OpenSSL_add_all_algorithms, OpenSSL_add_all_ciphers, OpenSSL_add_all_digests — add algorithms to internal table
OpenSSL keeps an internal table of digest algorithms and ciphers.
It uses this table to lookup ciphers via functions such as EVP_get_cipher_byname().
OpenSSL_add_all_digests() adds all digest algorithms to the
OpenSSL_add_all_algorithms() adds all algorithms to the table
(digests and ciphers).
OpenSSL_add_all_ciphers() adds all encryption algorithms to
the table including password based encryption algorithms.
EVP_cleanup() removes all ciphers and digests from the table.
None of the functions return a value.
A typical application will will call OpenSSL_add_all_algorithms()
initially and EVP_cleanup() before exiting.
An application does not need to add algorithms to use them
explicitly, for example by EVP_sha1(). It just needs to add them
if it (or any of the functions it calls) needs to lookup algorithms.
The cipher and digest lookup functions are used in many parts
of the library. If the table is not initialized several functions
will misbehave and complain they cannot find algorithms. This includes
the PEM, PKCS#12, SSL and S/MIME libraries. This is a common query
in the OpenSSL mailing lists.
Calling OpenSSL_add_all_algorithms() links in all algorithms:
as a result a statically linked executable can be quite large. If
this is important it is possible to just add the required ciphers
Although the functions do not return error codes it is possible
for them to fail. This will only happen as a result of a memory
allocation failure so this is not too much of a problem in practice.
evp(3), EVP_DigestInit(3), EVP_EncryptInit(3)