std: make address resolution weirdness local to SGX

Author: joboet

library/std/src/io/error.rs

@@ -95,6 +95,9 @@ impl Error {
 
     pub(crate) const ZERO_TIMEOUT: Self =
         const_error!(ErrorKind::InvalidInput, "cannot set a 0 duration timeout");
+
+    pub(crate) const NO_ADDRESSES: Self =
+        const_error!(ErrorKind::InvalidInput, "could not resolve to any addresses");
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]

library/std/src/net/mod.rs

@@ -34,7 +34,6 @@ pub use self::tcp::IntoIncoming;
 pub use self::tcp::{Incoming, TcpListener, TcpStream};
 #[stable(feature = "rust1", since = "1.0.0")]
 pub use self::udp::UdpSocket;
-use crate::io::{self, ErrorKind};
 
 mod ip_addr;
 mod socket_addr;
@@ -67,23 +66,3 @@ pub enum Shutdown {
     #[stable(feature = "rust1", since = "1.0.0")]
     Both,
 }
-
-fn each_addr<A: ToSocketAddrs, F, T>(addr: A, mut f: F) -> io::Result<T>
-where
-    F: FnMut(io::Result<&SocketAddr>) -> io::Result<T>,
-{
-    let addrs = match addr.to_socket_addrs() {
-        Ok(addrs) => addrs,
-        Err(e) => return f(Err(e)),
-    };
-    let mut last_err = None;
-    for addr in addrs {
-        match f(Ok(&addr)) {
-            Ok(l) => return Ok(l),
-            Err(e) => last_err = Some(e),
-        }
-    }
-    Err(last_err.unwrap_or_else(|| {
-        io::const_error!(ErrorKind::InvalidInput, "could not resolve to any addresses")
-    }))
-}

library/std/src/net/tcp.rs

@@ -167,7 +167,7 @@ impl TcpStream {
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn connect<A: ToSocketAddrs>(addr: A) -> io::Result<TcpStream> {
-        super::each_addr(addr, net_imp::TcpStream::connect).map(TcpStream)
+        net_imp::TcpStream::connect(addr).map(TcpStream)
     }
 
     /// Opens a TCP connection to a remote host with a timeout.
@@ -782,7 +782,7 @@ impl TcpListener {
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn bind<A: ToSocketAddrs>(addr: A) -> io::Result<TcpListener> {
-        super::each_addr(addr, net_imp::TcpListener::bind).map(TcpListener)
+        net_imp::TcpListener::bind(addr).map(TcpListener)
     }
 
     /// Returns the local socket address of this listener.

library/std/src/net/udp.rs

@@ -120,7 +120,7 @@ impl UdpSocket {
     /// [`Ipv4Addr::UNSPECIFIED`] or [`Ipv6Addr::UNSPECIFIED`].
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn bind<A: ToSocketAddrs>(addr: A) -> io::Result<UdpSocket> {
-        super::each_addr(addr, net_imp::UdpSocket::bind).map(UdpSocket)
+        net_imp::UdpSocket::bind(addr).map(UdpSocket)
     }
 
     /// Receives a single datagram message on the socket. On success, returns the number
@@ -677,7 +677,7 @@ impl UdpSocket {
     /// on the platform.
     #[stable(feature = "net2_mutators", since = "1.9.0")]
     pub fn connect<A: ToSocketAddrs>(&self, addr: A) -> io::Result<()> {
-        super::each_addr(addr, |addr| self.0.connect(addr))
+        self.0.connect(addr)
     }
 
     /// Sends data on the socket to the remote address to which it is connected.

library/std/src/sys/net/connection/mod.rs

@@ -0,0 +1,52 @@
+cfg_if::cfg_if! {
+    if #[cfg(any(
+        all(target_family = "unix", not(target_os = "l4re")),
+        target_os = "windows",
+        target_os = "hermit",
+        all(target_os = "wasi", target_env = "p2"),
+        target_os = "solid_asp3",
+    ))] {
+        mod socket;
+        pub use socket::*;
+    } else if #[cfg(all(target_vendor = "fortanix", target_env = "sgx"))] {
+        mod sgx;
+        pub use sgx::*;
+    } else if #[cfg(all(target_os = "wasi", target_env = "p1"))] {
+        mod wasip1;
+        pub use wasip1::*;
+    } else if #[cfg(target_os = "xous")] {
+        mod xous;
+        pub use xous::*;
+    } else if #[cfg(target_os = "uefi")] {
+        mod uefi;
+        pub use uefi::*;
+    } else {
+        mod unsupported;
+        pub use unsupported::*;
+    }
+}
+
+#[cfg_attr(
+    // Make sure that this is used on some platforms at least.
+    not(any(target_os = "linux", target_os = "windows")),
+    allow(dead_code)
+)]
+fn each_addr<A: crate::net::ToSocketAddrs, F, T>(addr: A, mut f: F) -> crate::io::Result<T>
+where
+    F: FnMut(&crate::net::SocketAddr) -> crate::io::Result<T>,
+{
+    use crate::io::Error;
+
+    let mut last_err = None;
+    for addr in addr.to_socket_addrs()? {
+        match f(&addr) {
+            Ok(l) => return Ok(l),
+            Err(e) => last_err = Some(e),
+        }
+    }
+
+    match last_err {
+        Some(err) => Err(err),
+        None => Err(Error::NO_ADDRESSES),
+    }
+}

library/std/src/sys/net/connection/sgx.rs

@@ -1,11 +1,12 @@
+use crate::error;
+use crate::fmt::{self, Write};
 use crate::io::{self, BorrowedCursor, IoSlice, IoSliceMut};
 use crate::net::{Ipv4Addr, Ipv6Addr, Shutdown, SocketAddr, ToSocketAddrs};
 use crate::sync::Arc;
 use crate::sys::abi::usercalls;
 use crate::sys::fd::FileDesc;
 use crate::sys::{AsInner, FromInner, IntoInner, TryIntoInner, sgx_ineffective, unsupported};
 use crate::time::Duration;
-use crate::{error, fmt};
 
 const DEFAULT_FAKE_TTL: u32 = 64;
 
@@ -63,18 +64,51 @@ impl fmt::Debug for TcpStream {
     }
 }
 
-fn io_err_to_addr(result: io::Result<&SocketAddr>) -> io::Result<String> {
-    match result {
-        Ok(saddr) => Ok(saddr.to_string()),
-        // need to downcast twice because io::Error::into_inner doesn't return the original
-        // value if the conversion fails
-        Err(e) => {
-            if e.get_ref().and_then(|e| e.downcast_ref::<NonIpSockAddr>()).is_some() {
-                Ok(e.into_inner().unwrap().downcast::<NonIpSockAddr>().unwrap().host)
-            } else {
-                Err(e)
+/// Converts each address in `addr` into a hostname.
+///
+/// SGX doesn't support DNS resolution but rather accepts hostnames in
+/// the same place as socket addresses. So, to make e.g.
+/// ```rust
+/// TcpStream::connect("example.com:80")`
+/// ```
+/// work, the DNS lookup returns a special error (`NonIpSockAddr`) instead,
+/// which contains the hostname being looked up. When `.to_socket_addrs()`
+/// fails, we inspect the error and try recover the hostname from it. If that
+/// succeeds, we thus continue with the hostname.
+///
+/// This is a terrible hack and leads to buggy code. For instance, when users
+/// use the result of `.to_socket_addrs()` in their own `ToSocketAddrs`
+/// implementation to select from a list of possible URLs, the only URL used
+/// will be that of the last item tried.
+// FIXME: This is a terrible, terrible hack.
+fn each_addr<A: ToSocketAddrs, F, T>(addr: A, mut f: F) -> io::Result<T>
+where
+    F: FnMut(&str) -> io::Result<T>,
+{
+    match addr.to_socket_addrs() {
+        Ok(addrs) => {
+            let mut last_err = None;
+            let mut encoded = String::new();
+            for addr in addrs {
+                write!(encoded, "{}", &addr).unwrap();
+                match f(&encoded) {
+                    Ok(val) => return Ok(val),
+                    Err(err) => {
+                        last_err = Some(err);
+                        encoded.clear();
+                    }
+                }
+            }
+
+            match last_err {
+                Some(err) => Err(err),
+                None => Err(io::Error::NO_ADDRESSES),
             }
         }
+        Err(err) => match err.get_ref().and_then(|e| e.downcast_ref::<NonIpSockAddr>()) {
+            Some(NonIpSockAddr { host }) => f(host),
+            None => Err(err),
+        },
     }
 }
 
@@ -86,17 +120,18 @@ fn addr_to_sockaddr(addr: Option<&str>) -> io::Result<SocketAddr> {
 }
 
 impl TcpStream {
-    pub fn connect(addr: io::Result<&SocketAddr>) -> io::Result<TcpStream> {
-        let addr = io_err_to_addr(addr)?;
-        let (fd, local_addr, peer_addr) = usercalls::connect_stream(&addr)?;
-        Ok(TcpStream { inner: Socket::new(fd, local_addr), peer_addr: Some(peer_addr) })
+    pub fn connect<A: ToSocketAddrs>(addr: A) -> io::Result<TcpStream> {
+        each_addr(addr, |addr| {
+            let (fd, local_addr, peer_addr) = usercalls::connect_stream(addr)?;
+            Ok(TcpStream { inner: Socket::new(fd, local_addr), peer_addr: Some(peer_addr) })
+        })
     }
 
     pub fn connect_timeout(addr: &SocketAddr, dur: Duration) -> io::Result<TcpStream> {
         if dur == Duration::default() {
             return Err(io::Error::ZERO_TIMEOUT);
         }
-        Self::connect(Ok(addr)) // FIXME: ignoring timeout
+        Self::connect(addr) // FIXME: ignoring timeout
     }
 
     pub fn set_read_timeout(&self, dur: Option<Duration>) -> io::Result<()> {
@@ -247,10 +282,11 @@ impl fmt::Debug for TcpListener {
 }
 
 impl TcpListener {
-    pub fn bind(addr: io::Result<&SocketAddr>) -> io::Result<TcpListener> {
-        let addr = io_err_to_addr(addr)?;
-        let (fd, local_addr) = usercalls::bind_stream(&addr)?;
-        Ok(TcpListener { inner: Socket::new(fd, local_addr) })
+    pub fn bind<A: ToSocketAddrs>(addr: A) -> io::Result<TcpListener> {
+        each_addr(addr, |addr| {
+            let (fd, local_addr) = usercalls::bind_stream(addr)?;
+            Ok(TcpListener { inner: Socket::new(fd, local_addr) })
+        })
     }
 
     pub fn socket_addr(&self) -> io::Result<SocketAddr> {
@@ -316,7 +352,7 @@ impl FromInner<Socket> for TcpListener {
 pub struct UdpSocket(!);
 
 impl UdpSocket {
-    pub fn bind(_: io::Result<&SocketAddr>) -> io::Result<UdpSocket> {
+    pub fn bind<A: ToSocketAddrs>(_: A) -> io::Result<UdpSocket> {
         unsupported()
     }
 
@@ -436,7 +472,7 @@ impl UdpSocket {
         self.0
     }
 
-    pub fn connect(&self, _: io::Result<&SocketAddr>) -> io::Result<()> {
+    pub fn connect<A: ToSocketAddrs>(&self, _: A) -> io::Result<()> {
         self.0
     }
 }