EVP_PKEY_ASN1_GET_COUNT(3)

💅 EVP_PKEY_ASN1_GET_COUNT(3) — like, the whole ASN.1 method roster

okay so bestie, this is a page from the Library Functions Manual and it's all about the libcrypto girlies who keep track of public key ASN.1 methods — the little descriptor objects (EVP_PKEY_ASN1_METHOD, aka ameth) that tell OpenSSL how each key type does its ASN.1 thing. We're literally just enumerating them, looking them up, and peeking inside. No cap, that's the whole vibe. 🦋

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✨ NAME ✨

EVP_PKEY_asn1_get_count, EVP_PKEY_asn1_get0, EVP_PKEY_get0_asn1, EVP_PKEY_asn1_find, EVP_PKEY_asn1_find_str, EVP_PKEY_asn1_get0_info — enumerate public key ASN.1 methods 🎀

🌸 SYNOPSIS 🌸

library “libcrypto”

#include <openssl/evp.h>

int
EVP_PKEY_asn1_get_count(void);

const EVP_PKEY_ASN1_METHOD *
EVP_PKEY_asn1_get0(int idx);

const EVP_PKEY_ASN1_METHOD *
EVP_PKEY_get0_asn1(const EVP_PKEY *pkey);

const EVP_PKEY_ASN1_METHOD *
EVP_PKEY_asn1_find(ENGINE **engine, int type);

const EVP_PKEY_ASN1_METHOD *
EVP_PKEY_asn1_find_str(ENGINE **engine, const char *str, int len);

int
EVP_PKEY_asn1_get0_info(int *ppkey_id, int *pkey_base_id,
    int *ppkey_flags, const char **pinfo, const char **ppem_str,
    const EVP_PKEY_ASN1_METHOD *ameth);

💖 DESCRIPTION 💖

So here's the tea on each one, mwah:

• EVP_PKEY_asn1_get_count() — returns the number of public key ASN.1 methods available. Like a headcount for the group chat. 👑
• EVP_PKEY_asn1_get0() — returns the public key ASN.1 method at index idx. Btw the value of idx must be in the range from zero to EVP_PKEY_asn1_get_count() - 1. Stay in your lane, bestie, or it's not gonna go how you want. 🙈
• EVP_PKEY_asn1_find() — looks up the method with NID type, which can be any of the values that EVP_PKEY_base_id(3) and EVP_PKEY_id(3) may return. And listen: if engine is not NULL, then *engine is set to NULL. That's it, that's the whole engine situation. 🫶
• EVP_PKEY_asn1_find_str() — looks up the method with the PEM type string given by the first len bytes of str. If len is -1, the strlen(3) of str is used instead (convenient, honestly 💅). The PEM type strings supported by default are listed in the EVP_PKEY_base_id(3) manual page — go look, iykyk. Just like EVP_PKEY_asn1_find(), if engine is not NULL, *engine is set to NULL. Same energy. ✨
• EVP_PKEY_asn1_get0_info() — retrieves the public key ID as returned by EVP_PKEY_id(3), the base public key ID as returned by EVP_PKEY_base_id(3) (both NIDs, fyi), any flags, and internal pointers owned by ameth pointing to its method description string and its PEM type string. It's giving "tell me everything about yourself." 🔥

🎀 the flags bits 🎀

The following flags bits can occur, OR'ed together in *ppkey_flags:

• ASN1_PKEY_ALIAS — this ameth object serves as an alias for another EVP_PKEY_ASN1_METHOD object and will never be returned from EVP_PKEY_asn1_find() or EVP_PKEY_asn1_find_str(). It's the understudy, not the main character. 💀
• ASN1_PKEY_DYNAMIC — this flag is unused. It could formerly be used to mark an ameth object as dynamically allocated. So yeah, retired icon, we still respect it. 🌈
• ASN1_PKEY_SIGPARAM_NULL — okay this one's a little more involved, stay with me: if the signing ctx uses an EVP_PKEY private key associated with this ameth, it instructs ASN1_item_sign_ctx(3) to use a parameter type of V_ASN1_NULL instead of the default V_ASN1_UNDEF when encoding the ASN.1 AlgorithmIdentifier objects with X509_ALGOR_set0(3). In particular, this is used for EVP_PKEY_RSA. Slay, RSA, we see you. 👑

🌟 RETURN VALUES 🌟

• EVP_PKEY_asn1_get_count() returns the number of available public key methods.
• EVP_PKEY_asn1_get0() returns a public key method or NULL if idx is out of range.
• EVP_PKEY_get0_asn1() returns the public key method used by pkey.
• EVP_PKEY_asn1_find() and EVP_PKEY_asn1_find_str() return a matching public key method or NULL if no match is found.
• EVP_PKEY_asn1_get0_info() returns 1 on success or 0 on failure.

ngl, NULL shows up a lot in these return values. That's not a bug, that's just what "didn't find it" looks like. 😭

🦋 SEE ALSO 🦋

EVP_PKEY_base_id(3), EVP_PKEY_new(3)

⭐ HISTORY ⭐

These functions first appeared in OpenSSL 1.0.0 and have been available since OpenBSD 4.9. Vintage but make it iconic. 💜

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and that's the whole page, bestie — sourced from Debian, dated June 8, 2025, filed under EVP_PKEY_ASN1_GET_COUNT(3). go forth and enumerate responsibly 🧚‍♀️💖