Added a utility function to ensure we never have an issue with 0-leng…

…th slices from pointers again

Added a clippy lint to ensure we use it.

clippy.toml

@@ -0,0 +1,4 @@
+disallowed-methods = [
+    { path = "std::slice::from_raw_parts", reason = "use util::from_raw_parts instead" },
+    { path = "std::slice::from_raw_parts_mut", reason = "use util::from_raw_parts_mut instead" },
+]

openssl/src/asn1.rs

@@ -32,7 +32,6 @@ use std::convert::TryInto;
 use std::ffi::CString;
 use std::fmt;
 use std::ptr;
-use std::slice;
 use std::str;
 
 use crate::bio::MemBio;
@@ -41,7 +40,7 @@ use crate::error::ErrorStack;
 use crate::nid::Nid;
 use crate::stack::Stackable;
 use crate::string::OpensslString;
-use crate::{cvt, cvt_p};
+use crate::{cvt, cvt_p, util};
 use openssl_macros::corresponds;
 
 foreign_type_and_impl_send_sync! {
@@ -457,7 +456,7 @@ impl Asn1StringRef {
     /// [`as_utf8`]: struct.Asn1String.html#method.as_utf8
     #[corresponds(ASN1_STRING_get0_data)]
     pub fn as_slice(&self) -> &[u8] {
-        unsafe { slice::from_raw_parts(ASN1_STRING_get0_data(self.as_ptr()), self.len()) }
+        unsafe { util::from_raw_parts(ASN1_STRING_get0_data(self.as_ptr()), self.len()) }
     }
 
     /// Returns the number of bytes in the string.
@@ -597,7 +596,7 @@ impl Asn1BitStringRef {
     /// Returns the Asn1BitString as a slice.
     #[corresponds(ASN1_STRING_get0_data)]
     pub fn as_slice(&self) -> &[u8] {
-        unsafe { slice::from_raw_parts(ASN1_STRING_get0_data(self.as_ptr() as *mut _), self.len()) }
+        unsafe { util::from_raw_parts(ASN1_STRING_get0_data(self.as_ptr() as *mut _), self.len()) }
     }
 
     /// Returns the number of bytes in the string.
@@ -637,7 +636,7 @@ impl Asn1OctetStringRef {
     /// Returns the octet string as an array of bytes.
     #[corresponds(ASN1_STRING_get0_data)]
     pub fn as_slice(&self) -> &[u8] {
-        unsafe { slice::from_raw_parts(ASN1_STRING_get0_data(self.as_ptr().cast()), self.len()) }
+        unsafe { util::from_raw_parts(ASN1_STRING_get0_data(self.as_ptr().cast()), self.len()) }
     }
 
     /// Returns the number of bytes in the octet string.
@@ -701,7 +700,7 @@ impl Asn1Object {
     pub fn as_slice(&self) -> &[u8] {
         unsafe {
             let len = ffi::OBJ_length(self.as_ptr());
-            slice::from_raw_parts(ffi::OBJ_get0_data(self.as_ptr()), len)
+            util::from_raw_parts(ffi::OBJ_get0_data(self.as_ptr()), len)
         }
     }
 }

openssl/src/bio.rs

@@ -2,10 +2,10 @@ use cfg_if::cfg_if;
 use libc::c_int;
 use std::marker::PhantomData;
 use std::ptr;
-use std::slice;
 
 use crate::cvt_p;
 use crate::error::ErrorStack;
+use crate::util;
 
 pub struct MemBioSlice<'a>(*mut ffi::BIO, PhantomData<&'a [u8]>);
 
@@ -66,7 +66,7 @@ impl MemBio {
             if len == 0 {
                 &[]
             } else {
-                slice::from_raw_parts(ptr as *const _ as *const _, len as usize)
+                util::from_raw_parts(ptr as *const _ as *const _, len as usize)
             }
         }
     }

openssl/src/ssl/bio.rs

@@ -9,10 +9,9 @@ use std::io;
 use std::io::prelude::*;
 use std::panic::{catch_unwind, AssertUnwindSafe};
 use std::ptr;
-use std::slice;
 
-use crate::cvt_p;
 use crate::error::ErrorStack;
+use crate::{cvt_p, util};
 
 pub struct StreamState<S> {
     pub stream: S,
@@ -89,7 +88,7 @@ unsafe extern "C" fn bwrite<S: Write>(bio: *mut BIO, buf: *const c_char, len: c_
     BIO_clear_retry_flags(bio);
 
     let state = state::<S>(bio);
-    let buf = slice::from_raw_parts(buf as *const _, len as usize);
+    let buf = util::from_raw_parts(buf as *const _, len as usize);
 
     match catch_unwind(AssertUnwindSafe(|| state.stream.write(buf))) {
         Ok(Ok(len)) => len as c_int,
@@ -111,7 +110,7 @@ unsafe extern "C" fn bread<S: Read>(bio: *mut BIO, buf: *mut c_char, len: c_int)
     BIO_clear_retry_flags(bio);
 
     let state = state::<S>(bio);
-    let buf = slice::from_raw_parts_mut(buf as *mut _, len as usize);
+    let buf = util::from_raw_parts_mut(buf as *mut _, len as usize);
 
     match catch_unwind(AssertUnwindSafe(|| state.stream.read(buf))) {
         Ok(Ok(len)) => len as c_int,

openssl/src/ssl/callbacks.rs

@@ -10,7 +10,6 @@ use libc::{c_int, c_uchar, c_uint, c_void};
 use std::ffi::CStr;
 use std::mem;
 use std::ptr;
-use std::slice;
 #[cfg(any(ossl111, boringssl))]
 use std::str;
 use std::sync::Arc;
@@ -28,6 +27,7 @@ use crate::ssl::{
 };
 #[cfg(ossl111)]
 use crate::ssl::{ClientHelloResponse, ExtensionContext};
+use crate::util;
 #[cfg(any(ossl111, boringssl))]
 use crate::util::ForeignTypeRefExt;
 #[cfg(ossl111)]
@@ -85,9 +85,9 @@ where
             None
         };
         // Give the callback mutable slices into which it can write the identity and psk.
-        let identity_sl = slice::from_raw_parts_mut(identity as *mut u8, max_identity_len as usize);
+        let identity_sl = util::from_raw_parts_mut(identity as *mut u8, max_identity_len as usize);
         #[allow(clippy::unnecessary_cast)]
-        let psk_sl = slice::from_raw_parts_mut(psk as *mut u8, max_psk_len as usize);
+        let psk_sl = util::from_raw_parts_mut(psk as *mut u8, max_psk_len as usize);
         match (*callback)(ssl, hint, identity_sl, psk_sl) {
             Ok(psk_len) => psk_len as u32,
             Err(e) => {
@@ -126,7 +126,7 @@ where
         };
         // Give the callback mutable slices into which it can write the psk.
         #[allow(clippy::unnecessary_cast)]
-        let psk_sl = slice::from_raw_parts_mut(psk as *mut u8, max_psk_len as usize);
+        let psk_sl = util::from_raw_parts_mut(psk as *mut u8, max_psk_len as usize);
         match (*callback)(ssl, identity, psk_sl) {
             Ok(psk_len) => psk_len as u32,
             Err(e) => {
@@ -197,7 +197,7 @@ where
             .ex_data(SslContext::cached_ex_index::<F>())
             .expect("BUG: alpn callback missing") as *const F;
         #[allow(clippy::unnecessary_cast)]
-        let protos = slice::from_raw_parts(inbuf as *const u8, inlen as usize);
+        let protos = util::from_raw_parts(inbuf as *const u8, inlen as usize);
 
         match (*callback)(ssl, protos) {
             Ok(proto) => {
@@ -416,7 +416,7 @@ where
         .ex_data(SslContext::cached_ex_index::<F>())
         .expect("BUG: get session callback missing") as *const F;
     #[allow(clippy::unnecessary_cast)]
-    let data = slice::from_raw_parts(data as *const u8, len as usize);
+    let data = util::from_raw_parts(data as *const u8, len as usize);
 
     match (*callback)(ssl, data) {
         Some(session) => {
@@ -460,7 +460,7 @@ where
         .ex_data(SslContext::cached_ex_index::<F>())
         .expect("BUG: stateless cookie generate callback missing") as *const F;
     #[allow(clippy::unnecessary_cast)]
-    let slice = slice::from_raw_parts_mut(cookie as *mut u8, ffi::SSL_COOKIE_LENGTH as usize);
+    let slice = util::from_raw_parts_mut(cookie as *mut u8, ffi::SSL_COOKIE_LENGTH as usize);
     match (*callback)(ssl, slice) {
         Ok(len) => {
             *cookie_len = len as size_t;
@@ -488,7 +488,7 @@ where
         .ex_data(SslContext::cached_ex_index::<F>())
         .expect("BUG: stateless cookie verify callback missing") as *const F;
     #[allow(clippy::unnecessary_cast)]
-    let slice = slice::from_raw_parts(cookie as *const c_uchar as *const u8, cookie_len);
+    let slice = util::from_raw_parts(cookie as *const c_uchar as *const u8, cookie_len);
     (*callback)(ssl, slice) as c_int
 }
 
@@ -511,7 +511,7 @@ where
         // compatibility. See comments in dtls1.h.
         #[allow(clippy::unnecessary_cast)]
         let slice =
-            slice::from_raw_parts_mut(cookie as *mut u8, ffi::DTLS1_COOKIE_LENGTH as usize - 1);
+            util::from_raw_parts_mut(cookie as *mut u8, ffi::DTLS1_COOKIE_LENGTH as usize - 1);
         match (*callback)(ssl, slice) {
             Ok(len) => {
                 *cookie_len = len as c_uint;
@@ -551,7 +551,7 @@ where
             .expect("BUG: cookie verify callback missing") as *const F;
         #[allow(clippy::unnecessary_cast)]
         let slice =
-            slice::from_raw_parts(cookie as *const c_uchar as *const u8, cookie_len as usize);
+            util::from_raw_parts(cookie as *const c_uchar as *const u8, cookie_len as usize);
         (*callback)(ssl, slice) as c_int
     }
 }
@@ -663,7 +663,7 @@ where
             .expect("BUG: custom ext parse callback missing") as *const F;
         let ectx = ExtensionContext::from_bits_truncate(context);
         #[allow(clippy::unnecessary_cast)]
-        let slice = slice::from_raw_parts(input as *const u8, inlen);
+        let slice = util::from_raw_parts(input as *const u8, inlen);
         let cert = if ectx.contains(ExtensionContext::TLS1_3_CERTIFICATE) {
             Some((chainidx, X509Ref::from_ptr(x)))
         } else {

openssl/src/ssl/mod.rs

@@ -77,6 +77,7 @@ use crate::ssl::bio::BioMethod;
 use crate::ssl::callbacks::*;
 use crate::ssl::error::InnerError;
 use crate::stack::{Stack, StackRef, Stackable};
+use crate::util;
 use crate::util::{ForeignTypeExt, ForeignTypeRefExt};
 use crate::x509::store::{X509Store, X509StoreBuilderRef, X509StoreRef};
 #[cfg(any(ossl102, boringssl, libressl261))]
@@ -101,7 +102,6 @@ use std::ops::{Deref, DerefMut};
 use std::panic::resume_unwind;
 use std::path::Path;
 use std::ptr;
-use std::slice;
 use std::str;
 use std::sync::{Arc, Mutex};
 
@@ -708,7 +708,7 @@ pub fn select_next_proto<'a>(server: &[u8], client: &'a [u8]) -> Option<&'a [u8]
             client.len() as c_uint,
         );
         if r == ffi::OPENSSL_NPN_NEGOTIATED {
-            Some(slice::from_raw_parts(out as *const u8, outlen as usize))
+            Some(util::from_raw_parts(out as *const u8, outlen as usize))
         } else {
             None
         }
@@ -2174,7 +2174,7 @@ impl SslSessionRef {
             let mut len = 0;
             let p = ffi::SSL_SESSION_get_id(self.as_ptr(), &mut len);
             #[allow(clippy::unnecessary_cast)]
-            slice::from_raw_parts(p as *const u8, len as usize)
+            util::from_raw_parts(p as *const u8, len as usize)
         }
     }
 
@@ -2650,7 +2650,7 @@ impl SslRef {
             if data.is_null() {
                 None
             } else {
-                Some(slice::from_raw_parts(data, len as usize))
+                Some(util::from_raw_parts(data, len as usize))
             }
         }
     }
@@ -2928,7 +2928,7 @@ impl SslRef {
             if len < 0 {
                 None
             } else {
-                Some(slice::from_raw_parts(p as *const u8, len as usize))
+                Some(util::from_raw_parts(p as *const u8, len as usize))
             }
         }
     }
@@ -3099,7 +3099,7 @@ impl SslRef {
             if len == 0 {
                 None
             } else {
-                Some(slice::from_raw_parts(ptr, len))
+                Some(util::from_raw_parts(ptr, len))
             }
         }
     }
@@ -3118,7 +3118,7 @@ impl SslRef {
             if len == 0 {
                 None
             } else {
-                Some(slice::from_raw_parts(ptr, len))
+                Some(util::from_raw_parts(ptr, len))
             }
         }
     }
@@ -3137,7 +3137,7 @@ impl SslRef {
             if len == 0 {
                 None
             } else {
-                Some(slice::from_raw_parts(ptr, len))
+                Some(util::from_raw_parts(ptr, len))
             }
         }
     }
@@ -3191,7 +3191,7 @@ impl SslRef {
             if len == 0 {
                 None
             } else {
-                Some(slice::from_raw_parts(ptr, len))
+                Some(util::from_raw_parts(ptr, len))
             }
         }
     }
@@ -3764,7 +3764,7 @@ impl<S: Read + Write> SslStream<S> {
     pub fn ssl_read(&mut self, buf: &mut [u8]) -> Result<usize, Error> {
         // SAFETY: `ssl_read_uninit` does not de-initialize the buffer.
         unsafe {
-            self.ssl_read_uninit(slice::from_raw_parts_mut(
+            self.ssl_read_uninit(util::from_raw_parts_mut(
                 buf.as_mut_ptr().cast::<MaybeUninit<u8>>(),
                 buf.len(),
             ))
@@ -3997,7 +3997,7 @@ impl<S: Read + Write> Read for SslStream<S> {
     fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
         // SAFETY: `read_uninit` does not de-initialize the buffer
         unsafe {
-            self.read_uninit(slice::from_raw_parts_mut(
+            self.read_uninit(util::from_raw_parts_mut(
                 buf.as_mut_ptr().cast::<MaybeUninit<u8>>(),
                 buf.len(),
             ))

openssl/src/util.rs

@@ -1,4 +1,5 @@
 use crate::error::ErrorStack;
+use crate::util;
 use foreign_types::{ForeignType, ForeignTypeRef};
 use libc::{c_char, c_int, c_void};
 use std::any::Any;
@@ -49,7 +50,7 @@ where
     let callback = &mut *(cb_state as *mut CallbackState<F>);
 
     let result = panic::catch_unwind(AssertUnwindSafe(|| {
-        let pass_slice = slice::from_raw_parts_mut(buf as *mut u8, size as usize);
+        let pass_slice = util::from_raw_parts_mut(buf as *mut u8, size as usize);
         callback.cb.take().unwrap()(pass_slice)
     }));
 
@@ -91,3 +92,27 @@ pub trait ForeignTypeRefExt: ForeignTypeRef {
     }
 }
 impl<FT: ForeignTypeRef> ForeignTypeRefExt for FT {}
+
+/// The same as `slice::from_raw_parts`, except that `data` may be `NULL` if
+/// `len` is 0.
+pub unsafe fn from_raw_parts<'a, T>(data: *const T, len: usize) -> &'a [T] {
+    if len == 0 {
+        &[]
+    } else {
+        // Using this to implement the preferred API
+        #[allow(clippy::disallowed_methods)]
+        slice::from_raw_parts(data, len)
+    }
+}
+
+/// The same as `slice::from_raw_parts_mut`, except that `data` may be `NULL`
+/// if `len` is 0.
+pub unsafe fn from_raw_parts_mut<'a, T>(data: *mut T, len: usize) -> &'a mut [T] {
+    if len == 0 {
+        &mut []
+    } else {
+        // Using this to implement the preferred API
+        #[allow(clippy::disallowed_methods)]
+        slice::from_raw_parts_mut(data, len)
+    }
+}