George MacKerron: code blog

//
//  NSThings+SHA1Additions.h
//
 
@interface NSData (GMSHA1)
 
- (NSData *)gm_SHA1Digest;
- (NSString *)gm_SHA1HexDigest;
 
@end
 
@interface NSString (GMSHA1)
 
- (NSData *)gm_SHA1Digest;
- (NSString *)gm_SHA1HexDigest;
 
@end

//
//  NSData+hexadecimalRepresentation.h
//
 
@interface NSData (GMNSDataHexAdditions)
 
- (NSString *)gm_hexadecimalEncodedString;
 
@end

//
//  NSThings+SHA1Additions.c
//
 
/*
 
SHA-1 in C
By Steve Reid <sreid@sea-to-sky.net>
100% Public Domain
 
-----------------
Modified 7/98
By James H. Brown <jbrown@burgoyne.com>
Still 100% Public Domain
 
Corrected a problem which generated improper hash values on 16 bit machines
Routine SHA1Update changed from
  void SHA1Update(SHA1_CTX* context, unsigned char* data, unsigned int len) 
to
  void SHA1Update(SHA1_CTX* context, unsigned char* data, unsigned long len)
 
The 'len' parameter was declared an int which works fine on 32 bit machines.
However, on 16 bit machines an int is too small for the shifts being done
against it.  This caused the hash function to generate incorrect values if len 
was greater than 8191 (8K - 1) due to the 'len << 3' on line 3 of 
SHA1Update().
 
Since the file IO in main() reads 16K at a time, any file 8K or larger would
be guaranteed to generate the wrong hash (e.g. Test Vector #3, a million
"a"s).
 
I also changed the declaration of variables i & j in SHA1Update tounsigned 
long from unsigned int for the same reason.
 
These changes should make no difference to any 32 bit implementations since
an int and a long are the same size in those environments.
 
--
I also corrected a few compiler warnings generated by Borland C.
1. Added #include <process.h> for exit() prototype
2. Removed unused variable 'j' in SHA1Final
3. Changed exit(0) to return(0) at end of main.
 
ALL changes I made can be located by searching for comments containing 'JHB'
-----------------
Modified 8/98
By Steve Reid <sreid@sea-to-sky.net>
Still 100% public domain
 
1- Removed #include <process.h> and used return() instead of exit()
2- Fixed overwriting of finalcount in SHA1Final() (discovered by Chris Hall)
3- Changed email address from steve@edmweb.com to sreid@sea-to-sky.net
 
-----------------
Modified 4/01
By Saul Kravitz <Saul.Kravitz@celera.com>
Still 100% PD
Modified to run on Compaq Alpha hardware.
 
-----------------
Modified 07/2002
By Ralph Giles <giles@ghostscript.com>
Still 100% public domain
modified for use with stdint types, autoconf
code cleanup, removed attribution comments
switched SHA1Final() argument order for consistency
use SHA1_ prefix for public api
move public api to sha1.h
 
-----------------
Modified 05/2012
By George MacKerron <george@mackerron.com>
Still public domain
Converted to Objective-C categories for use in iOS
Stripped out some #ifdef code paths
 
*/
 
#import "NSThings+SHA1Additions.h"
#import "NSData+HexAdditions.h"
 
#include <stdio.h>
#include <string.h>
#include <stdint.h>
 
#define SHA1_DIGEST_SIZE 20
 
typedef struct {
  uint32_t state[5];
  uint32_t count[2];
  uint8_t  buffer[64];
} SHA1_CTX;
 
void SHA1_Transform(uint32_t state[5], const uint8_t buffer[64]);
 
#define rol(value, bits) (((value) << (bits)) | ((value) >> (32 - (bits))))
 
/* blk0() and blk() perform the initial expand. */
/* I got the idea of expanding during the round function from SSLeay */
/* FIXME: can we do this in an endian-proof way? */
#ifdef WORDS_BIGENDIAN
#define blk0(i) block->l[i]
#else
#define blk0(i) (block->l[i] = (rol(block->l[i],24)&0xFF00FF00) \
|(rol(block->l[i],8)&0x00FF00FF))
#endif
#define blk(i) (block->l[i&15] = rol(block->l[(i+13)&15]^block->l[(i+8)&15] \
^block->l[(i+2)&15]^block->l[i&15],1))
 
/* (R0+R1), R2, R3, R4 are the different operations used in SHA1 */
#define R0(v,w,x,y,z,i) z+=((w&(x^y))^y)+blk0(i)+0x5A827999+rol(v,5);w=rol(w,30);
#define R1(v,w,x,y,z,i) z+=((w&(x^y))^y)+blk(i)+0x5A827999+rol(v,5);w=rol(w,30);
#define R2(v,w,x,y,z,i) z+=(w^x^y)+blk(i)+0x6ED9EBA1+rol(v,5);w=rol(w,30);
#define R3(v,w,x,y,z,i) z+=(((w|x)&y)|(w&x))+blk(i)+0x8F1BBCDC+rol(v,5);w=rol(w,30);
#define R4(v,w,x,y,z,i) z+=(w^x^y)+blk(i)+0xCA62C1D6+rol(v,5);w=rol(w,30);
 
/* Hash a single 512-bit block. This is the core of the algorithm. */
void SHA1_Transform(uint32_t state[5], const uint8_t buffer[64])
{
  uint32_t a, b, c, d, e;
  typedef union {
    uint8_t c[64];
    uint32_t l[16];
  } CHAR64LONG16;
  CHAR64LONG16* block;
 
  block = (CHAR64LONG16*)buffer;
 
  /* Copy context->state[] to working vars */
  a = state[0];
  b = state[1];
  c = state[2];
  d = state[3];
  e = state[4];
 
  /* 4 rounds of 20 operations each. Loop unrolled. */
  R0(a,b,c,d,e, 0); R0(e,a,b,c,d, 1); R0(d,e,a,b,c, 2); R0(c,d,e,a,b, 3);
  R0(b,c,d,e,a, 4); R0(a,b,c,d,e, 5); R0(e,a,b,c,d, 6); R0(d,e,a,b,c, 7);
  R0(c,d,e,a,b, 8); R0(b,c,d,e,a, 9); R0(a,b,c,d,e,10); R0(e,a,b,c,d,11);
  R0(d,e,a,b,c,12); R0(c,d,e,a,b,13); R0(b,c,d,e,a,14); R0(a,b,c,d,e,15);
  R1(e,a,b,c,d,16); R1(d,e,a,b,c,17); R1(c,d,e,a,b,18); R1(b,c,d,e,a,19);
  R2(a,b,c,d,e,20); R2(e,a,b,c,d,21); R2(d,e,a,b,c,22); R2(c,d,e,a,b,23);
  R2(b,c,d,e,a,24); R2(a,b,c,d,e,25); R2(e,a,b,c,d,26); R2(d,e,a,b,c,27);
  R2(c,d,e,a,b,28); R2(b,c,d,e,a,29); R2(a,b,c,d,e,30); R2(e,a,b,c,d,31);
  R2(d,e,a,b,c,32); R2(c,d,e,a,b,33); R2(b,c,d,e,a,34); R2(a,b,c,d,e,35);
  R2(e,a,b,c,d,36); R2(d,e,a,b,c,37); R2(c,d,e,a,b,38); R2(b,c,d,e,a,39);
  R3(a,b,c,d,e,40); R3(e,a,b,c,d,41); R3(d,e,a,b,c,42); R3(c,d,e,a,b,43);
  R3(b,c,d,e,a,44); R3(a,b,c,d,e,45); R3(e,a,b,c,d,46); R3(d,e,a,b,c,47);
  R3(c,d,e,a,b,48); R3(b,c,d,e,a,49); R3(a,b,c,d,e,50); R3(e,a,b,c,d,51);
  R3(d,e,a,b,c,52); R3(c,d,e,a,b,53); R3(b,c,d,e,a,54); R3(a,b,c,d,e,55);
  R3(e,a,b,c,d,56); R3(d,e,a,b,c,57); R3(c,d,e,a,b,58); R3(b,c,d,e,a,59);
  R4(a,b,c,d,e,60); R4(e,a,b,c,d,61); R4(d,e,a,b,c,62); R4(c,d,e,a,b,63);
  R4(b,c,d,e,a,64); R4(a,b,c,d,e,65); R4(e,a,b,c,d,66); R4(d,e,a,b,c,67);
  R4(c,d,e,a,b,68); R4(b,c,d,e,a,69); R4(a,b,c,d,e,70); R4(e,a,b,c,d,71);
  R4(d,e,a,b,c,72); R4(c,d,e,a,b,73); R4(b,c,d,e,a,74); R4(a,b,c,d,e,75);
  R4(e,a,b,c,d,76); R4(d,e,a,b,c,77); R4(c,d,e,a,b,78); R4(b,c,d,e,a,79);
 
  /* Add the working vars back into context.state[] */
  state[0] += a;
  state[1] += b;
  state[2] += c;
  state[3] += d;
  state[4] += e;
 
  /* Wipe variables */
  a = b = c = d = e = 0;
}
 
/* SHA1Init - Initialize new context */
void SHA1_Init(SHA1_CTX* context)
{
  /* SHA1 initialization constants */
  context->state[0] = 0x67452301;
  context->state[1] = 0xEFCDAB89;
  context->state[2] = 0x98BADCFE;
  context->state[3] = 0x10325476;
  context->state[4] = 0xC3D2E1F0;
  context->count[0] = context->count[1] = 0;
}
 
/* Run your data through this. */
void SHA1_Update(SHA1_CTX* context, const uint8_t* data, const size_t len)
{
  size_t i, j;
 
  j = (context->count[0] >> 3) & 63;
  if ((context->count[0] += len << 3) < (len << 3)) context->count[1]++;
  context->count[1] += (len >> 29);
  if ((j + len) > 63) {
    memcpy(&context->buffer[j], data, (i = 64-j));
    SHA1_Transform(context->state, context->buffer);
    for ( ; i + 63 < len; i += 64) {
      SHA1_Transform(context->state, data + i);
    }
    j = 0;
  }
  else i = 0;
  memcpy(&context->buffer[j], &data[i], len - i);
}
 
 
/* Add padding and return the message digest. */
void SHA1_Final(SHA1_CTX* context, uint8_t digest[SHA1_DIGEST_SIZE])
{
  uint32_t i;
  uint8_t  finalcount[8];
 
  for (i = 0; i < 8; i++) {
    finalcount[i] = (unsigned char)((context->count[(i >= 4 ? 0 : 1)]
                                     >> ((3-(i & 3)) * 8) ) & 255);  /* Endian independent */
  }
  SHA1_Update(context, (uint8_t *)"\200", 1);
  while ((context->count[0] & 504) != 448) {
    SHA1_Update(context, (uint8_t *)"\0", 1);
  }
  SHA1_Update(context, finalcount, 8);  /* Should cause a SHA1_Transform() */
  for (i = 0; i < SHA1_DIGEST_SIZE; i++) {
    digest[i] = (uint8_t)
    ((context->state[i>>2] >> ((3-(i & 3)) * 8) ) & 255);
  }
 
  /* Wipe variables */
  i = 0;
  memset(context->buffer, 0, 64);
  memset(context->state, 0, 20);
  memset(context->count, 0, 8);
  memset(finalcount, 0, 8);	/* SWR */
}
 
 
@implementation NSData (GMSHA1)
 
- (NSData *)gm_SHA1Digest {
  SHA1_CTX context;
  uint8_t digest[SHA1_DIGEST_SIZE];
 
  SHA1_Init(&context);
  SHA1_Update(&context, (uint8_t*)[self bytes], [self length]);
  SHA1_Final(&context, digest);
  return [NSData dataWithBytes:digest length:SHA1_DIGEST_SIZE];
}
 
- (NSString *)gm_SHA1HexDigest {
  return [[self gm_SHA1Digest] gm_hexadecimalEncodedString];
}
 
@end
 
@implementation NSString (GMSHA1)
 
- (NSData *)gm_SHA1Digest {
  NSData *data = [self dataUsingEncoding:NSUTF8StringEncoding allowLossyConversion:NO];
  return [data gm_SHA1Digest];
}
 
- (NSString *)gm_SHA1HexDigest {
  return [[self gm_SHA1Digest] gm_hexadecimalEncodedString];
}
 
@end

//
//  NSData+hexadecimalRepresentation.m
//
 
#import "NSData+HexAdditions.h"
 
@implementation NSData (GMNSDataHexAdditions)
 
- (NSString *)gm_hexadecimalEncodedString {
  static const char *hexChars = "0123456789ABCDEF";
  NSUInteger slen = [self length];
  NSUInteger dlen = slen * 2;
  const unsigned char	*src = (const unsigned char *)[self bytes];
  char *dst = (char *)NSZoneMalloc(NSDefaultMallocZone(), dlen);
  NSUInteger spos = 0;
  NSUInteger dpos = 0;
  unsigned char	c;
  while (spos < slen) {
    c = src[spos++];
    dst[dpos++] = hexChars[(c >> 4) & 0x0f];
    dst[dpos++] = hexChars[c & 0x0f];
  }
  NSData *data = [[NSData alloc] initWithBytesNoCopy:dst length:dlen];
  NSString *string = [[NSString alloc] initWithData:data encoding:NSASCIIStringEncoding];
  [data release];
  return [string autorelease];
}
 
@end