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1=pod
2
3=head1 NAME
4
5EVP_EncryptInit, EVP_EncryptUpdate, EVP_EncryptFinal, EVP_DecryptInit,
6EVP_DecryptUpdate, EVP_DecryptFinal, EVP_CipherInit, EVP_CipherUpdate,
7EVP_CipherFinal, EVP_CIPHER_CTX_set_key_length, EVP_CIPHER_CTX_ctrl,
8EVP_CIPHER_CTX_cleanup, EVP_get_cipherbyname, EVP_get_cipherbynid,
9EVP_get_cipherbyobj, EVP_CIPHER_nid, EVP_CIPHER_block_size,
10EVP_CIPHER_key_length, EVP_CIPHER_iv_length, EVP_CIPHER_flags,
11EVP_CIPHER_mode, EVP_CIPHER_type, EVP_CIPHER_CTX_cipher, EVP_CIPHER_CTX_nid,
12EVP_CIPHER_CTX_block_size, EVP_CIPHER_CTX_key_length, EVP_CIPHER_CTX_iv_length,
13EVP_CIPHER_CTX_get_app_data, EVP_CIPHER_CTX_set_app_data, EVP_CIPHER_CTX_type,
14EVP_CIPHER_CTX_flags, EVP_CIPHER_CTX_mode, EVP_CIPHER_param_to_asn1,
15EVP_CIPHER_asn1_to_param - EVP cipher routines
16
17=head1 SYNOPSIS
18
19 #include <openssl/evp.h>
20
21 int EVP_EncryptInit(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
22 unsigned char *key, unsigned char *iv);
23 int EVP_EncryptUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out,
24 int *outl, unsigned char *in, int inl);
25 int EVP_EncryptFinal(EVP_CIPHER_CTX *ctx, unsigned char *out,
26 int *outl);
27
28 int EVP_DecryptInit(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
29 unsigned char *key, unsigned char *iv);
30 int EVP_DecryptUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out,
31 int *outl, unsigned char *in, int inl);
32 int EVP_DecryptFinal(EVP_CIPHER_CTX *ctx, unsigned char *outm,
33 int *outl);
34
35 int EVP_CipherInit(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
36 unsigned char *key, unsigned char *iv, int enc);
37 int EVP_CipherUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out,
38 int *outl, unsigned char *in, int inl);
39 int EVP_CipherFinal(EVP_CIPHER_CTX *ctx, unsigned char *outm,
40 int *outl);
41
42 int EVP_CIPHER_CTX_set_key_length(EVP_CIPHER_CTX *x, int keylen);
43 int EVP_CIPHER_CTX_ctrl(EVP_CIPHER_CTX *ctx, int type, int arg, void *ptr);
44 int EVP_CIPHER_CTX_cleanup(EVP_CIPHER_CTX *a);
45
46 const EVP_CIPHER *EVP_get_cipherbyname(const char *name);
47 #define EVP_get_cipherbynid(a) EVP_get_cipherbyname(OBJ_nid2sn(a))
48 #define EVP_get_cipherbyobj(a) EVP_get_cipherbynid(OBJ_obj2nid(a))
49
50 #define EVP_CIPHER_nid(e) ((e)->nid)
51 #define EVP_CIPHER_block_size(e) ((e)->block_size)
52 #define EVP_CIPHER_key_length(e) ((e)->key_len)
53 #define EVP_CIPHER_iv_length(e) ((e)->iv_len)
54 #define EVP_CIPHER_flags(e) ((e)->flags)
55 #define EVP_CIPHER_mode(e) ((e)->flags) & EVP_CIPH_MODE)
56 int EVP_CIPHER_type(const EVP_CIPHER *ctx);
57
58 #define EVP_CIPHER_CTX_cipher(e) ((e)->cipher)
59 #define EVP_CIPHER_CTX_nid(e) ((e)->cipher->nid)
60 #define EVP_CIPHER_CTX_block_size(e) ((e)->cipher->block_size)
61 #define EVP_CIPHER_CTX_key_length(e) ((e)->key_len)
62 #define EVP_CIPHER_CTX_iv_length(e) ((e)->cipher->iv_len)
63 #define EVP_CIPHER_CTX_get_app_data(e) ((e)->app_data)
64 #define EVP_CIPHER_CTX_set_app_data(e,d) ((e)->app_data=(char *)(d))
65 #define EVP_CIPHER_CTX_type(c) EVP_CIPHER_type(EVP_CIPHER_CTX_cipher(c))
66 #define EVP_CIPHER_CTX_flags(e) ((e)->cipher->flags)
67 #define EVP_CIPHER_CTX_mode(e) ((e)->cipher->flags & EVP_CIPH_MODE)
68
69 int EVP_CIPHER_param_to_asn1(EVP_CIPHER_CTX *c, ASN1_TYPE *type);
70 int EVP_CIPHER_asn1_to_param(EVP_CIPHER_CTX *c, ASN1_TYPE *type);
71
72=head1 DESCRIPTION
73
74The EVP cipher routines are a high level interface to certain
75symmetric ciphers.
76
77EVP_EncryptInit() initializes a cipher context B<ctx> for encryption
78with cipher B<type>. B<type> is normally supplied by a function such
79as EVP_des_cbc() . B<key> is the symmetric key to use and B<iv> is the
80IV to use (if necessary), the actual number of bytes used for the
81key and IV depends on the cipher. It is possible to set all parameters
82to NULL except B<type> in an initial call and supply the remaining
83parameters in subsequent calls, all of which have B<type> set to NULL.
84This is done when the default cipher parameters are not appropriate.
85
86EVP_EncryptUpdate() encrypts B<inl> bytes from the buffer B<in> and
87writes the encrypted version to B<out>. This function can be called
88multiple times to encrypt successive blocks of data. The amount
89of data written depends on the block alignment of the encrypted data:
90as a result the amount of data written may be anything from zero bytes
91to (inl + cipher_block_size - 1) so B<outl> should contain sufficient
92room. The actual number of bytes written is placed in B<outl>.
93
94EVP_EncryptFinal() encrypts the "final" data, that is any data that
95remains in a partial block. It uses L<standard block padding|/NOTES> (aka PKCS
96padding). The encrypted final data is written to B<out> which should
97have sufficient space for one cipher block. The number of bytes written
98is placed in B<outl>. After this function is called the encryption operation
99is finished and no further calls to EVP_EncryptUpdate() should be made.
100
101EVP_DecryptInit(), EVP_DecryptUpdate() and EVP_DecryptFinal() are the
102corresponding decryption operations. EVP_DecryptFinal() will return an
103error code if the final block is not correctly formatted. The parameters
104and restrictions are identical to the encryption operations except that
105the decrypted data buffer B<out> passed to EVP_DecryptUpdate() should
106have sufficient room for (B<inl> + cipher_block_size) bytes unless the
107cipher block size is 1 in which case B<inl> bytes is sufficient.
108
109EVP_CipherInit(), EVP_CipherUpdate() and EVP_CipherFinal() are functions
110that can be used for decryption or encryption. The operation performed
111depends on the value of the B<enc> parameter. It should be set to 1 for
112encryption, 0 for decryption and -1 to leave the value unchanged (the
113actual value of 'enc' being supplied in a previous call).
114
115EVP_CIPHER_CTX_cleanup() clears all information from a cipher context.
116It should be called after all operations using a cipher are complete
117so sensitive information does not remain in memory.
118
119EVP_get_cipherbyname(), EVP_get_cipherbynid() and EVP_get_cipherbyobj()
120return an EVP_CIPHER structure when passed a cipher name, a NID or an
121ASN1_OBJECT structure.
122
123EVP_CIPHER_nid() and EVP_CIPHER_CTX_nid() return the NID of a cipher when
124passed an B<EVP_CIPHER> or B<EVP_CIPHER_CTX> structure. The actual NID
125value is an internal value which may not have a corresponding OBJECT
126IDENTIFIER.
127
128EVP_CIPHER_key_length() and EVP_CIPHER_CTX_key_length() return the key
129length of a cipher when passed an B<EVP_CIPHER> or B<EVP_CIPHER_CTX>
130structure. The constant B<EVP_MAX_KEY_LENGTH> is the maximum key length
131for all ciphers. Note: although EVP_CIPHER_key_length() is fixed for a
132given cipher, the value of EVP_CIPHER_CTX_key_length() may be different
133for variable key length ciphers.
134
135EVP_CIPHER_CTX_set_key_length() sets the key length of the cipher ctx.
136If the cipher is a fixed length cipher then attempting to set the key
137length to any value other than the fixed value is an error.
138
139EVP_CIPHER_iv_length() and EVP_CIPHER_CTX_iv_length() return the IV
140length of a cipher when passed an B<EVP_CIPHER> or B<EVP_CIPHER_CTX>.
141It will return zero if the cipher does not use an IV. The constant
142B<EVP_MAX_IV_LENGTH> is the maximum IV length for all ciphers.
143
144EVP_CIPHER_block_size() and EVP_CIPHER_CTX_block_size() return the block
145size of a cipher when passed an B<EVP_CIPHER> or B<EVP_CIPHER_CTX>
146structure. The constant B<EVP_MAX_IV_LENGTH> is also the maximum block
147length for all ciphers.
148
149EVP_CIPHER_type() and EVP_CIPHER_CTX_type() return the type of the passed
150cipher or context. This "type" is the actual NID of the cipher OBJECT
151IDENTIFIER as such it ignores the cipher parameters and 40 bit RC2 and
152128 bit RC2 have the same NID. If the cipher does not have an object
153identifier or does not have ASN1 support this function will return
154B<NID_undef>.
155
156EVP_CIPHER_CTX_cipher() returns the B<EVP_CIPHER> structure when passed
157an B<EVP_CIPHER_CTX> structure.
158
159EVP_CIPHER_mode() and EVP_CIPHER_CTX_mode() return the block cipher mode:
160EVP_CIPH_ECB_MODE, EVP_CIPH_CBC_MODE, EVP_CIPH_CFB_MODE or
161EVP_CIPH_OFB_MODE. If the cipher is a stream cipher then
162EVP_CIPH_STREAM_CIPHER is returned.
163
164EVP_CIPHER_param_to_asn1() sets the AlgorithmIdentifier "parameter" based
165on the passed cipher. This will typically include any parameters and an
166IV. The cipher IV (if any) must be set when this call is made. This call
167should be made before the cipher is actually "used" (before any
168EVP_EncryptUpdate(), EVP_DecryptUpdate() calls for example). This function
169may fail if the cipher does not have any ASN1 support.
170
171EVP_CIPHER_asn1_to_param() sets the cipher parameters based on an ASN1
172AlgorithmIdentifier "parameter". The precise effect depends on the cipher
173In the case of RC2, for example, it will set the IV and effective key length.
174This function should be called after the base cipher type is set but before
175the key is set. For example EVP_CipherInit() will be called with the IV and
176key set to NULL, EVP_CIPHER_asn1_to_param() will be called and finally
177EVP_CipherInit() again with all parameters except the key set to NULL. It is
178possible for this function to fail if the cipher does not have any ASN1 support
179or the parameters cannot be set (for example the RC2 effective key length
180is not supported.
181
182EVP_CIPHER_CTX_ctrl() allows various cipher specific parameters to be determined
183and set. Currently only the RC2 effective key length and the number of rounds of
184RC5 can be set.
185
186=head1 RETURN VALUES
187
188EVP_EncryptInit(), EVP_EncryptUpdate() and EVP_EncryptFinal() return 1 for success
189and 0 for failure.
190
191EVP_DecryptInit() and EVP_DecryptUpdate() return 1 for success and 0 for failure.
192EVP_DecryptFinal() returns 0 if the decrypt failed or 1 for success.
193
194EVP_CipherInit() and EVP_CipherUpdate() return 1 for success and 0 for failure.
195EVP_CipherFinal() returns 1 for a decryption failure or 1 for success.
196
197EVP_CIPHER_CTX_cleanup() returns 1 for success and 0 for failure.
198
199EVP_get_cipherbyname(), EVP_get_cipherbynid() and EVP_get_cipherbyobj()
200return an B<EVP_CIPHER> structure or NULL on error.
201
202EVP_CIPHER_nid() and EVP_CIPHER_CTX_nid() return a NID.
203
204EVP_CIPHER_block_size() and EVP_CIPHER_CTX_block_size() return the block
205size.
206
207EVP_CIPHER_key_length() and EVP_CIPHER_CTX_key_length() return the key
208length.
209
210EVP_CIPHER_iv_length() and EVP_CIPHER_CTX_iv_length() return the IV
211length or zero if the cipher does not use an IV.
212
213EVP_CIPHER_type() and EVP_CIPHER_CTX_type() return the NID of the cipher's
214OBJECT IDENTIFIER or NID_undef if it has no defined OBJECT IDENTIFIER.
215
216EVP_CIPHER_CTX_cipher() returns an B<EVP_CIPHER> structure.
217
218EVP_CIPHER_param_to_asn1() and EVP_CIPHER_asn1_to_param() return 1 for
219success or zero for failure.
220
221=head1 CIPHER LISTING
222
223All algorithms have a fixed key length unless otherwise stated.
224
225=over 4
226
227=item EVP_enc_null()
228
229Null cipher: does nothing.
230
231=item EVP_des_cbc(void), EVP_des_ecb(void), EVP_des_cfb(void), EVP_des_ofb(void)
232
233DES in CBC, ECB, CFB and OFB modes respectively.
234
235=item EVP_des_ede_cbc(void), EVP_des_ede(), EVP_des_ede_ofb(void), EVP_des_ede_cfb(void)
236
237Two key triple DES in CBC, ECB, CFB and OFB modes respectively.
238
239=item EVP_des_ede3_cbc(void), EVP_des_ede3(), EVP_des_ede3_ofb(void), EVP_des_ede3_cfb(void)
240
241Three key triple DES in CBC, ECB, CFB and OFB modes respectively.
242
243=item EVP_desx_cbc(void)
244
245DESX algorithm in CBC mode.
246
247=item EVP_rc4(void)
248
249RC4 stream cipher. This is a variable key length cipher with default key length 128 bits.
250
251=item EVP_rc4_40(void)
252
253RC4 stream cipher with 40 bit key length. This is obsolete and new code should use EVP_rc4()
254and the EVP_CIPHER_CTX_set_key_length() function.
255
256=item EVP_idea_cbc() EVP_idea_ecb(void), EVP_idea_cfb(void), EVP_idea_ofb(void), EVP_idea_cbc(void)
257
258IDEA encryption algorithm in CBC, ECB, CFB and OFB modes respectively.
259
260=item EVP_rc2_cbc(void), EVP_rc2_ecb(void), EVP_rc2_cfb(void), EVP_rc2_ofb(void)
261
262RC2 encryption algorithm in CBC, ECB, CFB and OFB modes respectively. This is a variable key
263length cipher with an additional parameter called "effective key bits" or "effective key length".
264By default both are set to 128 bits.
265
266=item EVP_rc2_40_cbc(void), EVP_rc2_64_cbc(void)
267
268RC2 algorithm in CBC mode with a default key length and effective key length of 40 and 64 bits.
269These are obsolete and new code should use EVP_rc2_cbc(), EVP_CIPHER_CTX_set_key_length() and
270EVP_CIPHER_CTX_ctrl() to set the key length and effective key length.
271
272=item EVP_bf_cbc(void), EVP_bf_ecb(void), EVP_bf_cfb(void), EVP_bf_ofb(void);
273
274Blowfish encryption algorithm in CBC, ECB, CFB and OFB modes respectively. This is a variable key
275length cipher.
276
277=item EVP_cast5_cbc(void), EVP_cast5_ecb(void), EVP_cast5_cfb(void), EVP_cast5_ofb(void)
278
279CAST encryption algorithm in CBC, ECB, CFB and OFB modes respectively. This is a variable key
280length cipher.
281
282=item EVP_rc5_32_12_16_cbc(void), EVP_rc5_32_12_16_ecb(void), EVP_rc5_32_12_16_cfb(void), EVP_rc5_32_12_16_ofb(void)
283
284RC5 encryption algorithm in CBC, ECB, CFB and OFB modes respectively. This is a variable key length
285cipher with an additional "number of rounds" parameter. By default the key length is set to 128
286bits and 12 rounds.
287
288=back
289
290=head1 NOTES
291
292Where possible the B<EVP> interface to symmetric ciphers should be used in
293preference to the low level interfaces. This is because the code then becomes
294transparent to the cipher used and much more flexible.
295
296PKCS padding works by adding B<n> padding bytes of value B<n> to make the total
297length of the encrypted data a multiple of the block size. Padding is always
298added so if the data is already a multiple of the block size B<n> will equal
299the block size. For example if the block size is 8 and 11 bytes are to be
300encrypted then 5 padding bytes of value 5 will be added.
301
302When decrypting the final block is checked to see if it has the correct form.
303
304Although the decryption operation can produce an error, it is not a strong
305test that the input data or key is correct. A random block has better than
3061 in 256 chance of being of the correct format and problems with the
307input data earlier on will not produce a final decrypt error.
308
309The functions EVP_EncryptInit(), EVP_EncryptUpdate(), EVP_EncryptFinal(),
310EVP_DecryptInit(), EVP_DecryptUpdate(), EVP_CipherInit() and EVP_CipherUpdate()
311and EVP_CIPHER_CTX_cleanup() did not return errors in OpenSSL version 0.9.5a or
312earlier. Software only versions of encryption algorithms will never return
313error codes for these functions, unless there is a programming error (for example
314and attempt to set the key before the cipher is set in EVP_EncryptInit() ).
315
316=head1 BUGS
317
318For RC5 the number of rounds can currently only be set to 8, 12 or 16. This is
319a limitation of the current RC5 code rather than the EVP interface.
320
321It should be possible to disable PKCS padding: currently it isn't.
322
323EVP_MAX_KEY_LENGTH and EVP_MAX_IV_LENGTH only refer to the internal ciphers with
324default key lengths. If custom ciphers exceed these values the results are
325unpredictable. This is because it has become standard practice to define a
326generic key as a fixed unsigned char array containing EVP_MAX_KEY_LENGTH bytes.
327
328The ASN1 code is incomplete (and sometimes inaccurate) it has only been tested
329for certain common S/MIME ciphers (RC2, DES, triple DES) in CBC mode.
330
331=head1 EXAMPLES
332
333Get the number of rounds used in RC5:
334
335 int nrounds;
336 EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_GET_RC5_ROUNDS, 0, &i);
337
338Get the RC2 effective key length:
339
340 int key_bits;
341 EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_GET_RC2_KEY_BITS, 0, &i);
342
343Set the number of rounds used in RC5:
344
345 int nrounds;
346 EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_SET_RC5_ROUNDS, i, NULL);
347
348Set the number of rounds used in RC2:
349
350 int nrounds;
351 EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_SET_RC2_KEY_BITS, i, NULL);
352
353=head1 SEE ALSO
354
355L<evp(3)|evp(3)>
356
357=head1 HISTORY
358
359=cut