EVP_SIGNATURE(3SSL)

📦

version 4.0.3 · 2 versions

4.0.3 · ubuntu stonking (latest)
4.1.0 · nixos 26.05, nixpkgs unstable

💖 EVP_SIGNATURE(3SSL) — the signature algorithm object page, bestie edition 💖

Okay so this is the OpenSSL manual page for all the EVP_SIGNATURE functions, from the 3SSL section. It's lowkey one of those "plumbing" pages, but it's iconic plumbing and you're gonna get it. 🫶

✨ NAME ✨

EVP_SIGNATURE, EVP_SIGNATURE_fetch, EVP_SIGNATURE_free, EVP_SIGNATURE_up_ref, EVP_SIGNATURE_is_a, EVP_SIGNATURE_get0_provider, EVP_SIGNATURE_do_all_provided, EVP_SIGNATURE_names_do_all, EVP_SIGNATURE_get0_name, EVP_SIGNATURE_get0_description, EVP_SIGNATURE_gettable_ctx_params, EVP_SIGNATURE_settable_ctx_params, EVP_SIGNATURE_has_message_update

— they're all here for one job: managing EVP_SIGNATURE algorithm objects. That's it, that's the whole assignment. 💅

📜 SYNOPSIS 📜

#include <openssl/evp.h>

typedef struct evp_signature_st EVP_SIGNATURE;

EVP_SIGNATURE *EVP_SIGNATURE_fetch(OSSL_LIB_CTX *ctx, const char *algorithm,
                                   const char *properties);
void EVP_SIGNATURE_free(EVP_SIGNATURE *signature);
int EVP_SIGNATURE_up_ref(EVP_SIGNATURE *signature);
const char *EVP_SIGNATURE_get0_name(const EVP_SIGNATURE *signature);
int EVP_SIGNATURE_is_a(const EVP_SIGNATURE *signature, const char *name);
OSSL_PROVIDER *EVP_SIGNATURE_get0_provider(const EVP_SIGNATURE *signature);
void EVP_SIGNATURE_do_all_provided(OSSL_LIB_CTX *libctx,
                                   void (*fn)(EVP_SIGNATURE *signature,
                                              void *arg),
                                   void *arg);
int EVP_SIGNATURE_names_do_all(const EVP_SIGNATURE *signature,
                               void (*fn)(const char *name, void *data),
                               void *data);
const char *EVP_SIGNATURE_get0_name(const EVP_SIGNATURE *signature);
const char *EVP_SIGNATURE_get0_description(const EVP_SIGNATURE *signature);
const OSSL_PARAM *EVP_SIGNATURE_gettable_ctx_params(const EVP_SIGNATURE *sig);
const OSSL_PARAM *EVP_SIGNATURE_settable_ctx_params(const EVP_SIGNATURE *sig);
int EVP_SIGNATURE_has_message_update(const EVP_SIGNATURE *sig);

(yes EVP_SIGNATURE_get0_name really does show up twice in there, that's not a typo on my end, the original did that too 💀)

💅 DESCRIPTION 💅

EVP_SIGNATURE_fetch() fetches the implementation for the given algorithm from any provider offering it, within the criteria given by the properties. The algorithm is gonna be one of those offering functions for doing signature related tasks, like signing and verifying. Wanna know more about the whole fetching thing? See "ALGORITHM FETCHING" in crypto(7) for further information.

The returned value must eventually be freed with EVP_SIGNATURE_free(). Not optional, bestie, free your stuff. 🧚

EVP_SIGNATURE_free() — decrements the reference count for the EVP_SIGNATURE structure. Typically you got this structure from an earlier call to EVP_SIGNATURE_fetch(). If the reference count drops to 0 then the structure is freed. If the argument is NULL, nothing is done. (Peaceful. Respectful. We love a no-op that doesn't crash. 😌)
EVP_SIGNATURE_up_ref() — increments the reference count for an EVP_SIGNATURE structure. Keeping it alive, main character energy 👑
EVP_SIGNATURE_is_a() — returns 1 if signature is an implementation of an algorithm that's identifiable with name, otherwise 0. Vibe check: passed or failed, no in-between.
EVP_SIGNATURE_get0_provider() — returns the provider that signature was fetched from. Basically "where did you come from, gorgeous?" 🌸
EVP_SIGNATURE_do_all_provided() — traverses all SIGNATURE implemented by all activated providers in the given library context libctx, and for each of the implementations, calls the given function fn with the implementation method and the given arg as argument. It's giving roll call. 📋
EVP_SIGNATURE_get0_name() — returns the algorithm name from the provided implementation for the given signature. Careful though: the signature may have multiple synonyms associated with it. In that case the first name from the algorithm definition is returned. Ownership of the returned string is retained by the signature object and should not be freed by the caller. 🙈
EVP_SIGNATURE_names_do_all() — traverses all names for signature, and calls fn with each name and data. Every alias gets its moment. ✨
EVP_SIGNATURE_get0_description() — returns a description of the signature, meant for display and human consumption. The description is at the discretion of the signature implementation. (So whatever it says is literally whatever the implementer decided to put there, no promises beyond that. 🤷)
EVP_SIGNATURE_gettable_ctx_params() and EVP_SIGNATURE_settable_ctx_params() — return a constant OSSL_PARAM(3) array that describes the names and types of key parameters that can be retrieved or set by a signature algorithm using EVP_PKEY_CTX_get_params(3) and EVP_PKEY_CTX_set_params(3).
EVP_SIGNATURE_has_message_update() — checks whether EVP_PKEY_sign_message_update() and EVP_PKEY_verify_message_update() are both supported. Both or nothing, it's a package deal. 🎀

🎀 RETURN VALUES 🎀

EVP_SIGNATURE_fetch() returns a pointer to an EVP_SIGNATURE for success or NULL for failure.
EVP_SIGNATURE_up_ref() returns 1 for success or 0 otherwise.
EVP_SIGNATURE_names_do_all() returns 1 if the callback was called for all names. A return value of 0 means that the callback was not called for any names.
EVP_SIGNATURE_gettable_ctx_params() and EVP_SIGNATURE_settable_ctx_params() return a constant OSSL_PARAM(3) array or NULL on error.
EVP_SIGNATURE_has_message_update() returns 1 if EVP_PKEY_sign_message_update() and EVP_PKEY_verify_message_update() are both supported, 0 otherwise.

👀 SEE ALSO 👀

"ALGORITHM FETCHING" in crypto(7), OSSL_PROVIDER(3)

🕰️ HISTORY 🕰️

Most functions described here were added in OpenSSL 3.0, except for EVP_PKEY_verify_message_update(), which was added in OpenSSL 4.0. (A little generational divide, we respect it. 🌈)

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 <https://www.openssl.org/source/license.html>.

That's the whole page, bestie — every flag, every function, every return value, all of it. Go forth and manage your signature algorithm objects responsibly. 💖

This was EVP_SIGNATURE(3SSL) from OpenSSL 4.0.3, dated 2026-09-29. Slay, stay signed, and remember: if you fetched it, you free it. ✨🦋

📦 where this page comes from

ubuntu stonking: libssl-doc 4.0.3-1ubuntu1 · Apache-2.0
💖 girlified by deepseek-ai/DeepSeek-V4.1-Flash on 2026-11-03: a language model's rewrite of the original, under its terms