Thu Jul 9 13:41:33 2009

Asterisk developer's documentation


sha1.c File Reference

Based on the RFC 3174. More...

#include "asterisk.h"
#include "asterisk/sha1.h"

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 context, SHA1ProcessMessageBlock(), shaNull, shaStateError, and shaSuccess.

Referenced by ast_sha1_hash().

00155 {
00156    if (!length) {
00157       return shaSuccess;
00158    }
00159 
00160    if (!context || !message_array) {
00161       return shaNull;
00162    }
00163 
00164    if (context->Computed) {
00165       context->Corrupted = shaStateError;
00166       return shaStateError;
00167    }
00168 
00169    if (context->Corrupted) {
00170       return context->Corrupted;
00171    }
00172 
00173    while (length-- && !context->Corrupted) {
00174       context->Message_Block[context->Message_Block_Index++] = (*message_array & 0xFF);
00175 
00176       context->Length_Low += 8;
00177       if (context->Length_Low == 0) {
00178          context->Length_High++;
00179          if (context->Length_High == 0) {
00180             /* Message is too long */
00181             context->Corrupted = 1;
00182          }
00183       }
00184 
00185       if (context->Message_Block_Index == 64) {
00186          SHA1ProcessMessageBlock(context);
00187       }
00188 
00189       message_array++;
00190    }
00191 
00192    return shaSuccess;
00193 }

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 context, and SHA1ProcessMessageBlock().

Referenced by SHA1Result().

00299 {
00300    /*
00301     *  Check to see if the current message block is too small to hold
00302     *  the initial padding bits and length.  If so, we will pad the
00303     *  block, process it, and then continue padding into a second
00304     *  block.
00305     */
00306    if (context->Message_Block_Index > 55) {
00307       context->Message_Block[context->Message_Block_Index++] = 0x80;
00308       while (context->Message_Block_Index < 64) {
00309          context->Message_Block[context->Message_Block_Index++] = 0;
00310       }
00311 
00312       SHA1ProcessMessageBlock(context);
00313 
00314       while (context->Message_Block_Index < 56) {
00315          context->Message_Block[context->Message_Block_Index++] = 0;
00316       }
00317    } else {
00318       context->Message_Block[context->Message_Block_Index++] = 0x80;
00319       while (context->Message_Block_Index < 56) {
00320          context->Message_Block[context->Message_Block_Index++] = 0;
00321       }
00322    }
00323 
00324    /*
00325     *  Store the message length as the last 8 octets
00326     */
00327    context->Message_Block[56] = context->Length_High >> 24;
00328    context->Message_Block[57] = context->Length_High >> 16;
00329    context->Message_Block[58] = context->Length_High >> 8;
00330    context->Message_Block[59] = context->Length_High;
00331    context->Message_Block[60] = context->Length_Low >> 24;
00332    context->Message_Block[61] = context->Length_Low >> 16;
00333    context->Message_Block[62] = context->Length_Low >> 8;
00334    context->Message_Block[63] = context->Length_Low;
00335 
00336    SHA1ProcessMessageBlock(context);
00337 }

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 context, and SHA1CircularShift.

Referenced by SHA1Input(), and SHA1PadMessage().

00204 {
00205    const uint32_t K[] =     {     /* Constants defined in SHA-1  */
00206                             0x5A827999,
00207                             0x6ED9EBA1,
00208                             0x8F1BBCDC,
00209                             0xCA62C1D6
00210                             };
00211    int           t;                 /* Loop counter                */
00212    uint32_t    temp;              /* Temporary word value        */
00213    uint32_t    W[80];             /* Word sequence               */
00214    uint32_t    A, B, C, D, E;     /* Word buffers                */
00215 
00216    /*
00217     *  Initialize the first 16 words in the array W
00218     */
00219    for (t = 0; t < 16; t++) {
00220       W[t] = context->Message_Block[t * 4] << 24;
00221       W[t] |= context->Message_Block[t * 4 + 1] << 16;
00222       W[t] |= context->Message_Block[t * 4 + 2] << 8;
00223       W[t] |= context->Message_Block[t * 4 + 3];
00224    }
00225 
00226    for (t = 16; t < 80; t++) {
00227       W[t] = SHA1CircularShift(1,W[t-3] ^ W[t-8] ^ W[t-14] ^ W[t-16]);
00228    }
00229 
00230    A = context->Intermediate_Hash[0];
00231    B = context->Intermediate_Hash[1];
00232    C = context->Intermediate_Hash[2];
00233    D = context->Intermediate_Hash[3];
00234    E = context->Intermediate_Hash[4];
00235 
00236    for (t = 0; t < 20; t++) {
00237       temp = SHA1CircularShift(5,A) + ((B & C) | ((~B) & D)) + E + W[t] + K[0];
00238       E = D;
00239       D = C;
00240       C = SHA1CircularShift(30,B);
00241       B = A;
00242       A = temp;
00243    }
00244 
00245    for (t = 20; t < 40; t++) {
00246       temp = SHA1CircularShift(5,A) + (B ^ C ^ D) + E + W[t] + K[1];
00247       E = D;
00248       D = C;
00249       C = SHA1CircularShift(30,B);
00250       B = A;
00251       A = temp;
00252    }
00253 
00254    for (t = 40; t < 60; t++) {
00255       temp = SHA1CircularShift(5,A) + ((B & C) | (B & D) | (C & D)) + E + W[t] + K[2];
00256       E = D;
00257       D = C;
00258       C = SHA1CircularShift(30,B);
00259       B = A;
00260       A = temp;
00261    }
00262 
00263    for (t = 60; t < 80; t++) {
00264       temp = SHA1CircularShift(5,A) + (B ^ C ^ D) + E + W[t] + K[3];
00265       E = D;
00266       D = C;
00267       C = SHA1CircularShift(30,B);
00268       B = A;
00269       A = temp;
00270    }
00271 
00272    context->Intermediate_Hash[0] += A;
00273    context->Intermediate_Hash[1] += B;
00274    context->Intermediate_Hash[2] += C;
00275    context->Intermediate_Hash[3] += D;
00276    context->Intermediate_Hash[4] += E;
00277 
00278    context->Message_Block_Index = 0;
00279 }

int SHA1Reset ( SHA1Context context  ) 

SHA1Reset.

Parameters:
context the 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 context, shaNull, and shaSuccess.

Referenced by ast_sha1_hash().

00082 {
00083    if (!context) {
00084       return shaNull;
00085    }
00086 
00087    context->Length_Low             = 0;
00088    context->Length_High            = 0;
00089    context->Message_Block_Index    = 0;
00090 
00091    context->Intermediate_Hash[0]   = 0x67452301;
00092    context->Intermediate_Hash[1]   = 0xEFCDAB89;
00093    context->Intermediate_Hash[2]   = 0x98BADCFE;
00094    context->Intermediate_Hash[3]   = 0x10325476;
00095    context->Intermediate_Hash[4]   = 0xC3D2E1F0;
00096 
00097    context->Computed               = 0;
00098    context->Corrupted              = 0;
00099 
00100    return shaSuccess;
00101 }

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 context, SHA1PadMessage(), shaNull, and shaSuccess.

Referenced by ast_sha1_hash().

00115 {
00116    int i;
00117 
00118    if (!context || !Message_Digest) {
00119       return shaNull;
00120    }
00121 
00122    if (context->Corrupted) {
00123       return context->Corrupted;
00124    }
00125 
00126    if (!context->Computed) {
00127       SHA1PadMessage(context);
00128       for (i = 0; i < 64; ++i) {
00129          /* message may be sensitive, clear it out */
00130          context->Message_Block[i] = 0;
00131       }
00132       context->Length_Low = 0;    /* and clear length */
00133       context->Length_High = 0;
00134       context->Computed = 1;
00135    }
00136 
00137    for (i = 0; i < SHA1HashSize; ++i) {
00138       Message_Digest[i] = context->Intermediate_Hash[i >> 2] >> 8 * ( 3 - ( i & 0x03 ) );
00139    }
00140 
00141    return shaSuccess;
00142 }


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