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Invalidly assumes the memory layout of SocketAddrV{4,6} #38

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faern opened this issue Nov 13, 2020 · 0 comments · Fixed by #39
Closed

Invalidly assumes the memory layout of SocketAddrV{4,6} #38

faern opened this issue Nov 13, 2020 · 0 comments · Fixed by #39

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@faern
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faern commented Nov 13, 2020

miow assumes that the memory layout of std::net::SocketAddrV{4,6} matches libc::sockaddr, but this can't be assumed. std makes no such promise to the outside world.

The offending code is here:

miow/src/net.rs

Lines 459 to 470 in c863739

fn socket_addr_to_ptrs(addr: &SocketAddr) -> (*const SOCKADDR, c_int) {
match *addr {
SocketAddr::V4(ref a) => (
a as *const _ as *const _,
mem::size_of::<SOCKADDR_IN>() as c_int,
),
SocketAddr::V6(ref a) => (
a as *const _ as *const _,
mem::size_of::<SOCKADDR_IN6_LH>() as c_int,
),
}
}

Some other crates made the same assumptions, and they are being fixed in tokio-rs/mio#1388, rust-lang/socket2#120 and deprecrated/net2-rs#106.

Until this is fixed and published it kind of blocks moving these fundamental network types into core and also stops them from having const fn constructors. See this PR on std for reference: rust-lang/rust#78802.

@faern faern closed this as completed in #39 Nov 15, 2020
bors added a commit to rust-lang-ci/rust that referenced this issue Jul 31, 2022
…lett

Implement network primitives with ideal Rust layout, not C system layout

This PR is the result of this internals forum thread: https://internals.rust-lang.org/t/why-are-socketaddrv4-socketaddrv6-based-on-low-level-sockaddr-in-6/13321.

Instead of basing `std:::net::{Ipv4Addr, Ipv6Addr, SocketAddrV4, SocketAddrV6}` on system (C) structs, they are encoded in a more optimal and idiomatic Rust way.

This changes the public API of std by introducing structural equality impls for all four types here, which means that `match ipv4addr { SOME_CONSTANT => ... }` will now compile, whereas previously this was an error. No other intentional changes are introduced to public API.

It's possible to observe the current layout of these types (e.g., by pointer casting); most but not all libraries which were found by Crater to do this have had updates issued and affected versions yanked. See report below.

### Benefits of this change

- It will become possible to move these fundamental network types from `std` into `core` ([RFC](rust-lang/rfcs#2832)).
- Some methods that can't be made `const fn`s today can be made `const fn`s with this change.
- `SocketAddrV4` only occupies 6 bytes instead of 16 bytes.
- These simple primitives become easier to read and uses less `unsafe`.
- Makes these types support structural equality, which means you can now (for instance) match an `Ipv4Addr` against a constant

### ~Remaining~ Previous problems

This change obviously changes the memory layout of the types. And it turns out some libraries invalidly assumes the memory layout and does very dangerous pointer casts to convert them. These libraries will have undefined behaviour and perform invalid memory access until patched.

- [x] - `mio` - Issue: tokio-rs/mio#1386.
  - [x] `0.7` branch tokio-rs/mio#1388
  - [x] `0.7.6` published tokio-rs/mio#1398
  - [x] Yank all `0.7` versions older than `0.7.6`
  - [x] Report `<0.7.6` to RustSec Advisory Database https://rustsec.org/advisories/RUSTSEC-2020-0081.html
- [x] - `socket2` - Issue: rust-lang/socket2#119.
  - [x] `0.3.x` branch rust-lang/socket2#120
  - [x] `0.3.16` published
  - [x] `master` branch rust-lang/socket2#122
  - [x] Yank all `0.3` versions older than `0.3.16`
  - [x] Report `<0.3.16` to RustSec Advisory Database https://rustsec.org/advisories/RUSTSEC-2020-0079.html
- [x] - `net2` - Issue: deprecrated/net2-rs#105
  - [x] deprecrated/net2-rs#106
  - [x] `0.2.36` published
  - [x] Yank all `0.2` versions older than `0.2.36`
  - [x] Report `<0.2.36` to RustSec Advisory Database https://rustsec.org/advisories/RUSTSEC-2020-0078.html
- [x] - `miow` - Issue: yoshuawuyts/miow#38
  - [x] `0.3.x` - yoshuawuyts/miow#39
  - [x] `0.3.6` published
  - [x] `0.2.x` - yoshuawuyts/miow#40
  - [x] `0.2.2` published
  - [x] Yanked all `0.2` versions older than `0.2.2`
  - [x] Yanked all `0.3` versions older than `0.3.6`
  - [x] Report `<0.2.2` and `<0.3.6` to RustSec Advisory Database https://rustsec.org/advisories/RUSTSEC-2020-0080.html
- [x] - `quinn master` (aka what became 0.7) - quinn-rs/quinn#968 quinn-rs/quinn#987
  - [x] - `quinn 0.6` - quinn-rs/quinn#1045
  - [x] - `quinn 0.5` - quinn-rs/quinn#1046
  - [x] - Release `0.7.0`, `0.6.2` and `0.5.4`
- [x] - `nb-connect` - smol-rs/nb-connect#1
  - [x] - Release `1.0.3`
  - [x] - Yank all versions older than `1.0.3`
- [x] - `shadowsocks-rust` - shadowsocks/shadowsocks-rust#462
- [ ] - `rio` - spacejam/rio#44
- [ ] - `seaslug` - spacejam/seaslug#1

#### Fixed crate versions

All crates I have found that assumed the memory layout have been fixed and published. The crates and versions that will continue working even as/if this PR is merged is (please upgrade these to help unblock this PR):

* `net2 0.2.36`
* `socket2 0.3.16`
* `miow 0.2.2`
* `miow 0.3.6`
* `mio 0.7.6`
* `mio 0.6.23` - Never had the invalid assumption itself, but has now been bumped to only allow fixed dependencies (`net2` + `miow`)
* `nb-connect 1.0.3`
* `quinn 0.5.4`
* `quinn 0.6.2`

### Release notes draft

This release changes the memory layout of `Ipv4Addr`, `Ipv6Addr`, `SocketAddrV4` and `SocketAddrV6`. The standard library no longer implements these as the corresponding `libc` structs (`sockaddr_in`, `sockaddr_in6` etc.). This internal representation was never exposed, but some crates relied on it anyway by unsafely transmuting. This change will cause those crates to make invalid memory accesses. Notably `net2 <0.2.36`, `socket2 <0.3.16`, `mio <0.7.6`, `miow <0.3.6` and a few other crates are affected. All known affected crates have been patched and have had fixed versions published over a year ago. If any affected crate is still in your dependency tree, you need to upgrade them before using this version of Rust.
workingjubilee pushed a commit to tcdi/postgrestd that referenced this issue Sep 15, 2022
Implement network primitives with ideal Rust layout, not C system layout

This PR is the result of this internals forum thread: https://internals.rust-lang.org/t/why-are-socketaddrv4-socketaddrv6-based-on-low-level-sockaddr-in-6/13321.

Instead of basing `std:::net::{Ipv4Addr, Ipv6Addr, SocketAddrV4, SocketAddrV6}` on system (C) structs, they are encoded in a more optimal and idiomatic Rust way.

This changes the public API of std by introducing structural equality impls for all four types here, which means that `match ipv4addr { SOME_CONSTANT => ... }` will now compile, whereas previously this was an error. No other intentional changes are introduced to public API.

It's possible to observe the current layout of these types (e.g., by pointer casting); most but not all libraries which were found by Crater to do this have had updates issued and affected versions yanked. See report below.

### Benefits of this change

- It will become possible to move these fundamental network types from `std` into `core` ([RFC](rust-lang/rfcs#2832)).
- Some methods that can't be made `const fn`s today can be made `const fn`s with this change.
- `SocketAddrV4` only occupies 6 bytes instead of 16 bytes.
- These simple primitives become easier to read and uses less `unsafe`.
- Makes these types support structural equality, which means you can now (for instance) match an `Ipv4Addr` against a constant

### ~Remaining~ Previous problems

This change obviously changes the memory layout of the types. And it turns out some libraries invalidly assumes the memory layout and does very dangerous pointer casts to convert them. These libraries will have undefined behaviour and perform invalid memory access until patched.

- [x] - `mio` - Issue: tokio-rs/mio#1386.
  - [x] `0.7` branch tokio-rs/mio#1388
  - [x] `0.7.6` published tokio-rs/mio#1398
  - [x] Yank all `0.7` versions older than `0.7.6`
  - [x] Report `<0.7.6` to RustSec Advisory Database https://rustsec.org/advisories/RUSTSEC-2020-0081.html
- [x] - `socket2` - Issue: rust-lang/socket2#119.
  - [x] `0.3.x` branch rust-lang/socket2#120
  - [x] `0.3.16` published
  - [x] `master` branch rust-lang/socket2#122
  - [x] Yank all `0.3` versions older than `0.3.16`
  - [x] Report `<0.3.16` to RustSec Advisory Database https://rustsec.org/advisories/RUSTSEC-2020-0079.html
- [x] - `net2` - Issue: deprecrated/net2-rs#105
  - [x] deprecrated/net2-rs#106
  - [x] `0.2.36` published
  - [x] Yank all `0.2` versions older than `0.2.36`
  - [x] Report `<0.2.36` to RustSec Advisory Database https://rustsec.org/advisories/RUSTSEC-2020-0078.html
- [x] - `miow` - Issue: yoshuawuyts/miow#38
  - [x] `0.3.x` - yoshuawuyts/miow#39
  - [x] `0.3.6` published
  - [x] `0.2.x` - yoshuawuyts/miow#40
  - [x] `0.2.2` published
  - [x] Yanked all `0.2` versions older than `0.2.2`
  - [x] Yanked all `0.3` versions older than `0.3.6`
  - [x] Report `<0.2.2` and `<0.3.6` to RustSec Advisory Database https://rustsec.org/advisories/RUSTSEC-2020-0080.html
- [x] - `quinn master` (aka what became 0.7) - quinn-rs/quinn#968 quinn-rs/quinn#987
  - [x] - `quinn 0.6` - quinn-rs/quinn#1045
  - [x] - `quinn 0.5` - quinn-rs/quinn#1046
  - [x] - Release `0.7.0`, `0.6.2` and `0.5.4`
- [x] - `nb-connect` - smol-rs/nb-connect#1
  - [x] - Release `1.0.3`
  - [x] - Yank all versions older than `1.0.3`
- [x] - `shadowsocks-rust` - shadowsocks/shadowsocks-rust#462
- [ ] - `rio` - spacejam/rio#44
- [ ] - `seaslug` - spacejam/seaslug#1

#### Fixed crate versions

All crates I have found that assumed the memory layout have been fixed and published. The crates and versions that will continue working even as/if this PR is merged is (please upgrade these to help unblock this PR):

* `net2 0.2.36`
* `socket2 0.3.16`
* `miow 0.2.2`
* `miow 0.3.6`
* `mio 0.7.6`
* `mio 0.6.23` - Never had the invalid assumption itself, but has now been bumped to only allow fixed dependencies (`net2` + `miow`)
* `nb-connect 1.0.3`
* `quinn 0.5.4`
* `quinn 0.6.2`

### Release notes draft

This release changes the memory layout of `Ipv4Addr`, `Ipv6Addr`, `SocketAddrV4` and `SocketAddrV6`. The standard library no longer implements these as the corresponding `libc` structs (`sockaddr_in`, `sockaddr_in6` etc.). This internal representation was never exposed, but some crates relied on it anyway by unsafely transmuting. This change will cause those crates to make invalid memory accesses. Notably `net2 <0.2.36`, `socket2 <0.3.16`, `mio <0.7.6`, `miow <0.3.6` and a few other crates are affected. All known affected crates have been patched and have had fixed versions published over a year ago. If any affected crate is still in your dependency tree, you need to upgrade them before using this version of Rust.
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