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authorLibravatar vnugent <public@vaughnnugent.com>2024-01-28 19:23:18 -0500
committerLibravatar vnugent <public@vaughnnugent.com>2024-01-28 19:23:18 -0500
commit626a8d8d3df8880991684d6d1a06b82f6685b51a (patch)
tree183c981ac44886445240ad1e1945f325ceaa9298 /include/mbedtls/gcm.h
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+/**
+ * \file gcm.h
+ *
+ * \brief This file contains GCM definitions and functions.
+ *
+ * The Galois/Counter Mode (GCM) for 128-bit block ciphers is defined
+ * in <em>D. McGrew, J. Viega, The Galois/Counter Mode of Operation
+ * (GCM), Natl. Inst. Stand. Technol.</em>
+ *
+ * For more information on GCM, see <em>NIST SP 800-38D: Recommendation for
+ * Block Cipher Modes of Operation: Galois/Counter Mode (GCM) and GMAC</em>.
+ *
+ */
+/*
+ * Copyright The Mbed TLS Contributors
+ * SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later
+ */
+
+#ifndef MBEDTLS_GCM_H
+#define MBEDTLS_GCM_H
+#include "mbedtls/private_access.h"
+
+#include "mbedtls/build_info.h"
+
+#include "mbedtls/cipher.h"
+
+#include <stdint.h>
+
+#define MBEDTLS_GCM_ENCRYPT 1
+#define MBEDTLS_GCM_DECRYPT 0
+
+/** Authenticated decryption failed. */
+#define MBEDTLS_ERR_GCM_AUTH_FAILED -0x0012
+/** Bad input parameters to function. */
+#define MBEDTLS_ERR_GCM_BAD_INPUT -0x0014
+/** An output buffer is too small. */
+#define MBEDTLS_ERR_GCM_BUFFER_TOO_SMALL -0x0016
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#if !defined(MBEDTLS_GCM_ALT)
+
+/**
+ * \brief The GCM context structure.
+ */
+typedef struct mbedtls_gcm_context {
+ mbedtls_cipher_context_t MBEDTLS_PRIVATE(cipher_ctx); /*!< The cipher context used. */
+ uint64_t MBEDTLS_PRIVATE(HL)[16]; /*!< Precalculated HTable low. */
+ uint64_t MBEDTLS_PRIVATE(HH)[16]; /*!< Precalculated HTable high. */
+ uint64_t MBEDTLS_PRIVATE(len); /*!< The total length of the encrypted data. */
+ uint64_t MBEDTLS_PRIVATE(add_len); /*!< The total length of the additional data. */
+ unsigned char MBEDTLS_PRIVATE(base_ectr)[16]; /*!< The first ECTR for tag. */
+ unsigned char MBEDTLS_PRIVATE(y)[16]; /*!< The Y working value. */
+ unsigned char MBEDTLS_PRIVATE(buf)[16]; /*!< The buf working value. */
+ int MBEDTLS_PRIVATE(mode); /*!< The operation to perform:
+ #MBEDTLS_GCM_ENCRYPT or
+ #MBEDTLS_GCM_DECRYPT. */
+}
+mbedtls_gcm_context;
+
+#else /* !MBEDTLS_GCM_ALT */
+#include "gcm_alt.h"
+#endif /* !MBEDTLS_GCM_ALT */
+
+/**
+ * \brief This function initializes the specified GCM context,
+ * to make references valid, and prepares the context
+ * for mbedtls_gcm_setkey() or mbedtls_gcm_free().
+ *
+ * The function does not bind the GCM context to a particular
+ * cipher, nor set the key. For this purpose, use
+ * mbedtls_gcm_setkey().
+ *
+ * \param ctx The GCM context to initialize. This must not be \c NULL.
+ */
+void mbedtls_gcm_init(mbedtls_gcm_context *ctx);
+
+/**
+ * \brief This function associates a GCM context with a
+ * cipher algorithm and a key.
+ *
+ * \param ctx The GCM context. This must be initialized.
+ * \param cipher The 128-bit block cipher to use.
+ * \param key The encryption key. This must be a readable buffer of at
+ * least \p keybits bits.
+ * \param keybits The key size in bits. Valid options are:
+ * <ul><li>128 bits</li>
+ * <li>192 bits</li>
+ * <li>256 bits</li></ul>
+ *
+ * \return \c 0 on success.
+ * \return A cipher-specific error code on failure.
+ */
+int mbedtls_gcm_setkey(mbedtls_gcm_context *ctx,
+ mbedtls_cipher_id_t cipher,
+ const unsigned char *key,
+ unsigned int keybits);
+
+/**
+ * \brief This function performs GCM encryption or decryption of a buffer.
+ *
+ * \note For encryption, the output buffer can be the same as the
+ * input buffer. For decryption, the output buffer cannot be
+ * the same as input buffer. If the buffers overlap, the output
+ * buffer must trail at least 8 Bytes behind the input buffer.
+ *
+ * \warning When this function performs a decryption, it outputs the
+ * authentication tag and does not verify that the data is
+ * authentic. You should use this function to perform encryption
+ * only. For decryption, use mbedtls_gcm_auth_decrypt() instead.
+ *
+ * \param ctx The GCM context to use for encryption or decryption. This
+ * must be initialized.
+ * \param mode The operation to perform:
+ * - #MBEDTLS_GCM_ENCRYPT to perform authenticated encryption.
+ * The ciphertext is written to \p output and the
+ * authentication tag is written to \p tag.
+ * - #MBEDTLS_GCM_DECRYPT to perform decryption.
+ * The plaintext is written to \p output and the
+ * authentication tag is written to \p tag.
+ * Note that this mode is not recommended, because it does
+ * not verify the authenticity of the data. For this reason,
+ * you should use mbedtls_gcm_auth_decrypt() instead of
+ * calling this function in decryption mode.
+ * \param length The length of the input data, which is equal to the length
+ * of the output data.
+ * \param iv The initialization vector. This must be a readable buffer of
+ * at least \p iv_len Bytes.
+ * \param iv_len The length of the IV.
+ * \param add The buffer holding the additional data. This must be of at
+ * least that size in Bytes.
+ * \param add_len The length of the additional data.
+ * \param input The buffer holding the input data. If \p length is greater
+ * than zero, this must be a readable buffer of at least that
+ * size in Bytes.
+ * \param output The buffer for holding the output data. If \p length is greater
+ * than zero, this must be a writable buffer of at least that
+ * size in Bytes.
+ * \param tag_len The length of the tag to generate.
+ * \param tag The buffer for holding the tag. This must be a writable
+ * buffer of at least \p tag_len Bytes.
+ *
+ * \return \c 0 if the encryption or decryption was performed
+ * successfully. Note that in #MBEDTLS_GCM_DECRYPT mode,
+ * this does not indicate that the data is authentic.
+ * \return #MBEDTLS_ERR_GCM_BAD_INPUT if the lengths or pointers are
+ * not valid or a cipher-specific error code if the encryption
+ * or decryption failed.
+ */
+int mbedtls_gcm_crypt_and_tag(mbedtls_gcm_context *ctx,
+ int mode,
+ size_t length,
+ const unsigned char *iv,
+ size_t iv_len,
+ const unsigned char *add,
+ size_t add_len,
+ const unsigned char *input,
+ unsigned char *output,
+ size_t tag_len,
+ unsigned char *tag);
+
+/**
+ * \brief This function performs a GCM authenticated decryption of a
+ * buffer.
+ *
+ * \note For decryption, the output buffer cannot be the same as
+ * input buffer. If the buffers overlap, the output buffer
+ * must trail at least 8 Bytes behind the input buffer.
+ *
+ * \param ctx The GCM context. This must be initialized.
+ * \param length The length of the ciphertext to decrypt, which is also
+ * the length of the decrypted plaintext.
+ * \param iv The initialization vector. This must be a readable buffer
+ * of at least \p iv_len Bytes.
+ * \param iv_len The length of the IV.
+ * \param add The buffer holding the additional data. This must be of at
+ * least that size in Bytes.
+ * \param add_len The length of the additional data.
+ * \param tag The buffer holding the tag to verify. This must be a
+ * readable buffer of at least \p tag_len Bytes.
+ * \param tag_len The length of the tag to verify.
+ * \param input The buffer holding the ciphertext. If \p length is greater
+ * than zero, this must be a readable buffer of at least that
+ * size.
+ * \param output The buffer for holding the decrypted plaintext. If \p length
+ * is greater than zero, this must be a writable buffer of at
+ * least that size.
+ *
+ * \return \c 0 if successful and authenticated.
+ * \return #MBEDTLS_ERR_GCM_AUTH_FAILED if the tag does not match.
+ * \return #MBEDTLS_ERR_GCM_BAD_INPUT if the lengths or pointers are
+ * not valid or a cipher-specific error code if the decryption
+ * failed.
+ */
+int mbedtls_gcm_auth_decrypt(mbedtls_gcm_context *ctx,
+ size_t length,
+ const unsigned char *iv,
+ size_t iv_len,
+ const unsigned char *add,
+ size_t add_len,
+ const unsigned char *tag,
+ size_t tag_len,
+ const unsigned char *input,
+ unsigned char *output);
+
+/**
+ * \brief This function starts a GCM encryption or decryption
+ * operation.
+ *
+ * \param ctx The GCM context. This must be initialized.
+ * \param mode The operation to perform: #MBEDTLS_GCM_ENCRYPT or
+ * #MBEDTLS_GCM_DECRYPT.
+ * \param iv The initialization vector. This must be a readable buffer of
+ * at least \p iv_len Bytes.
+ * \param iv_len The length of the IV.
+ *
+ * \return \c 0 on success.
+ */
+int mbedtls_gcm_starts(mbedtls_gcm_context *ctx,
+ int mode,
+ const unsigned char *iv,
+ size_t iv_len);
+
+/**
+ * \brief This function feeds an input buffer as associated data
+ * (authenticated but not encrypted data) in a GCM
+ * encryption or decryption operation.
+ *
+ * Call this function after mbedtls_gcm_starts() to pass
+ * the associated data. If the associated data is empty,
+ * you do not need to call this function. You may not
+ * call this function after calling mbedtls_cipher_update().
+ *
+ * \param ctx The GCM context. This must have been started with
+ * mbedtls_gcm_starts() and must not have yet received
+ * any input with mbedtls_gcm_update().
+ * \param add The buffer holding the additional data, or \c NULL
+ * if \p add_len is \c 0.
+ * \param add_len The length of the additional data. If \c 0,
+ * \p add may be \c NULL.
+ *
+ * \return \c 0 on success.
+ */
+int mbedtls_gcm_update_ad(mbedtls_gcm_context *ctx,
+ const unsigned char *add,
+ size_t add_len);
+
+/**
+ * \brief This function feeds an input buffer into an ongoing GCM
+ * encryption or decryption operation.
+ *
+ * You may call this function zero, one or more times
+ * to pass successive parts of the input: the plaintext to
+ * encrypt, or the ciphertext (not including the tag) to
+ * decrypt. After the last part of the input, call
+ * mbedtls_gcm_finish().
+ *
+ * This function may produce output in one of the following
+ * ways:
+ * - Immediate output: the output length is always equal
+ * to the input length.
+ * - Buffered output: the output consists of a whole number
+ * of 16-byte blocks. If the total input length so far
+ * (not including associated data) is 16 \* *B* + *A*
+ * with *A* < 16 then the total output length is 16 \* *B*.
+ *
+ * In particular:
+ * - It is always correct to call this function with
+ * \p output_size >= \p input_length + 15.
+ * - If \p input_length is a multiple of 16 for all the calls
+ * to this function during an operation, then it is
+ * correct to use \p output_size = \p input_length.
+ *
+ * \note For decryption, the output buffer cannot be the same as
+ * input buffer. If the buffers overlap, the output buffer
+ * must trail at least 8 Bytes behind the input buffer.
+ *
+ * \param ctx The GCM context. This must be initialized.
+ * \param input The buffer holding the input data. If \p input_length
+ * is greater than zero, this must be a readable buffer
+ * of at least \p input_length bytes.
+ * \param input_length The length of the input data in bytes.
+ * \param output The buffer for the output data. If \p output_size
+ * is greater than zero, this must be a writable buffer of
+ * of at least \p output_size bytes.
+ * \param output_size The size of the output buffer in bytes.
+ * See the function description regarding the output size.
+ * \param output_length On success, \p *output_length contains the actual
+ * length of the output written in \p output.
+ * On failure, the content of \p *output_length is
+ * unspecified.
+ *
+ * \return \c 0 on success.
+ * \return #MBEDTLS_ERR_GCM_BAD_INPUT on failure:
+ * total input length too long,
+ * unsupported input/output buffer overlap detected,
+ * or \p output_size too small.
+ */
+int mbedtls_gcm_update(mbedtls_gcm_context *ctx,
+ const unsigned char *input, size_t input_length,
+ unsigned char *output, size_t output_size,
+ size_t *output_length);
+
+/**
+ * \brief This function finishes the GCM operation and generates
+ * the authentication tag.
+ *
+ * It wraps up the GCM stream, and generates the
+ * tag. The tag can have a maximum length of 16 Bytes.
+ *
+ * \param ctx The GCM context. This must be initialized.
+ * \param tag The buffer for holding the tag. This must be a writable
+ * buffer of at least \p tag_len Bytes.
+ * \param tag_len The length of the tag to generate. This must be at least
+ * four.
+ * \param output The buffer for the final output.
+ * If \p output_size is nonzero, this must be a writable
+ * buffer of at least \p output_size bytes.
+ * \param output_size The size of the \p output buffer in bytes.
+ * This must be large enough for the output that
+ * mbedtls_gcm_update() has not produced. In particular:
+ * - If mbedtls_gcm_update() produces immediate output,
+ * or if the total input size is a multiple of \c 16,
+ * then mbedtls_gcm_finish() never produces any output,
+ * so \p output_size can be \c 0.
+ * - \p output_size never needs to be more than \c 15.
+ * \param output_length On success, \p *output_length contains the actual
+ * length of the output written in \p output.
+ * On failure, the content of \p *output_length is
+ * unspecified.
+ *
+ * \return \c 0 on success.
+ * \return #MBEDTLS_ERR_GCM_BAD_INPUT on failure:
+ * invalid value of \p tag_len,
+ * or \p output_size too small.
+ */
+int mbedtls_gcm_finish(mbedtls_gcm_context *ctx,
+ unsigned char *output, size_t output_size,
+ size_t *output_length,
+ unsigned char *tag, size_t tag_len);
+
+/**
+ * \brief This function clears a GCM context and the underlying
+ * cipher sub-context.
+ *
+ * \param ctx The GCM context to clear. If this is \c NULL, the call has
+ * no effect. Otherwise, this must be initialized.
+ */
+void mbedtls_gcm_free(mbedtls_gcm_context *ctx);
+
+#if defined(MBEDTLS_SELF_TEST)
+
+/**
+ * \brief The GCM checkup routine.
+ *
+ * \return \c 0 on success.
+ * \return \c 1 on failure.
+ */
+int mbedtls_gcm_self_test(int verbose);
+
+#endif /* MBEDTLS_SELF_TEST */
+
+#ifdef __cplusplus
+}
+#endif
+
+
+#endif /* gcm.h */