doc/man3/EVP_EncryptInit.pod

   1 =pod
   2
   3 =head1 NAME
   4
   5 EVP_CIPHER_fetch,
   6 EVP_CIPHER_up_ref,
   7 EVP_CIPHER_free,
   8 EVP_CIPHER_CTX_new,
   9 EVP_CIPHER_CTX_reset,
  10 EVP_CIPHER_CTX_free,
  11 EVP_EncryptInit_ex,
  12 EVP_EncryptUpdate,
  13 EVP_EncryptFinal_ex,
  14 EVP_DecryptInit_ex,
  15 EVP_DecryptUpdate,
  16 EVP_DecryptFinal_ex,
  17 EVP_CipherInit_ex,
  18 EVP_CipherUpdate,
  19 EVP_CipherFinal_ex,
  20 EVP_CIPHER_CTX_set_key_length,
  21 EVP_CIPHER_CTX_ctrl,
  22 EVP_EncryptInit,
  23 EVP_EncryptFinal,
  24 EVP_DecryptInit,
  25 EVP_DecryptFinal,
  26 EVP_CipherInit,
  27 EVP_CipherFinal,
  28 EVP_Cipher,
  29 EVP_get_cipherbyname,
  30 EVP_get_cipherbynid,
  31 EVP_get_cipherbyobj,
  32 EVP_CIPHER_is_a,
  33 EVP_CIPHER_name,
  34 EVP_CIPHER_number,
  35 EVP_CIPHER_names_do_all,
  36 EVP_CIPHER_provider,
  37 EVP_CIPHER_nid,
  38 EVP_CIPHER_get_params,
  39 EVP_CIPHER_gettable_params,
  40 EVP_CIPHER_block_size,
  41 EVP_CIPHER_key_length,
  42 EVP_CIPHER_iv_length,
  43 EVP_CIPHER_flags,
  44 EVP_CIPHER_mode,
  45 EVP_CIPHER_type,
  46 EVP_CIPHER_CTX_cipher,
  47 EVP_CIPHER_CTX_name,
  48 EVP_CIPHER_CTX_nid,
  49 EVP_CIPHER_CTX_get_params,
  50 EVP_CIPHER_gettable_ctx_params,
  51 EVP_CIPHER_CTX_set_params,
  52 EVP_CIPHER_settable_ctx_params,
  53 EVP_CIPHER_CTX_block_size,
  54 EVP_CIPHER_CTX_key_length,
  55 EVP_CIPHER_CTX_iv_length,
  56 EVP_CIPHER_CTX_tag_length,
  57 EVP_CIPHER_CTX_get_app_data,
  58 EVP_CIPHER_CTX_set_app_data,
  59 EVP_CIPHER_CTX_type,
  60 EVP_CIPHER_CTX_flags,
  61 EVP_CIPHER_CTX_mode,
  62 EVP_CIPHER_param_to_asn1,
  63 EVP_CIPHER_asn1_to_param,
  64 EVP_CIPHER_CTX_set_padding,
  65 EVP_enc_null,
  66 EVP_CIPHER_do_all_provided
  67 - EVP cipher routines
  68
  69 =head1 SYNOPSIS
  70
  71 =for openssl generic
  72
  73  #include <openssl/evp.h>
  74
  75  EVP_CIPHER *EVP_CIPHER_fetch(OSSL_LIB_CTX *ctx, const char *algorithm,
  76                               const char *properties);
  77  int EVP_CIPHER_up_ref(EVP_CIPHER *cipher);
  78  void EVP_CIPHER_free(EVP_CIPHER *cipher);
  79  EVP_CIPHER_CTX *EVP_CIPHER_CTX_new(void);
  80  int EVP_CIPHER_CTX_reset(EVP_CIPHER_CTX *ctx);
  81  void EVP_CIPHER_CTX_free(EVP_CIPHER_CTX *ctx);
  82
  83  int EVP_EncryptInit_ex(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
  84                         ENGINE *impl, const unsigned char *key, const unsigned char *iv);
  85  int EVP_EncryptUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out,
  86                        int *outl, const unsigned char *in, int inl);
  87  int EVP_EncryptFinal_ex(EVP_CIPHER_CTX *ctx, unsigned char *out, int *outl);
  88
  89  int EVP_DecryptInit_ex(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
  90                         ENGINE *impl, const unsigned char *key, const unsigned char *iv);
  91  int EVP_DecryptUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out,
  92                        int *outl, const unsigned char *in, int inl);
  93  int EVP_DecryptFinal_ex(EVP_CIPHER_CTX *ctx, unsigned char *outm, int *outl);
  94
  95  int EVP_CipherInit_ex(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
  96                        ENGINE *impl, const unsigned char *key, const unsigned char *iv, int enc);
  97  int EVP_CipherUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out,
  98                       int *outl, const unsigned char *in, int inl);
  99  int EVP_CipherFinal_ex(EVP_CIPHER_CTX *ctx, unsigned char *outm, int *outl);
 100
 101  int EVP_EncryptInit(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
 102                      const unsigned char *key, const unsigned char *iv);
 103  int EVP_EncryptFinal(EVP_CIPHER_CTX *ctx, unsigned char *out, int *outl);
 104
 105  int EVP_DecryptInit(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
 106                      const unsigned char *key, const unsigned char *iv);
 107  int EVP_DecryptFinal(EVP_CIPHER_CTX *ctx, unsigned char *outm, int *outl);
 108
 109  int EVP_CipherInit(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
 110                     const unsigned char *key, const unsigned char *iv, int enc);
 111  int EVP_CipherFinal(EVP_CIPHER_CTX *ctx, unsigned char *outm, int *outl);
 112
 113  int EVP_Cipher(EVP_CIPHER_CTX *ctx, unsigned char *out,
 114                 const unsigned char *in, unsigned int inl);
 115
 116  int EVP_CIPHER_CTX_set_padding(EVP_CIPHER_CTX *x, int padding);
 117  int EVP_CIPHER_CTX_set_key_length(EVP_CIPHER_CTX *x, int keylen);
 118  int EVP_CIPHER_CTX_ctrl(EVP_CIPHER_CTX *ctx, int type, int arg, void *ptr);
 119  int EVP_CIPHER_CTX_rand_key(EVP_CIPHER_CTX *ctx, unsigned char *key);
 120
 121  const EVP_CIPHER *EVP_get_cipherbyname(const char *name);
 122  const EVP_CIPHER *EVP_get_cipherbynid(int nid);
 123  const EVP_CIPHER *EVP_get_cipherbyobj(const ASN1_OBJECT *a);
 124
 125  int EVP_CIPHER_nid(const EVP_CIPHER *e);
 126  int EVP_CIPHER_number(const EVP_CIPHER *e);
 127  int EVP_CIPHER_is_a(const EVP_CIPHER *cipher, const char *name);
 128  int EVP_CIPHER_names_do_all(const EVP_CIPHER *cipher,
 129                              void (*fn)(const char *name, void *data),
 130                              void *data);
 131  const char *EVP_CIPHER_name(const EVP_CIPHER *cipher);
 132  const OSSL_PROVIDER *EVP_CIPHER_provider(const EVP_CIPHER *cipher);
 133  int EVP_CIPHER_block_size(const EVP_CIPHER *e);
 134  int EVP_CIPHER_key_length(const EVP_CIPHER *e);
 135  int EVP_CIPHER_iv_length(const EVP_CIPHER *e);
 136  unsigned long EVP_CIPHER_flags(const EVP_CIPHER *e);
 137  unsigned long EVP_CIPHER_mode(const EVP_CIPHER *e);
 138  int EVP_CIPHER_type(const EVP_CIPHER *ctx);
 139
 140  const EVP_CIPHER *EVP_CIPHER_CTX_cipher(const EVP_CIPHER_CTX *ctx);
 141  int EVP_CIPHER_CTX_nid(const EVP_CIPHER_CTX *ctx);
 142  const char *EVP_CIPHER_CTX_name(const EVP_CIPHER_CTX *ctx);
 143
 144  int EVP_CIPHER_get_params(EVP_CIPHER *cipher, OSSL_PARAM params[]);
 145  int EVP_CIPHER_CTX_set_params(EVP_CIPHER_CTX *ctx, const OSSL_PARAM params[]);
 146  int EVP_CIPHER_CTX_get_params(EVP_CIPHER_CTX *ctx, OSSL_PARAM params[]);
 147  const OSSL_PARAM *EVP_CIPHER_gettable_params(const EVP_CIPHER *cipher);
 148  const OSSL_PARAM *EVP_CIPHER_settable_ctx_params(const EVP_CIPHER *cipher);
 149  const OSSL_PARAM *EVP_CIPHER_gettable_ctx_params(const EVP_CIPHER *cipher);
 150  int EVP_CIPHER_CTX_block_size(const EVP_CIPHER_CTX *ctx);
 151  int EVP_CIPHER_CTX_key_length(const EVP_CIPHER_CTX *ctx);
 152  int EVP_CIPHER_CTX_iv_length(const EVP_CIPHER_CTX *ctx);
 153  int EVP_CIPHER_CTX_tag_length(const EVP_CIPHER_CTX *ctx);
 154  void *EVP_CIPHER_CTX_get_app_data(const EVP_CIPHER_CTX *ctx);
 155  void EVP_CIPHER_CTX_set_app_data(const EVP_CIPHER_CTX *ctx, void *data);
 156  int EVP_CIPHER_CTX_type(const EVP_CIPHER_CTX *ctx);
 157  int EVP_CIPHER_CTX_mode(const EVP_CIPHER_CTX *ctx);
 158
 159  int EVP_CIPHER_param_to_asn1(EVP_CIPHER_CTX *c, ASN1_TYPE *type);
 160  int EVP_CIPHER_asn1_to_param(EVP_CIPHER_CTX *c, ASN1_TYPE *type);
 161
 162  void EVP_CIPHER_do_all_provided(OSSL_LIB_CTX *libctx,
 163                                  void (*fn)(EVP_CIPHER *cipher, void *arg),
 164                                  void *arg);
 165
 166 =head1 DESCRIPTION
 167
 168 The EVP cipher routines are a high-level interface to certain
 169 symmetric ciphers.
 170
 171 The B<EVP_CIPHER> type is a structure for cipher method implementation.
 172
 173 EVP_CIPHER_fetch() fetches the cipher implementation for the given
 174 B<algorithm> from any provider offering it, within the criteria given
 175 by the B<properties>.
 176 See L<provider(7)/Fetching algorithms> for further information.
 177
 178 The returned value must eventually be freed with EVP_CIPHER_free().
 179
 180 EVP_CIPHER_up_ref() increments the reference count for an B<EVP_CIPHER>
 181 structure.
 182
 183 EVP_CIPHER_free() decrements the reference count for the B<EVP_CIPHER>
 184 structure.
 185 If the reference count drops to 0 then the structure is freed.
 186
 187 EVP_CIPHER_CTX_new() creates a cipher context.
 188
 189 EVP_CIPHER_CTX_free() clears all information from a cipher context
 190 and free up any allocated memory associate with it, including B<ctx>
 191 itself. This function should be called after all operations using a
 192 cipher are complete so sensitive information does not remain in
 193 memory.
 194
 195 EVP_EncryptInit_ex() sets up cipher context B<ctx> for encryption
 196 with cipher B<type>. B<type> is typically supplied by a function such
 197 as EVP_aes_256_cbc(), or a value explicitly fetched with
 198 EVP_CIPHER_fetch(). If B<impl> is non-NULL, its implementation of the
 199 cipher B<type> is used if there is one, and if not, the default
 200 implementation is used. B<key> is the symmetric key to use
 201 and B<iv> is the IV to use (if necessary), the actual number of bytes
 202 used for the key and IV depends on the cipher. It is possible to set
 203 all parameters to NULL except B<type> in an initial call and supply
 204 the remaining parameters in subsequent calls, all of which have B<type>
 205 set to NULL. This is done when the default cipher parameters are not
 206 appropriate.
 207 For EVP_CIPH_GCM_MODE the IV will be generated internally if it is not
 208 specified.
 209
 210 EVP_EncryptUpdate() encrypts B<inl> bytes from the buffer B<in> and
 211 writes the encrypted version to B<out>. This function can be called
 212 multiple times to encrypt successive blocks of data. The amount
 213 of data written depends on the block alignment of the encrypted data.
 214 For most ciphers and modes, the amount of data written can be anything
 215 from zero bytes to (inl + cipher_block_size - 1) bytes.
 216 For wrap cipher modes, the amount of data written can be anything
 217 from zero bytes to (inl + cipher_block_size) bytes.
 218 For stream ciphers, the amount of data written can be anything from zero
 219 bytes to inl bytes.
 220 Thus, B<out> should contain sufficient room for the operation being performed.
 221 The actual number of bytes written is placed in B<outl>. It also
 222 checks if B<in> and B<out> are partially overlapping, and if they are
 223 0 is returned to indicate failure.
 224
 225 If padding is enabled (the default) then EVP_EncryptFinal_ex() encrypts
 226 the "final" data, that is any data that remains in a partial block.
 227 It uses standard block padding (aka PKCS padding) as described in
 228 the NOTES section, below. The encrypted
 229 final data is written to B<out> which should have sufficient space for
 230 one cipher block. The number of bytes written is placed in B<outl>. After
 231 this function is called the encryption operation is finished and no further
 232 calls to EVP_EncryptUpdate() should be made.
 233
 234 If padding is disabled then EVP_EncryptFinal_ex() will not encrypt any more
 235 data and it will return an error if any data remains in a partial block:
 236 that is if the total data length is not a multiple of the block size.
 237
 238 EVP_DecryptInit_ex(), EVP_DecryptUpdate() and EVP_DecryptFinal_ex() are the
 239 corresponding decryption operations. EVP_DecryptFinal() will return an
 240 error code if padding is enabled and the final block is not correctly
 241 formatted. The parameters and restrictions are identical to the encryption
 242 operations except that if padding is enabled the decrypted data buffer B<out>
 243 passed to EVP_DecryptUpdate() should have sufficient room for
 244 (B<inl> + cipher_block_size) bytes unless the cipher block size is 1 in
 245 which case B<inl> bytes is sufficient.
 246
 247 EVP_CipherInit_ex(), EVP_CipherUpdate() and EVP_CipherFinal_ex() are
 248 functions that can be used for decryption or encryption. The operation
 249 performed depends on the value of the B<enc> parameter. It should be set
 250 to 1 for encryption, 0 for decryption and -1 to leave the value unchanged
 251 (the actual value of 'enc' being supplied in a previous call).
 252
 253 EVP_CIPHER_CTX_reset() clears all information from a cipher context
 254 and free up any allocated memory associate with it, except the B<ctx>
 255 itself. This function should be called anytime B<ctx> is to be reused
 256 for another EVP_CipherInit() / EVP_CipherUpdate() / EVP_CipherFinal()
 257 series of calls.
 258
 259 EVP_EncryptInit(), EVP_DecryptInit() and EVP_CipherInit() behave in a
 260 similar way to EVP_EncryptInit_ex(), EVP_DecryptInit_ex() and
 261 EVP_CipherInit_ex() except they always use the default cipher implementation.
 262
 263 EVP_EncryptFinal(), EVP_DecryptFinal() and EVP_CipherFinal() are
 264 identical to EVP_EncryptFinal_ex(), EVP_DecryptFinal_ex() and
 265 EVP_CipherFinal_ex(). In previous releases they also cleaned up
 266 the B<ctx>, but this is no longer done and EVP_CIPHER_CTX_clean()
 267 must be called to free any context resources.
 268
 269 EVP_Cipher() encrypts or decrypts a maximum I<inl> amount of bytes from
 270 I<in> and leaves the result in I<out>.
 271 If the cipher doesn't have the flag B<EVP_CIPH_FLAG_CUSTOM_CIPHER> set,
 272 then I<inl> must be a multiple of EVP_CIPHER_block_size().  If it isn't,
 273 the result is undefined.  If the cipher has that flag set, then I<inl>
 274 can be any size.
 275 This function is historic and shouldn't be used in an application, please
 276 consider using EVP_CipherUpdate() and EVP_CipherFinal_ex instead.
 277
 278 EVP_get_cipherbyname(), EVP_get_cipherbynid() and EVP_get_cipherbyobj()
 279 return an EVP_CIPHER structure when passed a cipher name, a NID or an
 280 ASN1_OBJECT structure.
 281
 282 EVP_CIPHER_nid() and EVP_CIPHER_CTX_nid() return the NID of a cipher when
 283 passed an B<EVP_CIPHER> or B<EVP_CIPHER_CTX> structure.  The actual NID
 284 value is an internal value which may not have a corresponding OBJECT
 285 IDENTIFIER.
 286
 287 EVP_CIPHER_CTX_set_padding() enables or disables padding. This
 288 function should be called after the context is set up for encryption
 289 or decryption with EVP_EncryptInit_ex(), EVP_DecryptInit_ex() or
 290 EVP_CipherInit_ex(). By default encryption operations are padded using
 291 standard block padding and the padding is checked and removed when
 292 decrypting. If the B<pad> parameter is zero then no padding is
 293 performed, the total amount of data encrypted or decrypted must then
 294 be a multiple of the block size or an error will occur.
 295
 296 EVP_CIPHER_get_params() retrieves the requested list of algorithm
 297 B<params> from a B<cipher>.
 298
 299 EVP_CIPHER_CTX_set_params() Sets the list of operation B<params> into a CIPHER
 300 context B<ctx>.
 301
 302 EVP_CIPHER_CTX_get_params() retrieves the requested list of operation
 303 B<params> from CIPHER context B<ctx>.
 304
 305 EVP_CIPHER_gettable_params(), EVP_CIPHER_gettable_ctx_params(), and
 306 EVP_CIPHER_settable_ctx_params() get a constant B<OSSL_PARAM> array
 307 that describes the retrievable and settable parameters, i.e. parameters
 308 that can be used with EVP_CIPHER_get_params(), EVP_CIPHER_CTX_get_params()
 309 and EVP_CIPHER_CTX_set_params(), respectively.
 310 See L<OSSL_PARAM(3)> for the use of B<OSSL_PARAM> as parameter descriptor.
 311
 312 EVP_CIPHER_key_length() and EVP_CIPHER_CTX_key_length() return the key
 313 length of a cipher when passed an B<EVP_CIPHER> or B<EVP_CIPHER_CTX>
 314 structure. The constant B<EVP_MAX_KEY_LENGTH> is the maximum key length
 315 for all ciphers. Note: although EVP_CIPHER_key_length() is fixed for a
 316 given cipher, the value of EVP_CIPHER_CTX_key_length() may be different
 317 for variable key length ciphers.
 318
 319 EVP_CIPHER_CTX_set_key_length() sets the key length of the cipher ctx.
 320 If the cipher is a fixed length cipher then attempting to set the key
 321 length to any value other than the fixed value is an error.
 322
 323 EVP_CIPHER_iv_length() and EVP_CIPHER_CTX_iv_length() return the IV
 324 length of a cipher when passed an B<EVP_CIPHER> or B<EVP_CIPHER_CTX>.
 325 It will return zero if the cipher does not use an IV.  The constant
 326 B<EVP_MAX_IV_LENGTH> is the maximum IV length for all ciphers.
 327
 328 EVP_CIPHER_CTX_tag_length() returns the tag length of a AEAD cipher when passed
 329 a B<EVP_CIPHER_CTX>. It will return zero if the cipher does not support a tag.
 330 It returns a default value if the tag length has not been set.
 331
 332 EVP_CIPHER_block_size() and EVP_CIPHER_CTX_block_size() return the block
 333 size of a cipher when passed an B<EVP_CIPHER> or B<EVP_CIPHER_CTX>
 334 structure. The constant B<EVP_MAX_BLOCK_LENGTH> is also the maximum block
 335 length for all ciphers.
 336
 337 EVP_CIPHER_type() and EVP_CIPHER_CTX_type() return the type of the passed
 338 cipher or context. This "type" is the actual NID of the cipher OBJECT
 339 IDENTIFIER as such it ignores the cipher parameters and 40 bit RC2 and
 340 128 bit RC2 have the same NID. If the cipher does not have an object
 341 identifier or does not have ASN1 support this function will return
 342 B<NID_undef>.
 343
 344 EVP_CIPHER_is_a() returns 1 if I<cipher> is an implementation of an
 345 algorithm that's identifiable with I<name>, otherwise 0.
 346 If I<cipher> is a legacy cipher (it's the return value from the likes
 347 of EVP_aes128() rather than the result of an EVP_CIPHER_fetch()), only
 348 cipher names registered with the default library context (see
 349 L<OSSL_LIB_CTX(3)>) will be considered.
 350
 351 EVP_CIPHER_number() returns the internal dynamic number assigned to
 352 the I<cipher>.  This is only useful with fetched B<EVP_CIPHER>s.
 353
 354 EVP_CIPHER_name() and EVP_CIPHER_CTX_name() return the name of the passed
 355 cipher or context.  For fetched ciphers with multiple names, only one
 356 of them is returned; it's recommended to use EVP_CIPHER_names_do_all()
 357 instead.
 358
 359 EVP_CIPHER_names_do_all() traverses all names for the I<cipher>, and
 360 calls I<fn> with each name and I<data>.  This is only useful with
 361 fetched B<EVP_CIPHER>s.
 362
 363 EVP_CIPHER_provider() returns an B<OSSL_PROVIDER> pointer to the provider
 364 that implements the given B<EVP_CIPHER>.
 365
 366 EVP_CIPHER_CTX_cipher() returns the B<EVP_CIPHER> structure when passed
 367 an B<EVP_CIPHER_CTX> structure.
 368
 369 EVP_CIPHER_mode() and EVP_CIPHER_CTX_mode() return the block cipher mode:
 370 EVP_CIPH_ECB_MODE, EVP_CIPH_CBC_MODE, EVP_CIPH_CFB_MODE, EVP_CIPH_OFB_MODE,
 371 EVP_CIPH_CTR_MODE, EVP_CIPH_GCM_MODE, EVP_CIPH_CCM_MODE, EVP_CIPH_XTS_MODE,
 372 EVP_CIPH_WRAP_MODE, EVP_CIPH_OCB_MODE or EVP_CIPH_SIV_MODE. If the cipher is a
 373 stream cipher then EVP_CIPH_STREAM_CIPHER is returned.
 374
 375 EVP_CIPHER_flags() returns any flags associated with the cipher. See
 376 EVP_CIPHER_meth_set_flags() for a list of currently defined flags.
 377
 378 EVP_CIPHER_param_to_asn1() sets the AlgorithmIdentifier "parameter" based
 379 on the passed cipher. This will typically include any parameters and an
 380 IV. The cipher IV (if any) must be set when this call is made. This call
 381 should be made before the cipher is actually "used" (before any
 382 EVP_EncryptUpdate(), EVP_DecryptUpdate() calls for example). This function
 383 may fail if the cipher does not have any ASN1 support.
 384
 385 EVP_CIPHER_asn1_to_param() sets the cipher parameters based on an ASN1
 386 AlgorithmIdentifier "parameter". The precise effect depends on the cipher
 387 In the case of RC2, for example, it will set the IV and effective key length.
 388 This function should be called after the base cipher type is set but before
 389 the key is set. For example EVP_CipherInit() will be called with the IV and
 390 key set to NULL, EVP_CIPHER_asn1_to_param() will be called and finally
 391 EVP_CipherInit() again with all parameters except the key set to NULL. It is
 392 possible for this function to fail if the cipher does not have any ASN1 support
 393 or the parameters cannot be set (for example the RC2 effective key length
 394 is not supported.
 395
 396 EVP_CIPHER_CTX_ctrl() allows various cipher specific parameters to be determined
 397 and set.
 398
 399 EVP_CIPHER_CTX_rand_key() generates a random key of the appropriate length
 400 based on the cipher context. The EVP_CIPHER can provide its own random key
 401 generation routine to support keys of a specific form. B<Key> must point to a
 402 buffer at least as big as the value returned by EVP_CIPHER_CTX_key_length().
 403
 404 EVP_CIPHER_do_all_provided() traverses all ciphers implemented by all activated
 405 providers in the given library context I<libctx>, and for each of the
 406 implementations, calls the given function I<fn> with the implementation method
 407 and the given I<arg> as argument.
 408
 409 =head1 RETURN VALUES
 410
 411 EVP_CIPHER_fetch() returns a pointer to a B<EVP_CIPHER> for success
 412 and B<NULL> for failure.
 413
 414 EVP_CIPHER_up_ref() returns 1 for success or 0 otherwise.
 415
 416 EVP_CIPHER_CTX_new() returns a pointer to a newly created
 417 B<EVP_CIPHER_CTX> for success and B<NULL> for failure.
 418
 419 EVP_EncryptInit_ex(), EVP_EncryptUpdate() and EVP_EncryptFinal_ex()
 420 return 1 for success and 0 for failure.
 421
 422 EVP_DecryptInit_ex() and EVP_DecryptUpdate() return 1 for success and 0 for failure.
 423 EVP_DecryptFinal_ex() returns 0 if the decrypt failed or 1 for success.
 424
 425 EVP_CipherInit_ex() and EVP_CipherUpdate() return 1 for success and 0 for failure.
 426 EVP_CipherFinal_ex() returns 0 for a decryption failure or 1 for success.
 427
 428 EVP_Cipher() returns the amount of encrypted / decrypted bytes, or -1
 429 on failure, if the flag B<EVP_CIPH_FLAG_CUSTOM_CIPHER> is set for the
 430 cipher.  EVP_Cipher() returns 1 on success or 0 on failure, if the flag
 431 B<EVP_CIPH_FLAG_CUSTOM_CIPHER> is not set for the cipher.
 432
 433 EVP_CIPHER_CTX_reset() returns 1 for success and 0 for failure.
 434
 435 EVP_get_cipherbyname(), EVP_get_cipherbynid() and EVP_get_cipherbyobj()
 436 return an B<EVP_CIPHER> structure or NULL on error.
 437
 438 EVP_CIPHER_nid() and EVP_CIPHER_CTX_nid() return a NID.
 439
 440 EVP_CIPHER_block_size() and EVP_CIPHER_CTX_block_size() return the block
 441 size.
 442
 443 EVP_CIPHER_key_length() and EVP_CIPHER_CTX_key_length() return the key
 444 length.
 445
 446 EVP_CIPHER_CTX_set_padding() always returns 1.
 447
 448 EVP_CIPHER_iv_length() and EVP_CIPHER_CTX_iv_length() return the IV
 449 length or zero if the cipher does not use an IV.
 450
 451 EVP_CIPHER_CTX_tag_length() return the tag length or zero if the cipher does not
 452 use a tag.
 453
 454 EVP_CIPHER_type() and EVP_CIPHER_CTX_type() return the NID of the cipher's
 455 OBJECT IDENTIFIER or NID_undef if it has no defined OBJECT IDENTIFIER.
 456
 457 EVP_CIPHER_CTX_cipher() returns an B<EVP_CIPHER> structure.
 458
 459 EVP_CIPHER_param_to_asn1() and EVP_CIPHER_asn1_to_param() return greater
 460 than zero for success and zero or a negative number on failure.
 461
 462 EVP_CIPHER_CTX_rand_key() returns 1 for success.
 463
 464 EVP_CIPHER_names_do_all() returns 1 if the callback was called for all names.
 465 A return value of 0 means that the callback was not called for any names.
 466
 467 =head1 CIPHER LISTING
 468
 469 All algorithms have a fixed key length unless otherwise stated.
 470
 471 Refer to L</SEE ALSO> for the full list of ciphers available through the EVP
 472 interface.
 473
 474 =over 4
 475
 476 =item EVP_enc_null()
 477
 478 Null cipher: does nothing.
 479
 480 =back
 481
 482 =head1 AEAD INTERFACE
 483
 484 The EVP interface for Authenticated Encryption with Associated Data (AEAD)
 485 modes are subtly altered and several additional I<ctrl> operations are supported
 486 depending on the mode specified.
 487
 488 To specify additional authenticated data (AAD), a call to EVP_CipherUpdate(),
 489 EVP_EncryptUpdate() or EVP_DecryptUpdate() should be made with the output
 490 parameter B<out> set to B<NULL>.
 491
 492 When decrypting, the return value of EVP_DecryptFinal() or EVP_CipherFinal()
 493 indicates whether the operation was successful. If it does not indicate success,
 494 the authentication operation has failed and any output data B<MUST NOT> be used
 495 as it is corrupted.
 496
 497 =head2 GCM and OCB Modes
 498
 499 The following I<ctrl>s are supported in GCM and OCB modes.
 500
 501 =over 4
 502
 503 =item EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_IVLEN, ivlen, NULL)
 504
 505 Sets the IV length. This call can only be made before specifying an IV. If
 506 not called a default IV length is used.
 507
 508 For GCM AES and OCB AES the default is 12 (i.e. 96 bits). For OCB mode the
 509 maximum is 15.
 510
 511 =item EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_GET_TAG, taglen, tag)
 512
 513 Writes C<taglen> bytes of the tag value to the buffer indicated by C<tag>.
 514 This call can only be made when encrypting data and B<after> all data has been
 515 processed (e.g. after an EVP_EncryptFinal() call).
 516
 517 For OCB, C<taglen> must either be 16 or the value previously set via
 518 B<EVP_CTRL_AEAD_SET_TAG>.
 519
 520 =item EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_TAG, taglen, tag)
 521
 522 Sets the expected tag to C<taglen> bytes from C<tag>.
 523 The tag length can only be set before specifying an IV.
 524 C<taglen> must be between 1 and 16 inclusive.
 525
 526 For GCM, this call is only valid when decrypting data.
 527
 528 For OCB, this call is valid when decrypting data to set the expected tag,
 529 and before encryption to set the desired tag length.
 530
 531 In OCB mode, calling this before encryption with C<tag> set to C<NULL> sets the
 532 tag length.  If this is not called prior to encryption, a default tag length is
 533 used.
 534
 535 For OCB AES, the default tag length is 16 (i.e. 128 bits).  It is also the
 536 maximum tag length for OCB.
 537
 538 =back
 539
 540 =head2 CCM Mode
 541
 542 The EVP interface for CCM mode is similar to that of the GCM mode but with a
 543 few additional requirements and different I<ctrl> values.
 544
 545 For CCM mode, the total plaintext or ciphertext length B<MUST> be passed to
 546 EVP_CipherUpdate(), EVP_EncryptUpdate() or EVP_DecryptUpdate() with the output
 547 and input parameters (B<in> and B<out>) set to B<NULL> and the length passed in
 548 the B<inl> parameter.
 549
 550 The following I<ctrl>s are supported in CCM mode.
 551
 552 =over 4
 553
 554 =item EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_TAG, taglen, tag)
 555
 556 This call is made to set the expected B<CCM> tag value when decrypting or
 557 the length of the tag (with the C<tag> parameter set to NULL) when encrypting.
 558 The tag length is often referred to as B<M>. If not set a default value is
 559 used (12 for AES). When decrypting, the tag needs to be set before passing
 560 in data to be decrypted, but as in GCM and OCB mode, it can be set after
 561 passing additional authenticated data (see L</AEAD INTERFACE>).
 562
 563 =item EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_CCM_SET_L, ivlen, NULL)
 564
 565 Sets the CCM B<L> value. If not set a default is used (8 for AES).
 566
 567 =item EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_IVLEN, ivlen, NULL)
 568
 569 Sets the CCM nonce (IV) length. This call can only be made before specifying a
 570 nonce value. The nonce length is given by B<15 - L> so it is 7 by default for
 571 AES.
 572
 573 =back
 574
 575 =head2 SIV Mode
 576
 577 For SIV mode ciphers the behaviour of the EVP interface is subtly
 578 altered and several additional ctrl operations are supported.
 579
 580 To specify any additional authenticated data (AAD) and/or a Nonce, a call to
 581 EVP_CipherUpdate(), EVP_EncryptUpdate() or EVP_DecryptUpdate() should be made
 582 with the output parameter B<out> set to B<NULL>.
 583
 584 RFC5297 states that the Nonce is the last piece of AAD before the actual
 585 encrypt/decrypt takes place. The API does not differentiate the Nonce from
 586 other AAD.
 587
 588 When decrypting the return value of EVP_DecryptFinal() or EVP_CipherFinal()
 589 indicates if the operation was successful. If it does not indicate success
 590 the authentication operation has failed and any output data B<MUST NOT>
 591 be used as it is corrupted.
 592
 593 The following ctrls are supported in both SIV modes.
 594
 595 =over 4
 596
 597 =item EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_GET_TAG, taglen, tag);
 598
 599 Writes B<taglen> bytes of the tag value to the buffer indicated by B<tag>.
 600 This call can only be made when encrypting data and B<after> all data has been
 601 processed (e.g. after an EVP_EncryptFinal() call). For SIV mode the taglen must
 602 be 16.
 603
 604 =item EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_TAG, taglen, tag);
 605
 606 Sets the expected tag to B<taglen> bytes from B<tag>. This call is only legal
 607 when decrypting data and must be made B<before> any data is processed (e.g.
 608 before any EVP_DecryptUpdate() call). For SIV mode the taglen must be 16.
 609
 610 =back
 611
 612 SIV mode makes two passes over the input data, thus, only one call to
 613 EVP_CipherUpdate(), EVP_EncryptUpdate() or EVP_DecryptUpdate() should be made
 614 with B<out> set to a non-B<NULL> value. A call to EVP_Decrypt_Final() or
 615 EVP_CipherFinal() is not required, but will indicate if the update
 616 operation succeeded.
 617
 618 =head2 ChaCha20-Poly1305
 619
 620 The following I<ctrl>s are supported for the ChaCha20-Poly1305 AEAD algorithm.
 621
 622 =over 4
 623
 624 =item EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_IVLEN, ivlen, NULL)
 625
 626 Sets the nonce length. This call can only be made before specifying the nonce.
 627 If not called a default nonce length of 12 (i.e. 96 bits) is used. The maximum
 628 nonce length is 12 bytes (i.e. 96-bits). If a nonce of less than 12 bytes is set
 629 then the nonce is automatically padded with leading 0 bytes to make it 12 bytes
 630 in length.
 631
 632 =item EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_GET_TAG, taglen, tag)
 633
 634 Writes C<taglen> bytes of the tag value to the buffer indicated by C<tag>.
 635 This call can only be made when encrypting data and B<after> all data has been
 636 processed (e.g. after an EVP_EncryptFinal() call).
 637
 638 C<taglen> specified here must be 16 (B<POLY1305_BLOCK_SIZE>, i.e. 128-bits) or
 639 less.
 640
 641 =item EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_TAG, taglen, tag)
 642
 643 Sets the expected tag to C<taglen> bytes from C<tag>.
 644 The tag length can only be set before specifying an IV.
 645 C<taglen> must be between 1 and 16 (B<POLY1305_BLOCK_SIZE>) inclusive.
 646 This call is only valid when decrypting data.
 647
 648 =back
 649
 650 =head1 NOTES
 651
 652 Where possible the B<EVP> interface to symmetric ciphers should be used in
 653 preference to the low-level interfaces. This is because the code then becomes
 654 transparent to the cipher used and much more flexible. Additionally, the
 655 B<EVP> interface will ensure the use of platform specific cryptographic
 656 acceleration such as AES-NI (the low-level interfaces do not provide the
 657 guarantee).
 658
 659 PKCS padding works by adding B<n> padding bytes of value B<n> to make the total
 660 length of the encrypted data a multiple of the block size. Padding is always
 661 added so if the data is already a multiple of the block size B<n> will equal
 662 the block size. For example if the block size is 8 and 11 bytes are to be
 663 encrypted then 5 padding bytes of value 5 will be added.
 664
 665 When decrypting the final block is checked to see if it has the correct form.
 666
 667 Although the decryption operation can produce an error if padding is enabled,
 668 it is not a strong test that the input data or key is correct. A random block
 669 has better than 1 in 256 chance of being of the correct format and problems with
 670 the input data earlier on will not produce a final decrypt error.
 671
 672 If padding is disabled then the decryption operation will always succeed if
 673 the total amount of data decrypted is a multiple of the block size.
 674
 675 The functions EVP_EncryptInit(), EVP_EncryptFinal(), EVP_DecryptInit(),
 676 EVP_CipherInit() and EVP_CipherFinal() are obsolete but are retained for
 677 compatibility with existing code. New code should use EVP_EncryptInit_ex(),
 678 EVP_EncryptFinal_ex(), EVP_DecryptInit_ex(), EVP_DecryptFinal_ex(),
 679 EVP_CipherInit_ex() and EVP_CipherFinal_ex() because they can reuse an
 680 existing context without allocating and freeing it up on each call.
 681
 682 There are some differences between functions EVP_CipherInit() and
 683 EVP_CipherInit_ex(), significant in some circumstances. EVP_CipherInit() fills
 684 the passed context object with zeros.  As a consequence, EVP_CipherInit() does
 685 not allow step-by-step initialization of the ctx when the I<key> and I<iv> are
 686 passed in separate calls. It also means that the flags set for the CTX are
 687 removed, and it is especially important for the
 688 B<EVP_CIPHER_CTX_FLAG_WRAP_ALLOW> flag treated specially in
 689 EVP_CipherInit_ex().
 690
 691 EVP_get_cipherbynid(), and EVP_get_cipherbyobj() are implemented as macros.
 692
 693 =head1 BUGS
 694
 695 B<EVP_MAX_KEY_LENGTH> and B<EVP_MAX_IV_LENGTH> only refer to the internal
 696 ciphers with default key lengths. If custom ciphers exceed these values the
 697 results are unpredictable. This is because it has become standard practice to
 698 define a generic key as a fixed unsigned char array containing
 699 B<EVP_MAX_KEY_LENGTH> bytes.
 700
 701 The ASN1 code is incomplete (and sometimes inaccurate) it has only been tested
 702 for certain common S/MIME ciphers (RC2, DES, triple DES) in CBC mode.
 703
 704 =head1 EXAMPLES
 705
 706 Encrypt a string using IDEA:
 707
 708  int do_crypt(char *outfile)
 709  {
 710      unsigned char outbuf[1024];
 711      int outlen, tmplen;
 712      /*
 713       * Bogus key and IV: we'd normally set these from
 714       * another source.
 715       */
 716      unsigned char key[] = {0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15};
 717      unsigned char iv[] = {1,2,3,4,5,6,7,8};
 718      char intext[] = "Some Crypto Text";
 719      EVP_CIPHER_CTX *ctx;
 720      FILE *out;
 721
 722      ctx = EVP_CIPHER_CTX_new();
 723      EVP_EncryptInit_ex(ctx, EVP_idea_cbc(), NULL, key, iv);
 724
 725      if (!EVP_EncryptUpdate(ctx, outbuf, &outlen, intext, strlen(intext))) {
 726          /* Error */
 727          EVP_CIPHER_CTX_free(ctx);
 728          return 0;
 729      }
 730      /*
 731       * Buffer passed to EVP_EncryptFinal() must be after data just
 732       * encrypted to avoid overwriting it.
 733       */
 734      if (!EVP_EncryptFinal_ex(ctx, outbuf + outlen, &tmplen)) {
 735          /* Error */
 736          EVP_CIPHER_CTX_free(ctx);
 737          return 0;
 738      }
 739      outlen += tmplen;
 740      EVP_CIPHER_CTX_free(ctx);
 741      /*
 742       * Need binary mode for fopen because encrypted data is
 743       * binary data. Also cannot use strlen() on it because
 744       * it won't be NUL terminated and may contain embedded
 745       * NULs.
 746       */
 747      out = fopen(outfile, "wb");
 748      if (out == NULL) {
 749          /* Error */
 750          return 0;
 751      }
 752      fwrite(outbuf, 1, outlen, out);
 753      fclose(out);
 754      return 1;
 755  }
 756
 757 The ciphertext from the above example can be decrypted using the B<openssl>
 758 utility with the command line (shown on two lines for clarity):
 759
 760  openssl idea -d \
 761      -K 000102030405060708090A0B0C0D0E0F -iv 0102030405060708 <filename
 762
 763 General encryption and decryption function example using FILE I/O and AES128
 764 with a 128-bit key:
 765
 766  int do_crypt(FILE *in, FILE *out, int do_encrypt)
 767  {
 768      /* Allow enough space in output buffer for additional block */
 769      unsigned char inbuf[1024], outbuf[1024 + EVP_MAX_BLOCK_LENGTH];
 770      int inlen, outlen;
 771      EVP_CIPHER_CTX *ctx;
 772      /*
 773       * Bogus key and IV: we'd normally set these from
 774       * another source.
 775       */
 776      unsigned char key[] = "0123456789abcdeF";
 777      unsigned char iv[] = "1234567887654321";
 778
 779      /* Don't set key or IV right away; we want to check lengths */
 780      ctx = EVP_CIPHER_CTX_new();
 781      EVP_CipherInit_ex(ctx, EVP_aes_128_cbc(), NULL, NULL, NULL,
 782                        do_encrypt);
 783      OPENSSL_assert(EVP_CIPHER_CTX_key_length(ctx) == 16);
 784      OPENSSL_assert(EVP_CIPHER_CTX_iv_length(ctx) == 16);
 785
 786      /* Now we can set key and IV */
 787      EVP_CipherInit_ex(ctx, NULL, NULL, key, iv, do_encrypt);
 788
 789      for (;;) {
 790          inlen = fread(inbuf, 1, 1024, in);
 791          if (inlen <= 0)
 792              break;
 793          if (!EVP_CipherUpdate(ctx, outbuf, &outlen, inbuf, inlen)) {
 794              /* Error */
 795              EVP_CIPHER_CTX_free(ctx);
 796              return 0;
 797          }
 798          fwrite(outbuf, 1, outlen, out);
 799      }
 800      if (!EVP_CipherFinal_ex(ctx, outbuf, &outlen)) {
 801          /* Error */
 802          EVP_CIPHER_CTX_free(ctx);
 803          return 0;
 804      }
 805      fwrite(outbuf, 1, outlen, out);
 806
 807      EVP_CIPHER_CTX_free(ctx);
 808      return 1;
 809  }
 810
 811 Encryption using AES-CBC with a 256-bit key with "CS1" ciphertext stealing.
 812
 813  int encrypt(const unsigned char *key, const unsigned char *iv,
 814              const unsigned char *msg, size_t msg_len, unsigned char *out)
 815  {
 816     /*
 817      * This assumes that key size is 32 bytes and the iv is 16 bytes.
 818      * For ciphertext stealing mode the length of the ciphertext "out" will be
 819      * the same size as the plaintext size "msg_len".
 820      * The "msg_len" can be any size >= 16.
 821      */
 822      int ret = 0, encrypt = 1, outlen, len;
 823      EVP_CIPHER_CTX *ctx = NULL;
 824      EVP_CIPHER *cipher = NULL;
 825      OSSL_PARAM params[2];
 826
 827      ctx = EVP_CIPHER_CTX_new();
 828      cipher = EVP_CIPHER_fetch(NULL, "AES-256-CBC-CTS", NULL);
 829      if (ctx == NULL || cipher == NULL)
 830          goto err;
 831
 832      if (!EVP_CipherInit_ex(ctx, cipher, NULL, key, iv, encrypt))
 833          goto err;
 834      /*
 835       * The default is "CS1" so this is not really needed,
 836       * but would be needed to set either "CS2" or "CS3".
 837       */
 838      params[0] = OSSL_PARAM_construct_utf8_string(OSSL_CIPHER_PARAM_CTS_MODE,
 839                                                   "CS1", 0);
 840      params[1] = OSSL_PARAM_construct_end();
 841      if (!EVP_CIPHER_CTX_set_params(ctx, params))
 842          goto err;
 843
 844      /* NOTE: CTS mode does not support multiple calls to EVP_CipherUpdate() */
 845      if (!EVP_CipherUpdate(ctx, encrypted, &outlen, msg, msglen))
 846          goto err;
 847       if (!EVP_CipherFinal_ex(ctx, encrypted + outlen, &len))
 848          goto err;
 849      ret = 1;
 850  err:
 851      EVP_CIPHER_free(cipher);
 852      EVP_CIPHER_CTX_free(ctx);
 853      return ret;
 854  }
 855
 856 =head1 SEE ALSO
 857
 858 L<evp(7)>
 859
 860 Supported ciphers are listed in:
 861
 862 L<EVP_aes_128_gcm(3)>,
 863 L<EVP_aria_128_gcm(3)>,
 864 L<EVP_bf_cbc(3)>,
 865 L<EVP_camellia_128_ecb(3)>,
 866 L<EVP_cast5_cbc(3)>,
 867 L<EVP_chacha20(3)>,
 868 L<EVP_des_cbc(3)>,
 869 L<EVP_desx_cbc(3)>,
 870 L<EVP_idea_cbc(3)>,
 871 L<EVP_rc2_cbc(3)>,
 872 L<EVP_rc4(3)>,
 873 L<EVP_rc5_32_12_16_cbc(3)>,
 874 L<EVP_seed_cbc(3)>,
 875 L<EVP_sm4_cbc(3)>
 876
 877 =head1 HISTORY
 878
 879 Support for OCB mode was added in OpenSSL 1.1.0.
 880
 881 B<EVP_CIPHER_CTX> was made opaque in OpenSSL 1.1.0.  As a result,
 882 EVP_CIPHER_CTX_reset() appeared and EVP_CIPHER_CTX_cleanup()
 883 disappeared.  EVP_CIPHER_CTX_init() remains as an alias for
 884 EVP_CIPHER_CTX_reset().
 885
 886 The EVP_CIPHER_fetch(), EVP_CIPHER_free(), EVP_CIPHER_up_ref(),
 887 EVP_CIPHER_CTX_set_params() and EVP_CIPHER_CTX_get_params() functions
 888 were added in 3.0.
 889
 890 =head1 COPYRIGHT
 891
 892 Copyright 2000-2020 The OpenSSL Project Authors. All Rights Reserved.
 893
 894 Licensed under the Apache License 2.0 (the "License").  You may not use
 895 this file except in compliance with the License.  You can obtain a copy
 896 in the file LICENSE in the source distribution or at
 897 L<https://www.openssl.org/source/license.html>.
 898
 899 =cut