byte_slice_is_c_like(bytes: &[u8]) -> bool {
if !bytes[..bytes.len() - 1].contains(&0x00) && bytes[bytes.len() - 1] == 0x00 {
return true;
}
false
}
/// Get a static `CStr` containing a single `NUL_BYTE`.
///
/// # Examples
///
/// When used as follows in a Rust FFI function, which could be called
/// from C:
///
/// ```
/// # extern crate libc;
/// # extern crate tor_util;
/// #
/// # use tor_util::strings::empty_static_cstr;
/// use libc::c_char;
/// use std::ffi::CStr;
///
/// pub extern "C" fn give_c_code_an_empty_static_string() -> *const c_char {
/// let empty: &'static CStr = empty_static_cstr();
/// # fn do_test() -> Result<&'static CStr, &'static str> {
/// let message: &'static str = "This is a test of the tsunami warning system.";
/// let tuesday: &'static CStr;
/// let original: &str;
///
/// empty.as_ptr()
/// }
/// tuesday = cstr!("This is a test of the tsunami warning system.");
/// original = tuesday.to_str().or(Err("Couldn't unwrap CStr!"))?;
///
/// assert!(original == message);
/// #
/// # Ok(tuesday)
/// # }
/// # fn main() {
/// # give_c_code_an_empty_static_string();
/// # do_test(); // so that we can use the ? operator in the test
/// # }
/// ```
/// It is also possible to pass several string literals to this macro. They
/// will be concatenated together in the order of the arguments, unmodified,
/// before finally being suffixed with a NUL byte:
///
/// This equates to an "empty" `const char*` static string in C.
pub fn empty_static_cstr() -> &'static CStr {
let empty: &'static CStr;
/// ```
/// #[macro_use]
/// extern crate tor_util;
/// #
/// # use std::ffi::CStr;
/// #
/// # fn do_test() -> Result<&'static CStr, &'static str> {
///
/// let quux: &'static CStr = cstr!("foo", "bar", "baz");
/// let orig: &'static str = quux.to_str().or(Err("Couldn't unwrap CStr!"))?;
///
/// assert!(orig == "foobarbaz");
/// # Ok(quux)
/// # }
/// # fn main() {
/// # do_test(); // so that we can use the ? operator in the test
/// # }
/// ```
/// This is useful for passing static strings to C from Rust FFI code. To do so
/// so, use the `.as_ptr()` method on the resulting `&'static CStr` to convert
/// it to the Rust equivalent of a C `const char*`:
///
/// ```
/// #[macro_use]
/// extern crate tor_util;
///
/// use std::ffi::CStr;
/// use std::os::raw::c_char;
///
/// pub extern "C" fn give_static_borrowed_string_to_c() -> *const c_char {
/// let hello: &'static CStr = cstr!("Hello, language my parents wrote.");
///
/// hello.as_ptr()
/// }
/// # fn main() {
/// # let greetings = give_static_borrowed_string_to_c();
/// # }
/// ```
/// Note that the C code this static borrowed string is passed to *MUST NOT*
/// attempt to free the memory for the string.
///
/// # Note
///
/// An unfortunate limitation of the rustc compiler (as of 1.25.0-nightly), is
/// that the above code compiles, however if we were to change the assignment of
/// `tuesday` as follows, it will fail to compile, because Rust macros are
/// expanded at parse time, and at parse time there is no symbols table
/// available.
///
/// ```ignore
/// tuesday = cstr!(message);
/// ```
/// with the error message `error: expected a literal`.
///
/// # Returns
///
/// If the string literals passed as arguments contain no NUL bytes anywhere,
/// then an `&'static CStr` containing the (concatenated) bytes of the string
/// literal(s) passed as arguments, with a NUL byte appended, is returned.
/// Otherwise, an `&'static CStr` containing a single NUL byte is returned (an
/// "empty" string in C).
#[macro_export]
macro_rules! cstr {
($($bytes:expr),*) => (
::std::ffi::CStr::from_bytes_with_nul(
concat!($($bytes),*, "\0").as_bytes()
).unwrap_or(
unsafe{
::std::ffi::CStr::from_bytes_with_nul_unchecked(b"\0")
}
)
)
}
unsafe {
empty = CStr::from_bytes_with_nul_unchecked(NUL_BYTE);
#[cfg(test)]
mod test {
use std::ffi::CStr;
#[test]
fn cstr_macro() {
let _: &'static CStr = cstr!("boo");
}
empty
#[test]
fn cstr_macro_multi_input() {
let quux: &'static CStr = cstr!("foo", "bar", "baz");
assert!(quux.to_str().unwrap() == "foobarbaz");
}
#[test]
fn cstr_macro_bad_input() {
let waving: &'static CStr = cstr!("waving not drowning o/");
let drowning: &'static CStr = cstr!("\0 drowning not waving");
assert!(waving.to_str().unwrap() == "waving not drowning o/");
assert!(drowning.to_str().unwrap() == "")
}
}