sha2.c File Reference

#include "sha2.h"

Functions
static uint32_t	SHA2ExecuteHash (const uint8_t *message, uint8_t *resultDigest, uint32_t *intermediateDigest, uint32_t totalMsgLength, uint32_t messageLength, uint32_t hashAlgorithm, bool initialHash, bool finalHash)
void	SHA2StartDMAOperation (uint8_t *channel0Addr, uint32_t channel0Length, uint8_t *channel1Addr, uint32_t channel1Length)
	Start a crypto DMA operation. More...
uint32_t	SHA2WaitForIRQFlags (uint32_t irqFlags)
	Poll the interrupt status register and clear when done. More...
uint32_t	SHA2ComputeInitialHash (const uint8_t *message, uint32_t *intermediateDigest, uint32_t hashAlgorithm, uint32_t initialMessageLength)
	Start a new SHA-2 hash operation. More...
uint32_t	SHA2ComputeIntermediateHash (const uint8_t *message, uint32_t *intermediateDigest, uint32_t hashAlgorithm, uint32_t intermediateMessageLength)
	Resume a SHA-2 hash operation but do not finalize it. More...
uint32_t	SHA2ComputeFinalHash (const uint8_t *message, uint8_t *resultDigest, uint32_t *intermediateDigest, uint32_t totalMsgLength, uint32_t messageLength, uint32_t hashAlgorithm)
	Resume a SHA-2 hash operation and finalize it. More...
uint32_t	SHA2ComputeHash (const uint8_t *message, uint8_t *resultDigest, uint32_t totalMsgLength, uint32_t hashAlgorithm)
	Start a SHA-2 hash operation and return the finalized digest. More...

Function Documentation

SHA2ExecuteHash()

static uint32_t SHA2ExecuteHash ( const uint8_t *  message, uint8_t *  resultDigest, uint32_t *  intermediateDigest, uint32_t  totalMsgLength, uint32_t  messageLength, uint32_t  hashAlgorithm, bool  initialHash, bool  finalHash  )

static

Referenced by SHA2ComputeFinalHash(), SHA2ComputeHash(), SHA2ComputeInitialHash(), and SHA2ComputeIntermediateHash().

{
    uint8_t digestLength = 0;
    uint32_t dmaAlgorithmSelect = 0;

    SHA2ClearDigestAvailableFlag();

    switch (hashAlgorithm) {
        case SHA2_MODE_SELECT_SHA224:
            digestLength = SHA2_SHA224_DIGEST_LENGTH_BYTES;
            dmaAlgorithmSelect = SHA2_ALGSEL_SHA256;
            break;
        case SHA2_MODE_SELECT_SHA256:
            digestLength = SHA2_SHA256_DIGEST_LENGTH_BYTES;
            dmaAlgorithmSelect = SHA2_ALGSEL_SHA256;
            break;
        case SHA2_MODE_SELECT_SHA384:
            digestLength = SHA2_SHA384_DIGEST_LENGTH_BYTES;
            dmaAlgorithmSelect = SHA2_ALGSEL_SHA512;
            break;
        case SHA2_MODE_SELECT_SHA512:
            digestLength = SHA2_SHA512_DIGEST_LENGTH_BYTES;
            dmaAlgorithmSelect = SHA2_ALGSEL_SHA512;
            break;
        default:
            return SHA2_INVALID_ALGORITHM;
    }

    if (initialHash && finalHash) {
        // The empty string is a perfectly valid message. It obviously has a length of 0. The DMA cannot
        // handle running with a transfer length of 0. This workaround depends on the hash engine adding the
        // trailing 1 bit and 0-padding bits after the DMAtransfer is complete and not in the DMA itself.
        // totalMsgLength is purposefully not altered as it is appended to the end of the message during finalization
        // and determines how many padding-bytes are added.
        // Altering totalMsgLength would alter the final hash digest.
        // Because totalMsgLength specifies that the message is of length 0, the content of the byte loaded
        // through the DMA is irrelevant. It is overwritten internally in the hash engine.
        messageLength = messageLength ? messageLength : 1;
    }

    // Setting the incorrect number of bits here leads to the calculation of the correct result
    // but a failure to read them out.
    // The tag bit is set to read out the digest via DMA rather than through the slave interface.
    SHA2SelectAlgorithm(dmaAlgorithmSelect | (resultDigest ? SHA2_ALGSEL_TAG : 0));
    SHA2IntClear(SHA2_DMA_IN_DONE | SHA2_RESULT_RDY);
    SHA2IntEnable(SHA2_DMA_IN_DONE | SHA2_RESULT_RDY);

    HWREG(CRYPTO_BASE + CRYPTO_O_HASHMODE) = hashAlgorithm | (initialHash ? CRYPTO_HASHMODE_NEW_HASH_M : 0);

    // Only load the intermediate digest if requested.
    if (intermediateDigest && !initialHash) {
        SHA2SetDigest(intermediateDigest, digestLength);
    }

    // If this is the final hash, finalization is required. This means appending a 1 bit, padding the message until this section
    // is 448 bytes long, and adding the 64 bit total length of the message in bits. Thankfully, this is all done in hardware.
    if (finalHash) {
        // This specific length must be specified in bits not bytes.
        SHA2SetMessageLength(totalMsgLength * 8);
        HWREG(CRYPTO_BASE + CRYPTO_O_HASHIOBUFCTRL) = CRYPTO_HASHIOBUFCTRL_PAD_DMA_MESSAGE_M;

    }

    // The cast is fine in this case. SHA2StartDMAOperation channel one serves as input and no one does
    // hash operations in-place.
    SHA2StartDMAOperation((uint8_t *)message, messageLength,  resultDigest, digestLength);

    return SHA2_SUCCESS;
}

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