OpenSSL_add_all_algorithms, OpenSSL_add_all_ciphers, OpenSSL_add_all_digests, EVP_cleanup - add algorithms to internal table
# if OPENSSL_API_COMPAT < 0x10100000L void OpenSSL_add_all_algorithms(void); void OpenSSL_add_all_ciphers(void); void OpenSSL_add_all_digests(void); void EVP_cleanup(void) # endif
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(). In OpenSSL versions prior to 1.1.0 these functions initialised and de-initialised this table. From OpenSSL 1.1.0 they are deprecated. No explicit initialisation or de-initialisation is required. See OPENSSL_init_crypto(3) for further information.
OpenSSL_add_all_digests() adds all digest algorithms to the table.
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.
In versions prior to 1.1.0 EVP_cleanup() removed all ciphers and digests from the table. It no longer has any effect in OpenSSL 1.1.0.
None of the functions return a value.
A typical application 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 and digests.
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.
The OpenSSL_add_all_algorithms(), OpenSSL_add_all_ciphers(), OpenSSL_add_all_digests(), and EVP_cleanup(), functions were deprecated in OpenSSL 1.1.0 by OPENSSL_init_crypto().
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