83f68df32f
Add note about when EVP_CIPHER_CTX_set_padding should be called. Reviewed-by: Dr. Stephen Henson <steve@openssl.org>
640 lines
26 KiB
Plaintext
640 lines
26 KiB
Plaintext
=pod
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=head1 NAME
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EVP_CIPHER_CTX_new, EVP_CIPHER_CTX_reset, EVP_CIPHER_CTX_free,
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EVP_EncryptInit_ex, EVP_EncryptUpdate, EVP_EncryptFinal_ex,
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EVP_DecryptInit_ex, EVP_DecryptUpdate, EVP_DecryptFinal_ex,
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EVP_CipherInit_ex, EVP_CipherUpdate, EVP_CipherFinal_ex,
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EVP_CIPHER_CTX_set_key_length, EVP_CIPHER_CTX_ctrl, EVP_EncryptInit,
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EVP_EncryptFinal, EVP_DecryptInit, EVP_DecryptFinal,
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EVP_CipherInit, EVP_CipherFinal, EVP_get_cipherbyname,
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EVP_get_cipherbynid, EVP_get_cipherbyobj, EVP_CIPHER_nid,
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EVP_CIPHER_block_size, EVP_CIPHER_key_length, EVP_CIPHER_iv_length,
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EVP_CIPHER_flags, EVP_CIPHER_mode, EVP_CIPHER_type, EVP_CIPHER_CTX_cipher,
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EVP_CIPHER_CTX_nid, EVP_CIPHER_CTX_block_size, EVP_CIPHER_CTX_key_length,
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EVP_CIPHER_CTX_iv_length, EVP_CIPHER_CTX_get_app_data,
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EVP_CIPHER_CTX_set_app_data, EVP_CIPHER_CTX_type, EVP_CIPHER_CTX_flags,
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EVP_CIPHER_CTX_mode, EVP_CIPHER_param_to_asn1, EVP_CIPHER_asn1_to_param,
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EVP_CIPHER_CTX_set_padding, EVP_enc_null, EVP_des_cbc, EVP_des_ecb,
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EVP_des_cfb, EVP_des_ofb, EVP_des_ede_cbc, EVP_des_ede, EVP_des_ede_ofb,
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EVP_des_ede_cfb, EVP_des_ede3_cbc, EVP_des_ede3, EVP_des_ede3_ofb,
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EVP_des_ede3_cfb, EVP_desx_cbc, EVP_rc4, EVP_rc4_40, EVP_idea_cbc,
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EVP_idea_ecb, EVP_idea_cfb, EVP_idea_ofb, EVP_rc2_cbc,
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EVP_rc2_ecb, EVP_rc2_cfb, EVP_rc2_ofb, EVP_rc2_40_cbc, EVP_rc2_64_cbc,
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EVP_bf_cbc, EVP_bf_ecb, EVP_bf_cfb, EVP_bf_ofb, EVP_cast5_cbc,
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EVP_cast5_ecb, EVP_cast5_cfb, EVP_cast5_ofb, EVP_rc5_32_12_16_cbc,
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EVP_rc5_32_12_16_ecb, EVP_rc5_32_12_16_cfb, EVP_rc5_32_12_16_ofb,
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EVP_aes_128_cbc, EVP_aes_128_ecb, EVP_aes_128_cfb, EVP_aes_128_ofb,
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EVP_aes_192_cbc, EVP_aes_192_ecb, EVP_aes_192_cfb, EVP_aes_192_ofb,
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EVP_aes_256_cbc, EVP_aes_256_ecb, EVP_aes_256_cfb, EVP_aes_256_ofb,
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EVP_aes_128_gcm, EVP_aes_192_gcm, EVP_aes_256_gcm,
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EVP_aes_128_ccm, EVP_aes_192_ccm, EVP_aes_256_ccm - EVP cipher routines
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=head1 SYNOPSIS
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#include <openssl/evp.h>
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EVP_CIPHER_CTX *EVP_CIPHER_CTX_new(void);
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int EVP_CIPHER_CTX_reset(EVP_CIPHER_CTX *ctx);
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void EVP_CIPHER_CTX_free(EVP_CIPHER_CTX *ctx);
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int EVP_EncryptInit_ex(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
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ENGINE *impl, unsigned char *key, unsigned char *iv);
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int EVP_EncryptUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out,
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int *outl, unsigned char *in, int inl);
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int EVP_EncryptFinal_ex(EVP_CIPHER_CTX *ctx, unsigned char *out,
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int *outl);
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int EVP_DecryptInit_ex(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
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ENGINE *impl, unsigned char *key, unsigned char *iv);
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int EVP_DecryptUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out,
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int *outl, unsigned char *in, int inl);
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int EVP_DecryptFinal_ex(EVP_CIPHER_CTX *ctx, unsigned char *outm,
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int *outl);
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int EVP_CipherInit_ex(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
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ENGINE *impl, unsigned char *key, unsigned char *iv, int enc);
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int EVP_CipherUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out,
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int *outl, unsigned char *in, int inl);
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int EVP_CipherFinal_ex(EVP_CIPHER_CTX *ctx, unsigned char *outm,
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int *outl);
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int EVP_EncryptInit(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
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unsigned char *key, unsigned char *iv);
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int EVP_EncryptFinal(EVP_CIPHER_CTX *ctx, unsigned char *out,
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int *outl);
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int EVP_DecryptInit(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
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unsigned char *key, unsigned char *iv);
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int EVP_DecryptFinal(EVP_CIPHER_CTX *ctx, unsigned char *outm,
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int *outl);
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int EVP_CipherInit(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
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unsigned char *key, unsigned char *iv, int enc);
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int EVP_CipherFinal(EVP_CIPHER_CTX *ctx, unsigned char *outm,
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int *outl);
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int EVP_CIPHER_CTX_set_padding(EVP_CIPHER_CTX *x, int padding);
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int EVP_CIPHER_CTX_set_key_length(EVP_CIPHER_CTX *x, int keylen);
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int EVP_CIPHER_CTX_ctrl(EVP_CIPHER_CTX *ctx, int type, int arg, void *ptr);
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const EVP_CIPHER *EVP_get_cipherbyname(const char *name);
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#define EVP_get_cipherbynid(a) EVP_get_cipherbyname(OBJ_nid2sn(a))
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#define EVP_get_cipherbyobj(a) EVP_get_cipherbynid(OBJ_obj2nid(a))
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#define EVP_CIPHER_nid(e) ((e)->nid)
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#define EVP_CIPHER_block_size(e) ((e)->block_size)
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#define EVP_CIPHER_key_length(e) ((e)->key_len)
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#define EVP_CIPHER_iv_length(e) ((e)->iv_len)
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#define EVP_CIPHER_flags(e) ((e)->flags)
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#define EVP_CIPHER_mode(e) ((e)->flags) & EVP_CIPH_MODE)
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int EVP_CIPHER_type(const EVP_CIPHER *ctx);
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const EVP_CIPHER *EVP_CIPHER_CTX_cipher(const EVP_CIPHER_CTX *ctx);
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int EVP_CIPHER_CTX_nid(const EVP_CIPHER_CTX *ctx);
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int EVP_CIPHER_CTX_block_size(const EVP_CIPHER_CTX *ctx);
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int EVP_CIPHER_CTX_key_length(const EVP_CIPHER_CTX *ctx);
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int EVP_CIPHER_CTX_iv_length(const EVP_CIPHER_CTX *ctx);
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void *EVP_CIPHER_CTX_get_app_data(const EVP_CIPHER_CTX *ctx);
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void EVP_CIPHER_CTX_set_app_data(const EVP_CIPHER_CTX *ctx, void *data);
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int EVP_CIPHER_CTX_type(const EVP_CIPHER_CTX *ctx);
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void EVP_CIPHER_CTX_set_flags(const EVP_CIPHER_CTX *ctx, int flags);
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void EVP_CIPHER_CTX_clear_flags(const EVP_CIPHER_CTX *ctx, int flags);
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int EVP_CIPHER_CTX_test_flags(const EVP_CIPHER_CTX *ctx, int flags);
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int EVP_CIPHER_CTX_mode(const EVP_CIPHER_CTX *ctx);
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int EVP_CIPHER_param_to_asn1(EVP_CIPHER_CTX *c, ASN1_TYPE *type);
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int EVP_CIPHER_asn1_to_param(EVP_CIPHER_CTX *c, ASN1_TYPE *type);
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=head1 DESCRIPTION
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The EVP cipher routines are a high level interface to certain
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symmetric ciphers.
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EVP_CIPHER_CTX_new() creates a cipher context.
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EVP_CIPHER_CTX_free() clears all information from a cipher context
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and free up any allocated memory associate with it, including B<ctx>
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itself. This function should be called after all operations using a
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cipher are complete so sensitive information does not remain in
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memory.
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EVP_EncryptInit_ex() sets up cipher context B<ctx> for encryption
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with cipher B<type> from ENGINE B<impl>. B<ctx> must be created
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before calling this function. B<type> is normally supplied
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by a function such as EVP_aes_256_cbc(). If B<impl> is NULL then the
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default implementation is used. B<key> is the symmetric key to use
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and B<iv> is the IV to use (if necessary), the actual number of bytes
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used for the key and IV depends on the cipher. It is possible to set
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all parameters to NULL except B<type> in an initial call and supply
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the remaining parameters in subsequent calls, all of which have B<type>
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set to NULL. This is done when the default cipher parameters are not
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appropriate.
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EVP_EncryptUpdate() encrypts B<inl> bytes from the buffer B<in> and
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writes the encrypted version to B<out>. This function can be called
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multiple times to encrypt successive blocks of data. The amount
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of data written depends on the block alignment of the encrypted data:
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as a result the amount of data written may be anything from zero bytes
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to (inl + cipher_block_size - 1) so B<out> should contain sufficient
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room. The actual number of bytes written is placed in B<outl>.
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If padding is enabled (the default) then EVP_EncryptFinal_ex() encrypts
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the "final" data, that is any data that remains in a partial block.
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It uses standard block padding (aka PKCS padding) as described in
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the NOTES section, below. The encrypted
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final data is written to B<out> which should have sufficient space for
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one cipher block. The number of bytes written is placed in B<outl>. After
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this function is called the encryption operation is finished and no further
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calls to EVP_EncryptUpdate() should be made.
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If padding is disabled then EVP_EncryptFinal_ex() will not encrypt any more
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data and it will return an error if any data remains in a partial block:
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that is if the total data length is not a multiple of the block size.
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EVP_DecryptInit_ex(), EVP_DecryptUpdate() and EVP_DecryptFinal_ex() are the
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corresponding decryption operations. EVP_DecryptFinal() will return an
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error code if padding is enabled and the final block is not correctly
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formatted. The parameters and restrictions are identical to the encryption
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operations except that if padding is enabled the decrypted data buffer B<out>
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passed to EVP_DecryptUpdate() should have sufficient room for
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(B<inl> + cipher_block_size) bytes unless the cipher block size is 1 in
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which case B<inl> bytes is sufficient.
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EVP_CipherInit_ex(), EVP_CipherUpdate() and EVP_CipherFinal_ex() are
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functions that can be used for decryption or encryption. The operation
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performed depends on the value of the B<enc> parameter. It should be set
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to 1 for encryption, 0 for decryption and -1 to leave the value unchanged
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(the actual value of 'enc' being supplied in a previous call).
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EVP_CIPHER_CTX_reset() clears all information from a cipher context
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and free up any allocated memory associate with it, except the B<ctx>
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itself. This function should be called anytime B<ctx> is to be reused
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for another EVP_CipherInit() / EVP_CipherUpdate() / EVP_CipherFinal()
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series of calls.
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EVP_EncryptInit(), EVP_DecryptInit() and EVP_CipherInit() behave in a
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similar way to EVP_EncryptInit_ex(), EVP_DecryptInit_ex() and
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EVP_CipherInit_ex() except the B<ctx> parameter does not need to be
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initialized and they always use the default cipher implementation.
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EVP_EncryptFinal(), EVP_DecryptFinal() and EVP_CipherFinal() are
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identical to EVP_EncryptFinal_ex(), EVP_DecryptFinal_ex() and
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EVP_CipherFinal_ex(). In previous releases they also cleaned up
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the B<ctx>, but this is no longer done and EVP_CIPHER_CTX_clean()
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must be called to free any context resources.
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EVP_get_cipherbyname(), EVP_get_cipherbynid() and EVP_get_cipherbyobj()
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return an EVP_CIPHER structure when passed a cipher name, a NID or an
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ASN1_OBJECT structure.
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EVP_CIPHER_nid() and EVP_CIPHER_CTX_nid() return the NID of a cipher when
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passed an B<EVP_CIPHER> or B<EVP_CIPHER_CTX> structure. The actual NID
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value is an internal value which may not have a corresponding OBJECT
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IDENTIFIER.
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EVP_CIPHER_CTX_set_padding() enables or disables padding. This
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function should be called after the context is set up for encryption
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or decryption with EVP_EncryptInit_ex(), EVP_DecryptInit_ex() or
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EVP_CipherInit_ex(). By default encryption operations are padded using
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standard block padding and the padding is checked and removed when
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decrypting. If the B<pad> parameter is zero then no padding is
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performed, the total amount of data encrypted or decrypted must then
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be a multiple of the block size or an error will occur.
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EVP_CIPHER_key_length() and EVP_CIPHER_CTX_key_length() return the key
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length of a cipher when passed an B<EVP_CIPHER> or B<EVP_CIPHER_CTX>
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structure. The constant B<EVP_MAX_KEY_LENGTH> is the maximum key length
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for all ciphers. Note: although EVP_CIPHER_key_length() is fixed for a
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given cipher, the value of EVP_CIPHER_CTX_key_length() may be different
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for variable key length ciphers.
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EVP_CIPHER_CTX_set_key_length() sets the key length of the cipher ctx.
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If the cipher is a fixed length cipher then attempting to set the key
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length to any value other than the fixed value is an error.
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EVP_CIPHER_iv_length() and EVP_CIPHER_CTX_iv_length() return the IV
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length of a cipher when passed an B<EVP_CIPHER> or B<EVP_CIPHER_CTX>.
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It will return zero if the cipher does not use an IV. The constant
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B<EVP_MAX_IV_LENGTH> is the maximum IV length for all ciphers.
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EVP_CIPHER_block_size() and EVP_CIPHER_CTX_block_size() return the block
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size of a cipher when passed an B<EVP_CIPHER> or B<EVP_CIPHER_CTX>
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structure. The constant B<EVP_MAX_IV_LENGTH> is also the maximum block
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length for all ciphers.
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EVP_CIPHER_type() and EVP_CIPHER_CTX_type() return the type of the passed
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cipher or context. This "type" is the actual NID of the cipher OBJECT
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IDENTIFIER as such it ignores the cipher parameters and 40 bit RC2 and
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128 bit RC2 have the same NID. If the cipher does not have an object
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identifier or does not have ASN1 support this function will return
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B<NID_undef>.
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EVP_CIPHER_CTX_cipher() returns the B<EVP_CIPHER> structure when passed
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an B<EVP_CIPHER_CTX> structure.
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EVP_CIPHER_mode() and EVP_CIPHER_CTX_mode() return the block cipher mode:
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EVP_CIPH_ECB_MODE, EVP_CIPH_CBC_MODE, EVP_CIPH_CFB_MODE or
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EVP_CIPH_OFB_MODE. If the cipher is a stream cipher then
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EVP_CIPH_STREAM_CIPHER is returned.
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EVP_CIPHER_param_to_asn1() sets the AlgorithmIdentifier "parameter" based
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on the passed cipher. This will typically include any parameters and an
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IV. The cipher IV (if any) must be set when this call is made. This call
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should be made before the cipher is actually "used" (before any
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EVP_EncryptUpdate(), EVP_DecryptUpdate() calls for example). This function
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may fail if the cipher does not have any ASN1 support.
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EVP_CIPHER_asn1_to_param() sets the cipher parameters based on an ASN1
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AlgorithmIdentifier "parameter". The precise effect depends on the cipher
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In the case of RC2, for example, it will set the IV and effective key length.
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This function should be called after the base cipher type is set but before
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the key is set. For example EVP_CipherInit() will be called with the IV and
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key set to NULL, EVP_CIPHER_asn1_to_param() will be called and finally
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EVP_CipherInit() again with all parameters except the key set to NULL. It is
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possible for this function to fail if the cipher does not have any ASN1 support
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or the parameters cannot be set (for example the RC2 effective key length
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is not supported.
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EVP_CIPHER_CTX_ctrl() allows various cipher specific parameters to be determined
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and set.
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=head1 RETURN VALUES
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EVP_CIPHER_CTX_new() returns a pointer to a newly created
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B<EVP_CIPHER_CTX> for success and B<NULL> for failure.
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EVP_EncryptInit_ex(), EVP_EncryptUpdate() and EVP_EncryptFinal_ex()
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return 1 for success and 0 for failure.
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EVP_DecryptInit_ex() and EVP_DecryptUpdate() return 1 for success and 0 for failure.
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EVP_DecryptFinal_ex() returns 0 if the decrypt failed or 1 for success.
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EVP_CipherInit_ex() and EVP_CipherUpdate() return 1 for success and 0 for failure.
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EVP_CipherFinal_ex() returns 0 for a decryption failure or 1 for success.
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EVP_CIPHER_CTX_reset() returns 1 for success and 0 for failure.
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EVP_get_cipherbyname(), EVP_get_cipherbynid() and EVP_get_cipherbyobj()
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return an B<EVP_CIPHER> structure or NULL on error.
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EVP_CIPHER_nid() and EVP_CIPHER_CTX_nid() return a NID.
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EVP_CIPHER_block_size() and EVP_CIPHER_CTX_block_size() return the block
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size.
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EVP_CIPHER_key_length() and EVP_CIPHER_CTX_key_length() return the key
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length.
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EVP_CIPHER_CTX_set_padding() always returns 1.
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EVP_CIPHER_iv_length() and EVP_CIPHER_CTX_iv_length() return the IV
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length or zero if the cipher does not use an IV.
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EVP_CIPHER_type() and EVP_CIPHER_CTX_type() return the NID of the cipher's
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OBJECT IDENTIFIER or NID_undef if it has no defined OBJECT IDENTIFIER.
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EVP_CIPHER_CTX_cipher() returns an B<EVP_CIPHER> structure.
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EVP_CIPHER_param_to_asn1() and EVP_CIPHER_asn1_to_param() return greater
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than zero for success and zero or a negative number.
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=head1 CIPHER LISTING
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All algorithms have a fixed key length unless otherwise stated.
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=over 4
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=item EVP_enc_null()
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Null cipher: does nothing.
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=item EVP_aes_128_cbc(), EVP_aes_128_ecb(), EVP_aes_128_cfb(), EVP_aes_128_ofb()
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AES with a 128-bit key in CBC, ECB, CFB and OFB modes respectively.
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=item EVP_aes_192_cbc(), EVP_aes_192_ecb(), EVP_aes_192_cfb(), EVP_aes_192_ofb()
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AES with a 192-bit key in CBC, ECB, CFB and OFB modes respectively.
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=item EVP_aes_256_cbc(), EVP_aes_256_ecb(), EVP_aes_256_cfb(), EVP_aes_256_ofb()
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AES with a 256-bit key in CBC, ECB, CFB and OFB modes respectively.
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=item EVP_des_cbc(), EVP_des_ecb(), EVP_des_cfb(), EVP_des_ofb()
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DES in CBC, ECB, CFB and OFB modes respectively.
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=item EVP_des_ede_cbc(), EVP_des_ede(), EVP_des_ede_ofb(), EVP_des_ede_cfb()
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Two key triple DES in CBC, ECB, CFB and OFB modes respectively.
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=item EVP_des_ede3_cbc(), EVP_des_ede3(), EVP_des_ede3_ofb(), EVP_des_ede3_cfb()
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Three key triple DES in CBC, ECB, CFB and OFB modes respectively.
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=item EVP_desx_cbc()
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DESX algorithm in CBC mode.
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=item EVP_rc4()
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RC4 stream cipher. This is a variable key length cipher with default key length 128 bits.
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=item EVP_rc4_40()
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RC4 stream cipher with 40 bit key length.
|
|
This is obsolete and new code should use EVP_rc4()
|
|
and the EVP_CIPHER_CTX_set_key_length() function.
|
|
|
|
=item EVP_idea_cbc() EVP_idea_ecb(), EVP_idea_cfb(), EVP_idea_ofb()
|
|
|
|
IDEA encryption algorithm in CBC, ECB, CFB and OFB modes respectively.
|
|
|
|
=item EVP_rc2_cbc(), EVP_rc2_ecb(), EVP_rc2_cfb(), EVP_rc2_ofb()
|
|
|
|
RC2 encryption algorithm in CBC, ECB, CFB and OFB modes respectively. This is a variable key
|
|
length cipher with an additional parameter called "effective key bits" or "effective key length".
|
|
By default both are set to 128 bits.
|
|
|
|
=item EVP_rc2_40_cbc(), EVP_rc2_64_cbc()
|
|
|
|
RC2 algorithm in CBC mode with a default key length and effective key length of 40 and 64 bits.
|
|
These are obsolete and new code should use EVP_rc2_cbc(), EVP_CIPHER_CTX_set_key_length() and
|
|
EVP_CIPHER_CTX_ctrl() to set the key length and effective key length.
|
|
|
|
=item EVP_bf_cbc(), EVP_bf_ecb(), EVP_bf_cfb(), EVP_bf_ofb()
|
|
|
|
Blowfish encryption algorithm in CBC, ECB, CFB and OFB modes respectively. This is a variable key
|
|
length cipher.
|
|
|
|
=item EVP_cast5_cbc(), EVP_cast5_ecb(), EVP_cast5_cfb(), EVP_cast5_ofb()
|
|
|
|
CAST encryption algorithm in CBC, ECB, CFB and OFB modes respectively. This is a variable key
|
|
length cipher.
|
|
|
|
=item EVP_rc5_32_12_16_cbc(), EVP_rc5_32_12_16_ecb(), EVP_rc5_32_12_16_cfb(), EVP_rc5_32_12_16_ofb()
|
|
|
|
RC5 encryption algorithm in CBC, ECB, CFB and OFB modes respectively. This is a variable key length
|
|
cipher with an additional "number of rounds" parameter. By default the key length is set to 128
|
|
bits and 12 rounds.
|
|
|
|
=item EVP_aes_128_gcm(), EVP_aes_192_gcm(), EVP_aes_256_gcm()
|
|
|
|
AES Galois Counter Mode (GCM) for 128, 192 and 256 bit keys respectively.
|
|
These ciphers require additional control operations to function correctly: see
|
|
the L<GCM and OCB modes> section below for details.
|
|
|
|
=item EVP_aes_128_ocb(void), EVP_aes_192_ocb(void), EVP_aes_256_ocb(void)
|
|
|
|
Offest Codebook Mode (OCB) for 128, 192 and 256 bit keys respectively.
|
|
These ciphers require additional control operations to function correctly: see
|
|
the L<GCM and OCB modes> section below for details.
|
|
|
|
=item EVP_aes_128_ccm(), EVP_aes_192_ccm(), EVP_aes_256_ccm()
|
|
|
|
AES Counter with CBC-MAC Mode (CCM) for 128, 192 and 256 bit keys respectively.
|
|
These ciphers require additional control operations to function correctly: see
|
|
CCM mode section below for details.
|
|
|
|
=back
|
|
|
|
=head1 GCM and OCB Modes
|
|
|
|
For GCM and OCB 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) a call to EVP_CipherUpdate(),
|
|
EVP_EncryptUpdate() or EVP_DecryptUpdate() should be made with the output
|
|
parameter B<out> set to B<NULL>.
|
|
|
|
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 B<MUST NOT>
|
|
be used as it is corrupted.
|
|
|
|
The following ctrls are supported in both GCM and OCB modes:
|
|
|
|
EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_IVLEN, ivlen, NULL);
|
|
|
|
Sets the IV length: this call can only be made before specifying an IV. If
|
|
not called a default IV length is used. For GCM AES and OCB AES the default is
|
|
12 (i.e. 96 bits). For OCB mode the maximum is 15.
|
|
|
|
EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_GET_TAG, taglen, tag);
|
|
|
|
Writes B<taglen> bytes of the tag value to the buffer indicated by B<tag>.
|
|
This call can only be made when encrypting data and B<after> all data has been
|
|
processed (e.g. after an EVP_EncryptFinal() call). For OCB mode the taglen must
|
|
either be 16 or the value previously set via EVP_CTRL_OCB_SET_TAGLEN.
|
|
|
|
EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_TAG, taglen, tag);
|
|
|
|
Sets the expected tag to B<taglen> bytes from B<tag>. This call is only legal
|
|
when decrypting data and must be made B<before> any data is processed (e.g.
|
|
before any EVP_DecryptUpdate() call). For OCB mode the taglen must
|
|
either be 16 or the value previously set via EVP_CTRL_AEAD_SET_TAG.
|
|
|
|
In OCB mode calling this with B<tag> set to NULL sets the tag length. The tag
|
|
length can only be set before specifying an IV. If not called a default tag
|
|
length is used. For OCB AES the default is 16 (i.e. 128 bits). This is also the
|
|
maximum tag length for OCB.
|
|
|
|
See L<EXAMPLES> below for an example of the use of GCM mode.
|
|
|
|
=head1 CCM Mode
|
|
|
|
The behaviour of CCM mode ciphers is similar to GCM mode but with a few
|
|
additional requirements and different ctrl values.
|
|
|
|
Like GCM and OCB modes any additional authenticated data (AAD) is passed by calling
|
|
EVP_CipherUpdate(), EVP_EncryptUpdate() or EVP_DecryptUpdate() with the output
|
|
parameter B<out> set to B<NULL>. Additionally the total plaintext or ciphertext
|
|
length B<MUST> be passed to EVP_CipherUpdate(), EVP_EncryptUpdate() or
|
|
EVP_DecryptUpdate() with the output and input parameters (B<in> and B<out>)
|
|
set to B<NULL> and the length passed in the B<inl> parameter.
|
|
|
|
The following ctrls are supported in CCM mode:
|
|
|
|
EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_TAG, taglen, tag);
|
|
|
|
This call is made to set the expected B<CCM> tag value when decrypting or
|
|
the length of the tag (with the B<tag> parameter set to NULL) when encrypting.
|
|
The tag length is often referred to as B<M>. If not set a default value is
|
|
used (12 for AES).
|
|
|
|
EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_CCM_SET_L, ivlen, NULL);
|
|
|
|
Sets the CCM B<L> value. If not set a default is used (8 for AES).
|
|
|
|
EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_IVLEN, ivlen, NULL);
|
|
|
|
Sets the CCM nonce (IV) length: this call can only be made before specifying
|
|
an nonce value. The nonce length is given by B<15 - L> so it is 7 by default
|
|
for AES.
|
|
|
|
|
|
|
|
=head1 NOTES
|
|
|
|
Where possible the B<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
|
|
B<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 B<n> padding bytes of value B<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 B<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_EncryptFinal(), EVP_DecryptInit(),
|
|
EVP_CipherInit() and EVP_CipherFinal() are obsolete but are retained for
|
|
compatibility with existing code. New code should use EVP_EncryptInit_ex(),
|
|
EVP_EncryptFinal_ex(), EVP_DecryptInit_ex(), EVP_DecryptFinal_ex(),
|
|
EVP_CipherInit_ex() and EVP_CipherFinal_ex() because they can reuse an
|
|
existing context without allocating and freeing it up on each call.
|
|
|
|
=head1 BUGS
|
|
|
|
For RC5 the number of rounds can currently only be set to 8, 12 or 16. This is
|
|
a limitation of the current RC5 code rather than the EVP interface.
|
|
|
|
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.
|
|
|
|
=head1 EXAMPLES
|
|
|
|
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();
|
|
EVP_EncryptInit_ex(ctx, EVP_idea_cbc(), NULL, key, iv);
|
|
|
|
if(!EVP_EncryptUpdate(ctx, outbuf, &outlen, intext, strlen(intext)))
|
|
{
|
|
/* Error */
|
|
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 */
|
|
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 wont be null terminated and may contain embedded
|
|
* nulls.
|
|
*/
|
|
out = fopen(outfile, "wb");
|
|
fwrite(outbuf, 1, outlen, out);
|
|
fclose(out);
|
|
return 1;
|
|
}
|
|
|
|
The ciphertext from the above example can be decrypted using the B<openssl>
|
|
utility with the command line (shown on two lines for clarity):
|
|
|
|
openssl idea -d <filename
|
|
-K 000102030405060708090A0B0C0D0E0F -iv 0102030405060708
|
|
|
|
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_ex(&ctx, EVP_aes_128_cbc(), NULL, NULL, NULL,
|
|
do_encrypt);
|
|
OPENSSL_assert(EVP_CIPHER_CTX_key_length(ctx) == 16);
|
|
OPENSSL_assert(EVP_CIPHER_CTX_iv_length(ctx) == 16);
|
|
|
|
/* Now we can set key and IV */
|
|
EVP_CipherInit_ex(ctx, NULL, NULL, key, iv, do_encrypt);
|
|
|
|
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;
|
|
}
|
|
|
|
|
|
=head1 SEE ALSO
|
|
|
|
L<evp(3)>
|
|
|
|
=head1 HISTORY
|
|
|
|
Support for OCB mode was added in OpenSSL 1.1.0
|
|
|
|
B<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().
|
|
|
|
=cut
|