/Users/baford/proj/netsteria/sst/lib/hmac.h

/*** Simple HMAC-SHA256-128 implementation ***/

#ifndef SST_HMAC_H
#define SST_HMAC_H

#include "sha2.h"

namespace SST {


// Length of symmetric key material for HMAC-SHA-256-128
#define HMACKEYLEN      (256/8)

// We use SHA-256 hashes truncated to 128 bits for HMAC generation
#define HMACLEN         (128/8)


typedef SHA256_CTX hmac_ctx;


// Low-level functions
void hmac_init(hmac_ctx *ctx, const uint8_t *hkey);
void hmac_update(hmac_ctx *ctx, const void *data, size_t len);
void hmac_final(hmac_ctx *ctx, const uint8_t *hkey,
                        uint8_t *outbuf, unsigned outlen);


class HMAC : public SecureHash
{
private:
        hmac_ctx ictx, octx;

        // Not usable in this implementation of IODevice
        bool reset();

public:
        HMAC(const QByteArray &key);
        HMAC(const HMAC &other);

        // Write data to the HMAC
        qint64 writeData(const char *data, qint64 len);

        // Produce the output, with the default (truncated) size of HMACLEN.
        int outSize();
        QByteArray final();

        // Produce the output with a specified size.
        QByteArray final(int macsize);

        // Update with the contents of a message
        // and append a MAC to the message.
        inline void finalAppend(QByteArray &msg, int macsize = HMACLEN)
                { update(msg); msg += final(macsize); }

        // Update with the contents of a message minus its MAC trailer,
        // verify the MAC trailer, and cut it from the message.
        bool finalVerify(QByteArray &msg, int macsize = HMACLEN); 


        // These functions are const because they copy the HMAC state
        // to temporary storage before computing their result.

        // Compute an HMAC check over a message
        QByteArray calc(const void *msg, int msgsize,
                                int macsize = HMACLEN) const;
        inline QByteArray calc(QByteArray &msg, int macsize = HMACLEN) const
                { return calc(msg.data(), msg.size(), macsize); }

        // Compute and append HMAC check field to a message.
        void calcAppend(QByteArray &msg, int macsize = HMACLEN) const;

        // Strip and check the HMAC check field on receive.
        bool calcVerify(QByteArray &msg, int macsize = HMACLEN) const;
};

} // namespace SST

#endif  // SST_HMAC_H

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