| EVP_ENCRYPTINIT(3SSL) | OpenSSL | EVP_ENCRYPTINIT(3SSL) |
EVP_CIPHER_fetch, EVP_CIPHER_up_ref, EVP_CIPHER_free, EVP_CIPHER_CTX_new, EVP_CIPHER_CTX_reset, EVP_CIPHER_CTX_free, EVP_EncryptInit_ex, EVP_EncryptInit_ex2, EVP_EncryptUpdate, EVP_EncryptFinal_ex, EVP_DecryptInit_ex, EVP_DecryptInit_ex2, EVP_DecryptUpdate, EVP_DecryptFinal_ex, EVP_CipherInit_ex, EVP_CipherInit_ex2, EVP_CipherUpdate, EVP_CipherFinal_ex, EVP_CIPHER_CTX_set_key_length, EVP_CIPHER_CTX_ctrl, EVP_EncryptInit, EVP_EncryptFinal, EVP_DecryptInit, EVP_DecryptFinal, EVP_CipherInit, EVP_CipherFinal, EVP_Cipher, EVP_get_cipherbyname, EVP_get_cipherbynid, EVP_get_cipherbyobj, EVP_CIPHER_is_a, EVP_CIPHER_get0_name, EVP_CIPHER_get0_description, EVP_CIPHER_names_do_all, EVP_CIPHER_get0_provider, EVP_CIPHER_get_nid, EVP_CIPHER_get_params, EVP_CIPHER_gettable_params, EVP_CIPHER_get_block_size, EVP_CIPHER_get_key_length, EVP_CIPHER_get_iv_length, EVP_CIPHER_get_flags, EVP_CIPHER_get_mode, EVP_CIPHER_get_type, EVP_CIPHER_CTX_cipher, EVP_CIPHER_CTX_get0_cipher, EVP_CIPHER_CTX_get1_cipher, EVP_CIPHER_CTX_get0_name, EVP_CIPHER_CTX_get_nid, EVP_CIPHER_CTX_get_params, EVP_CIPHER_gettable_ctx_params, EVP_CIPHER_CTX_gettable_params, EVP_CIPHER_CTX_set_params, EVP_CIPHER_settable_ctx_params, EVP_CIPHER_CTX_settable_params, EVP_CIPHER_CTX_get_block_size, EVP_CIPHER_CTX_get_key_length, EVP_CIPHER_CTX_get_iv_length, EVP_CIPHER_CTX_get_tag_length, EVP_CIPHER_CTX_get_app_data, EVP_CIPHER_CTX_set_app_data, EVP_CIPHER_CTX_flags, EVP_CIPHER_CTX_set_flags, EVP_CIPHER_CTX_clear_flags, EVP_CIPHER_CTX_test_flags, EVP_CIPHER_CTX_get_type, EVP_CIPHER_CTX_get_mode, EVP_CIPHER_CTX_get_num, EVP_CIPHER_CTX_set_num, EVP_CIPHER_CTX_is_encrypting, EVP_CIPHER_param_to_asn1, EVP_CIPHER_asn1_to_param, EVP_CIPHER_CTX_set_padding, EVP_enc_null, EVP_CIPHER_do_all_provided, 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_encrypting, 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, EVP_CIPHER_CTX_mode - EVP cipher routines
#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);
The EVP cipher routines are a high-level interface to certain symmetric ciphers.
The EVP_CIPHER type is a structure for cipher method implementation.
The returned value must eventually be freed with EVP_CIPHER_free().
Fetched EVP_CIPHER structures are reference counted.
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.
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, the buffer pointed to by out must contain sufficient room for the operation being performed. The actual number of bytes written is placed in outl.
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.
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() 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().
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.
See OSSL_PARAM(3) for information about passing parameters.
When EVP_CIPHER_fetch() is called it internally calls EVP_CIPHER_get_params() and caches the results.
EVP_CIPHER_get_params() can be used with the following OSSL_PARAM(3) keys:
The following OSSL_PARAM(3) keys can be used with both EVP_CIPHER_CTX_get_params() and EVP_CIPHER_CTX_set_params().
Valid values for the mode are:
The default is "CS1". This is only supported for "AES-128-CBC-CTS", "AES-192-CBC-CTS", "AES-256-CBC-CTS", "CAMELLIA-128-CBC-CTS", "CAMELLIA-192-CBC-CTS" and "CAMELLIA-256-CBC-CTS".
The following OSSL_PARAM(3) keys can be used with EVP_CIPHER_CTX_get_params():
The following OSSL_PARAM(3) keys can be used with EVP_CIPHER_CTX_set_params():
This can be set using EVP_CIPHER_CTX_set_flags(ctx, EVP_CIPH_FLAG_LENGTH_BITS).
When encrypting a record the first bytes of the input buffer should be empty to allow space for the explicit IV, as will the final bytes where the tag will be written. The length of the input buffer will include the length of the explicit IV, the payload, and the tag bytes. The cipher implementation should generate the explicit IV and write it to the beginning of the output buffer, do "in place" encryption of the payload and write that to the output buffer, and finally add the tag onto the end of the output buffer.
Whether encrypting or decrypting the value written to *outl in the OSSL_FUNC_cipher_cipher call should be the length of the payload excluding the explicit IV length and the tag length.
"tls1multi_interleave" must also be set for this operation.
The Mappings from EVP_CIPHER_CTX_ctrl() identifiers to PARAMETERS are listed in the following section. See the "PARAMETERS" section for more details.
EVP_CIPHER_CTX_ctrl() can be used to send the following standard controls:
EVP_CIPHER_CTX_set_flags(), EVP_CIPHER_CTX_clear_flags() and EVP_CIPHER_CTX_test_flags(). can be used to manipulate and test these EVP_CIPHER_CTX flags:
See also "Gettable and Settable EVP_CIPHER_CTX parameters" "padding"
EVP_CIPHER_flags() uses the following flags that have mappings to "Gettable EVP_CIPHER parameters":
EVP_CIPHER_flags() uses the following flags for legacy purposes only:
EVP_CIPHER_fetch() returns a pointer to a EVP_CIPHER for success and NULL for failure.
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 1 on success or 0 on failure, if the flag EVP_CIPH_FLAG_CUSTOM_CIPHER is not set for the cipher. EVP_Cipher() returns the number of bytes written to out for encryption / decryption, or the number of bytes authenticated in a call specifying AAD for an AEAD cipher, if the flag EVP_CIPH_FLAG_CUSTOM_CIPHER is 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 and zero or a negative number for failure.
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.
All algorithms have a fixed key length unless otherwise stated.
Refer to "SEE ALSO" for the full list of ciphers available through the EVP interface.
The EVP interface for Authenticated Encryption with Associated Data (AEAD) modes are subtly altered and several additional ctrl operations are supported depending on the mode specified.
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. In this case, on success, the parameter outl is set to the number of bytes authenticated.
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.
The following ctrls are supported in GCM and OCB modes.
For GCM AES and OCB AES the default is 12 (i.e. 96 bits). For OCB mode the maximum is 15.
For OCB, "taglen" must either be 16 or the value previously set via EVP_CTRL_AEAD_SET_TAG.
For GCM, this call is only valid when decrypting data.
For OCB, this call is valid when decrypting data to set the expected tag, and when encrypting to set the desired tag length.
In OCB mode, calling this when encrypting with "tag" set to "NULL" sets the tag length. The tag length can only be set before specifying an IV. If this is not called prior to setting the IV during encryption, then a default tag length is used.
For OCB AES, the default tag length is 16 (i.e. 128 bits). It is also the maximum tag length for OCB.
The EVP interface for CCM mode is similar to that of the GCM mode but with a few additional requirements and different ctrl values.
For CCM mode, the total plaintext or ciphertext length MUST be passed to EVP_CipherUpdate(), EVP_EncryptUpdate() or EVP_DecryptUpdate() with the output and input parameters (in and out) set to NULL and the length passed in the inl parameter.
The following ctrls are supported in CCM mode.
For SIV mode ciphers the behaviour of the EVP interface is subtly altered and several additional ctrl operations are supported.
To specify any additional authenticated data (AAD) and/or a Nonce, a call to EVP_CipherUpdate(), EVP_EncryptUpdate() or EVP_DecryptUpdate() should be made with the output parameter out set to NULL.
RFC5297 states that the Nonce is the last piece of AAD before the actual encrypt/decrypt takes place. The API does not differentiate the Nonce from other AAD.
When decrypting the return value of EVP_DecryptFinal() or EVP_CipherFinal() indicates if 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.
The API does not store the the SIV (Synthetic Initialization Vector) in the cipher text. Instead, it is stored as the tag within the EVP_CIPHER_CTX. The SIV must be retrieved from the context after encryption, and set into the context before decryption.
This differs from RFC5297 in that the cipher output from encryption, and the cipher input to decryption, does not contain the SIV. This also means that the plain text and cipher text lengths are identical.
The following ctrls are supported in SIV mode, and are used to get and set the Synthetic Initialization Vector:
SIV mode makes two passes over the input data, thus, only one call to EVP_CipherUpdate(), EVP_EncryptUpdate() or EVP_DecryptUpdate() should be made with out set to a non-NULL value. A call to EVP_DecryptFinal() or EVP_CipherFinal() is not required, but will indicate if the update operation succeeded.
The following ctrls are supported for the ChaCha20-Poly1305 AEAD algorithm.
"taglen" specified here must be 16 (POLY1305_BLOCK_SIZE, i.e. 128-bits) or less.
Where possible the EVP interface to symmetric ciphers should be used in preference to the low-level interfaces. This is because the code then becomes transparent to the cipher used and much more flexible. Additionally, the EVP interface will ensure the use of platform specific cryptographic acceleration such as AES-NI (the low-level interfaces do not provide the guarantee).
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().
Ignoring failure returns of the EVP_CIPHER_CTX initialization functions can lead to subsequent undefined behavior when calling the functions that update or finalize the context. The only valid calls on the EVP_CIPHER_CTX when initialization fails are calls that attempt another initialization of the context or release the context.
EVP_get_cipherbynid(), and EVP_get_cipherbyobj() are implemented as macros.
EVP_MAX_KEY_LENGTH and EVP_MAX_IV_LENGTH only refer to the internal ciphers with default key lengths. If custom ciphers exceed these values the results are unpredictable. This is because it has become standard practice to define a generic key as a fixed unsigned char array containing EVP_MAX_KEY_LENGTH bytes.
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.
Encrypt a string using IDEA:
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();
if (!EVP_EncryptInit_ex2(ctx, EVP_idea_cbc(), key, iv, NULL)) {
/* Error */
EVP_CIPHER_CTX_free(ctx);
return 0;
}
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();
if (!EVP_CipherInit_ex2(ctx, EVP_aes_128_cbc(), NULL, NULL,
do_encrypt, NULL)) {
/* Error */
EVP_CIPHER_CTX_free(ctx);
return 0;
}
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 */
if (!EVP_CipherInit_ex2(ctx, NULL, key, iv, do_encrypt, NULL)) {
/* Error */
EVP_CIPHER_CTX_free(ctx);
return 0;
}
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, out, &outlen, msg, msg_len))
goto err;
if (!EVP_CipherFinal_ex(ctx, out + outlen, &len))
goto err;
ret = 1;
err:
EVP_CIPHER_free(cipher);
EVP_CIPHER_CTX_free(ctx);
return ret;
}
evp(7), property(7), "ALGORITHM FETCHING" in crypto(7), provider-cipher(7), life_cycle-cipher(7)
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),
Support for OCB mode was added in OpenSSL 1.1.0.
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 2000-2023 The OpenSSL Project Authors. All Rights Reserved.
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>.
| 2024-08-20 | 3.0.13 |