EVP_PKEY_ASN1_METHOD(3ossl)
🌸 NAME 🌸
okay bestie, welcome to the EVP_PKEY_ASN1_METHOD(3ossl) page — the OpenSSL manual page that's literally all about manipulating and registering the EVP_PKEY_ASN1_METHOD structure. no cap, this is the backstage pass for the ASN.1 method machinery, and the whole squad is listed right here:
EVP_PKEY_ASN1_METHODEVP_PKEY_asn1_newEVP_PKEY_asn1_copyEVP_PKEY_asn1_freeEVP_PKEY_asn1_add0EVP_PKEY_asn1_add_aliasEVP_PKEY_asn1_set_publicEVP_PKEY_asn1_set_privateEVP_PKEY_asn1_set_paramEVP_PKEY_asn1_set_freeEVP_PKEY_asn1_set_ctrlEVP_PKEY_asn1_set_itemEVP_PKEY_asn1_set_siginfEVP_PKEY_asn1_set_checkEVP_PKEY_asn1_set_public_checkEVP_PKEY_asn1_set_param_checkEVP_PKEY_asn1_set_security_bitsEVP_PKEY_asn1_set_set_priv_keyEVP_PKEY_asn1_set_set_pub_keyEVP_PKEY_asn1_set_get_priv_keyEVP_PKEY_asn1_set_get_pub_keyEVP_PKEY_get0_asn1
that's the whole cast, and yes, they all matter — even the little set_ double-name ones, iykyk 💅
✨ SYNOPSIS ✨
here's the exact shape of it, bestie — do not retype this from memory, just vibe with the signatures:
#include <openssl/evp.h>
typedef struct evp_pkey_asn1_method_st EVP_PKEY_ASN1_METHOD;
EVP_PKEY_ASN1_METHOD *EVP_PKEY_asn1_new(int id, int flags,
const char *pem_str,
const char *info);
void EVP_PKEY_asn1_copy(EVP_PKEY_ASN1_METHOD *dst,
const EVP_PKEY_ASN1_METHOD *src);
void EVP_PKEY_asn1_free(EVP_PKEY_ASN1_METHOD *ameth);
int EVP_PKEY_asn1_add0(const EVP_PKEY_ASN1_METHOD *ameth);
int EVP_PKEY_asn1_add_alias(int to, int from);
void EVP_PKEY_asn1_set_public(EVP_PKEY_ASN1_METHOD *ameth,
int (*pub_decode) (EVP_PKEY *pk,
const X509_PUBKEY *pub),
int (*pub_encode) (X509_PUBKEY *pub,
const EVP_PKEY *pk),
int (*pub_cmp) (const EVP_PKEY *a,
const EVP_PKEY *b),
int (*pub_print) (BIO *out,
const EVP_PKEY *pkey,
int indent, ASN1_PCTX *pctx),
int (*pkey_size) (const EVP_PKEY *pk),
int (*pkey_bits) (const EVP_PKEY *pk));
void EVP_PKEY_asn1_set_private(EVP_PKEY_ASN1_METHOD *ameth,
int (*priv_decode) (EVP_PKEY *pk,
const PKCS8_PRIV_KEY_INFO
*p8inf),
int (*priv_encode) (PKCS8_PRIV_KEY_INFO *p8,
const EVP_PKEY *pk),
int (*priv_print) (BIO *out,
const EVP_PKEY *pkey,
int indent,
ASN1_PCTX *pctx));
void EVP_PKEY_asn1_set_param(EVP_PKEY_ASN1_METHOD *ameth,
int (*param_decode) (EVP_PKEY *pkey,
const unsigned char **pder,
int derlen),
int (*param_encode) (const EVP_PKEY *pkey,
unsigned char **pder),
int (*param_missing) (const EVP_PKEY *pk),
int (*param_copy) (EVP_PKEY *to,
const EVP_PKEY *from),
int (*param_cmp) (const EVP_PKEY *a,
const EVP_PKEY *b),
int (*param_print) (BIO *out,
const EVP_PKEY *pkey,
int indent,
ASN1_PCTX *pctx));
void EVP_PKEY_asn1_set_free(EVP_PKEY_ASN1_METHOD *ameth,
void (*pkey_free) (EVP_PKEY *pkey));
void EVP_PKEY_asn1_set_ctrl(EVP_PKEY_ASN1_METHOD *ameth,
int (*pkey_ctrl) (EVP_PKEY *pkey, int op,
long arg1, void *arg2));
void EVP_PKEY_asn1_set_item(EVP_PKEY_ASN1_METHOD *ameth,
int (*item_verify) (EVP_MD_CTX *ctx,
const ASN1_ITEM *it,
void *asn,
X509_ALGOR *a,
ASN1_BIT_STRING *sig,
EVP_PKEY *pkey),
int (*item_sign) (EVP_MD_CTX *ctx,
const ASN1_ITEM *it,
void *asn,
X509_ALGOR *alg1,
X509_ALGOR *alg2,
ASN1_BIT_STRING *sig));
void EVP_PKEY_asn1_set_siginf(EVP_PKEY_ASN1_METHOD *ameth,
int (*siginf_set) (X509_SIG_INFO *siginf,
const X509_ALGOR *alg,
const ASN1_STRING *sig));
void EVP_PKEY_asn1_set_check(EVP_PKEY_ASN1_METHOD *ameth,
int (*pkey_check) (const EVP_PKEY *pk));
void EVP_PKEY_asn1_set_public_check(EVP_PKEY_ASN1_METHOD *ameth,
int (*pkey_pub_check) (const EVP_PKEY *pk));
void EVP_PKEY_asn1_set_param_check(EVP_PKEY_ASN1_METHOD *ameth,
int (*pkey_param_check) (const EVP_PKEY *pk));
void EVP_PKEY_asn1_set_security_bits(EVP_PKEY_ASN1_METHOD *ameth,
int (*pkey_security_bits) (const EVP_PKEY
*pk));
void EVP_PKEY_asn1_set_set_priv_key(EVP_PKEY_ASN1_METHOD *ameth,
int (*set_priv_key) (EVP_PKEY *pk,
const unsigned char
*priv,
size_t len));
void EVP_PKEY_asn1_set_set_pub_key(EVP_PKEY_ASN1_METHOD *ameth,
int (*set_pub_key) (EVP_PKEY *pk,
const unsigned char *pub,
size_t len));
void EVP_PKEY_asn1_set_get_priv_key(EVP_PKEY_ASN1_METHOD *ameth,
int (*get_priv_key) (const EVP_PKEY *pk,
unsigned char *priv,
size_t *len));
void EVP_PKEY_asn1_set_get_pub_key(EVP_PKEY_ASN1_METHOD *ameth,
int (*get_pub_key) (const EVP_PKEY *pk,
unsigned char *pub,
size_t *len));
const EVP_PKEY_ASN1_METHOD *EVP_PKEY_get0_asn1(const EVP_PKEY *pkey);that's the full signature dump, and it's giving very much "yes, every one of these is a function pointer vibe" 🔥 part 2 is gonna break down what all of this actually means, but the signatures stay exactly like that — periodt.
💖 DESCRIPTION 💖
okay so <pink>EVP_PKEY_ASN1_METHOD</pink> is a structure, and it's basically the whole personality pack for one specific public key algorithm — it holds a set of ASN.1 conversion, printing and information methods. it's giving "algorithm's entire vibe, neatly packaged." 💅
and there are exactly two places where these EVP_PKEY_ASN1_METHOD objects live:
- one is a built-in array — the standard methods for the different algorithms
- the other is a stack of user-defined, application-specific methods, which you can manipulate using
EVP_PKEY_asn1_add0(3)
🌸 Methods 🌸
These methods are the underlying implementations of a particular public key algorithm, as presented by the EVP_PKEY object. no cap, they're the real MVPs.
int (*pub_decode) (EVP_PKEY *pk, const X509_PUBKEY *pub);
int (*pub_encode) (X509_PUBKEY *pub, const EVP_PKEY *pk);
int (*pub_cmp) (const EVP_PKEY *a, const EVP_PKEY *b);
int (*pub_print) (BIO *out, const EVP_PKEY *pkey, int indent,
ASN1_PCTX *pctx);The pub_decode() and pub_encode() methods get called to decode / encode X509_PUBKEY ASN.1 parameters to / from pk. they MUST return 0 on error and 1 on success, periodt. they're called by X509_PUBKEY_get0(3) and X509_PUBKEY_set(3).
The pub_cmp() method is the one that shows up when two public keys need comparing. it MUST return 1 when the keys are equal and 0 otherwise. it's called by EVP_PKEY_eq(3).
The pub_print() method prints a public key in humanly readable text to out, indented by indent spaces. it MUST return 0 on error and 1 on success. it's called by EVP_PKEY_print_public(3). 🎀
int (*priv_decode) (EVP_PKEY *pk, const PKCS8_PRIV_KEY_INFO *p8inf);
int (*priv_encode) (PKCS8_PRIV_KEY_INFO *p8, const EVP_PKEY *pk);
int (*priv_print) (BIO *out, const EVP_PKEY *pkey, int indent,
ASN1_PCTX *pctx);The priv_decode() and priv_encode() methods get called to decode / encode a PKCS8_PRIV_KEY_INFO form private key to / from pk. they MUST return 0 on error and 1 on success. they're called by EVP_PKCS82PKEY(3) and EVP_PKEY2PKCS8(3).
The priv_print() method prints a private key in humanly readable text to out, indented by indent spaces. it MUST return 0 on error and 1 on success. it's called by EVP_PKEY_print_private(3).
int (*pkey_size) (const EVP_PKEY *pk);
int (*pkey_bits) (const EVP_PKEY *pk);
int (*pkey_security_bits) (const EVP_PKEY *pk);The pkey_size() method returns the key size in bytes. it's called by EVP_PKEY_get_size(3).
The pkey_bits() method returns the key size in bits. it's called by EVP_PKEY_get_bits(3).
yes bestie, bytes vs bits — read the unit, don't get caught lacking 😭
int (*param_decode) (EVP_PKEY *pkey,
const unsigned char **pder, int derlen);
int (*param_encode) (const EVP_PKEY *pkey, unsigned char **pder);
int (*param_missing) (const EVP_PKEY *pk);
int (*param_copy) (EVP_PKEY *to, const EVP_PKEY *from);
int (*param_cmp) (const EVP_PKEY *a, const EVP_PKEY *b);
int (*param_print) (BIO *out, const EVP_PKEY *pkey, int indent,
ASN1_PCTX *pctx);The param_decode() and param_encode() methods get called to decode / encode DER formatted parameters to / from pk. they MUST return 0 on error and 1 on success. they're called by PEM_read_bio_Parameters(3) and the file: OSSL_STORE_LOADER(3).
The param_missing() method returns 0 if a key parameter is missing, otherwise 1. it's called by EVP_PKEY_missing_parameters(3).
The param_copy() method copies key parameters from from to to. it MUST return 0 on error and 1 on success. it's called by EVP_PKEY_copy_parameters(3).
The param_cmp() method compares the parameters of keys a and b. it MUST return 1 when the keys are equal, 0 when they're not equal, or a negative number on error. it's called by EVP_PKEY_parameters_eq(3).
The param_print() method prints the private key parameters in humanly readable text to out, indented by indent spaces. it MUST return 0 on error and 1 on success. it's called by EVP_PKEY_print_params(3).
int (*sig_print) (BIO *out,
const X509_ALGOR *sigalg, const ASN1_STRING *sig,
int indent, ASN1_PCTX *pctx);The sig_print() method prints a signature in humanly readable text to out, indented by indent spaces. sigalg contains the exact signature algorithm. and listen — if the signature in sig doesn't correspond to what this method expects, then X509_signature_dump() must be used as a last resort. 🚨 it MUST return 0 on error and 1 on success. it's called by X509_signature_print(3).
void (*pkey_free) (EVP_PKEY *pkey);The pkey_free() method helps with freeing the internals of pkey. it's called by EVP_PKEY_free(3), EVP_PKEY_set_type(3), EVP_PKEY_set_type_str(3) and EVP_PKEY_assign(3).
int (*pkey_ctrl) (EVP_PKEY *pkey, int op, long arg1, void *arg2);The pkey_ctrl() method adds extra algorithm-specific control. it's called by EVP_PKEY_get_default_digest_nid(3), EVP_PKEY_set1_encoded_public_key(3), EVP_PKEY_get1_encoded_public_key(3), PKCS7_SIGNER_INFO_set(3), PKCS7_RECIP_INFO_set(3), ...
the ... is doing a lot of heavy lifting there, but that's literally what the page says, so we're keeping it 🫶
int (*old_priv_decode) (EVP_PKEY *pkey,
const unsigned char **pder, int derlen);
int (*old_priv_encode) (const EVP_PKEY *pkey, unsigned char **pder);The old_priv_decode() and old_priv_encode() methods decode / encode the private key pkey from / to a DER formatted array. these are exclusively used to help decode / encode older (pre PKCS#8) PEM formatted encrypted private keys — like, vintage keys, ok? 🙈 old_priv_decode() MUST return 0 on error and 1 on success. old_priv_encode() MUST return the same kind of values as i2d_PrivateKey(). they're called by d2i_PrivateKey(3) and i2d_PrivateKey(3).
int (*item_verify) (EVP_MD_CTX *ctx, const ASN1_ITEM *it, void *asn,
X509_ALGOR *a, ASN1_BIT_STRING *sig, EVP_PKEY *pkey);
int (*item_sign) (EVP_MD_CTX *ctx, const ASN1_ITEM *it, void *asn,
X509_ALGOR *alg1, X509_ALGOR *alg2,
ASN1_BIT_STRING *sig);The item_sign() and item_verify() methods make it possible to have algorithm-specific signatures, plus algorithm-specific verification of those signatures. iconique behavior honestly. 👑
item_sign() MUST return one of:
<=0— error1—item_sign()did everything, OpenSSL internals just needs to pass the signature length back2—item_sign()did nothing, OpenSSL internal standard routines are expected to continue with the default signature production3—item_sign()set the algorithm identifieralgor1andalgor2, and OpenSSL internals should just sign using those algorithms
item_verify() MUST return one of:
<=0— error1—item_sign()did everything, OpenSSL internals just needs to pass the signature length back2—item_sign()did nothing, OpenSSL internal standard routines are expected to continue with the default signature production
yep, that second list does say item_sign() — we are faithfully relaying the lore, not editing it 💀
item_verify() and item_sign() are called by ASN1_item_verify(3) and ASN1_item_sign(3), and by extension, X509_verify(3), X509_REQ_verify(3), X509_sign(3), X509_REQ_sign(3), ...
int (*siginf_set) (X509_SIG_INFO *siginf, const X509_ALGOR *alg,
const ASN1_STRING *sig);The siginf_set() method is used to set custom X509_SIG_INFO parameters. it MUST return 0 on error, or 1 on success. it's called as part of X509_check_purpose(3), X509_check_ca(3) and X509_check_issued(3).
int (*pkey_check) (const EVP_PKEY *pk);
int (*pkey_public_check) (const EVP_PKEY *pk);
int (*pkey_param_check) (const EVP_PKEY *pk);The pkey_check(), pkey_public_check() and pkey_param_check() methods are used to check the validity of pk for key-pair, public component and parameters respectively. they MUST return 0 for an invalid key, or 1 for a valid key. they are called by EVP_PKEY_check(3), EVP_PKEY_public_check(3) and EVP_PKEY_param_check(3) respectively. vibe check, but for keys. ✅
int (*set_priv_key) (EVP_PKEY *pk, const unsigned char *priv, size_t len);
int (*set_pub_key) (EVP_PKEY *pk, const unsigned char *pub, size_t len);The set_priv_key() and set_pub_key() methods are used to set the raw private and public key data for an EVP_PKEY. they MUST return 0 on error, or 1 on success. they are called by EVP_PKEY_new_raw_private_key(3) and EVP_PKEY_new_raw_public_key(3) respectively.
size_t (*dirty) (const EVP_PKEY *pk);
void *(*export_to) (const EVP_PKEY *pk, EVP_KEYMGMT *keymgmt);dirty_cnt() returns the internal key's dirty count. this can be used to synchronise different copies of the same keys. 🔄
The export_to() method exports the key material from the given key to a provider, through the EVP_KEYMGMT(3) interface — but only if that provider supports importing key material, iykyk.
✨ Functions ✨
EVP_PKEY_asn1_new() creates and returns a new EVP_PKEY_ASN1_METHOD object, and associates the given id, flags, pem_str and info. id is a NID, pem_str is the PEM type string, and info is a descriptive string. the following flags are supported:
🦋 ASN1_PKEY_SIGPARAM_NULL
If ASN1_PKEY_SIGPARAM_NULL is set, then the signature algorithm parameters are given the type V_ASN1_NULL by default — otherwise they'll be given the type V_ASN1_UNDEF (i.e. the parameter is omitted). see X509_ALGOR_set0(3) for more information. 🌈
EVP_PKEY_asn1_copy() copies an EVP_PKEY_ASN1_METHOD object from src to dst. heads up bestie: this function is not thread safe, it's recommended to only use this when initializing the application.
EVP_PKEY_asn1_free() frees an existing EVP_PKEY_ASN1_METHOD pointed to by ameth. if the argument is NULL, nothing is done. no drama, no crash. 🎀
EVP_PKEY_asn1_add0() adds ameth to the user defined stack of methods, unless another EVP_PKEY_ASN1_METHOD with the same NID is already there. this function is not thread safe, it's recommended to only use this when initializing the application.
EVP_PKEY_asn1_add_alias() creates an alias with the NID to for the EVP_PKEY_ASN1_METHOD with NID from, unless another EVP_PKEY_ASN1_METHOD with the same NID is already added. this function is not thread safe, it's recommended to only use this when initializing the application.
EVP_PKEY_asn1_set_public(), EVP_PKEY_asn1_set_private(), EVP_PKEY_asn1_set_param(), EVP_PKEY_asn1_set_free(), EVP_PKEY_asn1_set_ctrl(), EVP_PKEY_asn1_set_item(), EVP_PKEY_asn1_set_siginf(), EVP_PKEY_asn1_set_check(), EVP_PKEY_asn1_set_public_check(), EVP_PKEY_asn1_set_param_check(), EVP_PKEY_asn1_set_security_bits(), EVP_PKEY_asn1_set_set_priv_key(), EVP_PKEY_asn1_set_set_pub_key(), EVP_PKEY_asn1_set_get_priv_key() and EVP_PKEY_asn1_set_get_pub_key() set the diverse methods of the given EVP_PKEY_ASN1_METHOD object. yes, that's a whole lotta setters — collect them all 💅
EVP_PKEY_get0_asn1() finds the EVP_PKEY_ASN1_METHOD associated with the key pkey.
🌟 RETURN VALUES 🌟
EVP_PKEY_asn1_new() returns NULL on error, or a pointer to an EVP_PKEY_ASN1_METHOD object otherwise.
EVP_PKEY_asn1_add0() and EVP_PKEY_asn1_add_alias() return 0 on error, or 1 on success.
EVP_PKEY_get0_asn1() returns NULL on error, or a pointer to a constant EVP_PKEY_ASN1_METHOD object otherwise. 🫶
✨ HISTORY ✨
okay so tiny lil glow-up alert 🫶 — the signature of the pub_decode functional argument of EVP_PKEY_asn1_set_public() has changed in OpenSSL 3.0, so its pub parameter is now constified. that’s literally the whole history note, bestie 💅✨
💖 COPYRIGHT 💖
Copyright 2017-2024 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 <https://www.openssl.org/source/license.html>. 💖
bestie pls respect the license, it’s giving legal main character energy 👑 no cap.
and that’s the whole manual page, mwah 💋 — OpenSSL 3.5.6, dated 2026-04-07, signing off 🎀✨
📦 where this page comes from
- freebsd 15.1: base 15.1
- 💖 girlified by deepseek-ai/DeepSeek-V4.1-Flash-1017 on : a language model's rewrite of the original, under its terms