Rollup merge of rust-lang#37233 - michaelwoerister:blake2-for-ich, r=…

…nikomatsakis

ICH: Use 128-bit Blake2b hash instead of 64-bit SipHash for incr. comp. fingerprints

This PR makes incr. comp. hashes 128 bits wide in order to push collision probability below a threshold that we need to worry about. It also replaces SipHash, which has been mentioned multiple times as not being built for fingerprinting, with the [BLAKE2b hash function](https://blake2.net/), an improved version of the BLAKE sha-3 finalist.

I was worried that using a cryptographic hash function would make ICH computation noticeably slower, but after doing some performance tests, I'm not any more. Most of the time BLAKE2b is actually faster than using two SipHashes (in order to get 128 bits):

```
SipHash
libcore: 0.199 seconds
libstd:  0.090 seconds

BLAKE2b
libcore: 0.162 seconds
libstd:  0.078 seconds
```

If someone can prove that something like MetroHash128 provides a comparably low collision probability as BLAKE2, I'm happy to switch. But for now we are at least not taking a performance hit.

I also suggest that we throw out the sha-256 implementation in the compiler and replace it with BLAKE2, since our sha-256 implementation is two to three times slower than the BLAKE2 implementation in this PR (cc @alexcrichton @eddyb @brson)

r? @nikomatsakis (although there's not much incr. comp. specific in here, so feel free to re-assign)

src/librustc_data_structures/blake2b.rs

@@ -0,0 +1,286 @@
+// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+
+// An implementation of the Blake2b cryptographic hash function.
+// The implementation closely follows: https://tools.ietf.org/html/rfc7693
+//
+// "BLAKE2 is a cryptographic hash function faster than MD5, SHA-1, SHA-2, and
+//  SHA-3, yet is at least as secure as the latest standard SHA-3."
+// according to their own website :)
+//
+// Indeed this implementation is two to three times as fast as our SHA-256
+// implementation. If you have the luxury of being able to use crates from
+// crates.io, you can go there and find still faster implementations.
+
+pub struct Blake2bCtx {
+    b: [u8; 128],
+    h: [u64; 8],
+    t: [u64; 2],
+    c: usize,
+    outlen: usize,
+}
+
+impl ::std::fmt::Debug for Blake2bCtx {
+    fn fmt(&self, fmt: &mut ::std::fmt::Formatter) -> Result<(), ::std::fmt::Error> {
+        write!(fmt, "{:?}", self.h)
+    }
+}
+
+#[inline(always)]
+fn b2b_g(v: &mut [u64; 16],
+         a: usize,
+         b: usize,
+         c: usize,
+         d: usize,
+         x: u64,
+         y: u64)
+{
+    v[a] = v[a].wrapping_add(v[b]).wrapping_add(x);
+    v[d] = (v[d] ^ v[a]).rotate_right(32);
+    v[c] = v[c].wrapping_add(v[d]);
+    v[b] = (v[b] ^ v[c]).rotate_right(24);
+    v[a] = v[a].wrapping_add(v[b]).wrapping_add(y);
+    v[d] = (v[d] ^ v[a]).rotate_right(16);
+    v[c] = v[c].wrapping_add(v[d]);
+    v[b] = (v[b] ^ v[c]).rotate_right(63);
+}
+
+// Initialization vector
+const BLAKE2B_IV: [u64; 8] = [
+   0x6A09E667F3BCC908, 0xBB67AE8584CAA73B,
+   0x3C6EF372FE94F82B, 0xA54FF53A5F1D36F1,
+   0x510E527FADE682D1, 0x9B05688C2B3E6C1F,
+   0x1F83D9ABFB41BD6B, 0x5BE0CD19137E2179
+];
+
+fn blake2b_compress(ctx: &mut Blake2bCtx, last: bool) {
+
+    const SIGMA: [[usize; 16]; 12] = [
+        [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 ],
+        [14, 10, 4, 8, 9, 15, 13, 6, 1, 12, 0, 2, 11, 7, 5, 3 ],
+        [11, 8, 12, 0, 5, 2, 15, 13, 10, 14, 3, 6, 7, 1, 9, 4 ],
+        [7, 9, 3, 1, 13, 12, 11, 14, 2, 6, 5, 10, 4, 0, 15, 8 ],
+        [9, 0, 5, 7, 2, 4, 10, 15, 14, 1, 11, 12, 6, 8, 3, 13 ],
+        [2, 12, 6, 10, 0, 11, 8, 3, 4, 13, 7, 5, 15, 14, 1, 9 ],
+        [12, 5, 1, 15, 14, 13, 4, 10, 0, 7, 6, 3, 9, 2, 8, 11 ],
+        [13, 11, 7, 14, 12, 1, 3, 9, 5, 0, 15, 4, 8, 6, 2, 10 ],
+        [6, 15, 14, 9, 11, 3, 0, 8, 12, 2, 13, 7, 1, 4, 10, 5 ],
+        [10, 2, 8, 4, 7, 6, 1, 5, 15, 11, 9, 14, 3, 12, 13, 0 ],
+        [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 ],
+        [14, 10, 4, 8, 9, 15, 13, 6, 1, 12, 0, 2, 11, 7, 5, 3 ]
+    ];
+
+    let mut v: [u64; 16] = [
+        ctx.h[0],
+        ctx.h[1],
+        ctx.h[2],
+        ctx.h[3],
+        ctx.h[4],
+        ctx.h[5],
+        ctx.h[6],
+        ctx.h[7],
+
+        BLAKE2B_IV[0],
+        BLAKE2B_IV[1],
+        BLAKE2B_IV[2],
+        BLAKE2B_IV[3],
+        BLAKE2B_IV[4],
+        BLAKE2B_IV[5],
+        BLAKE2B_IV[6],
+        BLAKE2B_IV[7],
+    ];
+
+    v[12] ^= ctx.t[0]; // low 64 bits of offset
+    v[13] ^= ctx.t[1]; // high 64 bits
+    if last {
+        v[14] = !v[14];
+    }
+
+    {
+        // Re-interpret the input buffer in the state as u64s
+        let m: &mut [u64; 16] = unsafe {
+            let b: &mut [u8; 128] = &mut ctx.b;
+            ::std::mem::transmute(b)
+        };
+
+        // It's OK to modify the buffer in place since this is the last time
+        // this data will be accessed before it's overwritten
+        if cfg!(target_endian = "big") {
+            for word in &mut m[..] {
+                *word = word.to_be();
+            }
+        }
+
+        for i in 0 .. 12 {
+            b2b_g(&mut v, 0, 4,  8, 12, m[SIGMA[i][ 0]], m[SIGMA[i][ 1]]);
+            b2b_g(&mut v, 1, 5,  9, 13, m[SIGMA[i][ 2]], m[SIGMA[i][ 3]]);
+            b2b_g(&mut v, 2, 6, 10, 14, m[SIGMA[i][ 4]], m[SIGMA[i][ 5]]);
+            b2b_g(&mut v, 3, 7, 11, 15, m[SIGMA[i][ 6]], m[SIGMA[i][ 7]]);
+            b2b_g(&mut v, 0, 5, 10, 15, m[SIGMA[i][ 8]], m[SIGMA[i][ 9]]);
+            b2b_g(&mut v, 1, 6, 11, 12, m[SIGMA[i][10]], m[SIGMA[i][11]]);
+            b2b_g(&mut v, 2, 7,  8, 13, m[SIGMA[i][12]], m[SIGMA[i][13]]);
+            b2b_g(&mut v, 3, 4,  9, 14, m[SIGMA[i][14]], m[SIGMA[i][15]]);
+        }
+    }
+
+    for i in 0 .. 8 {
+        ctx.h[i] ^= v[i] ^ v[i + 8];
+    }
+}
+
+pub fn blake2b_new(outlen: usize, key: &[u8]) -> Blake2bCtx {
+    assert!(outlen > 0 && outlen <= 64 && key.len() <= 64);
+
+    let mut ctx = Blake2bCtx {
+        b: [0; 128],
+        h: BLAKE2B_IV,
+        t: [0; 2],
+        c: 0,
+        outlen: outlen,
+    };
+
+    ctx.h[0] ^= 0x01010000 ^ ((key.len() << 8) as u64) ^ (outlen as u64);
+
+    if key.len() > 0 {
+       blake2b_update(&mut ctx, key);
+       ctx.c = ctx.b.len();
+    }
+
+    ctx
+}
+
+pub fn blake2b_update(ctx: &mut Blake2bCtx, mut data: &[u8])
+{
+    let mut bytes_to_copy = data.len();
+    let mut space_in_buffer = ctx.b.len() - ctx.c;
+
+    while bytes_to_copy > space_in_buffer {
+        checked_mem_copy(data, &mut ctx.b[ctx.c .. ], space_in_buffer);
+
+        ctx.t[0] = ctx.t[0].wrapping_add(ctx.b.len() as u64);
+        if ctx.t[0] < (ctx.b.len() as u64) {
+            ctx.t[1] += 1;
+        }
+        blake2b_compress(ctx, false);
+        ctx.c = 0;
+
+        data = &data[space_in_buffer .. ];
+        bytes_to_copy -= space_in_buffer;
+        space_in_buffer = ctx.b.len();
+    }
+
+    if bytes_to_copy > 0 {
+        checked_mem_copy(data, &mut ctx.b[ctx.c .. ], bytes_to_copy);
+        ctx.c += bytes_to_copy;
+    }
+}
+
+pub fn blake2b_final(mut ctx: Blake2bCtx, out: &mut [u8])
+{
+    ctx.t[0] = ctx.t[0].wrapping_add(ctx.c as u64);
+    if ctx.t[0] < ctx.c as u64 {
+        ctx.t[1] += 1;
+    }
+
+    while ctx.c < 128 {
+        ctx.b[ctx.c] = 0;
+        ctx.c += 1;
+    }
+
+    blake2b_compress(&mut ctx, true);
+
+    if cfg!(target_endian = "big") {
+        // Make sure that the data is in memory in little endian format, as is
+        // demanded by BLAKE2
+        for word in &mut ctx.h {
+            *word = word.to_le();
+        }
+    }
+
+    checked_mem_copy(&ctx.h, out, ctx.outlen);
+}
+
+#[inline(always)]
+fn checked_mem_copy<T1, T2>(from: &[T1], to: &mut [T2], byte_count: usize) {
+    let from_size = from.len() * ::std::mem::size_of::<T1>();
+    let to_size = to.len() * ::std::mem::size_of::<T2>();
+    assert!(from_size >= byte_count);
+    assert!(to_size >= byte_count);
+    let from_byte_ptr = from.as_ptr() as * const u8;
+    let to_byte_ptr = to.as_mut_ptr() as * mut u8;
+    unsafe {
+        ::std::ptr::copy_nonoverlapping(from_byte_ptr, to_byte_ptr, byte_count);
+    }
+}
+
+pub fn blake2b(out: &mut [u8], key: &[u8],  data: &[u8])
+{
+    let mut ctx = blake2b_new(out.len(), key);
+    blake2b_update(&mut ctx, data);
+    blake2b_final(ctx, out);
+}
+
+#[cfg(test)]
+fn selftest_seq(out: &mut [u8], seed: u32)
+{
+   let mut a: u32 = 0xDEAD4BADu32.wrapping_mul(seed);
+   let mut b: u32 = 1;
+
+   for i in 0 .. out.len() {
+       let t: u32 = a.wrapping_add(b);
+       a = b;
+       b = t;
+       out[i] = ((t >> 24) & 0xFF) as u8;
+   }
+}
+
+#[test]
+fn blake2b_selftest()
+{
+    // grand hash of hash results
+    const BLAKE2B_RES: [u8; 32] = [
+        0xC2, 0x3A, 0x78, 0x00, 0xD9, 0x81, 0x23, 0xBD,
+        0x10, 0xF5, 0x06, 0xC6, 0x1E, 0x29, 0xDA, 0x56,
+        0x03, 0xD7, 0x63, 0xB8, 0xBB, 0xAD, 0x2E, 0x73,
+        0x7F, 0x5E, 0x76, 0x5A, 0x7B, 0xCC, 0xD4, 0x75
+    ];
+
+    // parameter sets
+    const B2B_MD_LEN: [usize; 4] = [20, 32, 48, 64];
+    const B2B_IN_LEN: [usize; 6] = [0, 3, 128, 129, 255, 1024];
+
+    let mut data = [0u8; 1024];
+    let mut md = [0u8; 64];
+    let mut key = [0u8; 64];
+
+    let mut ctx = blake2b_new(32, &[]);
+
+    for i in 0 .. 4 {
+       let outlen = B2B_MD_LEN[i];
+       for j in 0 .. 6 {
+            let inlen = B2B_IN_LEN[j];
+
+            selftest_seq(&mut data[.. inlen], inlen as u32); // unkeyed hash
+            blake2b(&mut md[.. outlen], &[], &data[.. inlen]);
+            blake2b_update(&mut ctx, &md[.. outlen]); // hash the hash
+
+            selftest_seq(&mut key[0 .. outlen], outlen as u32); // keyed hash
+            blake2b(&mut md[.. outlen], &key[.. outlen], &data[.. inlen]);
+            blake2b_update(&mut ctx, &md[.. outlen]); // hash the hash
+       }
+    }
+
+    // compute and compare the hash of hashes
+    blake2b_final(ctx, &mut md[..]);
+    for i in 0 .. 32 {
+        assert_eq!(md[i], BLAKE2B_RES[i]);
+    }
+}

src/librustc_data_structures/lib.rs

@@ -42,6 +42,7 @@ extern crate serialize as rustc_serialize; // used by deriving
 extern crate libc;
 
 pub mod bitslice;
+pub mod blake2b;
 pub mod bitvec;
 pub mod graph;
 pub mod ivar;

src/librustc_incremental/calculate_svh/hasher.rs

@@ -9,38 +9,64 @@
 // except according to those terms.
 
 use std::hash::Hasher;
-use std::collections::hash_map::DefaultHasher;
+use std::mem;
+use rustc_data_structures::blake2b;
+use ich::Fingerprint;
 
 #[derive(Debug)]
 pub struct IchHasher {
-    // FIXME: this should use SHA1, not DefaultHasher. DefaultHasher is not
-    // built to avoid collisions.
-    state: DefaultHasher,
+    state: blake2b::Blake2bCtx,
     bytes_hashed: u64,
 }
 
 impl IchHasher {
     pub fn new() -> IchHasher {
         IchHasher {
-            state: DefaultHasher::new(),
+            state: blake2b::blake2b_new(mem::size_of::<Fingerprint>(), &[]),
             bytes_hashed: 0
         }
     }
 
     pub fn bytes_hashed(&self) -> u64 {
         self.bytes_hashed
     }
+
+    pub fn finish(self) -> Fingerprint {
+        let mut fingerprint = Fingerprint::zero();
+        blake2b::blake2b_final(self.state, &mut fingerprint.0);
+        fingerprint
+    }
 }
 
 impl Hasher for IchHasher {
-    #[inline]
     fn finish(&self) -> u64 {
-        self.state.finish()
+        bug!("Use other finish() implementation to get the full 128-bit hash.");
     }
 
     #[inline]
     fn write(&mut self, bytes: &[u8]) {
-        self.state.write(bytes);
+        blake2b::blake2b_update(&mut self.state, bytes);
         self.bytes_hashed += bytes.len() as u64;
     }
+
+    #[inline]
+    fn write_u16(&mut self, i: u16) {
+        self.write(&unsafe { mem::transmute::<_, [u8; 2]>(i.to_le()) })
+    }
+
+    #[inline]
+    fn write_u32(&mut self, i: u32) {
+        self.write(&unsafe { mem::transmute::<_, [u8; 4]>(i.to_le()) })
+    }
+
+    #[inline]
+    fn write_u64(&mut self, i: u64) {
+        self.write(&unsafe { mem::transmute::<_, [u8; 8]>(i.to_le()) })
+    }
+
+    #[inline]
+    fn write_usize(&mut self, i: usize) {
+        // always hash as u64, so we don't depend on the size of `usize`
+        self.write_u64(i as u64);
+    }
 }