ASN1_TYPE_GET(3ossl)

💅 ASN1_TYPE_GET(3ossl) — OpenSSL ASN1_TYPE utility functions ✨

🌸 NAME 🌸

Okay bestie, this whole page is about the ASN1_TYPE utility functions, and they are: ASN1_TYPE_get, ASN1_TYPE_set, ASN1_TYPE_set1, ASN1_TYPE_cmp, ASN1_TYPE_unpack_sequence, and ASN1_TYPE_pack_sequence. That’s the squad. 🫶

✨ SYNOPSIS ✨

#include <openssl/asn1.h>

int ASN1_TYPE_get(const ASN1_TYPE *a);
void ASN1_TYPE_set(ASN1_TYPE *a, int type, void *value);
int ASN1_TYPE_set1(ASN1_TYPE *a, int type, const void *value);
int ASN1_TYPE_cmp(const ASN1_TYPE *a, const ASN1_TYPE *b);

void *ASN1_TYPE_unpack_sequence(const ASN1_ITEM *it, const ASN1_TYPE *t);
ASN1_TYPE *ASN1_TYPE_pack_sequence(const ASN1_ITEM *it, void *s,
                                   ASN1_TYPE **t);

🌈 DESCRIPTION 🌈

These functions let you manipulate an ASN1_TYPE structure. The ASN1_TYPE structure can hold any ASN.1 type or constructed type — like a SEQUENCE — and it’s effectively equivalent to the ASN.1 ANY type. Iconic little container, honestly. 🎀

• ASN1_TYPE_get() — returns the type of a, or 0 if it fails. Vibe check on the type, basically.
• ASN1_TYPE_set() — sets the value of a to type and value. It uses the pointer value internally, so you must not free it up after the call. Do not touch that pointer afterward, bestie. 🙈
• ASN1_TYPE_set1() — sets the value of a to type, using a copy of value. So this one does the copying for you. Slay.
• ASN1_TYPE_cmp() — compares ASN.1 types a and b and returns 0 if they are identical and nonzero otherwise. Equal means 0 here, which is giving reverse logic, but that’s C for you. 💀
• ASN1_TYPE_unpack_sequence() — attempts to parse the SEQUENCE present in t using the ASN.1 structure it. If successful, it returns a pointer to the ASN.1 structure corresponding to it, which must be freed by the caller. If it fails, it returns NULL. Free it, okay? That’s the rule. 🧚
• ASN1_TYPE_pack_sequence() — attempts to encode the ASN.1 structure s corresponding to it into an ASN1_TYPE. If successful, the encoded ASN1_TYPE is returned. If t and *t are not NULL, the encoded type is written to t, overwriting any existing data. If t is not NULL but *t is NULL, the returned ASN1_TYPE is written to *t. Pointer-to-pointer behavior, main character energy. 🔥

🦋 NOTES 🦋

The type and meaning of the value parameter for ASN1_TYPE_set() and ASN1_TYPE_set1() is determined by the type parameter. Here’s the tea:

• If type is V_ASN1_NULL, value is ignored.
• If type is V_ASN1_BOOLEAN, then the boolean is set to TRUE if value is not NULL.
• If type is V_ASN1_OBJECT, then value is an ASN1_OBJECT structure.
• Otherwise, value is an ASN1_STRING structure.

If type corresponds to a primitive type (or a string type), then the contents of the ASN1_STRING contain the content octets of the type. If type corresponds to a constructed type or a tagged type (V_ASN1_SEQUENCE, V_ASN1_SET, or V_ASN1_OTHER), then the ASN1_STRING contains the entire ASN.1 encoding verbatim — including tag and length octets. Verbatim means verbatim, no edits. 👑

ASN1_TYPE_cmp() may not return zero if two types are equivalent but have different encodings. For example, the single content octet of the boolean TRUE value under BER can have any nonzero encoding, but ASN1_TYPE_cmp() will only return zero if the values are the same. So like, same vibe ≠ same bytes. 😭

If either or both of the parameters passed to ASN1_TYPE_cmp() is NULL, the return value is nonzero. Technically, if both parameters are NULL the two types could be absent OPTIONAL fields and so should match — however, passing NULL values could also indicate a programming error (for example an unparsable type which returns NULL) for types which do not match. So applications should handle the case of two absent values separately. This is one of those “handle it yourself, bestie” situations. 🫶

⭐ RETURN VALUES ⭐

• ASN1_TYPE_get() returns the type of the ASN1_TYPE argument.
• ASN1_TYPE_set() does not return a value. It’s a void icon.
• ASN1_TYPE_set1() returns 1 for success and 0 for failure.
• ASN1_TYPE_cmp() returns 0 if the types are identical and nonzero otherwise.
• ASN1_TYPE_unpack_sequence() returns a pointer to an ASN.1 structure or NULL on failure.
• ASN1_TYPE_pack_sequence() returns an ASN1_TYPE structure if it succeeds or NULL on failure.

📜 COPYRIGHT 📜

Copyright 2015-2020 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>.

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Okay, that’s the whole page from OpenSSL 3.5.0, dated 2026-09-25. Go forth and handle your ASN1_TYPEs, bestie 💖✨🎀