Don't assume memory layout of std::net::SocketAddr

Fixes #120

Author: faern

Cargo.toml

@@ -21,7 +21,7 @@ features = ["handleapi", "ws2def", "ws2ipdef", "ws2tcpip", "minwindef"]
 
 [target."cfg(any(unix, target_os = \"redox\"))".dependencies]
 cfg-if = "0.1.6"
-libc = "0.2.66"
+libc = { version = "0.2.66", features = ["align"] }
 
 [target."cfg(target_os = \"redox\")".dependencies]
 redox_syscall = "0.1.38"

src/sockaddr.rs

@@ -1,20 +1,24 @@
 use std::fmt;
 use std::mem::{self, MaybeUninit};
-use std::net::{SocketAddr, SocketAddrV4, SocketAddrV6};
+use std::net::{Ipv4Addr, Ipv6Addr, SocketAddr, SocketAddrV4, SocketAddrV6};
 use std::ptr;
 
 #[cfg(any(unix, target_os = "redox"))]
 use libc::{
-    sa_family_t, sockaddr, sockaddr_in, sockaddr_in6, sockaddr_storage, socklen_t, AF_INET,
-    AF_INET6,
+    in6_addr, in_addr, sa_family_t, sockaddr, sockaddr_in, sockaddr_in6, sockaddr_storage,
+    socklen_t, AF_INET, AF_INET6,
 };
 #[cfg(windows)]
+use winapi::shared::in6addr::{in6_addr_u, IN6_ADDR as in6_addr};
+#[cfg(windows)]
+use winapi::shared::inaddr::{in_addr_S_un, IN_ADDR as in_addr};
+#[cfg(windows)]
 use winapi::shared::ws2def::{
     ADDRESS_FAMILY as sa_family_t, AF_INET, AF_INET6, SOCKADDR as sockaddr,
     SOCKADDR_IN as sockaddr_in, SOCKADDR_STORAGE as sockaddr_storage,
 };
 #[cfg(windows)]
-use winapi::shared::ws2ipdef::SOCKADDR_IN6_LH as sockaddr_in6;
+use winapi::shared::ws2ipdef::{SOCKADDR_IN6_LH_u, SOCKADDR_IN6_LH as sockaddr_in6};
 #[cfg(windows)]
 use winapi::um::ws2tcpip::socklen_t;
 
@@ -43,17 +47,17 @@ impl fmt::Debug for SockAddr {
 impl SockAddr {
     /// Constructs a `SockAddr` from its raw components.
     pub unsafe fn from_raw_parts(addr: *const sockaddr, len: socklen_t) -> SockAddr {
-        let mut storage = MaybeUninit::<sockaddr_storage>::uninit();
+        let mut storage = MaybeUninit::<sockaddr_storage>::zeroed();
         ptr::copy_nonoverlapping(
             addr as *const _ as *const u8,
-            &mut storage as *mut _ as *mut u8,
+            storage.as_mut_ptr() as *mut u8,
             len as usize,
         );
 
         SockAddr {
             // This is safe as we written the address to `storage` above.
             storage: storage.assume_init(),
-            len: len,
+            len,
         }
     }
 
@@ -120,33 +124,60 @@ impl SockAddr {
         }
     }
 
-    unsafe fn as_<T>(&self, family: sa_family_t) -> Option<T> {
-        if self.storage.ss_family != family {
-            return None;
-        }
-
-        Some(mem::transmute_copy(&self.storage))
-    }
-
     /// Returns this address as a `SocketAddrV4` if it is in the `AF_INET`
     /// family.
     pub fn as_inet(&self) -> Option<SocketAddrV4> {
-        unsafe { self.as_(AF_INET as sa_family_t) }
+        match self.as_std() {
+            Some(SocketAddr::V4(addr)) => Some(addr),
+            _ => None,
+        }
     }
 
     /// Returns this address as a `SocketAddrV6` if it is in the `AF_INET6`
     /// family.
     pub fn as_inet6(&self) -> Option<SocketAddrV6> {
-        unsafe { self.as_(AF_INET6 as sa_family_t) }
+        match self.as_std() {
+            Some(SocketAddr::V6(addr)) => Some(addr),
+            _ => None,
+        }
     }
 
     /// Returns this address as a `SocketAddr` if it is in the `AF_INET`
     /// or `AF_INET6` family, otherwise returns `None`.
     pub fn as_std(&self) -> Option<SocketAddr> {
-        if let Some(addr) = self.as_inet() {
-            Some(SocketAddr::V4(addr))
-        } else if let Some(addr) = self.as_inet6() {
-            Some(SocketAddr::V6(addr))
+        if self.storage.ss_family == AF_INET as sa_family_t {
+            // Safety: if the ss_family field is AF_INET then storage must be a sockaddr_in.
+            let addr = unsafe { &*(&self.storage as *const _ as *const sockaddr_in) };
+
+            #[cfg(unix)]
+            let ip = Ipv4Addr::from(addr.sin_addr.s_addr.to_ne_bytes());
+            #[cfg(windows)]
+            let ip = {
+                let ip_bytes = unsafe { addr.sin_addr.S_un.S_un_b() };
+                Ipv4Addr::from([ip_bytes.s_b1, ip_bytes.s_b2, ip_bytes.s_b3, ip_bytes.s_b4])
+            };
+            let port = u16::from_be(addr.sin_port);
+            Some(SocketAddr::V4(SocketAddrV4::new(ip, port)))
+        } else if self.storage.ss_family == AF_INET6 as sa_family_t {
+            // Safety: if the ss_family field is AF_INET6 then storage must be a sockaddr_in6.
+            let addr = unsafe { &*(&self.storage as *const _ as *const sockaddr_in6) };
+
+            #[cfg(unix)]
+            let ip = Ipv6Addr::from(addr.sin6_addr.s6_addr);
+            #[cfg(windows)]
+            let ip = Ipv6Addr::from(*unsafe { addr.sin6_addr.u.Byte() });
+            let port = u16::from_be(addr.sin6_port);
+            Some(SocketAddr::V6(SocketAddrV6::new(
+                ip,
+                port,
+                addr.sin6_flowinfo,
+                #[cfg(unix)]
+                addr.sin6_scope_id,
+                #[cfg(windows)]
+                unsafe {
+                    *addr.u.sin6_scope_id()
+                },
+            )))
         } else {
             None
         }
@@ -168,34 +199,90 @@ impl SockAddr {
     }
 }
 
-// SocketAddrV4 and SocketAddrV6 are just wrappers around sockaddr_in and sockaddr_in6
-
-// check to make sure that the sizes at least match up
-fn _size_checks(v4: SocketAddrV4, v6: SocketAddrV6) {
-    unsafe {
-        mem::transmute::<SocketAddrV4, sockaddr_in>(v4);
-        mem::transmute::<SocketAddrV6, sockaddr_in6>(v6);
-    }
-}
-
 impl From<SocketAddrV4> for SockAddr {
     fn from(addr: SocketAddrV4) -> SockAddr {
-        unsafe {
-            SockAddr::from_raw_parts(
-                &addr as *const _ as *const _,
-                mem::size_of::<SocketAddrV4>() as socklen_t,
-            )
+        #[cfg(unix)]
+        let sin_addr = in_addr {
+            s_addr: u32::from_ne_bytes(addr.ip().octets()),
+        };
+        #[cfg(windows)]
+        let sin_addr = unsafe {
+            let mut s_un = mem::zeroed::<in_addr_S_un>();
+            *s_un.S_addr_mut() = u32::from_ne_bytes(addr.ip().octets());
+            in_addr { S_un: s_un }
+        };
+
+        let sockaddr_in = sockaddr_in {
+            sin_family: AF_INET as sa_family_t,
+            sin_port: addr.port().to_be(),
+            sin_addr,
+            sin_zero: [0; 8],
+            #[cfg(any(
+                target_os = "dragonfly",
+                target_os = "freebsd",
+                target_os = "ios",
+                target_os = "macos",
+                target_os = "netbsd",
+                target_os = "openbsd"
+            ))]
+            sin_len: 0,
+        };
+        let mut storage = MaybeUninit::<sockaddr_storage>::zeroed();
+        // Safety: A `sockaddr_in` is memory compatible with a `sockaddr_storage`
+        unsafe { (storage.as_mut_ptr() as *mut sockaddr_in).write(sockaddr_in) };
+        SockAddr {
+            storage: unsafe { storage.assume_init() },
+            len: mem::size_of::<sockaddr_in>() as socklen_t,
         }
     }
 }
 
 impl From<SocketAddrV6> for SockAddr {
     fn from(addr: SocketAddrV6) -> SockAddr {
-        unsafe {
-            SockAddr::from_raw_parts(
-                &addr as *const _ as *const _,
-                mem::size_of::<SocketAddrV6>() as socklen_t,
-            )
+        #[cfg(unix)]
+        let sin6_addr = in6_addr {
+            s6_addr: addr.ip().octets(),
+        };
+        #[cfg(windows)]
+        let sin6_addr = unsafe {
+            let mut u = mem::zeroed::<in6_addr_u>();
+            *u.Byte_mut() = addr.ip().octets();
+            in6_addr { u }
+        };
+        #[cfg(windows)]
+        let u = unsafe {
+            let mut u = mem::zeroed::<SOCKADDR_IN6_LH_u>();
+            *u.sin6_scope_id_mut() = addr.scope_id();
+            u
+        };
+
+        let sockaddr_in6 = sockaddr_in6 {
+            sin6_family: AF_INET6 as sa_family_t,
+            sin6_port: addr.port().to_be(),
+            sin6_addr,
+            sin6_flowinfo: addr.flowinfo(),
+            #[cfg(unix)]
+            sin6_scope_id: addr.scope_id(),
+            #[cfg(windows)]
+            u,
+            #[cfg(any(
+                target_os = "dragonfly",
+                target_os = "freebsd",
+                target_os = "ios",
+                target_os = "macos",
+                target_os = "netbsd",
+                target_os = "openbsd"
+            ))]
+            sin6_len: 0,
+            #[cfg(any(target_os = "solaris", target_os = "illumos"))]
+            __sin6_src_id: 0,
+        };
+        let mut storage = MaybeUninit::<sockaddr_storage>::zeroed();
+        // Safety: A `sockaddr_in6` is memory compatible with a `sockaddr_storage`
+        unsafe { (storage.as_mut_ptr() as *mut sockaddr_in6).write(sockaddr_in6) };
+        SockAddr {
+            storage: unsafe { storage.assume_init() },
+            len: mem::size_of::<sockaddr_in6>() as socklen_t,
         }
     }
 }