1 | /**
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2 | * \file gcm.h
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3 | *
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4 | * \brief This file contains GCM definitions and functions.
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5 | *
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6 | * The Galois/Counter Mode (GCM) for 128-bit block ciphers is defined
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7 | * in <em>D. McGrew, J. Viega, The Galois/Counter Mode of Operation
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8 | * (GCM), Natl. Inst. Stand. Technol.</em>
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9 | *
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10 | * For more information on GCM, see <em>NIST SP 800-38D: Recommendation for
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11 | * Block Cipher Modes of Operation: Galois/Counter Mode (GCM) and GMAC</em>.
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12 | *
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13 | */
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14 | /*
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15 | * Copyright (C) 2006-2018, Arm Limited (or its affiliates), All Rights Reserved
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16 | * SPDX-License-Identifier: Apache-2.0
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17 | *
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18 | * Licensed under the Apache License, Version 2.0 (the "License"); you may
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19 | * not use this file except in compliance with the License.
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20 | * You may obtain a copy of the License at
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21 | *
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22 | * http://www.apache.org/licenses/LICENSE-2.0
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23 | *
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24 | * Unless required by applicable law or agreed to in writing, software
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25 | * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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26 | * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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27 | * See the License for the specific language governing permissions and
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28 | * limitations under the License.
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29 | *
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30 | * This file is part of Mbed TLS (https://tls.mbed.org)
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31 | */
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32 |
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33 | #ifndef MBEDTLS_GCM_H
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34 | #define MBEDTLS_GCM_H
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35 |
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36 | #if !defined(MBEDTLS_CONFIG_FILE)
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37 | #include "config.h"
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38 | #else
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39 | #include MBEDTLS_CONFIG_FILE
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40 | #endif
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41 |
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42 | #include "cipher.h"
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43 |
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44 | #include <stdint.h>
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45 |
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46 | #define MBEDTLS_GCM_ENCRYPT 1
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47 | #define MBEDTLS_GCM_DECRYPT 0
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48 |
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49 | #define MBEDTLS_ERR_GCM_AUTH_FAILED -0x0012 /**< Authenticated decryption failed. */
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50 |
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51 | /* MBEDTLS_ERR_GCM_HW_ACCEL_FAILED is deprecated and should not be used. */
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52 | #define MBEDTLS_ERR_GCM_HW_ACCEL_FAILED -0x0013 /**< GCM hardware accelerator failed. */
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53 |
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54 | #define MBEDTLS_ERR_GCM_BAD_INPUT -0x0014 /**< Bad input parameters to function. */
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55 |
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56 | #ifdef __cplusplus
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57 | extern "C" {
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58 | #endif
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59 |
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60 | #if !defined(MBEDTLS_GCM_ALT)
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61 |
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62 | /**
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63 | * \brief The GCM context structure.
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64 | */
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65 | typedef struct mbedtls_gcm_context
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66 | {
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67 | mbedtls_cipher_context_t cipher_ctx; /*!< The cipher context used. */
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68 | uint64_t HL[16]; /*!< Precalculated HTable low. */
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69 | uint64_t HH[16]; /*!< Precalculated HTable high. */
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70 | uint64_t len; /*!< The total length of the encrypted data. */
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71 | uint64_t add_len; /*!< The total length of the additional data. */
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72 | unsigned char base_ectr[16]; /*!< The first ECTR for tag. */
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73 | unsigned char y[16]; /*!< The Y working value. */
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74 | unsigned char buf[16]; /*!< The buf working value. */
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75 | int mode; /*!< The operation to perform:
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76 | #MBEDTLS_GCM_ENCRYPT or
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77 | #MBEDTLS_GCM_DECRYPT. */
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78 | }
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79 | mbedtls_gcm_context;
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80 |
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81 | #else /* !MBEDTLS_GCM_ALT */
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82 | #include "gcm_alt.h"
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83 | #endif /* !MBEDTLS_GCM_ALT */
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84 |
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85 | /**
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86 | * \brief This function initializes the specified GCM context,
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87 | * to make references valid, and prepares the context
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88 | * for mbedtls_gcm_setkey() or mbedtls_gcm_free().
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89 | *
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90 | * The function does not bind the GCM context to a particular
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91 | * cipher, nor set the key. For this purpose, use
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92 | * mbedtls_gcm_setkey().
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93 | *
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94 | * \param ctx The GCM context to initialize. This must not be \c NULL.
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95 | */
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96 | void mbedtls_gcm_init( mbedtls_gcm_context *ctx );
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97 |
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98 | /**
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99 | * \brief This function associates a GCM context with a
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100 | * cipher algorithm and a key.
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101 | *
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102 | * \param ctx The GCM context. This must be initialized.
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103 | * \param cipher The 128-bit block cipher to use.
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104 | * \param key The encryption key. This must be a readable buffer of at
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105 | * least \p keybits bits.
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106 | * \param keybits The key size in bits. Valid options are:
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107 | * <ul><li>128 bits</li>
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108 | * <li>192 bits</li>
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109 | * <li>256 bits</li></ul>
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110 | *
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111 | * \return \c 0 on success.
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112 | * \return A cipher-specific error code on failure.
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113 | */
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114 | int mbedtls_gcm_setkey( mbedtls_gcm_context *ctx,
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115 | mbedtls_cipher_id_t cipher,
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116 | const unsigned char *key,
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117 | unsigned int keybits );
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118 |
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119 | /**
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120 | * \brief This function performs GCM encryption or decryption of a buffer.
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121 | *
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122 | * \note For encryption, the output buffer can be the same as the
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123 | * input buffer. For decryption, the output buffer cannot be
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124 | * the same as input buffer. If the buffers overlap, the output
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125 | * buffer must trail at least 8 Bytes behind the input buffer.
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126 | *
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127 | * \warning When this function performs a decryption, it outputs the
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128 | * authentication tag and does not verify that the data is
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129 | * authentic. You should use this function to perform encryption
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130 | * only. For decryption, use mbedtls_gcm_auth_decrypt() instead.
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131 | *
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132 | * \param ctx The GCM context to use for encryption or decryption. This
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133 | * must be initialized.
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134 | * \param mode The operation to perform:
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135 | * - #MBEDTLS_GCM_ENCRYPT to perform authenticated encryption.
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136 | * The ciphertext is written to \p output and the
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137 | * authentication tag is written to \p tag.
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138 | * - #MBEDTLS_GCM_DECRYPT to perform decryption.
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139 | * The plaintext is written to \p output and the
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140 | * authentication tag is written to \p tag.
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141 | * Note that this mode is not recommended, because it does
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142 | * not verify the authenticity of the data. For this reason,
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143 | * you should use mbedtls_gcm_auth_decrypt() instead of
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144 | * calling this function in decryption mode.
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145 | * \param length The length of the input data, which is equal to the length
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146 | * of the output data.
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147 | * \param iv The initialization vector. This must be a readable buffer of
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148 | * at least \p iv_len Bytes.
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149 | * \param iv_len The length of the IV.
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150 | * \param add The buffer holding the additional data. This must be of at
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151 | * least that size in Bytes.
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152 | * \param add_len The length of the additional data.
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153 | * \param input The buffer holding the input data. If \p length is greater
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154 | * than zero, this must be a readable buffer of at least that
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155 | * size in Bytes.
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156 | * \param output The buffer for holding the output data. If \p length is greater
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157 | * than zero, this must be a writable buffer of at least that
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158 | * size in Bytes.
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159 | * \param tag_len The length of the tag to generate.
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160 | * \param tag The buffer for holding the tag. This must be a readable
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161 | * buffer of at least \p tag_len Bytes.
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162 | *
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163 | * \return \c 0 if the encryption or decryption was performed
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164 | * successfully. Note that in #MBEDTLS_GCM_DECRYPT mode,
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165 | * this does not indicate that the data is authentic.
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166 | * \return #MBEDTLS_ERR_GCM_BAD_INPUT if the lengths or pointers are
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167 | * not valid or a cipher-specific error code if the encryption
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168 | * or decryption failed.
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169 | */
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170 | int mbedtls_gcm_crypt_and_tag( mbedtls_gcm_context *ctx,
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171 | int mode,
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172 | size_t length,
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173 | const unsigned char *iv,
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174 | size_t iv_len,
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175 | const unsigned char *add,
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176 | size_t add_len,
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177 | const unsigned char *input,
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178 | unsigned char *output,
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179 | size_t tag_len,
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180 | unsigned char *tag );
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181 |
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182 | /**
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183 | * \brief This function performs a GCM authenticated decryption of a
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184 | * buffer.
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185 | *
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186 | * \note For decryption, the output buffer cannot be the same as
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187 | * input buffer. If the buffers overlap, the output buffer
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188 | * must trail at least 8 Bytes behind the input buffer.
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189 | *
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190 | * \param ctx The GCM context. This must be initialized.
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191 | * \param length The length of the ciphertext to decrypt, which is also
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192 | * the length of the decrypted plaintext.
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193 | * \param iv The initialization vector. This must be a readable buffer
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194 | * of at least \p iv_len Bytes.
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195 | * \param iv_len The length of the IV.
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196 | * \param add The buffer holding the additional data. This must be of at
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197 | * least that size in Bytes.
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198 | * \param add_len The length of the additional data.
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199 | * \param tag The buffer holding the tag to verify. This must be a
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200 | * readable buffer of at least \p tag_len Bytes.
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201 | * \param tag_len The length of the tag to verify.
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202 | * \param input The buffer holding the ciphertext. If \p length is greater
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203 | * than zero, this must be a readable buffer of at least that
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204 | * size.
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205 | * \param output The buffer for holding the decrypted plaintext. If \p length
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206 | * is greater than zero, this must be a writable buffer of at
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207 | * least that size.
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208 | *
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209 | * \return \c 0 if successful and authenticated.
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210 | * \return #MBEDTLS_ERR_GCM_AUTH_FAILED if the tag does not match.
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211 | * \return #MBEDTLS_ERR_GCM_BAD_INPUT if the lengths or pointers are
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212 | * not valid or a cipher-specific error code if the decryption
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213 | * failed.
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214 | */
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215 | int mbedtls_gcm_auth_decrypt( mbedtls_gcm_context *ctx,
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216 | size_t length,
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217 | const unsigned char *iv,
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218 | size_t iv_len,
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219 | const unsigned char *add,
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220 | size_t add_len,
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221 | const unsigned char *tag,
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222 | size_t tag_len,
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223 | const unsigned char *input,
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224 | unsigned char *output );
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225 |
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226 | /**
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227 | * \brief This function starts a GCM encryption or decryption
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228 | * operation.
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229 | *
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230 | * \param ctx The GCM context. This must be initialized.
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231 | * \param mode The operation to perform: #MBEDTLS_GCM_ENCRYPT or
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232 | * #MBEDTLS_GCM_DECRYPT.
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233 | * \param iv The initialization vector. This must be a readable buffer of
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234 | * at least \p iv_len Bytes.
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235 | * \param iv_len The length of the IV.
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236 | * \param add The buffer holding the additional data, or \c NULL
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237 | * if \p add_len is \c 0.
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238 | * \param add_len The length of the additional data. If \c 0,
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239 | * \p add may be \c NULL.
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240 | *
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241 | * \return \c 0 on success.
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242 | */
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243 | int mbedtls_gcm_starts( mbedtls_gcm_context *ctx,
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244 | int mode,
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245 | const unsigned char *iv,
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246 | size_t iv_len,
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247 | const unsigned char *add,
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248 | size_t add_len );
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249 |
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250 | /**
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251 | * \brief This function feeds an input buffer into an ongoing GCM
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252 | * encryption or decryption operation.
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253 | *
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254 | * ` The function expects input to be a multiple of 16
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255 | * Bytes. Only the last call before calling
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256 | * mbedtls_gcm_finish() can be less than 16 Bytes.
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257 | *
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258 | * \note For decryption, the output buffer cannot be the same as
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259 | * input buffer. If the buffers overlap, the output buffer
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260 | * must trail at least 8 Bytes behind the input buffer.
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261 | *
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262 | * \param ctx The GCM context. This must be initialized.
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263 | * \param length The length of the input data. This must be a multiple of
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264 | * 16 except in the last call before mbedtls_gcm_finish().
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265 | * \param input The buffer holding the input data. If \p length is greater
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266 | * than zero, this must be a readable buffer of at least that
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267 | * size in Bytes.
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268 | * \param output The buffer for holding the output data. If \p length is
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269 | * greater than zero, this must be a writable buffer of at
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270 | * least that size in Bytes.
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271 | *
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272 | * \return \c 0 on success.
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273 | * \return #MBEDTLS_ERR_GCM_BAD_INPUT on failure.
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274 | */
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275 | int mbedtls_gcm_update( mbedtls_gcm_context *ctx,
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276 | size_t length,
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277 | const unsigned char *input,
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278 | unsigned char *output );
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279 |
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280 | /**
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281 | * \brief This function finishes the GCM operation and generates
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282 | * the authentication tag.
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283 | *
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284 | * It wraps up the GCM stream, and generates the
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285 | * tag. The tag can have a maximum length of 16 Bytes.
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286 | *
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287 | * \param ctx The GCM context. This must be initialized.
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288 | * \param tag The buffer for holding the tag. This must be a readable
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289 | * buffer of at least \p tag_len Bytes.
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290 | * \param tag_len The length of the tag to generate. This must be at least
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291 | * four.
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292 | *
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293 | * \return \c 0 on success.
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294 | * \return #MBEDTLS_ERR_GCM_BAD_INPUT on failure.
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295 | */
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296 | int mbedtls_gcm_finish( mbedtls_gcm_context *ctx,
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297 | unsigned char *tag,
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298 | size_t tag_len );
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299 |
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300 | /**
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301 | * \brief This function clears a GCM context and the underlying
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302 | * cipher sub-context.
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303 | *
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304 | * \param ctx The GCM context to clear. If this is \c NULL, the call has
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305 | * no effect. Otherwise, this must be initialized.
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306 | */
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307 | void mbedtls_gcm_free( mbedtls_gcm_context *ctx );
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308 |
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309 | #if defined(MBEDTLS_SELF_TEST)
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310 |
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311 | /**
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312 | * \brief The GCM checkup routine.
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313 | *
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314 | * \return \c 0 on success.
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315 | * \return \c 1 on failure.
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316 | */
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317 | int mbedtls_gcm_self_test( int verbose );
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318 |
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319 | #endif /* MBEDTLS_SELF_TEST */
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320 |
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321 | #ifdef __cplusplus
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322 | }
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323 | #endif
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324 |
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325 |
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326 | #endif /* gcm.h */
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