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Commit ce5cb037 authored by Keith Randall's avatar Keith Randall
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runtime: use some startup randomness in the fallback hashes 

Fold in some startup randomness to make the hash vary across
different runs.  This helps prevent attackers from choosing
keys that all map to the same bucket.

Also, reorganize the hash a bit.  Move the *m1 multiply to after
the xor of the current hash and the message.  For hash quality
it doesn't really matter, but for DDOS resistance it helps a lot
(any processing done to the message before it is merged with the
random seed is useless, as it is easily inverted by an attacker).

Update #9365

Change-Id: Ib19968168e1bbc541d1d28be2701bb83e53f1e24
Reviewed-on: https://go-review.googlesource.com/2344Reviewed-by: default avatarIan Lance Taylor <iant@golang.org>
parent 31775c5a
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Inline Side-by-side
Showing with 75 additions and 82 deletions
src/runtime/alg.go
View file @ ce5cb037
......@@ -285,20 +285,21 @@ func memclrBytes(b []byte) {
memclr(s.array, uintptr(s.len))
}
// used in asm_{386,amd64}.s
const hashRandomBytes = ptrSize / 4 * 64
// used in asm_{386,amd64}.s to seed the hash function
var aeskeysched [hashRandomBytes]byte
func init() {
if GOOS == "nacl" {
return
}
// used in hash{32,64}.go to seed the hash function
var hashkey [4]uintptr
func init() {
// Install aes hash algorithm if we have the instructions we need
if (cpuid_ecx&(1<<25)) != 0 && // aes (aesenc)
(cpuid_ecx&(1<<9)) != 0 && // sse3 (pshufb)
(cpuid_ecx&(1<<19)) != 0 { // sse4.1 (pinsr{d,q})
if (GOARCH == "386" || GOARCH == "amd64") &&
GOOS != "nacl" &&
cpuid_ecx&(1<<25) != 0 && // aes (aesenc)
cpuid_ecx&(1<<9) != 0 && // sse3 (pshufb)
cpuid_ecx&(1<<19) != 0 { // sse4.1 (pinsr{d,q})
useAeshash = true
algarray[alg_MEM].hash = aeshash
algarray[alg_MEM8].hash = aeshash
......@@ -309,5 +310,8 @@ func init() {
algarray[alg_STRING].hash = aeshashstr
// Initialize with random data so hash collisions will be hard to engineer.
getRandomData(aeskeysched[:])
return
}
getRandomData((*[len(hashkey) * ptrSize]byte)(unsafe.Pointer(&hashkey))[:])
hashkey[0] |= 1 // make sure this number is odd
}
src/runtime/hash32.go
View file @ ce5cb037
......@@ -24,54 +24,53 @@ func memhash(p unsafe.Pointer, s, seed uintptr) uintptr {
if GOARCH == "386" && GOOS != "nacl" && useAeshash {
return aeshash(p, s, seed)
}
h := uint32(seed + s)
h := uint32(seed + s*hashkey[0])
tail:
switch {
case s == 0:
case s < 4:
w := uint32(*(*byte)(p))
w += uint32(*(*byte)(add(p, s>>1))) << 8
w += uint32(*(*byte)(add(p, s-1))) << 16
h ^= w * m1
h ^= uint32(*(*byte)(p))
h ^= uint32(*(*byte)(add(p, s>>1))) << 8
h ^= uint32(*(*byte)(add(p, s-1))) << 16
h = rotl_15(h*m1) * m2
case s == 4:
h ^= readUnaligned32(p) * m1
h ^= readUnaligned32(p)
h = rotl_15(h*m1) * m2
case s <= 8:
h ^= readUnaligned32(p) * m1
h = rotl_15(h) * m2
h = rotl_11(h)
h ^= readUnaligned32(add(p, s-4)) * m1
h ^= readUnaligned32(p)
h = rotl_15(h*m1) * m2
h ^= readUnaligned32(add(p, s-4))
h = rotl_15(h*m1) * m2
case s <= 16:
h ^= readUnaligned32(p) * m1
h = rotl_15(h) * m2
h = rotl_11(h)
h ^= readUnaligned32(add(p, 4)) * m1
h = rotl_15(h) * m2
h = rotl_11(h)
h ^= readUnaligned32(add(p, s-8)) * m1
h = rotl_15(h) * m2
h = rotl_11(h)
h ^= readUnaligned32(add(p, s-4)) * m1
h ^= readUnaligned32(p)
h = rotl_15(h*m1) * m2
h ^= readUnaligned32(add(p, 4))
h = rotl_15(h*m1) * m2
h ^= readUnaligned32(add(p, s-8))
h = rotl_15(h*m1) * m2
h ^= readUnaligned32(add(p, s-4))
h = rotl_15(h*m1) * m2
default:
v1 := h
v2 := h + m1
v3 := h + m2
v4 := h + m3
v2 := uint32(hashkey[1])
v3 := uint32(hashkey[2])
v4 := uint32(hashkey[3])
for s >= 16 {
v1 ^= readUnaligned32(p) * m1
v1 = rotl_15(v1) * m2
v1 ^= readUnaligned32(p)
v1 = rotl_15(v1*m1) * m2
p = add(p, 4)
v2 ^= readUnaligned32(p) * m1
v2 = rotl_15(v2) * m2
v2 ^= readUnaligned32(p)
v2 = rotl_15(v2*m2) * m3
p = add(p, 4)
v3 ^= readUnaligned32(p) * m1
v3 = rotl_15(v3) * m2
v3 ^= readUnaligned32(p)
v3 = rotl_15(v3*m3) * m4
p = add(p, 4)
v4 ^= readUnaligned32(p) * m1
v4 = rotl_15(v4) * m2
v4 ^= readUnaligned32(p)
v4 = rotl_15(v4*m4) * m1
p = add(p, 4)
s -= 16
}
h = rotl_11(v1)*m1 + rotl_11(v2)*m2 + rotl_11(v3)*m3 + rotl_11(v4)*m4
h = v1 ^ v2 ^ v3 ^ v4
goto tail
}
h ^= h >> 17
......@@ -88,6 +87,3 @@ tail:
func rotl_15(x uint32) uint32 {
return (x << 15) | (x >> (32 - 15))
}
func rotl_11(x uint32) uint32 {
return (x << 11) | (x >> (32 - 11))
}
src/runtime/hash64.go
View file @ ce5cb037
......@@ -24,61 +24,57 @@ func memhash(p unsafe.Pointer, s, seed uintptr) uintptr {
if GOARCH == "amd64" && GOOS != "nacl" && useAeshash {
return aeshash(p, s, seed)
}
h := uint64(seed + s)
h := uint64(seed + s*hashkey[0])
tail:
switch {
case s == 0:
case s < 4:
w := uint64(*(*byte)(p))
w += uint64(*(*byte)(add(p, s>>1))) << 8
w += uint64(*(*byte)(add(p, s-1))) << 16
h ^= w * m1
h ^= uint64(*(*byte)(p))
h ^= uint64(*(*byte)(add(p, s>>1))) << 8
h ^= uint64(*(*byte)(add(p, s-1))) << 16
h = rotl_31(h*m1) * m2
case s <= 8:
w := uint64(readUnaligned32(p))
w += uint64(readUnaligned32(add(p, s-4))) << 32
h ^= w * m1
h ^= uint64(readUnaligned32(p))
h ^= uint64(readUnaligned32(add(p, s-4))) << 32
h = rotl_31(h*m1) * m2
case s <= 16:
h ^= readUnaligned64(p) * m1
h = rotl_31(h) * m2
h = rotl_27(h)
h ^= readUnaligned64(add(p, s-8)) * m1
h ^= readUnaligned64(p)
h = rotl_31(h*m1) * m2
h ^= readUnaligned64(add(p, s-8))
h = rotl_31(h*m1) * m2
case s <= 32:
h ^= readUnaligned64(p) * m1
h = rotl_31(h) * m2
h = rotl_27(h)
h ^= readUnaligned64(add(p, 8)) * m1
h = rotl_31(h) * m2
h = rotl_27(h)
h ^= readUnaligned64(add(p, s-16)) * m1
h = rotl_31(h) * m2
h = rotl_27(h)
h ^= readUnaligned64(add(p, s-8)) * m1
h ^= readUnaligned64(p)
h = rotl_31(h*m1) * m2
h ^= readUnaligned64(add(p, 8))
h = rotl_31(h*m1) * m2
h ^= readUnaligned64(add(p, s-16))
h = rotl_31(h*m1) * m2
h ^= readUnaligned64(add(p, s-8))
h = rotl_31(h*m1) * m2
default:
v1 := h
v2 := h + m1
v3 := h + m2
v4 := h + m3
v2 := uint64(hashkey[1])
v3 := uint64(hashkey[2])
v4 := uint64(hashkey[3])
for s >= 32 {
v1 ^= readUnaligned64(p) * m1
v1 = rotl_31(v1) * m2
v1 ^= readUnaligned64(p)
v1 = rotl_31(v1*m1) * m2
p = add(p, 8)
v2 ^= readUnaligned64(p) * m1
v2 = rotl_31(v2) * m2
v2 ^= readUnaligned64(p)
v2 = rotl_31(v2*m2) * m3
p = add(p, 8)
v3 ^= readUnaligned64(p) * m1
v3 = rotl_31(v3) * m2
v3 ^= readUnaligned64(p)
v3 = rotl_31(v3*m3) * m4
p = add(p, 8)
v4 ^= readUnaligned64(p) * m1
v4 = rotl_31(v4) * m2
v4 ^= readUnaligned64(p)
v4 = rotl_31(v4*m4) * m1
p = add(p, 8)
s -= 32
}
h = rotl_27(v1)*m1 + rotl_27(v2)*m2 + rotl_27(v3)*m3 + rotl_27(v4)*m4
h = v1 ^ v2 ^ v3 ^ v4
goto tail
}
h ^= h >> 33
h *= m2
h ^= h >> 29
h *= m3
h ^= h >> 32
......@@ -91,6 +87,3 @@ tail:
func rotl_31(x uint64) uint64 {
return (x << 31) | (x >> (64 - 31))
}
func rotl_27(x uint64) uint64 {
return (x << 27) | (x >> (64 - 27))
}
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