ASN1_STRING_LENGTH(3SSL)

📦
version 3.5.7 · 12 versions
, in debian trixie

💅 ASN1_STRING_LENGTH — the ASN1_STRING glow-up guide (3SSL)

okay so bestie, this is the OpenSSL manual page for the ASN1_STRING utility functions, and honestly? it's giving "small API, huge personality." there are eight of them and they all live in <openssl/asn1.h>, so like… buckle up 🎀

✨ NAME ✨

ASN1_STRING_dup, ASN1_STRING_cmp, ASN1_STRING_set, ASN1_STRING_length, ASN1_STRING_type, ASN1_STRING_get0_data, ASN1_STRING_data, ASN1_STRING_to_UTF8 — literally the ASN1_STRING utility functions, the whole friend group 🫶

🦋 SYNOPSIS 🦋

#include <openssl/asn1.h>

int ASN1_STRING_length(ASN1_STRING *x);
const unsigned char *ASN1_STRING_get0_data(const ASN1_STRING *x);
unsigned char *ASN1_STRING_data(ASN1_STRING *x);

ASN1_STRING *ASN1_STRING_dup(const ASN1_STRING *a);

int ASN1_STRING_cmp(ASN1_STRING *a, ASN1_STRING *b);

int ASN1_STRING_set(ASN1_STRING *str, const void *data, int len);

int ASN1_STRING_type(const ASN1_STRING *x);

int ASN1_STRING_to_UTF8(unsigned char **out, const ASN1_STRING *in);

🌸 DESCRIPTION 🌸

these functions are your whole toolkit for manipulating an ASN1_STRING structure. one struct, eight little helpers, main character energy all around 👑

  • ASN1_STRING_length() — returns the length of the content of x. and x MUST NOT be NULL, no cap, that's a hard boundary 🚫
  • ASN1_STRING_get0_data() — returns an internal pointer to the data of x. since it's internal, do not free it and do not modify it in any way, bestie, hands off 🙅‍♀️ and again: x MUST NOT be NULL.
  • ASN1_STRING_data() — basically the same vibe as ASN1_STRING_get0_data() except the returned value is not constant. this one is deprecated 💀 — applications should use ASN1_STRING_get0_data() instead. it's giving "we don't do that anymore."
  • ASN1_STRING_dup() — returns a copy of the structure a. twin behavior, iconic ✨
  • ASN1_STRING_cmp() — compares a and b, returning 0 if the two are identical. it compares both the string types and the content, so no skipping the type check, iykyk.
  • ASN1_STRING_set() — sets the data of string str to the buffer data, with length len. the supplied data is copied (so it's yours to reuse, slay). if len is -1 then the length is determined by strlen(data) 🎀
  • ASN1_STRING_type() — returns the type of x, using standard constants such as V_ASN1_OCTET_STRING.
  • ASN1_STRING_to_UTF8() — converts the string in in to UTF8 format, and the converted data is allocated in a buffer in *out. it returns the length of out or a negative error code. and bestie, the buffer *out should be freed using OPENSSL_free() — every allocated buffer deserves its closure 😭

🧚 NOTES 🧚

almost all ASN1 types in OpenSSL are represented as an ASN1_STRING structure — yes, literally everyone is using the same struct, it's that one friend everyone knows. other types such as ASN1_OCTET_STRING are simply typedef'ed to ASN1_STRING and the functions just call the ASN1_STRING equivalents. ASN1_STRING is also used for some CHOICE types which consist entirely of primitive string types such as DirectoryString and Time. versatile queen 💜

⚠️ real talk: these functions should not be used to examine or modify ASN1_INTEGER or ASN1_ENUMERATED types — the relevant INTEGER or ENUMERATED utility functions should be used instead. wrong tool for the job, we don't do that here 🙈

in general, you cannot assume that the data returned by ASN1_STRING_data() is null terminated or that it doesn't contain embedded nulls. the actual format of the data depends on the actual string type itself:

  • for an IA5String, the data will be ASCII
  • for a BMPString, two bytes per character in big endian format
  • for a UTF8String, it will be in UTF8 format

similar care should be taken to ensure the data is in the correct format when calling ASN1_STRING_set(). vibe check your types, fr fr 🔥

⭐ RETURN VALUES ⭐

  • ASN1_STRING_length() — returns the length of the content of x.
  • ASN1_STRING_get0_data() and ASN1_STRING_data() — return an internal pointer to the data of x.
  • ASN1_STRING_dup() — returns a valid ASN1_STRING structure or NULL if an error occurred.
  • ASN1_STRING_cmp() — returns an integer greater than, equal to, or less than 0, according to whether a is greater than, equal to, or less than b.
  • ASN1_STRING_set() — returns 1 on success or 0 on error.
  • ASN1_STRING_type() — returns the type of x.
  • ASN1_STRING_to_UTF8() — returns the number of bytes in output string out or a negative value if an error occurred.

🌈 SEE ALSO 🌈

Copyright 2002-2020 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>.

and that's the whole page, periodt 💅 this was ASN1_STRING_LENGTH(3SSL) from OpenSSL 3.5.7, dated 2026-06-09 — screenshot it, bookmark it, send it to the group chat, mwah 🍓💖

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