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runtime: use some startup randomness in the fallback hashes
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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 golang#9365

Change-Id: Ib19968168e1bbc541d1d28be2701bb83e53f1e24
Reviewed-on: https://go-review.googlesource.com/2344
Reviewed-by: Ian Lance Taylor <[email protected]>
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@randall77
randall77 committed Jan 7, 2015
1 parent 31775c5 commit ce5cb03
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Showing 3 changed files with 75 additions and 82 deletions.
20 changes: 12 additions & 8 deletions src/runtime/alg.go
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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
Expand All @@ -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
}
66 changes: 31 additions & 35 deletions src/runtime/hash32.go
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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
Expand All @@ -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))
}
71 changes: 32 additions & 39 deletions src/runtime/hash64.go
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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
Expand All @@ -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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