| From 51fc6dc8f948047364f7d42a4ed89b416c6cc0a3 Mon Sep 17 00:00:00 2001 |
| From: Alexey Dobriyan <adobriyan@gmail.com> |
| Date: Sat, 14 Jan 2012 21:40:57 +0300 |
| Subject: crypto: sha512 - reduce stack usage to safe number |
| |
| From: Alexey Dobriyan <adobriyan@gmail.com> |
| |
| commit 51fc6dc8f948047364f7d42a4ed89b416c6cc0a3 upstream. |
| |
| For rounds 16--79, W[i] only depends on W[i - 2], W[i - 7], W[i - 15] and W[i - 16]. |
| Consequently, keeping all W[80] array on stack is unnecessary, |
| only 16 values are really needed. |
| |
| Using W[16] instead of W[80] greatly reduces stack usage |
| (~750 bytes to ~340 bytes on x86_64). |
| |
| Line by line explanation: |
| * BLEND_OP |
| array is "circular" now, all indexes have to be modulo 16. |
| Round number is positive, so remainder operation should be |
| without surprises. |
| |
| * initial full message scheduling is trimmed to first 16 values which |
| come from data block, the rest is calculated before it's needed. |
| |
| * original loop body is unrolled version of new SHA512_0_15 and |
| SHA512_16_79 macros, unrolling was done to not do explicit variable |
| renaming. Otherwise it's the very same code after preprocessing. |
| See sha1_transform() code which does the same trick. |
| |
| Patch survives in-tree crypto test and original bugreport test |
| (ping flood with hmac(sha512). |
| |
| See FIPS 180-2 for SHA-512 definition |
| http://csrc.nist.gov/publications/fips/fips180-2/fips180-2withchangenotice.pdf |
| |
| Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com> |
| Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| |
| --- |
| crypto/sha512_generic.c | 58 ++++++++++++++++++++++++++++-------------------- |
| 1 file changed, 34 insertions(+), 24 deletions(-) |
| |
| --- a/crypto/sha512_generic.c |
| +++ b/crypto/sha512_generic.c |
| @@ -78,7 +78,7 @@ static inline void LOAD_OP(int I, u64 *W |
| |
| static inline void BLEND_OP(int I, u64 *W) |
| { |
| - W[I] = s1(W[I-2]) + W[I-7] + s0(W[I-15]) + W[I-16]; |
| + W[I % 16] += s1(W[(I-2) % 16]) + W[(I-7) % 16] + s0(W[(I-15) % 16]); |
| } |
| |
| static void |
| @@ -87,38 +87,48 @@ sha512_transform(u64 *state, const u8 *i |
| u64 a, b, c, d, e, f, g, h, t1, t2; |
| |
| int i; |
| - u64 W[80]; |
| + u64 W[16]; |
| |
| /* load the input */ |
| for (i = 0; i < 16; i++) |
| LOAD_OP(i, W, input); |
| |
| - for (i = 16; i < 80; i++) { |
| - BLEND_OP(i, W); |
| - } |
| - |
| /* load the state into our registers */ |
| a=state[0]; b=state[1]; c=state[2]; d=state[3]; |
| e=state[4]; f=state[5]; g=state[6]; h=state[7]; |
| |
| - /* now iterate */ |
| - for (i=0; i<80; i+=8) { |
| - t1 = h + e1(e) + Ch(e,f,g) + sha512_K[i ] + W[i ]; |
| - t2 = e0(a) + Maj(a,b,c); d+=t1; h=t1+t2; |
| - t1 = g + e1(d) + Ch(d,e,f) + sha512_K[i+1] + W[i+1]; |
| - t2 = e0(h) + Maj(h,a,b); c+=t1; g=t1+t2; |
| - t1 = f + e1(c) + Ch(c,d,e) + sha512_K[i+2] + W[i+2]; |
| - t2 = e0(g) + Maj(g,h,a); b+=t1; f=t1+t2; |
| - t1 = e + e1(b) + Ch(b,c,d) + sha512_K[i+3] + W[i+3]; |
| - t2 = e0(f) + Maj(f,g,h); a+=t1; e=t1+t2; |
| - t1 = d + e1(a) + Ch(a,b,c) + sha512_K[i+4] + W[i+4]; |
| - t2 = e0(e) + Maj(e,f,g); h+=t1; d=t1+t2; |
| - t1 = c + e1(h) + Ch(h,a,b) + sha512_K[i+5] + W[i+5]; |
| - t2 = e0(d) + Maj(d,e,f); g+=t1; c=t1+t2; |
| - t1 = b + e1(g) + Ch(g,h,a) + sha512_K[i+6] + W[i+6]; |
| - t2 = e0(c) + Maj(c,d,e); f+=t1; b=t1+t2; |
| - t1 = a + e1(f) + Ch(f,g,h) + sha512_K[i+7] + W[i+7]; |
| - t2 = e0(b) + Maj(b,c,d); e+=t1; a=t1+t2; |
| +#define SHA512_0_15(i, a, b, c, d, e, f, g, h) \ |
| + t1 = h + e1(e) + Ch(e, f, g) + sha512_K[i] + W[i]; \ |
| + t2 = e0(a) + Maj(a, b, c); \ |
| + d += t1; \ |
| + h = t1 + t2 |
| + |
| +#define SHA512_16_79(i, a, b, c, d, e, f, g, h) \ |
| + BLEND_OP(i, W); \ |
| + t1 = h + e1(e) + Ch(e, f, g) + sha512_K[i] + W[(i)%16]; \ |
| + t2 = e0(a) + Maj(a, b, c); \ |
| + d += t1; \ |
| + h = t1 + t2 |
| + |
| + for (i = 0; i < 16; i += 8) { |
| + SHA512_0_15(i, a, b, c, d, e, f, g, h); |
| + SHA512_0_15(i + 1, h, a, b, c, d, e, f, g); |
| + SHA512_0_15(i + 2, g, h, a, b, c, d, e, f); |
| + SHA512_0_15(i + 3, f, g, h, a, b, c, d, e); |
| + SHA512_0_15(i + 4, e, f, g, h, a, b, c, d); |
| + SHA512_0_15(i + 5, d, e, f, g, h, a, b, c); |
| + SHA512_0_15(i + 6, c, d, e, f, g, h, a, b); |
| + SHA512_0_15(i + 7, b, c, d, e, f, g, h, a); |
| + } |
| + for (i = 16; i < 80; i += 8) { |
| + SHA512_16_79(i, a, b, c, d, e, f, g, h); |
| + SHA512_16_79(i + 1, h, a, b, c, d, e, f, g); |
| + SHA512_16_79(i + 2, g, h, a, b, c, d, e, f); |
| + SHA512_16_79(i + 3, f, g, h, a, b, c, d, e); |
| + SHA512_16_79(i + 4, e, f, g, h, a, b, c, d); |
| + SHA512_16_79(i + 5, d, e, f, g, h, a, b, c); |
| + SHA512_16_79(i + 6, c, d, e, f, g, h, a, b); |
| + SHA512_16_79(i + 7, b, c, d, e, f, g, h, a); |
| } |
| |
| state[0] += a; state[1] += b; state[2] += c; state[3] += d; |