Andrew Boyson / crypto

A simple library to support serving https.

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hmac/hmac-sha256.c@9:f354b4859b0b, 2019-09-11 (annotated)

Committer:
andrewboyson
Date:
Wed Sep 11 07:24:21 2019 +0000
Revision:
9:f354b4859b0b
Got application data to be returned but not encrypted yet

Who changed what in which revision?

UserRevisionLine numberNew contents of line
andrewboyson 9:f354b4859b0b 1 #include <stdint.h>
andrewboyson 9:f354b4859b0b 2
andrewboyson 9:f354b4859b0b 3 #include "hmac-sha256.h"
andrewboyson 9:f354b4859b0b 4 #include "sha256.h"
andrewboyson 9:f354b4859b0b 5
andrewboyson 9:f354b4859b0b 6 #define BLOCK_SIZE 64
andrewboyson 9:f354b4859b0b 7 #define HASH_SIZE 32
andrewboyson 9:f354b4859b0b 8
andrewboyson 9:f354b4859b0b 9 void HmacSha256Start(struct HmacSha256Struct* md, const uint8_t* key, int keyLength)
andrewboyson 9:f354b4859b0b 10 {
andrewboyson 9:f354b4859b0b 11 //Make the key BLOCK_SIZE bytes long by hashing longer ones or padding shorter one with 0s
andrewboyson 9:f354b4859b0b 12 if (keyLength > BLOCK_SIZE)
andrewboyson 9:f354b4859b0b 13 {
andrewboyson 9:f354b4859b0b 14 Sha256(key, keyLength, md->hmacKey);
andrewboyson 9:f354b4859b0b 15 for (int i = HASH_SIZE; i < BLOCK_SIZE; i++) md->hmacKey[i] = 0;
andrewboyson 9:f354b4859b0b 16 }
andrewboyson 9:f354b4859b0b 17 else
andrewboyson 9:f354b4859b0b 18 {
andrewboyson 9:f354b4859b0b 19 for (int i = 0; i < keyLength; i++) md->hmacKey[i] = key[i];
andrewboyson 9:f354b4859b0b 20 for (int i = keyLength; i < BLOCK_SIZE; i++) md->hmacKey[i] = 0;
andrewboyson 9:f354b4859b0b 21 }
andrewboyson 9:f354b4859b0b 22 Sha256Start(&md->shaStruct);
andrewboyson 9:f354b4859b0b 23
andrewboyson 9:f354b4859b0b 24 //Make the inner and outer padded keys
andrewboyson 9:f354b4859b0b 25 uint8_t iKeyPad[BLOCK_SIZE];
andrewboyson 9:f354b4859b0b 26 for (int i = 0; i < BLOCK_SIZE; i++)
andrewboyson 9:f354b4859b0b 27 {
andrewboyson 9:f354b4859b0b 28 iKeyPad[i] = md->hmacKey[i] ^ 0x36; //Inner padded key
andrewboyson 9:f354b4859b0b 29 }
andrewboyson 9:f354b4859b0b 30 Sha256Add(&md->shaStruct, iKeyPad, BLOCK_SIZE);
andrewboyson 9:f354b4859b0b 31 }
andrewboyson 9:f354b4859b0b 32 void HmacSha256Add(struct HmacSha256Struct* md, const uint8_t* message, int messageLength)
andrewboyson 9:f354b4859b0b 33 {
andrewboyson 9:f354b4859b0b 34 Sha256Add(&md->shaStruct, message, messageLength);
andrewboyson 9:f354b4859b0b 35 }
andrewboyson 9:f354b4859b0b 36 void HmacSha256Finish(struct HmacSha256Struct* md, uint8_t* mac)
andrewboyson 9:f354b4859b0b 37 {
andrewboyson 9:f354b4859b0b 38 //Make the inner and outer padded keys
andrewboyson 9:f354b4859b0b 39 uint8_t oKeyPad[BLOCK_SIZE];
andrewboyson 9:f354b4859b0b 40 for (int i = 0; i < BLOCK_SIZE; i++)
andrewboyson 9:f354b4859b0b 41 {
andrewboyson 9:f354b4859b0b 42 oKeyPad[i] = md->hmacKey[i] ^ 0x5c; //Outer padded key
andrewboyson 9:f354b4859b0b 43 }
andrewboyson 9:f354b4859b0b 44
andrewboyson 9:f354b4859b0b 45 uint8_t innerHash[HASH_SIZE];
andrewboyson 9:f354b4859b0b 46 Sha256Finish(&md->shaStruct, innerHash);
andrewboyson 9:f354b4859b0b 47
andrewboyson 9:f354b4859b0b 48 Sha256Start(&md->shaStruct);
andrewboyson 9:f354b4859b0b 49 Sha256Add(&md->shaStruct, oKeyPad, BLOCK_SIZE);
andrewboyson 9:f354b4859b0b 50 Sha256Add(&md->shaStruct, innerHash, HASH_SIZE);
andrewboyson 9:f354b4859b0b 51
andrewboyson 9:f354b4859b0b 52 Sha256Finish(&md->shaStruct, mac);
andrewboyson 9:f354b4859b0b 53 }
andrewboyson 9:f354b4859b0b 54
andrewboyson 9:f354b4859b0b 55 void HmacSha256(const uint8_t* key, int keyLength, const uint8_t* message, int messageLength, uint8_t* mac)
andrewboyson 9:f354b4859b0b 56 {
andrewboyson 9:f354b4859b0b 57 struct HmacSha256Struct md;
andrewboyson 9:f354b4859b0b 58 HmacSha256Start (&md, key, keyLength);
andrewboyson 9:f354b4859b0b 59 HmacSha256Add (&md, message, messageLength);
andrewboyson 9:f354b4859b0b 60 HmacSha256Finish(&md, mac);
andrewboyson 9:f354b4859b0b 61 }