/*
* sha1.c
*
* Description:
* This file implements the Secure Hashing Algorithm 1 as
* defined in FIPS PUB 180-1 published April 17, 1995.
*
* The SHA-1, produces a 160-bit message digest for a given
* data stream. It should take about 2**n steps to find a
* message with the same digest as a given message and
* 2**(n/2) to find any two messages with the same digest,
* when n is the digest size in bits. Therefore, this
* algorithm can serve as a means of providing a
* "fingerprint" for a message.
*
* Portability Issues:
* SHA-1 is defined in terms of 32-bit "words". This code
* uses <stdint.h> (included via "sha1.h" to define 32 and 8
* bit unsigned integer types. If your C compiler does not
* support 32 bit unsigned integers, this code is not
* appropriate.
*
* Caveats:
* SHA-1 is designed to work with messages less than 2^64 bits
* long. Although SHA-1 allows a message digest to be generated
* for messages of any number of bits less than 2^64, this
* implementation only works with messages with a length that is
* a multiple of the size of an 8-bit character.
*
*/
#include "sha1.h"
/*
* Define the SHA1 circular left shift macro
*/
#define SHA1CircularShift(bits,word) \
(((word) << (bits)) | ((word) >> (32-(bits))))
/* Local Function Prototyptes */
static void SHA1PadMessage(SHA1Context *);
static void SHA1ProcessMessageBlock(SHA1Context *);
/*
* SHA1Reset
*
* Description:
* This function will initialize the SHA1Context in preparation
* for computing a new SHA1 message digest.
*
* Parameters:
* context: [in/out]
* The context to reset.
*
* Returns:
* sha Error Code.
*
*/
static int SHA1Reset(SHA1Context *context)
{
if (!context)
{
return shaNull;
}
context->Length_Low = 0;
context->Length_High = 0;
context->Message_Block_Index = 0;
context->Intermediate_Hash[0] = 0x67452301;
context->Intermediate_Hash[1] = 0xEFCDAB89;
context->Intermediate_Hash[2] = 0x98BADCFE;
context->Intermediate_Hash[3] = 0x10325476;
context->Intermediate_Hash[4] = 0xC3D2E1F0;
context->Computed = 0;
context->Corrupted = 0;
return shaSuccess;
}
/*
* SHA1Result
*
* Description:
* This function will return the 160-bit message digest into the
* Message_Digest array provided by the caller.
* NOTE: The first octet of hash is stored in the 0th element,
* the last octet of hash in the 19th element.
*
* Parameters:
* context: [in/out]
* The context to use to calculate the SHA-1 hash.
* Message_Digest: [out]
* Where the digest is returned.
*
* Returns:
* sha Error Code.
*
*/
static int SHA1Result( SHA1Context *context,
uint8_t Message_Digest[SHA1HashSize])
{
int i;
if (!context || !Message_Digest)
{
return shaNull;
}
if (context->Corrupted)
{
return context->Corrupted;
}
if (!context->Computed)
{
SHA1PadMessage(context);
for(i=0; i<64; ++i)
{
/* message may be sensitive, clear it out */
context->Message_Block[i] = 0;
}
context->Length_Low = 0; /* and clear length */
context->Length_High = 0;
context->Computed = 1;
}
for(i = 0; i < SHA1HashSize; ++i)
{
Message_Digest[i] = context->Intermediate_Hash[i>>2]
>> 8 * ( 3 - ( i & 0x03 ) );
}
return shaSuccess;
}
/*
* SHA1Input
*
* Description:
* This function accepts an array of octets as the next portion
* of the message.
*
* Parameters:
* context: [in/out]
* The SHA context to update
* message_array: [in]
* An array of characters representing the next portion of
* the message.
* length: [in]
* The length of the message in message_array
*
* Returns:
* sha Error Code.
*
*/
static int SHA1Input( SHA1Context *context,
const uint8_t *message_array,
unsigned length)
{
if (!length)
{
return shaSuccess;
}
if (!context || !message_array)
{
return shaNull;
}
if (context->Computed)
{
context->Corrupted = shaStateError;
return shaStateError;
}
if (context->Corrupted)
{
return context->Corrupted;
}
while(length-- && !context->Corrupted)
{
context->Message_Block[context->Message_Block_Index++] =
(*message_array & 0xFF);
context->Length_Low += 8;
if (context->Length_Low == 0)
{
context->Length_High++;
if (context->Length_High == 0)
{
/* Message is too long */
context->Corrupted = 1;
}
}
if (context->Message_Block_Index == 64)
{
SHA1ProcessMessageBlock(context);
}
message_array++;
}
return shaSuccess;
}
/*
* SHA1ProcessMessageBlock
*
* Description:
* This function will process the next 512 bits of the message
* stored in the Message_Block array.
*
* Parameters:
* None.
*
* Returns:
* Nothing.
*
* Comments:
* Many of the variable names in this code, especially the
* single character names, were used because those were the
* names used in the publication.
*
*
*/
static void SHA1ProcessMessageBlock(SHA1Context *context)
{
const uint32_t K[] = { /* Constants defined in SHA-1 */
0x5A827999,
0x6ED9EBA1,
0x8F1BBCDC,
0xCA62C1D6
};
int t; /* Loop counter */
uint32_t temp; /* Temporary word value */
uint32_t W[80]; /* Word sequence */
uint32_t A, B, C, D, E; /* Word buffers */
/*
* Initialize the first 16 words in the array W
*/
for(t = 0; t < 16; t++)
{
W[t] = context->Message_Block[t * 4] << 24;
W[t] |= context->Message_Block[t * 4 + 1] << 16;
W[t] |= context->Message_Block[t * 4 + 2] << 8;
W[t] |= context->Message_Block[t * 4 + 3];
}
for(t = 16; t < 80; t++)
{
W[t] = SHA1CircularShift(1,W[t-3] ^ W[t-8] ^ W[t-14] ^ W[t-16]);
}
A = context->Intermediate_Hash[0];
B = context->Intermediate_Hash[1];
C = context->Intermediate_Hash[2];
D = context->Intermediate_Hash[3];
E = context->Intermediate_Hash[4];
for(t = 0; t < 20; t++)
{
temp = SHA1CircularShift(5,A) +
((B & C) | ((~B) & D)) + E + W[t] + K[0];
E = D;
D = C;
C = SHA1CircularShift(30,B);
B = A;
A = temp;
}
for(t = 20; t < 40; t++)
{
temp = SHA1CircularShift(5,A) + (B ^ C ^ D) + E + W[t] + K[1];
E = D;
D = C;
C = SHA1CircularShift(30,B);
B = A;
A = temp;
}
for(t = 40; t < 60; t++)
{
temp = SHA1CircularShift(5,A) +
((B & C) | (B & D) | (C & D)) + E + W[t] + K[2];
E = D;
D = C;
C = SHA1CircularShift(30,B);
B = A;
A = temp;
}
for(t = 60; t < 80; t++)
{
temp = SHA1CircularShift(5,A) + (B ^ C ^ D) + E + W[t] + K[3];
E = D;
D = C;
C = SHA1CircularShift(30,B);
B = A;
A = temp;
}
context->Intermediate_Hash[0] += A;
context->Intermediate_Hash[1] += B;
context->Intermediate_Hash[2] += C;
context->Intermediate_Hash[3] += D;
context->Intermediate_Hash[4] += E;
context->Message_Block_Index = 0;
}
/*
* SHA1PadMessage
*
* Description:
* According to the standard, the message must be padded to an even
* 512 bits. The first padding bit must be a '1'. The last 64
* bits represent the length of the original message. All bits in
* between should be 0. This function will pad the message
* according to those rules by filling the Message_Block array
* accordingly. It will also call the ProcessMessageBlock function
* provided appropriately. When it returns, it can be assumed that
* the message digest has been computed.
*
* Parameters:
* context: [in/out]
* The context to pad
* ProcessMessageBlock: [in]
* The appropriate SHA*ProcessMessageBlock function
* Returns:
* Nothing.
*
*/
static void SHA1PadMessage(SHA1Context *context)
{
/*
* Check to see if the current message block is too small to hold
* the initial padding bits and length. If so, we will pad the
* block, process it, and then continue padding into a second
* block.
*/
if (context->Message_Block_Index > 55)
{
context->Message_Block[context->Message_Block_Index++] = 0x80;
while(context->Message_Block_Index < 64)
{
context->Message_Block[context->Message_Block_Index++] = 0;
}
SHA1ProcessMessageBlock(context);
while(context->Message_Block_Index < 56)
{
context->Message_Block[context->Message_Block_Index++] = 0;
}
}
else
{
context->Message_Block[context->Message_Block_Index++] = 0x80;
while(context->Message_Block_Index < 56)
{
context->Message_Block[context->Message_Block_Index++] = 0;
}
}
/*
* Store the message length as the last 8 octets
*/
context->Message_Block[56] = context->Length_High >> 24;
context->Message_Block[57] = context->Length_High >> 16;
context->Message_Block[58] = context->Length_High >> 8;
context->Message_Block[59] = context->Length_High;
context->Message_Block[60] = context->Length_Low >> 24;
context->Message_Block[61] = context->Length_Low >> 16;
context->Message_Block[62] = context->Length_Low >> 8;
context->Message_Block[63] = context->Length_Low;
SHA1ProcessMessageBlock(context);
}
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