104 lines
4.1 KiB
C
104 lines
4.1 KiB
C
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#ifndef SHA_256_H
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#define SHA_256_H
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#include <stdint.h>
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#include <string.h>
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#ifdef __cplusplus
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extern "C" {
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#endif
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/*
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* @brief Size of the SHA-256 sum. This times eight is 256 bits.
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*/
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#define SIZE_OF_SHA_256_HASH 32
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/*
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* @brief Size of the chunks used for the calculations.
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*
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* @note This should mostly be ignored by the user, although when using the streaming API, it has an impact for
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* performance. Add chunks whose size is a multiple of this, and you will avoid a lot of superfluous copying in RAM!
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*/
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#define SIZE_OF_SHA_256_CHUNK 64
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/*
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* @brief The opaque SHA-256 type, that should be instantiated when using the streaming API.
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*
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* @note Although the details are exposed here, in order to make instantiation easy, you should refrain from directly
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* accessing the fields, as they may change in the future.
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*/
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struct Sha_256 {
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uint8_t *hash;
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uint8_t chunk[SIZE_OF_SHA_256_CHUNK];
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uint8_t *chunk_pos;
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size_t space_left;
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size_t total_len;
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uint32_t h[8];
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};
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/*
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* @brief The simple SHA-256 calculation function.
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* @param hash Hash array, where the result is delivered.
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* @param input Pointer to the data the hash shall be calculated on.
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* @param len Length of the input data, in byte.
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*
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* @note If all of the data you are calculating the hash value on is available in a contiguous buffer in memory, this is
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* the function you should use.
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*
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* @note If either of the passed pointers is NULL, the results are unpredictable.
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*/
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void calc_sha_256(uint8_t hash[SIZE_OF_SHA_256_HASH], const void *input, size_t len);
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/*
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* @brief Initialize a SHA-256 streaming calculation.
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* @param sha_256 A pointer to a SHA-256 structure.
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* @param hash Hash array, where the result will be delivered.
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*
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* @note If all of the data you are calculating the hash value on is not available in a contiguous buffer in memory, this is
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* where you should start. Instantiate a SHA-256 structure, for instance by simply declaring it locally, make your hash
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* buffer available, and invoke this function. Once a SHA-256 hash has been calculated (see further below) a SHA-256
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* structure can be initialized again for the next calculation.
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*
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* @note If either of the passed pointers is NULL, the results are unpredictable.
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*/
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void sha_256_init(struct Sha_256 *sha_256, uint8_t hash[SIZE_OF_SHA_256_HASH]);
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/*
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* @brief Stream more input data for an on-going SHA-256 calculation.
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* @param sha_256 A pointer to a previously initialized SHA-256 structure.
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* @param data Pointer to the data to be added to the calculation.
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* @param len Length of the data to add, in byte.
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*
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* @note This function may be invoked an arbitrary number of times between initialization and closing, but the maximum
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* data length is limited by the SHA-256 algorithm: the total number of bits (i.e. the total number of bytes times
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* eight) must be representable by a 64-bit unsigned integer. While that is not a practical limitation, the results are
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* unpredictable if that limit is exceeded.
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*
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* @note This function may be invoked on empty data (zero length), although that obviously will not add any data.
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*
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* @note If either of the passed pointers is NULL, the results are unpredictable.
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*/
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void sha_256_write(struct Sha_256 *sha_256, const void *data, size_t len);
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/*
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* @brief Conclude a SHA-256 streaming calculation, making the hash value available.
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* @param sha_256 A pointer to a previously initialized SHA-256 structure.
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* @return Pointer to the hash array, where the result is delivered.
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*
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* @note After this function has been invoked, the result is available in the hash buffer that initially was provided. A
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* pointer to the hash value is returned for convenience, but you should feel free to ignore it: it is simply a pointer
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* to the first byte of your initially provided hash array.
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*
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* @note If the passed pointer is NULL, the results are unpredictable.
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*
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* @note Invoking this function for a calculation with no data (the writing function has never been invoked, or it only
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* has been invoked with empty data) is legal. It will calculate the SHA-256 value of the empty string.
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*/
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uint8_t *sha_256_close(struct Sha_256 *sha_256);
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#ifdef __cplusplus
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}
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#endif
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#endif
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