LIBRESSL-RSA_SIGN_ASN1_OCTET_STRING(3)

📦 version 4.4.0, in alpine 3.24, arch rolling

💅 NAME 💅

okay so bestie, welcome to the RSA_SIGN_ASN1_OCTET_STRING(3) page — it lives in section 3, the Library Functions Manual, and it's literally all about the two functions RSA_sign_ASN1_OCTET_STRING and RSA_verify_ASN1_OCTET_STRING, aka RSA signatures 🎀

✨ SYNOPSIS ✨

like, here's the whole thing, character for character, no cap:

library “libcrypto” #include <openssl/rsa.h>

int
RSA_sign_ASN1_OCTET_STRING(int dummy, unsigned char *m,
    unsigned int m_len, unsigned char *sigret, unsigned int *siglen,
    RSA *rsa);

int
RSA_verify_ASN1_OCTET_STRING(int dummy, unsigned char *m,
    unsigned int m_len, unsigned char *sigbuf, unsigned int siglen,
    RSA *rsa);

🌸 DESCRIPTION 🌸

So RSA_sign_ASN1_OCTET_STRING() signs the octet string m of size m_len using the private key rsa — and that key is represented in DER using PKCS #1 padding, periodt 💅 It drops the signature into sigret and the signature size into siglen.

⚠️ Important vibe check: sigret must point to RSA_size(rsa) bytes of memory. Like, don't skimp on the buffer, bestie, it will not end well 😭

And dummy? Completely ignored. Not even a little bit. It's giving decorative parameter energy 🫶

RSA_verify_ASN1_OCTET_STRING() is the other half of the duo — it verifies that the signature sigbuf of size siglen is the DER representation of a given octet string m of size m_len. dummy is ignored here too (iconic of it 🙈), and rsa is the signer's public key.

🎀 RETURN VALUES 🎀

  • RSA_sign_ASN1_OCTET_STRING() returns 1 on success, or 0 otherwise 💖
  • RSA_verify_ASN1_OCTET_STRING() returns 1 on successful verification, or 0 otherwise 💖

If you gotta know why something flopped, the error codes can be obtained by ERR_get_error(3) — go find out, queen 👑

🦋 SEE ALSO 🦋

👑 HISTORY 👑

RSA_sign_ASN1_OCTET_STRING() and RSA_verify_ASN1_OCTET_STRING() first appeared in SSLeay 0.8.0, and they've been available since OpenBSD 2.4 — elder emoji status fr fr 🔥

💀 BUGS 💀

Screenshot this and send it to the group chat: these functions serve no recognizable purpose. That's it. That's the bug note. The manpage said what it said 💀😭

so yeah, that's the whole page 🧚 this one's from the Debian crew, dated June 8, 2025, and the page title is RSA_SIGN_ASN1_OCTET_STRING(3) — mwah, stan, bye 💜🌈

📦 where this page comes from