Thu Apr 28 2011 17:16:21

Asterisk developer's documentation


sha1.c File Reference

Based on the RFC 3174. More...

#include "asterisk.h"
#include "asterisk/sha1.h"
Include dependency graph for sha1.c:

Go to the source code of this file.

Defines

#define SHA1CircularShift(bits, word)   (((word) << (bits)) | ((word) >> (32-(bits))))

Functions

int SHA1Input (SHA1Context *context, const uint8_t *message_array, unsigned length)
 SHA1Input.
void SHA1PadMessage (SHA1Context *context)
 Pad message to be 512 bits.
void SHA1ProcessMessageBlock (SHA1Context *context)
 Process the next 512 bits of the message stored in the Message_Block array.
int SHA1Reset (SHA1Context *context)
 SHA1Reset.
int SHA1Result (SHA1Context *context, uint8_t Message_Digest[SHA1HashSize])
 SHA1Result.

Detailed Description

Based on the RFC 3174.

Full Copyright Statement

Copyright (C) The Internet Society (2001). All Rights Reserved.

This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise explain it or assist in its implementation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. However, this document itself may not be modified in any way, such as by removing the copyright notice or references to the Internet Society or other Internet organizations, except as needed for the purpose of developing Internet standards in which case the procedures for copyrights defined in the Internet Standards process must be followed, or as required to translate it into languages other than English.

The limited permissions granted above are perpetual and will not be revoked by the Internet Society or its successors or assigns.

This document and the information contained herein is provided on an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

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.

Definition in file sha1.c.


Define Documentation

#define SHA1CircularShift (   bits,
  word 
)    (((word) << (bits)) | ((word) >> (32-(bits))))

Define the SHA1 circular left shift macro

Definition at line 67 of file sha1.c.

Referenced by SHA1ProcessMessageBlock().


Function Documentation

int SHA1Input ( SHA1Context context,
const uint8_t *  message_array,
unsigned  length 
)

SHA1Input.

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. This function accepts an array of octets as the next portion of the message.
Returns:
sha Error Code.

Definition at line 154 of file sha1.c.

References SHA1Context::Computed, SHA1Context::Corrupted, SHA1Context::Length_High, SHA1Context::Length_Low, SHA1Context::Message_Block, SHA1Context::Message_Block_Index, SHA1ProcessMessageBlock(), shaNull, shaStateError, and shaSuccess.

Referenced by ast_sha1_hash().

{
   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;
}
void SHA1PadMessage ( SHA1Context context)

Pad message to be 512 bits.

Parameters:
context[in/out] The context to pad.

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.

Returns:
nothing.

Definition at line 298 of file sha1.c.

References SHA1Context::Length_High, SHA1Context::Length_Low, SHA1Context::Message_Block, SHA1Context::Message_Block_Index, and SHA1ProcessMessageBlock().

Referenced by SHA1Result().

{
   /*
    *  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);
}
void SHA1ProcessMessageBlock ( SHA1Context context)

Process the next 512 bits of the message stored in the Message_Block array.

Parameters:
context[in/out] The SHA context to update
Note:
Many of the variable names in this code, especially the single character names, were used because those were the names used in the publication.
Returns:
nothing.

Definition at line 203 of file sha1.c.

References SHA1Context::Intermediate_Hash, SHA1Context::Message_Block, SHA1Context::Message_Block_Index, and SHA1CircularShift.

Referenced by SHA1Input(), and SHA1PadMessage().

{
   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;
}
int SHA1Reset ( SHA1Context context)

SHA1Reset.

Parameters:
contextthe context to be reset. This function will initialize the SHA1Context in preparation for computing a new SHA1 message digest.
Returns:
sha Error Code.

Definition at line 81 of file sha1.c.

References SHA1Context::Computed, SHA1Context::Corrupted, SHA1Context::Intermediate_Hash, SHA1Context::Length_High, SHA1Context::Length_Low, SHA1Context::Message_Block_Index, shaNull, and shaSuccess.

Referenced by ast_sha1_hash().

{
   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;
}
int SHA1Result ( SHA1Context context,
uint8_t  Message_Digest[SHA1HashSize] 
)

SHA1Result.

Parameters:
context[in/out] The context to use to calculate the SHA-1 hash.
Message_Digest[out] Where the digest is returned. 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.
Returns:
sha Error Code.

Definition at line 113 of file sha1.c.

References SHA1Context::Computed, SHA1Context::Corrupted, SHA1Context::Intermediate_Hash, SHA1Context::Length_High, SHA1Context::Length_Low, SHA1Context::Message_Block, SHA1HashSize, SHA1PadMessage(), shaNull, and shaSuccess.

Referenced by ast_sha1_hash().

{
   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;
}