NAME

SYNOPSIS

 #include <openssl/evp.h>

 EVP_CIPHER *EVP_CIPHER_fetch(OSSL_LIB_CTX *ctx, const char *algorithm,
                              const char *properties);
 int EVP_CIPHER_up_ref(EVP_CIPHER *cipher);
 void EVP_CIPHER_free(EVP_CIPHER *cipher);
 EVP_CIPHER_CTX *EVP_CIPHER_CTX_new(void);
 int EVP_CIPHER_CTX_reset(EVP_CIPHER_CTX *ctx);
 void EVP_CIPHER_CTX_free(EVP_CIPHER_CTX *ctx);

 int EVP_EncryptInit_ex(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
                        ENGINE *impl, const unsigned char *key, const unsigned char *iv);
 int EVP_EncryptInit_ex2(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
                         const unsigned char *key, const unsigned char *iv,
                         const OSSL_PARAM params[]);
 int EVP_EncryptUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out,
                       int *outl, const unsigned char *in, int inl);
 int EVP_EncryptFinal_ex(EVP_CIPHER_CTX *ctx, unsigned char *out, int *outl);

 int EVP_DecryptInit_ex(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
                        ENGINE *impl, const unsigned char *key, const unsigned char *iv);
 int EVP_DecryptInit_ex2(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
                         const unsigned char *key, const unsigned char *iv,
                         const OSSL_PARAM params[]);
 int EVP_DecryptUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out,
                       int *outl, const unsigned char *in, int inl);
 int EVP_DecryptFinal_ex(EVP_CIPHER_CTX *ctx, unsigned char *outm, int *outl);

 int EVP_CipherInit_ex(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
                       ENGINE *impl, const unsigned char *key, const unsigned char *iv, int enc);
 int EVP_CipherInit_ex2(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
                        const unsigned char *key, const unsigned char *iv,
                        int enc, const OSSL_PARAM params[]);
 int EVP_CipherUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out,
                      int *outl, const unsigned char *in, int inl);
 int EVP_CipherFinal_ex(EVP_CIPHER_CTX *ctx, unsigned char *outm, int *outl);

 int EVP_EncryptInit(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
                     const unsigned char *key, const unsigned char *iv);
 int EVP_EncryptFinal(EVP_CIPHER_CTX *ctx, unsigned char *out, int *outl);

 int EVP_DecryptInit(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
                     const unsigned char *key, const unsigned char *iv);
 int EVP_DecryptFinal(EVP_CIPHER_CTX *ctx, unsigned char *outm, int *outl);

 int EVP_CipherInit(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
                    const unsigned char *key, const unsigned char *iv, int enc);
 int EVP_CipherFinal(EVP_CIPHER_CTX *ctx, unsigned char *outm, int *outl);

 int EVP_Cipher(EVP_CIPHER_CTX *ctx, unsigned char *out,
                const unsigned char *in, unsigned int inl);

 int EVP_CIPHER_CTX_set_padding(EVP_CIPHER_CTX *x, int padding);
 int EVP_CIPHER_CTX_set_key_length(EVP_CIPHER_CTX *x, int keylen);
 int EVP_CIPHER_CTX_ctrl(EVP_CIPHER_CTX *ctx, int cmd, int p1, void *p2);
 int EVP_CIPHER_CTX_rand_key(EVP_CIPHER_CTX *ctx, unsigned char *key);
 void EVP_CIPHER_CTX_set_flags(EVP_CIPHER_CTX *ctx, int flags);
 void EVP_CIPHER_CTX_clear_flags(EVP_CIPHER_CTX *ctx, int flags);
 int EVP_CIPHER_CTX_test_flags(const EVP_CIPHER_CTX *ctx, int flags);

 const EVP_CIPHER *EVP_get_cipherbyname(const char *name);
 const EVP_CIPHER *EVP_get_cipherbynid(int nid);
 const EVP_CIPHER *EVP_get_cipherbyobj(const ASN1_OBJECT *a);

 int EVP_CIPHER_get_nid(const EVP_CIPHER *e);
 int EVP_CIPHER_is_a(const EVP_CIPHER *cipher, const char *name);
 int EVP_CIPHER_names_do_all(const EVP_CIPHER *cipher,
                             void (*fn)(const char *name, void *data),
                             void *data);
 const char *EVP_CIPHER_get0_name(const EVP_CIPHER *cipher);
 const char *EVP_CIPHER_get0_description(const EVP_CIPHER *cipher);
 const OSSL_PROVIDER *EVP_CIPHER_get0_provider(const EVP_CIPHER *cipher);
 int EVP_CIPHER_get_block_size(const EVP_CIPHER *e);
 int EVP_CIPHER_get_key_length(const EVP_CIPHER *e);
 int EVP_CIPHER_get_iv_length(const EVP_CIPHER *e);
 unsigned long EVP_CIPHER_get_flags(const EVP_CIPHER *e);
 unsigned long EVP_CIPHER_get_mode(const EVP_CIPHER *e);
 int EVP_CIPHER_get_type(const EVP_CIPHER *cipher);

 const EVP_CIPHER *EVP_CIPHER_CTX_get0_cipher(const EVP_CIPHER_CTX *ctx);
 EVP_CIPHER *EVP_CIPHER_CTX_get1_cipher(const EVP_CIPHER_CTX *ctx);
 int EVP_CIPHER_CTX_get_nid(const EVP_CIPHER_CTX *ctx);
 const char *EVP_CIPHER_CTX_get0_name(const EVP_CIPHER_CTX *ctx);

 int EVP_CIPHER_get_params(EVP_CIPHER *cipher, OSSL_PARAM params[]);
 int EVP_CIPHER_CTX_set_params(EVP_CIPHER_CTX *ctx, const OSSL_PARAM params[]);
 int EVP_CIPHER_CTX_get_params(EVP_CIPHER_CTX *ctx, OSSL_PARAM params[]);
 const OSSL_PARAM *EVP_CIPHER_gettable_params(const EVP_CIPHER *cipher);
 const OSSL_PARAM *EVP_CIPHER_settable_ctx_params(const EVP_CIPHER *cipher);
 const OSSL_PARAM *EVP_CIPHER_gettable_ctx_params(const EVP_CIPHER *cipher);
 const OSSL_PARAM *EVP_CIPHER_CTX_settable_params(EVP_CIPHER_CTX *ctx);
 const OSSL_PARAM *EVP_CIPHER_CTX_gettable_params(EVP_CIPHER_CTX *ctx);
 int EVP_CIPHER_CTX_get_block_size(const EVP_CIPHER_CTX *ctx);
 int EVP_CIPHER_CTX_get_key_length(const EVP_CIPHER_CTX *ctx);
 int EVP_CIPHER_CTX_get_iv_length(const EVP_CIPHER_CTX *ctx);
 int EVP_CIPHER_CTX_get_tag_length(const EVP_CIPHER_CTX *ctx);
 void *EVP_CIPHER_CTX_get_app_data(const EVP_CIPHER_CTX *ctx);
 void EVP_CIPHER_CTX_set_app_data(const EVP_CIPHER_CTX *ctx, void *data);
 int EVP_CIPHER_CTX_get_type(const EVP_CIPHER_CTX *ctx);
 int EVP_CIPHER_CTX_get_mode(const EVP_CIPHER_CTX *ctx);
 int EVP_CIPHER_CTX_get_num(const EVP_CIPHER_CTX *ctx);
 int EVP_CIPHER_CTX_set_num(EVP_CIPHER_CTX *ctx, int num);
 int EVP_CIPHER_CTX_is_encrypting(const EVP_CIPHER_CTX *ctx);

 int EVP_CIPHER_param_to_asn1(EVP_CIPHER_CTX *c, ASN1_TYPE *type);
 int EVP_CIPHER_asn1_to_param(EVP_CIPHER_CTX *c, ASN1_TYPE *type);

 void EVP_CIPHER_do_all_provided(OSSL_LIB_CTX *libctx,
                                 void (*fn)(EVP_CIPHER *cipher, void *arg),
                                 void *arg);

 #define EVP_CIPHER_nid EVP_CIPHER_get_nid
 #define EVP_CIPHER_name EVP_CIPHER_get0_name
 #define EVP_CIPHER_block_size EVP_CIPHER_get_block_size
 #define EVP_CIPHER_key_length EVP_CIPHER_get_key_length
 #define EVP_CIPHER_iv_length EVP_CIPHER_get_iv_length
 #define EVP_CIPHER_flags EVP_CIPHER_get_flags
 #define EVP_CIPHER_mode EVP_CIPHER_get_mode
 #define EVP_CIPHER_type EVP_CIPHER_get_type
 #define EVP_CIPHER_CTX_encrypting EVP_CIPHER_CTX_is_encrypting
 #define EVP_CIPHER_CTX_nid EVP_CIPHER_CTX_get_nid
 #define EVP_CIPHER_CTX_block_size EVP_CIPHER_CTX_get_block_size
 #define EVP_CIPHER_CTX_key_length EVP_CIPHER_CTX_get_key_length
 #define EVP_CIPHER_CTX_iv_length EVP_CIPHER_CTX_get_iv_length
 #define EVP_CIPHER_CTX_tag_length EVP_CIPHER_CTX_get_tag_length
 #define EVP_CIPHER_CTX_num EVP_CIPHER_CTX_get_num
 #define EVP_CIPHER_CTX_type EVP_CIPHER_CTX_get_type
 #define EVP_CIPHER_CTX_mode EVP_CIPHER_CTX_get_mode

The following function has been deprecated since OpenSSL 3.0, and can be hidden entirely by defining OPENSSL_API_COMPAT with a suitable version value, see openssl_user_macros(7):

 const EVP_CIPHER *EVP_CIPHER_CTX_cipher(const EVP_CIPHER_CTX *ctx);

The following function has been deprecated since OpenSSL 1.1.0, and can be hidden entirely by defining OPENSSL_API_COMPAT with a suitable version value, see openssl_user_macros(7):

 int EVP_CIPHER_CTX_flags(const EVP_CIPHER_CTX *ctx);

DESCRIPTION

The EVP_CIPHER type is a structure for cipher method implementation.

EVP_CIPHER_fetch()

Fetches the cipher implementation for the given algorithm from any provider offering it, within the criteria given by the properties. See "ALGORITHM FETCHING" in crypto(7) for further information.

The returned value must eventually be freed with EVP_CIPHER_free().

Fetched EVP_CIPHER structures are reference counted.

EVP_CIPHER_up_ref()

Increments the reference count for an EVP_CIPHER structure.

EVP_CIPHER_free()

Decrements the reference count for the fetched EVP_CIPHER structure. If the reference count drops to 0 then the structure is freed.

EVP_CIPHER_CTX_new()

Allocates and returns a cipher context.

EVP_CIPHER_CTX_free()

Clears all information from a cipher context and frees any allocated memory associated with it, including ctx itself. This function should be called after all operations using a cipher are complete so sensitive information does not remain in memory.

EVP_CIPHER_CTX_ctrl()

This is a legacy method. EVP_CIPHER_CTX_set_params() and EVP_CIPHER_CTX_get_params() is the mechanism that should be used to set and get parameters that are used by providers.

Performs cipher-specific control actions on context ctx. The control command is indicated in cmd and any additional arguments in p1 and p2. EVP_CIPHER_CTX_ctrl() must be called after EVP_CipherInit_ex2(). Other restrictions may apply depending on the control type and cipher implementation.

If this function happens to be used with a fetched EVP_CIPHER, it will translate the controls that are known to OpenSSL into OSSL_PARAM(3) parameters with keys defined by OpenSSL and call EVP_CIPHER_CTX_get_params() or EVP_CIPHER_CTX_set_params() as is appropriate for each control command.

See "CONTROLS" below for more information, including what translations are being done.

EVP_CIPHER_get_params()

Retrieves the requested list of algorithm params from a CIPHER cipher. See "PARAMETERS" below for more information.

EVP_CIPHER_CTX_get_params()

Retrieves the requested list of params from CIPHER context ctx. See "PARAMETERS" below for more information.

EVP_CIPHER_CTX_set_params()

Sets the list of params into a CIPHER context ctx. See "PARAMETERS" below for more information.

EVP_CIPHER_gettable_params()

Get a constant OSSL_PARAM array that describes the retrievable parameters that can be used with EVP_CIPHER_get_params(). See OSSL_PARAM(3) for the use of OSSL_PARAM as a parameter descriptor.

EVP_CIPHER_gettable_ctx_params() and EVP_CIPHER_CTX_gettable_params()

Get a constant OSSL_PARAM array that describes the retrievable parameters that can be used with EVP_CIPHER_CTX_get_params(). EVP_CIPHER_gettable_ctx_params() returns the parameters that can be retrieved from the algorithm, whereas EVP_CIPHER_CTX_gettable_params() returns the parameters that can be retrieved in the context's current state. See OSSL_PARAM(3) for the use of OSSL_PARAM as a parameter descriptor.

EVP_CIPHER_settable_ctx_params() and EVP_CIPHER_CTX_settable_params()

Get a constant OSSL_PARAM array that describes the settable parameters that can be used with EVP_CIPHER_CTX_set_params(). EVP_CIPHER_settable_ctx_params() returns the parameters that can be set from the algorithm, whereas EVP_CIPHER_CTX_settable_params() returns the parameters that can be set in the context's current state. See OSSL_PARAM(3) for the use of OSSL_PARAM as a parameter descriptor.

EVP_EncryptInit_ex2()

Sets up cipher context ctx for encryption with cipher type. type is typically supplied by calling EVP_CIPHER_fetch(). type may also be set using legacy functions such as EVP_aes_256_cbc(), but this is not recommended for new applications. key is the symmetric key to use and iv is the IV to use (if necessary), the actual number of bytes used for the key and IV depends on the cipher. The parameters params will be set on the context after initialisation. It is possible to set all parameters to NULL except type in an initial call and supply the remaining parameters in subsequent calls, all of which have type set to NULL. This is done when the default cipher parameters are not appropriate. For EVP_CIPH_GCM_MODE the IV will be generated internally if it is not specified.

EVP_EncryptInit_ex()

This legacy function is similar to EVP_EncryptInit_ex2() when impl is NULL. The implementation of the type from the impl engine will be used if it exists.

EVP_EncryptUpdate()

Encrypts inl bytes from the buffer in and writes the encrypted version to out. This function can be called multiple times to encrypt successive blocks of data. The amount of data written depends on the block alignment of the encrypted data. For most ciphers and modes, the amount of data written can be anything from zero bytes to (inl + cipher_block_size - 1) bytes. For wrap cipher modes, the amount of data written can be anything from zero bytes to (inl + cipher_block_size) bytes. For stream ciphers, the amount of data written can be anything from zero bytes to inl bytes. Thus, out should contain sufficient room for the operation being performed. The actual number of bytes written is placed in outl. It also checks if in and out are partially overlapping, and if they are 0 is returned to indicate failure.

If padding is enabled (the default) then EVP_EncryptFinal_ex() encrypts the "final" data, that is any data that remains in a partial block. It uses standard block padding (aka PKCS padding) as described in the NOTES section, below. The encrypted final data is written to out which should have sufficient space for one cipher block. The number of bytes written is placed in outl. After this function is called the encryption operation is finished and no further calls to EVP_EncryptUpdate() should be made.

If padding is disabled then EVP_EncryptFinal_ex() will not encrypt any more data and it will return an error if any data remains in a partial block: that is if the total data length is not a multiple of the block size.

EVP_DecryptInit_ex2(), EVP_DecryptInit_ex(), EVP_DecryptUpdate() and EVP_DecryptFinal_ex()

These functions are the corresponding decryption operations. EVP_DecryptFinal() will return an error code if padding is enabled and the final block is not correctly formatted. The parameters and restrictions are identical to the encryption operations except that if padding is enabled the decrypted data buffer out passed to EVP_DecryptUpdate() should have sufficient room for (inl + cipher_block_size) bytes unless the cipher block size is 1 in which case inl bytes is sufficient.

EVP_CipherInit_ex2(), EVP_CipherInit_ex(), EVP_CipherUpdate() and EVP_CipherFinal_ex()

These functions can be used for decryption or encryption. The operation performed depends on the value of the enc parameter. It should be set to 1 for encryption, 0 for decryption and -1 to leave the value unchanged (the actual value of 'enc' being supplied in a previous call).

EVP_CIPHER_CTX_reset()

Clears all information from a cipher context and free up any allocated memory associated with it, except the ctx itself. This function should be called anytime ctx is reused by another EVP_CipherInit() / EVP_CipherUpdate() / EVP_CipherFinal() series of calls.

EVP_EncryptInit(), EVP_DecryptInit() and EVP_CipherInit()

Behave in a similar way to EVP_EncryptInit_ex(), EVP_DecryptInit_ex() and EVP_CipherInit_ex() except if the type is not a fetched cipher they use the default implementation of the type.

EVP_EncryptFinal(), EVP_DecryptFinal() and EVP_CipherFinal()

Identical to EVP_EncryptFinal_ex(), EVP_DecryptFinal_ex() and EVP_CipherFinal_ex(). In previous releases they also cleaned up the ctx, but this is no longer done and EVP_CIPHER_CTX_cleanup() must be called to free any context resources.

EVP_Cipher()

Encrypts or decrypts a maximum inl amount of bytes from in and leaves the result in out.

For legacy ciphers - If the cipher doesn't have the flag EVP_CIPH_FLAG_CUSTOM_CIPHER set, then inl must be a multiple of EVP_CIPHER_get_block_size(). If it isn't, the result is undefined. If the cipher has that flag set, then inl can be any size.

Due to the constraints of the API contract of this function it shouldn't be used in applications, please consider using EVP_CipherUpdate() and EVP_CipherFinal_ex() instead.

EVP_get_cipherbyname(), EVP_get_cipherbynid() and EVP_get_cipherbyobj()

Returns an EVP_CIPHER structure when passed a cipher name, a cipher NID or an ASN1_OBJECT structure respectively.

EVP_get_cipherbyname() will return NULL for algorithms such as "AES-128-SIV", "AES-128-CBC-CTS" and "CAMELLIA-128-CBC-CTS" which were previously only accessible via low level interfaces.

The EVP_get_cipherbyname() function is present for backwards compatibility with OpenSSL prior to version 3 and is different to the EVP_CIPHER_fetch() function since it does not attempt to "fetch" an implementation of the cipher. Additionally, it only knows about ciphers that are built-in to OpenSSL and have an associated NID. Similarly EVP_get_cipherbynid() and EVP_get_cipherbyobj() also return objects without an associated implementation.

When the cipher objects returned by these functions are used (such as in a call to EVP_EncryptInit_ex()) an implementation of the cipher will be implicitly fetched from the loaded providers. This fetch could fail if no suitable implementation is available. Use EVP_CIPHER_fetch() instead to explicitly fetch the algorithm and an associated implementation from a provider.

See "ALGORITHM FETCHING" in crypto(7) for more information about fetching.

The cipher objects returned from these functions do not need to be freed with EVP_CIPHER_free().

EVP_CIPHER_get_nid() and EVP_CIPHER_CTX_get_nid()

Return the NID of a cipher when passed an EVP_CIPHER or EVP_CIPHER_CTX structure. The actual NID value is an internal value which may not have a corresponding OBJECT IDENTIFIER.

EVP_CIPHER_CTX_set_flags(), EVP_CIPHER_CTX_clear_flags() and EVP_CIPHER_CTX_test_flags()

Sets, clears and tests ctx flags. See "FLAGS" below for more information.

For provided ciphers EVP_CIPHER_CTX_set_flags() should be called only after the fetched cipher has been assigned to the ctx. It is recommended to use "PARAMETERS" instead.

EVP_CIPHER_CTX_set_padding()

Enables or disables padding. This function should be called after the context is set up for encryption or decryption with EVP_EncryptInit_ex2(), EVP_DecryptInit_ex2() or EVP_CipherInit_ex2(). By default encryption operations are padded using standard block padding and the padding is checked and removed when decrypting. If the pad parameter is zero then no padding is performed, the total amount of data encrypted or decrypted must then be a multiple of the block size or an error will occur.

EVP_CIPHER_get_key_length() and EVP_CIPHER_CTX_get_key_length()

Return the key length of a cipher when passed an EVP_CIPHER or EVP_CIPHER_CTX structure. The constant EVP_MAX_KEY_LENGTH is the maximum key length for all ciphers. Note: although EVP_CIPHER_get_key_length() is fixed for a given cipher, the value of EVP_CIPHER_CTX_get_key_length() may be different for variable key length ciphers.

EVP_CIPHER_CTX_set_key_length()

Sets the key length of the cipher context. If the cipher is a fixed length cipher then attempting to set the key length to any value other than the fixed value is an error.

EVP_CIPHER_get_iv_length() and EVP_CIPHER_CTX_get_iv_length()

Return the IV length of a cipher when passed an EVP_CIPHER or EVP_CIPHER_CTX. It will return zero if the cipher does not use an IV. The constant EVP_MAX_IV_LENGTH is the maximum IV length for all ciphers.

EVP_CIPHER_CTX_get_tag_length()

Returns the tag length of an AEAD cipher when passed a EVP_CIPHER_CTX. It will return zero if the cipher does not support a tag. It returns a default value if the tag length has not been set.

EVP_CIPHER_get_block_size() and EVP_CIPHER_CTX_get_block_size()

Return the block size of a cipher when passed an EVP_CIPHER or EVP_CIPHER_CTX structure. The constant EVP_MAX_BLOCK_LENGTH is also the maximum block length for all ciphers.

EVP_CIPHER_get_type() and EVP_CIPHER_CTX_get_type()

Return the type of the passed cipher or context. This "type" is the actual NID of the cipher OBJECT IDENTIFIER and as such it ignores the cipher parameters (40 bit RC2 and 128 bit RC2 have the same NID). If the cipher does not have an object identifier or does not have ASN1 support this function will return NID_undef.

EVP_CIPHER_is_a()

Returns 1 if cipher is an implementation of an algorithm that's identifiable with name, otherwise 0. If cipher is a legacy cipher (it's the return value from the likes of EVP_aes128() rather than the result of an EVP_CIPHER_fetch()), only cipher names registered with the default library context (see OSSL_LIB_CTX(3)) will be considered.

EVP_CIPHER_get0_name() and EVP_CIPHER_CTX_get0_name()

Return the name of the passed cipher or context. For fetched ciphers with multiple names, only one of them is returned. See also EVP_CIPHER_names_do_all().

EVP_CIPHER_names_do_all()

Traverses all names for the cipher, and calls fn with each name and data. This is only useful with fetched EVP_CIPHERs.

EVP_CIPHER_get0_description()

Returns a description of the cipher, meant for display and human consumption. The description is at the discretion of the cipher implementation.

EVP_CIPHER_get0_provider()

Returns an OSSL_PROVIDER pointer to the provider that implements the given EVP_CIPHER.

EVP_CIPHER_CTX_get0_cipher()

Returns the EVP_CIPHER structure when passed an EVP_CIPHER_CTX structure. EVP_CIPHER_CTX_get1_cipher() is the same except the ownership is passed to the caller.

EVP_CIPHER_get_mode() and EVP_CIPHER_CTX_get_mode()

Return the block cipher mode: EVP_CIPH_ECB_MODE, EVP_CIPH_CBC_MODE, EVP_CIPH_CFB_MODE, EVP_CIPH_OFB_MODE, EVP_CIPH_CTR_MODE, EVP_CIPH_GCM_MODE, EVP_CIPH_CCM_MODE, EVP_CIPH_XTS_MODE, EVP_CIPH_WRAP_MODE, EVP_CIPH_OCB_MODE or EVP_CIPH_SIV_MODE. If the cipher is a stream cipher then EVP_CIPH_STREAM_CIPHER is returned.

EVP_CIPHER_get_flags()

Returns any flags associated with the cipher. See "FLAGS" for a list of currently defined flags.

EVP_CIPHER_CTX_get_num() and EVP_CIPHER_CTX_set_num()

Gets or sets the cipher specific "num" parameter for the associated ctx. Built-in ciphers typically use this to track how much of the current underlying block has been "used" already.

EVP_CIPHER_CTX_is_encrypting()

Reports whether the ctx is being used for encryption or decryption.

EVP_CIPHER_CTX_flags()

A deprecated macro calling "EVP_CIPHER_get_flags(EVP_CIPHER_CTX_get0_cipher(ctx))". Do not use.

EVP_CIPHER_param_to_asn1()

Sets the AlgorithmIdentifier "parameter" based on the passed cipher. This will typically include any parameters and an IV. The cipher IV (if any) must be set when this call is made. This call should be made before the cipher is actually "used" (before any EVP_EncryptUpdate(), EVP_DecryptUpdate() calls for example). This function may fail if the cipher does not have any ASN1 support.

EVP_CIPHER_asn1_to_param()

Sets the cipher parameters based on an ASN1 AlgorithmIdentifier "parameter". The precise effect depends on the cipher. In the case of RC2, for example, it will set the IV and effective key length. This function should be called after the base cipher type is set but before the key is set. For example EVP_CipherInit() will be called with the IV and key set to NULL, EVP_CIPHER_asn1_to_param() will be called and finally EVP_CipherInit() again with all parameters except the key set to NULL. It is possible for this function to fail if the cipher does not have any ASN1 support or the parameters cannot be set (for example the RC2 effective key length is not supported.

EVP_CIPHER_CTX_rand_key()

Generates a random key of the appropriate length based on the cipher context. The EVP_CIPHER can provide its own random key generation routine to support keys of a specific form. key must point to a buffer at least as big as the value returned by EVP_CIPHER_CTX_get_key_length().

EVP_CIPHER_do_all_provided()

Traverses all ciphers implemented by all activated providers in the given library context libctx, and for each of the implementations, calls the given function fn with the implementation method and the given arg as argument.

PARAMETERS

CONTROLS

EVP_CIPHER_CTX_ctrl() can be used to send the following standard controls:

EVP_CTRL_AEAD_SET_IVLEN and EVP_CTRL_GET_IVLEN

When used with a fetched EVP_CIPHER, EVP_CIPHER_CTX_set_params() and EVP_CIPHER_CTX_get_params() get called with an OSSL_PARAM(3) item with the key "ivlen" (OSSL_CIPHER_PARAM_IVLEN).

EVP_CTRL_AEAD_SET_IV_FIXED

When used with a fetched EVP_CIPHER, EVP_CIPHER_CTX_set_params() gets called with an OSSL_PARAM(3) item with the key "tlsivfixed" (OSSL_CIPHER_PARAM_AEAD_TLS1_IV_FIXED).

EVP_CTRL_AEAD_SET_MAC_KEY

When used with a fetched EVP_CIPHER, EVP_CIPHER_CTX_set_params() gets called with an OSSL_PARAM(3) item with the key "mackey" (OSSL_CIPHER_PARAM_AEAD_MAC_KEY).

EVP_CTRL_AEAD_SET_TAG and EVP_CTRL_AEAD_GET_TAG

When used with a fetched EVP_CIPHER, EVP_CIPHER_CTX_set_params() and EVP_CIPHER_CTX_get_params() get called with an OSSL_PARAM(3) item with the key "tag" (OSSL_CIPHER_PARAM_AEAD_TAG).

EVP_CTRL_CCM_SET_L

When used with a fetched EVP_CIPHER, EVP_CIPHER_CTX_set_params() gets called with an OSSL_PARAM(3) item with the key "ivlen" (OSSL_CIPHER_PARAM_IVLEN) with a value of (15 - L)

EVP_CTRL_COPY

There is no OSSL_PARAM mapping for this. Use EVP_CIPHER_CTX_copy() instead.

EVP_CTRL_GCM_SET_IV_INV

When used with a fetched EVP_CIPHER, EVP_CIPHER_CTX_set_params() gets called with an OSSL_PARAM(3) item with the key "tlsivinv" (OSSL_CIPHER_PARAM_AEAD_TLS1_SET_IV_INV).

EVP_CTRL_RAND_KEY

When used with a fetched EVP_CIPHER, EVP_CIPHER_CTX_set_params() gets called with an OSSL_PARAM(3) item with the key "randkey" (OSSL_CIPHER_PARAM_RANDOM_KEY).

EVP_CTRL_SET_KEY_LENGTH

When used with a fetched EVP_CIPHER, EVP_CIPHER_CTX_set_params() gets called with an OSSL_PARAM(3) item with the key "keylen" (OSSL_CIPHER_PARAM_KEYLEN).

EVP_CTRL_SET_RC2_KEY_BITS and EVP_CTRL_GET_RC2_KEY_BITS

When used with a fetched EVP_CIPHER, EVP_CIPHER_CTX_set_params() and EVP_CIPHER_CTX_get_params() get called with an OSSL_PARAM(3) item with the key "keybits" (OSSL_CIPHER_PARAM_RC2_KEYBITS).

EVP_CTRL_SET_RC5_ROUNDS and EVP_CTRL_GET_RC5_ROUNDS

When used with a fetched EVP_CIPHER, EVP_CIPHER_CTX_set_params() and EVP_CIPHER_CTX_get_params() get called with an OSSL_PARAM(3) item with the key "rounds" (OSSL_CIPHER_PARAM_ROUNDS).

EVP_CTRL_SET_SPEED

When used with a fetched EVP_CIPHER, EVP_CIPHER_CTX_set_params() gets called with an OSSL_PARAM(3) item with the key "speed" (OSSL_CIPHER_PARAM_SPEED).

EVP_CTRL_GCM_IV_GEN

When used with a fetched EVP_CIPHER, EVP_CIPHER_CTX_get_params() gets called with an OSSL_PARAM(3) item with the key "tlsivgen" (OSSL_CIPHER_PARAM_AEAD_TLS1_GET_IV_GEN).

EVP_CTRL_AEAD_TLS1_AAD

When used with a fetched EVP_CIPHER, EVP_CIPHER_CTX_set_params() get called with an OSSL_PARAM(3) item with the key "tlsaadpad" (OSSL_CIPHER_PARAM_AEAD_TLS1_AAD) followed by EVP_CIPHER_CTX_get_params() with a key of "tlsaadpad" (OSSL_CIPHER_PARAM_AEAD_TLS1_AAD_PAD).

EVP_CTRL_TLS1_1_MULTIBLOCK_MAX_BUFSIZE

When used with a fetched EVP_CIPHER, EVP_CIPHER_CTX_set_params() gets called with an OSSL_PARAM(3) item with the key OSSL_CIPHER_PARAM_TLS1_MULTIBLOCK_MAX_SEND_FRAGMENT followed by EVP_CIPHER_CTX_get_params() with a key of "tls1multi_maxbufsz" (OSSL_CIPHER_PARAM_TLS1_MULTIBLOCK_MAX_BUFSIZE).

EVP_CTRL_TLS1_1_MULTIBLOCK_AAD

When used with a fetched EVP_CIPHER, EVP_CIPHER_CTX_set_params() gets called with OSSL_PARAM(3) items with the keys "tls1multi_aad" (OSSL_CIPHER_PARAM_TLS1_MULTIBLOCK_AAD) and "tls1multi_interleave" (OSSL_CIPHER_PARAM_TLS1_MULTIBLOCK_INTERLEAVE) followed by EVP_CIPHER_CTX_get_params() with keys of "tls1multi_aadpacklen" (OSSL_CIPHER_PARAM_TLS1_MULTIBLOCK_AAD_PACKLEN) and "tls1multi_interleave" (OSSL_CIPHER_PARAM_TLS1_MULTIBLOCK_INTERLEAVE).

EVP_CTRL_TLS1_1_MULTIBLOCK_ENCRYPT

When used with a fetched EVP_CIPHER, EVP_CIPHER_CTX_set_params() gets called with OSSL_PARAM(3) items with the keys "tls1multi_enc" (OSSL_CIPHER_PARAM_TLS1_MULTIBLOCK_ENC), "tls1multi_encin" (OSSL_CIPHER_PARAM_TLS1_MULTIBLOCK_ENC_IN) and "tls1multi_interleave" (OSSL_CIPHER_PARAM_TLS1_MULTIBLOCK_INTERLEAVE), followed by EVP_CIPHER_CTX_get_params() with a key of "tls1multi_enclen" (OSSL_CIPHER_PARAM_TLS1_MULTIBLOCK_ENC_LEN).

FLAGS

EVP_CIPH_NO_PADDING

Used by EVP_CIPHER_CTX_set_padding().

See also "Gettable and Settable EVP_CIPHER_CTX parameters" "padding"

EVP_CIPH_FLAG_LENGTH_BITS

See "Settable EVP_CIPHER_CTX parameters" "use-bits".

EVP_CIPHER_CTX_FLAG_WRAP_ALLOW

Used for Legacy purposes only. This flag needed to be set to indicate the cipher handled wrapping.

EVP_CIPHER_flags() uses the following flags that have mappings to "Gettable EVP_CIPHER parameters":

EVP_CIPH_FLAG_AEAD_CIPHER

See "Gettable EVP_CIPHER parameters" "aead".

EVP_CIPH_CUSTOM_IV

See "Gettable EVP_CIPHER parameters" "custom-iv".

EVP_CIPH_FLAG_CTS

See "Gettable EVP_CIPHER parameters" "cts".

EVP_CIPH_FLAG_TLS1_1_MULTIBLOCK;

See "Gettable EVP_CIPHER parameters" "tls-multi".

EVP_CIPH_RAND_KEY

See "Gettable EVP_CIPHER parameters" "has-randkey".

EVP_CIPHER_flags() uses the following flags for legacy purposes only:

EVP_CIPH_VARIABLE_LENGTH

EVP_CIPH_FLAG_CUSTOM_CIPHER

EVP_CIPH_ALWAYS_CALL_INIT

EVP_CIPH_CTRL_INIT

EVP_CIPH_CUSTOM_KEY_LENGTH

EVP_CIPH_CUSTOM_COPY

EVP_CIPH_FLAG_DEFAULT_ASN1

See EVP_CIPHER_meth_set_flags(3) for further information related to the above flags.

RETURN VALUES

EVP_CIPHER_up_ref() returns 1 for success or 0 otherwise.

EVP_CIPHER_CTX_new() returns a pointer to a newly created EVP_CIPHER_CTX for success and NULL for failure.

EVP_EncryptInit_ex2(), EVP_EncryptUpdate() and EVP_EncryptFinal_ex() return 1 for success and 0 for failure.

EVP_DecryptInit_ex2() and EVP_DecryptUpdate() return 1 for success and 0 for failure. EVP_DecryptFinal_ex() returns 0 if the decrypt failed or 1 for success.

EVP_CipherInit_ex2() and EVP_CipherUpdate() return 1 for success and 0 for failure. EVP_CipherFinal_ex() returns 0 for a decryption failure or 1 for success.

EVP_Cipher() returns the amount of encrypted / decrypted bytes, or -1 on failure if the flag EVP_CIPH_FLAG_CUSTOM_CIPHER is set for the cipher. EVP_Cipher() returns 1 on success or 0 on failure, if the flag EVP_CIPH_FLAG_CUSTOM_CIPHER is not set for the cipher.

EVP_CIPHER_CTX_reset() returns 1 for success and 0 for failure.

EVP_get_cipherbyname(), EVP_get_cipherbynid() and EVP_get_cipherbyobj() return an EVP_CIPHER structure or NULL on error.

EVP_CIPHER_get_nid() and EVP_CIPHER_CTX_get_nid() return a NID.

EVP_CIPHER_get_block_size() and EVP_CIPHER_CTX_get_block_size() return the block size.

EVP_CIPHER_get_key_length() and EVP_CIPHER_CTX_get_key_length() return the key length.

EVP_CIPHER_CTX_set_padding() always returns 1.

EVP_CIPHER_get_iv_length() and EVP_CIPHER_CTX_get_iv_length() return the IV length or zero if the cipher does not use an IV.

EVP_CIPHER_CTX_get_tag_length() return the tag length or zero if the cipher does not use a tag.

EVP_CIPHER_get_type() and EVP_CIPHER_CTX_get_type() return the NID of the cipher's OBJECT IDENTIFIER or NID_undef if it has no defined OBJECT IDENTIFIER.

EVP_CIPHER_CTX_cipher() returns an EVP_CIPHER structure.

EVP_CIPHER_CTX_get_num() returns a nonnegative num value or EVP_CTRL_RET_UNSUPPORTED if the implementation does not support the call or on any other error.

EVP_CIPHER_CTX_set_num() returns 1 on success and 0 if the implementation does not support the call or on any other error.

EVP_CIPHER_CTX_is_encrypting() returns 1 if the ctx is set up for encryption 0 otherwise.

EVP_CIPHER_param_to_asn1() and EVP_CIPHER_asn1_to_param() return greater than zero for success and zero or a negative number on failure.

EVP_CIPHER_CTX_rand_key() returns 1 for success.

EVP_CIPHER_names_do_all() returns 1 if the callback was called for all names. A return value of 0 means that the callback was not called for any names.

CIPHER LISTING

Refer to "SEE ALSO" for the full list of ciphers available through the EVP interface.

EVP_enc_null()

Null cipher: does nothing.

AEAD INTERFACE

To specify additional authenticated data (AAD), a call to EVP_CipherUpdate(), EVP_EncryptUpdate() or EVP_DecryptUpdate() should be made with the output parameter out set to NULL.

When decrypting, the return value of EVP_DecryptFinal() or EVP_CipherFinal() indicates whether the operation was successful. If it does not indicate success, the authentication operation has failed and any output data MUST NOT be used as it is corrupted.

NOTES

PKCS padding works by adding n padding bytes of value n to make the total length of the encrypted data a multiple of the block size. Padding is always added so if the data is already a multiple of the block size n will equal the block size. For example if the block size is 8 and 11 bytes are to be encrypted then 5 padding bytes of value 5 will be added.

When decrypting the final block is checked to see if it has the correct form.

Although the decryption operation can produce an error if padding is enabled, it is not a strong test that the input data or key is correct. A random block has better than 1 in 256 chance of being of the correct format and problems with the input data earlier on will not produce a final decrypt error.

If padding is disabled then the decryption operation will always succeed if the total amount of data decrypted is a multiple of the block size.

The functions EVP_EncryptInit(), EVP_EncryptInit_ex(), EVP_EncryptFinal(), EVP_DecryptInit(), EVP_DecryptInit_ex(), EVP_CipherInit(), EVP_CipherInit_ex() and EVP_CipherFinal() are obsolete but are retained for compatibility with existing code. New code should use EVP_EncryptInit_ex2(), EVP_EncryptFinal_ex(), EVP_DecryptInit_ex2(), EVP_DecryptFinal_ex(), EVP_CipherInit_ex2() and EVP_CipherFinal_ex() because they can reuse an existing context without allocating and freeing it up on each call.

There are some differences between functions EVP_CipherInit() and EVP_CipherInit_ex(), significant in some circumstances. EVP_CipherInit() fills the passed context object with zeros. As a consequence, EVP_CipherInit() does not allow step-by-step initialization of the ctx when the key and iv are passed in separate calls. It also means that the flags set for the CTX are removed, and it is especially important for the EVP_CIPHER_CTX_FLAG_WRAP_ALLOW flag treated specially in EVP_CipherInit_ex().

EVP_get_cipherbynid(), and EVP_get_cipherbyobj() are implemented as macros.

BUGS

The ASN1 code is incomplete (and sometimes inaccurate) it has only been tested for certain common S/MIME ciphers (RC2, DES, triple DES) in CBC mode.

EXAMPLES

 int do_crypt(char *outfile)
 {
     unsigned char outbuf[1024];
     int outlen, tmplen;
     /*
      * Bogus key and IV: we'd normally set these from
      * another source.
      */
     unsigned char key[] = {0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15};
     unsigned char iv[] = {1,2,3,4,5,6,7,8};
     char intext[] = "Some Crypto Text";
     EVP_CIPHER_CTX *ctx;
     FILE *out;

     ctx = EVP_CIPHER_CTX_new();
     EVP_EncryptInit_ex2(ctx, EVP_idea_cbc(), key, iv, NULL);

     if (!EVP_EncryptUpdate(ctx, outbuf, &outlen, intext, strlen(intext))) {
         /* Error */
         EVP_CIPHER_CTX_free(ctx);
         return 0;
     }
     /*
      * Buffer passed to EVP_EncryptFinal() must be after data just
      * encrypted to avoid overwriting it.
      */
     if (!EVP_EncryptFinal_ex(ctx, outbuf + outlen, &tmplen)) {
         /* Error */
         EVP_CIPHER_CTX_free(ctx);
         return 0;
     }
     outlen += tmplen;
     EVP_CIPHER_CTX_free(ctx);
     /*
      * Need binary mode for fopen because encrypted data is
      * binary data. Also cannot use strlen() on it because
      * it won't be NUL terminated and may contain embedded
      * NULs.
      */
     out = fopen(outfile, "wb");
     if (out == NULL) {
         /* Error */
         return 0;
     }
     fwrite(outbuf, 1, outlen, out);
     fclose(out);
     return 1;
 }

The ciphertext from the above example can be decrypted using the openssl utility with the command line (shown on two lines for clarity):

 openssl idea -d \
     -K 000102030405060708090A0B0C0D0E0F -iv 0102030405060708 <filename

General encryption and decryption function example using FILE I/O and AES128 with a 128-bit key:

 int do_crypt(FILE *in, FILE *out, int do_encrypt)
 {
     /* Allow enough space in output buffer for additional block */
     unsigned char inbuf[1024], outbuf[1024 + EVP_MAX_BLOCK_LENGTH];
     int inlen, outlen;
     EVP_CIPHER_CTX *ctx;
     /*
      * Bogus key and IV: we'd normally set these from
      * another source.
      */
     unsigned char key[] = "0123456789abcdeF";
     unsigned char iv[] = "1234567887654321";

     /* Don't set key or IV right away; we want to check lengths */
     ctx = EVP_CIPHER_CTX_new();
     EVP_CipherInit_ex2(ctx, EVP_aes_128_cbc(), NULL, NULL,
                        do_encrypt, NULL);
     OPENSSL_assert(EVP_CIPHER_CTX_get_key_length(ctx) == 16);
     OPENSSL_assert(EVP_CIPHER_CTX_get_iv_length(ctx) == 16);

     /* Now we can set key and IV */
     EVP_CipherInit_ex2(ctx, NULL, key, iv, do_encrypt, NULL);

     for (;;) {
         inlen = fread(inbuf, 1, 1024, in);
         if (inlen <= 0)
             break;
         if (!EVP_CipherUpdate(ctx, outbuf, &outlen, inbuf, inlen)) {
             /* Error */
             EVP_CIPHER_CTX_free(ctx);
             return 0;
         }
         fwrite(outbuf, 1, outlen, out);
     }
     if (!EVP_CipherFinal_ex(ctx, outbuf, &outlen)) {
         /* Error */
         EVP_CIPHER_CTX_free(ctx);
         return 0;
     }
     fwrite(outbuf, 1, outlen, out);

     EVP_CIPHER_CTX_free(ctx);
     return 1;
 }

Encryption using AES-CBC with a 256-bit key with "CS1" ciphertext stealing.

 int encrypt(const unsigned char *key, const unsigned char *iv,
             const unsigned char *msg, size_t msg_len, unsigned char *out)
 {
    /*
     * This assumes that key size is 32 bytes and the iv is 16 bytes.
     * For ciphertext stealing mode the length of the ciphertext "out" will be
     * the same size as the plaintext size "msg_len".
     * The "msg_len" can be any size >= 16.
     */
     int ret = 0, encrypt = 1, outlen, len;
     EVP_CIPHER_CTX *ctx = NULL;
     EVP_CIPHER *cipher = NULL;
     OSSL_PARAM params[2];

     ctx = EVP_CIPHER_CTX_new();
     cipher = EVP_CIPHER_fetch(NULL, "AES-256-CBC-CTS", NULL);
     if (ctx == NULL || cipher == NULL)
         goto err;

     /*
      * The default is "CS1" so this is not really needed,
      * but would be needed to set either "CS2" or "CS3".
      */
     params[0] = OSSL_PARAM_construct_utf8_string(OSSL_CIPHER_PARAM_CTS_MODE,
                                                  "CS1", 0);
     params[1] = OSSL_PARAM_construct_end();

     if (!EVP_CipherInit_ex2(ctx, cipher, key, iv, encrypt, params))
         goto err;

     /* NOTE: CTS mode does not support multiple calls to EVP_CipherUpdate() */
     if (!EVP_CipherUpdate(ctx, encrypted, &outlen, msg, msglen))
         goto err;
      if (!EVP_CipherFinal_ex(ctx, encrypted + outlen, &len))
         goto err;
     ret = 1;
 err:
     EVP_CIPHER_free(cipher);
     EVP_CIPHER_CTX_free(ctx);
     return ret;
 }

SEE ALSO

Supported ciphers are listed in:

EVP_aes_128_gcm(3), EVP_aria_128_gcm(3), EVP_bf_cbc(3), EVP_camellia_128_ecb(3), EVP_cast5_cbc(3), EVP_chacha20(3), EVP_des_cbc(3), EVP_desx_cbc(3), EVP_idea_cbc(3), EVP_rc2_cbc(3), EVP_rc4(3), EVP_rc5_32_12_16_cbc(3), EVP_seed_cbc(3), EVP_sm4_cbc(3),

HISTORY

EVP_CIPHER_CTX was made opaque in OpenSSL 1.1.0. As a result, EVP_CIPHER_CTX_reset() appeared and EVP_CIPHER_CTX_cleanup() disappeared. EVP_CIPHER_CTX_init() remains as an alias for EVP_CIPHER_CTX_reset().

The EVP_CIPHER_CTX_cipher() function was deprecated in OpenSSL 3.0; use EVP_CIPHER_CTX_get0_cipher() instead.

The EVP_EncryptInit_ex2(), EVP_DecryptInit_ex2(), EVP_CipherInit_ex2(), EVP_CIPHER_fetch(), EVP_CIPHER_free(), EVP_CIPHER_up_ref(), EVP_CIPHER_CTX_get0_cipher(), EVP_CIPHER_CTX_get1_cipher(), EVP_CIPHER_get_params(), EVP_CIPHER_CTX_set_params(), EVP_CIPHER_CTX_get_params(), EVP_CIPHER_gettable_params(), EVP_CIPHER_settable_ctx_params(), EVP_CIPHER_gettable_ctx_params(), EVP_CIPHER_CTX_settable_params() and EVP_CIPHER_CTX_gettable_params() functions were added in 3.0.

The EVP_CIPHER_nid(), EVP_CIPHER_name(), EVP_CIPHER_block_size(), EVP_CIPHER_key_length(), EVP_CIPHER_iv_length(), EVP_CIPHER_flags(), EVP_CIPHER_mode(), EVP_CIPHER_type(), EVP_CIPHER_CTX_nid(), EVP_CIPHER_CTX_block_size(), EVP_CIPHER_CTX_key_length(), EVP_CIPHER_CTX_iv_length(), EVP_CIPHER_CTX_tag_length(), EVP_CIPHER_CTX_num(), EVP_CIPHER_CTX_type(), and EVP_CIPHER_CTX_mode() functions were renamed to include "get" or "get0" in their names in OpenSSL 3.0, respectively. The old names are kept as non-deprecated alias macros.

The EVP_CIPHER_CTX_encrypting() function was renamed to EVP_CIPHER_CTX_is_encrypting() in OpenSSL 3.0. The old name is kept as non-deprecated alias macro.

The EVP_CIPHER_CTX_flags() macro was deprecated in OpenSSL 1.1.0.

COPYRIGHT

Licensed under the Apache License 2.0 (the "License"). You may not use this file except in compliance with the License. You can obtain a copy in the file LICENSE in the source distribution or at <https://www.openssl.org/source/license.html>.