The Tor Browser: mfbt/SHA1.cpp@97036ab72558 (annotated)

mfbt/SHA1.cpp@97036ab72558 (annotated)

mfbt/SHA1.cpp

Tue, 06 Jan 2015 21:39:09 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Tue, 06 Jan 2015 21:39:09 +0100
branch: TOR_BUG_9701
changeset 8: 97036ab72558
permissions: -rw-r--r--

Conditionally force memory storage according to privacy.thirdparty.isolate;
This solves Tor bug #9701, complying with disk avoidance documented in
https://www.torproject.org/projects/torbrowser/design/#disk-avoidance.

 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 #include "mozilla/Assertions.h"
 #include "mozilla/Endian.h"
 #include "mozilla/SHA1.h"
 #include <string.h>
 using mozilla::NativeEndian;
 using mozilla::SHA1Sum;
 static inline uint32_t
 SHA_ROTL(uint32_t t, uint32_t n)
 {
   MOZ_ASSERT(n < 32);
   return (t << n) | (t >> (32 - n));
 }
 static void
 shaCompress(volatile unsigned* X, const uint32_t* datain);
 #define SHA_F1(X, Y, Z) ((((Y) ^ (Z)) & (X)) ^ (Z))
 #define SHA_F2(X, Y, Z) ((X) ^ (Y) ^ (Z))
 #define SHA_F3(X, Y, Z) (((X) & (Y)) | ((Z) & ((X) | (Y))))
 #define SHA_F4(X, Y, Z) ((X) ^ (Y) ^ (Z))
 #define SHA_MIX(n, a, b, c)    XW(n) = SHA_ROTL(XW(a) ^ XW(b) ^ XW(c) ^XW(n), 1)
 SHA1Sum::SHA1Sum()
   : size(0), mDone(false)
 {
   // Initialize H with constants from FIPS180-1.
   H[0] = 0x67452301L;
   H[1] = 0xefcdab89L;
   H[2] = 0x98badcfeL;
   H[3] = 0x10325476L;
   H[4] = 0xc3d2e1f0L;
 }
 /*
  * Explanation of H array and index values:
  *
  * The context's H array is actually the concatenation of two arrays
  * defined by SHA1, the H array of state variables (5 elements),
  * and the W array of intermediate values, of which there are 16 elements.
  * The W array starts at H[5], that is W[0] is H[5].
  * Although these values are defined as 32-bit values, we use 64-bit
  * variables to hold them because the AMD64 stores 64 bit values in
  * memory MUCH faster than it stores any smaller values.
  *
  * Rather than passing the context structure to shaCompress, we pass
  * this combined array of H and W values.  We do not pass the address
  * of the first element of this array, but rather pass the address of an
  * element in the middle of the array, element X.  Presently X[0] is H[11].
  * So we pass the address of H[11] as the address of array X to shaCompress.
  * Then shaCompress accesses the members of the array using positive AND
  * negative indexes.
  *
  * Pictorially: (each element is 8 bytes)
  * H | H0 H1 H2 H3 H4 W0 W1 W2 W3 W4 W5 W6 W7 W8 W9 Wa Wb Wc Wd We Wf |
  * X |-11-10 -9 -8 -7 -6 -5 -4 -3 -2 -1 X0 X1 X2 X3 X4 X5 X6 X7 X8 X9 |
  *
  * The byte offset from X[0] to any member of H and W is always
  * representable in a signed 8-bit value, which will be encoded
  * as a single byte offset in the X86-64 instruction set.
  * If we didn't pass the address of H[11], and instead passed the
  * address of H[0], the offsets to elements H[16] and above would be
  * greater than 127, not representable in a signed 8-bit value, and the
  * x86-64 instruction set would encode every such offset as a 32-bit
  * signed number in each instruction that accessed element H[16] or
  * higher.  This results in much bigger and slower code.
  */
 #define H2X 11 /* X[0] is H[11], and H[0] is X[-11] */
 #define W2X  6 /* X[0] is W[6],  and W[0] is X[-6]  */
 /*
  *  SHA: Add data to context.
  */
 void
 SHA1Sum::update(const void* dataIn, uint32_t len)
 {
   MOZ_ASSERT(!mDone, "SHA1Sum can only be used to compute a single hash.");
   const uint8_t* data = static_cast<const uint8_t*>(dataIn);
   if (len == 0)
     return;
   /* Accumulate the byte count. */
   unsigned int lenB = static_cast<unsigned int>(size) & 63U;
   size += len;
   /* Read the data into W and process blocks as they get full. */
   unsigned int togo;
   if (lenB > 0) {
     togo = 64U - lenB;
     if (len < togo)
       togo = len;
     memcpy(u.b + lenB, data, togo);
     len -= togo;
     data += togo;
     lenB = (lenB + togo) & 63U;
     if (!lenB)
       shaCompress(&H[H2X], u.w);
   }
   while (len >= 64U) {
     len -= 64U;
     shaCompress(&H[H2X], reinterpret_cast<const uint32_t*>(data));
     data += 64U;
   }
   if (len > 0)
     memcpy(u.b, data, len);
 }
 /*
  *  SHA: Generate hash value
  */
 void
 SHA1Sum::finish(SHA1Sum::Hash& hashOut)
 {
   MOZ_ASSERT(!mDone, "SHA1Sum can only be used to compute a single hash.");
   uint64_t size2 = size;
   uint32_t lenB = uint32_t(size2) & 63;
   static const uint8_t bulk_pad[64] =
     { 0x80,0,0,0,0,0,0,0,0,0,
 ,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
 ,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0 };
   /* Pad with a binary 1 (e.g. 0x80), then zeroes, then length in bits. */
   update(bulk_pad, (((55 + 64) - lenB) & 63) + 1);
   MOZ_ASSERT((uint32_t(size) & 63) == 56);
   /* Convert size from bytes to bits. */
   size2 <<= 3;
   u.w[14] = NativeEndian::swapToBigEndian(uint32_t(size2 >> 32));
   u.w[15] = NativeEndian::swapToBigEndian(uint32_t(size2));
   shaCompress(&H[H2X], u.w);
   /* Output hash. */
   u.w[0] = NativeEndian::swapToBigEndian(H[0]);
   u.w[1] = NativeEndian::swapToBigEndian(H[1]);
   u.w[2] = NativeEndian::swapToBigEndian(H[2]);
   u.w[3] = NativeEndian::swapToBigEndian(H[3]);
   u.w[4] = NativeEndian::swapToBigEndian(H[4]);
   memcpy(hashOut, u.w, 20);
   mDone = true;
 }
 /*
  *  SHA: Compression function, unrolled.
  *
  * Some operations in shaCompress are done as 5 groups of 16 operations.
  * Others are done as 4 groups of 20 operations.
  * The code below shows that structure.
  *
  * The functions that compute the new values of the 5 state variables
  * A-E are done in 4 groups of 20 operations (or you may also think
  * of them as being done in 16 groups of 5 operations).  They are
  * done by the SHA_RNDx macros below, in the right column.
  *
  * The functions that set the 16 values of the W array are done in
  * 5 groups of 16 operations.  The first group is done by the
  * LOAD macros below, the latter 4 groups are done by SHA_MIX below,
  * in the left column.
  *
  * gcc's optimizer observes that each member of the W array is assigned
  * a value 5 times in this code.  It reduces the number of store
  * operations done to the W array in the context (that is, in the X array)
  * by creating a W array on the stack, and storing the W values there for
  * the first 4 groups of operations on W, and storing the values in the
  * context's W array only in the fifth group.  This is undesirable.
  * It is MUCH bigger code than simply using the context's W array, because
  * all the offsets to the W array in the stack are 32-bit signed offsets,
  * and it is no faster than storing the values in the context's W array.
  *
  * The original code for sha_fast.c prevented this creation of a separate
  * W array in the stack by creating a W array of 80 members, each of
  * whose elements is assigned only once. It also separated the computations
  * of the W array values and the computations of the values for the 5
  * state variables into two separate passes, W's, then A-E's so that the
  * second pass could be done all in registers (except for accessing the W
  * array) on machines with fewer registers.  The method is suboptimal
  * for machines with enough registers to do it all in one pass, and it
  * necessitates using many instructions with 32-bit offsets.
  *
  * This code eliminates the separate W array on the stack by a completely
  * different means: by declaring the X array volatile.  This prevents
  * the optimizer from trying to reduce the use of the X array by the
  * creation of a MORE expensive W array on the stack. The result is
  * that all instructions use signed 8-bit offsets and not 32-bit offsets.
  *
  * The combination of this code and the -O3 optimizer flag on GCC 3.4.3
  * results in code that is 3 times faster than the previous NSS sha_fast
  * code on AMD64.
  */
 static void
 shaCompress(volatile unsigned *X, const uint32_t *inbuf)
 {
   unsigned A, B, C, D, E;
 #define XH(n) X[n - H2X]
 #define XW(n) X[n - W2X]
 #define K0 0x5a827999L
 #define K1 0x6ed9eba1L
 #define K2 0x8f1bbcdcL
 #define K3 0xca62c1d6L
 #define SHA_RND1(a, b, c, d, e, n) \
   a = SHA_ROTL(b, 5) + SHA_F1(c, d, e) + a + XW(n) + K0; c = SHA_ROTL(c, 30)
 #define SHA_RND2(a, b, c, d, e, n) \
   a = SHA_ROTL(b, 5) + SHA_F2(c, d, e) + a + XW(n) + K1; c = SHA_ROTL(c, 30)
 #define SHA_RND3(a, b, c, d, e, n) \
   a = SHA_ROTL(b, 5) + SHA_F3(c, d, e) + a + XW(n) + K2; c = SHA_ROTL(c, 30)
 #define SHA_RND4(a, b, c, d, e, n) \
   a = SHA_ROTL(b ,5) + SHA_F4(c, d, e) + a + XW(n) + K3; c = SHA_ROTL(c, 30)
 #define LOAD(n) XW(n) = NativeEndian::swapToBigEndian(inbuf[n])
   A = XH(0);
   B = XH(1);
   C = XH(2);
   D = XH(3);
   E = XH(4);
   LOAD(0);		   SHA_RND1(E,A,B,C,D, 0);
   LOAD(1);		   SHA_RND1(D,E,A,B,C, 1);
   LOAD(2);		   SHA_RND1(C,D,E,A,B, 2);
   LOAD(3);		   SHA_RND1(B,C,D,E,A, 3);
   LOAD(4);		   SHA_RND1(A,B,C,D,E, 4);
   LOAD(5);		   SHA_RND1(E,A,B,C,D, 5);
   LOAD(6);		   SHA_RND1(D,E,A,B,C, 6);
   LOAD(7);		   SHA_RND1(C,D,E,A,B, 7);
   LOAD(8);		   SHA_RND1(B,C,D,E,A, 8);
   LOAD(9);		   SHA_RND1(A,B,C,D,E, 9);
   LOAD(10);		   SHA_RND1(E,A,B,C,D,10);
   LOAD(11);		   SHA_RND1(D,E,A,B,C,11);
   LOAD(12);		   SHA_RND1(C,D,E,A,B,12);
   LOAD(13);		   SHA_RND1(B,C,D,E,A,13);
   LOAD(14);		   SHA_RND1(A,B,C,D,E,14);
   LOAD(15);		   SHA_RND1(E,A,B,C,D,15);
   SHA_MIX( 0, 13,  8,  2); SHA_RND1(D,E,A,B,C, 0);
   SHA_MIX( 1, 14,  9,  3); SHA_RND1(C,D,E,A,B, 1);
   SHA_MIX( 2, 15, 10,  4); SHA_RND1(B,C,D,E,A, 2);
   SHA_MIX( 3,  0, 11,  5); SHA_RND1(A,B,C,D,E, 3);
   SHA_MIX( 4,  1, 12,  6); SHA_RND2(E,A,B,C,D, 4);
   SHA_MIX( 5,  2, 13,  7); SHA_RND2(D,E,A,B,C, 5);
   SHA_MIX( 6,  3, 14,  8); SHA_RND2(C,D,E,A,B, 6);
   SHA_MIX( 7,  4, 15,  9); SHA_RND2(B,C,D,E,A, 7);
   SHA_MIX( 8,  5,  0, 10); SHA_RND2(A,B,C,D,E, 8);
   SHA_MIX( 9,  6,  1, 11); SHA_RND2(E,A,B,C,D, 9);
   SHA_MIX(10,  7,  2, 12); SHA_RND2(D,E,A,B,C,10);
   SHA_MIX(11,  8,  3, 13); SHA_RND2(C,D,E,A,B,11);
   SHA_MIX(12,  9,  4, 14); SHA_RND2(B,C,D,E,A,12);
   SHA_MIX(13, 10,  5, 15); SHA_RND2(A,B,C,D,E,13);
   SHA_MIX(14, 11,  6,  0); SHA_RND2(E,A,B,C,D,14);
   SHA_MIX(15, 12,  7,  1); SHA_RND2(D,E,A,B,C,15);
   SHA_MIX( 0, 13,  8,  2); SHA_RND2(C,D,E,A,B, 0);
   SHA_MIX( 1, 14,  9,  3); SHA_RND2(B,C,D,E,A, 1);
   SHA_MIX( 2, 15, 10,  4); SHA_RND2(A,B,C,D,E, 2);
   SHA_MIX( 3,  0, 11,  5); SHA_RND2(E,A,B,C,D, 3);
   SHA_MIX( 4,  1, 12,  6); SHA_RND2(D,E,A,B,C, 4);
   SHA_MIX( 5,  2, 13,  7); SHA_RND2(C,D,E,A,B, 5);
   SHA_MIX( 6,  3, 14,  8); SHA_RND2(B,C,D,E,A, 6);
   SHA_MIX( 7,  4, 15,  9); SHA_RND2(A,B,C,D,E, 7);
   SHA_MIX( 8,  5,  0, 10); SHA_RND3(E,A,B,C,D, 8);
   SHA_MIX( 9,  6,  1, 11); SHA_RND3(D,E,A,B,C, 9);
   SHA_MIX(10,  7,  2, 12); SHA_RND3(C,D,E,A,B,10);
   SHA_MIX(11,  8,  3, 13); SHA_RND3(B,C,D,E,A,11);
   SHA_MIX(12,  9,  4, 14); SHA_RND3(A,B,C,D,E,12);
   SHA_MIX(13, 10,  5, 15); SHA_RND3(E,A,B,C,D,13);
   SHA_MIX(14, 11,  6,  0); SHA_RND3(D,E,A,B,C,14);
   SHA_MIX(15, 12,  7,  1); SHA_RND3(C,D,E,A,B,15);
   SHA_MIX( 0, 13,  8,  2); SHA_RND3(B,C,D,E,A, 0);
   SHA_MIX( 1, 14,  9,  3); SHA_RND3(A,B,C,D,E, 1);
   SHA_MIX( 2, 15, 10,  4); SHA_RND3(E,A,B,C,D, 2);
   SHA_MIX( 3,  0, 11,  5); SHA_RND3(D,E,A,B,C, 3);
   SHA_MIX( 4,  1, 12,  6); SHA_RND3(C,D,E,A,B, 4);
   SHA_MIX( 5,  2, 13,  7); SHA_RND3(B,C,D,E,A, 5);
   SHA_MIX( 6,  3, 14,  8); SHA_RND3(A,B,C,D,E, 6);
   SHA_MIX( 7,  4, 15,  9); SHA_RND3(E,A,B,C,D, 7);
   SHA_MIX( 8,  5,  0, 10); SHA_RND3(D,E,A,B,C, 8);
   SHA_MIX( 9,  6,  1, 11); SHA_RND3(C,D,E,A,B, 9);
   SHA_MIX(10,  7,  2, 12); SHA_RND3(B,C,D,E,A,10);
   SHA_MIX(11,  8,  3, 13); SHA_RND3(A,B,C,D,E,11);
   SHA_MIX(12,  9,  4, 14); SHA_RND4(E,A,B,C,D,12);
   SHA_MIX(13, 10,  5, 15); SHA_RND4(D,E,A,B,C,13);
   SHA_MIX(14, 11,  6,  0); SHA_RND4(C,D,E,A,B,14);
   SHA_MIX(15, 12,  7,  1); SHA_RND4(B,C,D,E,A,15);
   SHA_MIX( 0, 13,  8,  2); SHA_RND4(A,B,C,D,E, 0);
   SHA_MIX( 1, 14,  9,  3); SHA_RND4(E,A,B,C,D, 1);
   SHA_MIX( 2, 15, 10,  4); SHA_RND4(D,E,A,B,C, 2);
   SHA_MIX( 3,  0, 11,  5); SHA_RND4(C,D,E,A,B, 3);
   SHA_MIX( 4,  1, 12,  6); SHA_RND4(B,C,D,E,A, 4);
   SHA_MIX( 5,  2, 13,  7); SHA_RND4(A,B,C,D,E, 5);
   SHA_MIX( 6,  3, 14,  8); SHA_RND4(E,A,B,C,D, 6);
   SHA_MIX( 7,  4, 15,  9); SHA_RND4(D,E,A,B,C, 7);
   SHA_MIX( 8,  5,  0, 10); SHA_RND4(C,D,E,A,B, 8);
   SHA_MIX( 9,  6,  1, 11); SHA_RND4(B,C,D,E,A, 9);
   SHA_MIX(10,  7,  2, 12); SHA_RND4(A,B,C,D,E,10);
   SHA_MIX(11,  8,  3, 13); SHA_RND4(E,A,B,C,D,11);
   SHA_MIX(12,  9,  4, 14); SHA_RND4(D,E,A,B,C,12);
   SHA_MIX(13, 10,  5, 15); SHA_RND4(C,D,E,A,B,13);
   SHA_MIX(14, 11,  6,  0); SHA_RND4(B,C,D,E,A,14);
   SHA_MIX(15, 12,  7,  1); SHA_RND4(A,B,C,D,E,15);
   XH(0) += A;
   XH(1) += B;
   XH(2) += C;
   XH(3) += D;
   XH(4) += E;
 }

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mfbt/SHA1.cpp@97036ab72558 (annotated)

mfbt/SHA1.cpp