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openssl/doc/man7/life_cycle-cipher.pod
Pauli c0fc3fe349 doc: add cipher life cycle documentation 
Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/15637)
2021-06-08 18:56:53 +10:00

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=pod
=head1 NAME
life_cycle-cipher - The cipher algorithm life-cycle
=head1 DESCRIPTION
All symmetric ciphers (CIPHERs) go through a number of stages in their
life-cycle:
=over 4
=item start
This state represents the CIPHER before it has been allocated. It is the
starting state for any life-cycle transitions.
=item newed
This state represents the CIPHER after it has been allocated.
=item initialised
These states represent the CIPHER when it is set up and capable of processing
input. There are three possible initialised states:
=over 4
=item initialised using EVP_CipherInit
=item initialised for decryption using EVP_DecryptInit
=item initialised for encryption using EVP_EncryptInit
=back
=item updated
These states represent the CIPHER when it is set up and capable of processing
additional input or generating output. The three possible states directly
correspond to those for initialised above. The three different streams should
not be mixed.
=item finaled
This state represents the CIPHER when it has generated output.
=item freed
This state is entered when the CIPHER is freed. It is the terminal state
for all life-cycle transitions.
=back
=head2 State Transition Diagram
The usual life-cycle of a CIPHER is illustrated:
=begin man
+---------------------------+
| |
| start |
| |
+---------------------------+ + - - - - - - - - - - - - - +
| ' any of the initialised '
| EVP_CIPHER_CTX_new ' updated or finaled states '
v ' '
+---------------------------+ + - - - - - - - - - - - - - +
| | |
| newed | | EVP_CIPHER_CTX_reset
| | <----+
+---------------------------+
| | |
+---------+ | +---------+
EVP_DecryptInit | | EVP_CipherInit | EVP_EncryptInit
v v v
+---------------------------+ +---------------------------+ +---------------------------+
| | | | | |
| initialised | | initialised | | initialised |
| for decryption | | | | for encryption |
+---------------------------+ +---------------------------+ +---------------------------+
| | |
| EVP_DecryptUpdate | EVP_CipherUpdate EVP_EncryptUpdate |
| v |
| +---------------------------+ |
| | |--------------------+ |
| | updated | EVP_CipherUpdate | |
| | | <------------------+ |
v +---------------------------+ v
+---------------------------+ | +---------------------------+
| |---------------------+ | | |
| updated | EVP_DecryptUpdate | | | updated |------+
| for decryption | <-------------------+ | | for encryption | |
+---------------------------+ | +---------------------------+ |
| EVP_CipherFinal | | ^ |
+-------+ | +--------+ | |
EVP_DecryptFinal | | | EVP_EncryptFinal +-------------------+
v v v EVP_EncryptUpdate
+---------------------------+
| |-----------------------------+
| finaled | |
| | <---------------------------+
+---------------------------+ EVP_CIPHER_CTX_get_params
| (AEAD encryption)
| EVP_CIPHER_CTX_free
v
+---------------------------+
| |
| freed |
| |
+---------------------------+
=end man
=for html <img src="img/cipher.png">
=head2 Formal State Transitions
This section defines all of the legal state transitions.
This is the canonical list.
=begin man
Function Call ---------------------------------------------- Current State -----------------------------------------------
start newed initialised updated finaled initialised updated initialised updated freed
decryption decryption encryption encryption
EVP_CIPHER_CTX_new newed
EVP_CipherInit initialised initialised initialised initialised initialised initialised initialised initialised
EVP_DecryptInit initialised initialised initialised initialised initialised initialised initialised initialised
decryption decryption decryption decryption decryption decryption decryption decryption
EVP_EncryptInit initialised initialised initialised initialised initialised initialised initialised initialised
encryption encryption encryption encryption encryption encryption encryption encryption
EVP_CipherUpdate updated updated
EVP_DecryptUpdate updated updated
decryption decryption
EVP_EncryptUpdate updated updated
encryption encryption
EVP_CipherFinal finaled
EVP_DecryptFinal finaled
EVP_EncryptFinal finaled
EVP_CIPHER_CTX_free freed freed freed freed freed freed freed freed freed
EVP_CIPHER_CTX_reset newed newed newed newed newed newed newed newed
EVP_CIPHER_CTX_get_params newed initialised updated initialised updated initialised updated
decryption decryption encryption encryption
EVP_CIPHER_CTX_set_params newed initialised updated initialised updated initialised updated
decryption decryption encryption encryption
EVP_CIPHER_CTX_gettable_params newed initialised updated initialised updated initialised updated
decryption decryption encryption encryption
EVP_CIPHER_CTX_settable_params newed initialised updated initialised updated initialised updated
decryption decryption encryption encryption
=end man
=begin html
<table style="border:1px solid; border-collapse:collapse">
<tr><th style="border:1px solid" align="left">Function Call</th>
<th style="border:1px solid" colspan="10">Current State</th></tr>
<tr><th style="border:1px solid"></th>
<th style="border:1px solid" align="center">start</th>
<th style="border:1px solid" align="center">newed</th>
<th style="border:1px solid" align="center">initialised</th>
<th style="border:1px solid" align="center">updated</th>
<th style="border:1px solid" align="center">finaled</th>
<th style="border:1px solid" align="center">initialised<br>decryption</th>
<th style="border:1px solid" align="center">updated<br>decryption</th>
<th style="border:1px solid" align="center">initialised<br>encryption</th>
<th style="border:1px solid" align="center">updated<br>encryption</th>
<th style="border:1px solid" align="center">freed</th></tr>
<tr><th style="border:1px solid" align="left">EVP_CIPHER_CTX_new</th>
<td style="border:1px solid" align="center">newed</td>
<td style="border:1px solid" align="center"></td>
<td style="border:1px solid" align="center"></td>
<td style="border:1px solid" align="center"></td>
<td style="border:1px solid" align="center"></td>
<td style="border:1px solid" align="center"></td>
<td style="border:1px solid" align="center"></td>
<td style="border:1px solid" align="center"></td>
<td style="border:1px solid" align="center"></td>
<td style="border:1px solid" align="center"></td></tr>
<tr><th style="border:1px solid" align="left">EVP_CipherInit</th>
<td style="border:1px solid" align="center"></td>
<td style="border:1px solid" align="center">initialised</td>
<td style="border:1px solid" align="center">initialised</td>
<td style="border:1px solid" align="center">initialised</td>
<td style="border:1px solid" align="center">initialised</td>
<td style="border:1px solid" align="center">initialised</td>
<td style="border:1px solid" align="center">initialised</td>
<td style="border:1px solid" align="center">initialised</td>
<td style="border:1px solid" align="center">initialised</td>
<td style="border:1px solid" align="center"></td></tr>
<tr><th style="border:1px solid" align="left">EVP_DecryptInit</th>
<td style="border:1px solid" align="center"></td>
<td style="border:1px solid" align="center">initialised<br>decryption</td>
<td style="border:1px solid" align="center">initialised<br>decryption</td>
<td style="border:1px solid" align="center">initialised<br>decryption</td>
<td style="border:1px solid" align="center">initialised<br>decryption</td>
<td style="border:1px solid" align="center">initialised<br>decryption</td>
<td style="border:1px solid" align="center">initialised<br>decryption</td>
<td style="border:1px solid" align="center">initialised<br>decryption</td>
<td style="border:1px solid" align="center">initialised<br>decryption</td>
<td style="border:1px solid" align="center"></td></tr>
<tr><th style="border:1px solid" align="left">EVP_EncryptInit</th>
<td style="border:1px solid" align="center"></td>
<td style="border:1px solid" align="center">initialised<br>encryption</td>
<td style="border:1px solid" align="center">initialised<br>encryption</td>
<td style="border:1px solid" align="center">initialised<br>encryption</td>
<td style="border:1px solid" align="center">initialised<br>encryption</td>
<td style="border:1px solid" align="center">initialised<br>encryption</td>
<td style="border:1px solid" align="center">initialised<br>encryption</td>
<td style="border:1px solid" align="center">initialised<br>encryption</td>
<td style="border:1px solid" align="center">initialised<br>encryption</td>
<td style="border:1px solid" align="center"></td></tr>
<tr><th style="border:1px solid" align="left">EVP_CipherUpdate</th>
<td style="border:1px solid" align="center"></td>
<td style="border:1px solid" align="center"></td>
<td style="border:1px solid" align="center">updated</td>
<td style="border:1px solid" align="center">updated</td>
<td style="border:1px solid" align="center"></td>
<td style="border:1px solid" align="center"></td>
<td style="border:1px solid" align="center"></td>
<td style="border:1px solid" align="center"></td>
<td style="border:1px solid" align="center"></td>
<td style="border:1px solid" align="center"></td></tr>
<tr><th style="border:1px solid" align="left">EVP_DecryptUpdate</th>
<td style="border:1px solid" align="center"></td>
<td style="border:1px solid" align="center"></td>
<td style="border:1px solid" align="center"></td>
<td style="border:1px solid" align="center"></td>
<td style="border:1px solid" align="center"></td>
<td style="border:1px solid" align="center">updated<br>decryption</td>
<td style="border:1px solid" align="center">updated<br>decryption</td>
<td style="border:1px solid" align="center"></td>
<td style="border:1px solid" align="center"></td>
<td style="border:1px solid" align="center"></td></tr>
<tr><th style="border:1px solid" align="left">EVP_EncryptUpdate</th>
<td style="border:1px solid" align="center"></td>
<td style="border:1px solid" align="center"></td>
<td style="border:1px solid" align="center"></td>
<td style="border:1px solid" align="center"></td>
<td style="border:1px solid" align="center"></td>
<td style="border:1px solid" align="center"></td>
<td style="border:1px solid" align="center"></td>
<td style="border:1px solid" align="center">updated<br>encryption</td>
<td style="border:1px solid" align="center">updated<br>encryption</td>
<td style="border:1px solid" align="center"></td></tr>
<tr><th style="border:1px solid" align="left">EVP_CipherFinal</th>
<td style="border:1px solid" align="center"></td>
<td style="border:1px solid" align="center"></td>
<td style="border:1px solid" align="center"></td>
<td style="border:1px solid" align="center">finaled</td>
<td style="border:1px solid" align="center"></td>
<td style="border:1px solid" align="center"></td>
<td style="border:1px solid" align="center"></td>
<td style="border:1px solid" align="center"></td>
<td style="border:1px solid" align="center"></td>
<td style="border:1px solid" align="center"></td></tr>
<tr><th style="border:1px solid" align="left">EVP_DecryptFinal</th>
<td style="border:1px solid" align="center"></td>
<td style="border:1px solid" align="center"></td>
<td style="border:1px solid" align="center"></td>
<td style="border:1px solid" align="center"></td>
<td style="border:1px solid" align="center"></td>
<td style="border:1px solid" align="center"></td>
<td style="border:1px solid" align="center">finaled<br>decryption</td>
<td style="border:1px solid" align="center"></td>
<td style="border:1px solid" align="center"></td>
<td style="border:1px solid" align="center"></td></tr>
<tr><th style="border:1px solid" align="left">EVP_EncryptFinal</th>
<td style="border:1px solid" align="center"></td>
<td style="border:1px solid" align="center"></td>
<td style="border:1px solid" align="center"></td>
<td style="border:1px solid" align="center"></td>
<td style="border:1px solid" align="center"></td>
<td style="border:1px solid" align="center"></td>
<td style="border:1px solid" align="center"></td>
<td style="border:1px solid" align="center"></td>
<td style="border:1px solid" align="center">finaled<br>decryption</td>
<td style="border:1px solid" align="center"></td></tr>
<tr><th style="border:1px solid" align="left">EVP_CIPHER_CTX_free</th>
<td style="border:1px solid" align="center">freed</td>
<td style="border:1px solid" align="center">freed</td>
<td style="border:1px solid" align="center">freed</td>
<td style="border:1px solid" align="center">freed</td>
<td style="border:1px solid" align="center">freed</td>
<td style="border:1px solid" align="center">freed</td>
<td style="border:1px solid" align="center">freed</td>
<td style="border:1px solid" align="center">freed</td>
<td style="border:1px solid" align="center">freed</td>
<td style="border:1px solid" align="center"></td></tr>
<tr><th style="border:1px solid" align="left">EVP_CIPHER_CTX_reset</th>
<td style="border:1px solid" align="center"></td>
<td style="border:1px solid" align="center"></td>
<td style="border:1px solid" align="center">newed</td>
<td style="border:1px solid" align="center">newed</td>
<td style="border:1px solid" align="center">newed</td>
<td style="border:1px solid" align="center">newed</td>
<td style="border:1px solid" align="center">newed</td>
<td style="border:1px solid" align="center">newed</td>
<td style="border:1px solid" align="center">newed</td>
<td style="border:1px solid" align="center"></td></tr>
<tr><th style="border:1px solid" align="left">EVP_CIPHER_CTX_get_params</th>
<td style="border:1px solid" align="center"></td>
<td style="border:1px solid" align="center">newed</td>
<td style="border:1px solid" align="center">initialised</td>
<td style="border:1px solid" align="center">updated</td>
<td style="border:1px solid" align="center"></td>
<td style="border:1px solid" align="center">initialised<br>decryption</td>
<td style="border:1px solid" align="center">updated<br>decryption</td>
<td style="border:1px solid" align="center">initialised<br>encryption</td>
<td style="border:1px solid" align="center">updated<br>encryption</td>
<td style="border:1px solid" align="center"></td></tr>
<tr><th style="border:1px solid" align="left">EVP_CIPHER_CTX_set_params</th>
<td style="border:1px solid" align="center"></td>
<td style="border:1px solid" align="center">newed</td>
<td style="border:1px solid" align="center">initialised</td>
<td style="border:1px solid" align="center">updated</td>
<td style="border:1px solid" align="center"></td>
<td style="border:1px solid" align="center">initialised<br>decryption</td>
<td style="border:1px solid" align="center">updated<br>decryption</td>
<td style="border:1px solid" align="center">initialised<br>encryption</td>
<td style="border:1px solid" align="center">updated<br>encryption</td>
<td style="border:1px solid" align="center"></td></tr>
<tr><th style="border:1px solid" align="left">EVP_CIPHER_CTX_gettable_params</th>
<td style="border:1px solid" align="center"></td>
<td style="border:1px solid" align="center">newed</td>
<td style="border:1px solid" align="center">initialised</td>
<td style="border:1px solid" align="center">updated</td>
<td style="border:1px solid" align="center"></td>
<td style="border:1px solid" align="center">initialised<br>decryption</td>
<td style="border:1px solid" align="center">updated<br>decryption</td>
<td style="border:1px solid" align="center">initialised<br>encryption</td>
<td style="border:1px solid" align="center">updated<br>encryption</td>
<td style="border:1px solid" align="center"></td></tr>
<tr><th style="border:1px solid" align="left">EVP_CIPHER_CTX_settable_params</th>
<td style="border:1px solid" align="center"></td>
<td style="border:1px solid" align="center">newed</td>
<td style="border:1px solid" align="center">initialised</td>
<td style="border:1px solid" align="center">updated</td>
<td style="border:1px solid" align="center"></td>
<td style="border:1px solid" align="center">initialised<br>decryption</td>
<td style="border:1px solid" align="center">updated<br>decryption</td>
<td style="border:1px solid" align="center">initialised<br>encryption</td>
<td style="border:1px solid" align="center">updated<br>encryption</td>
<td style="border:1px solid" align="center"></td></tr>
</table>
=end html
=head1 NOTES
At some point the EVP layer will begin enforcing the transitions described
herein.
=head1 SEE ALSO
L<provider-cipher(7)>, L<EVP_EncryptInit(3)>
=head1 COPYRIGHT
Copyright 2021 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
L<https://www.openssl.org/source/license.html>.
=cut
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