SMIME_WRITE_PKCS7(3SSL)

📦
version 4.0.3 · 14 versions
, in ubuntu stonking

💖 SMIME_WRITE_PKCS7(3SSL) — the OpenSSL glow-up where your PKCS#7 structure becomes an actual S/MIME message ✨

okay bestie, sit down, hydrate, because this one is the little function that dresses your PKCS7 structure up in MIME headers so it can go out into the world as a real S/MIME message. it's in the OpenSSL family, no cap. 💅

🌸 NAME 🌸

SMIME_write_PKCS7 — the way you convert a PKCS#7 structure into S/MIME format. literally that's it, that's the job. 🎀

🦋 SYNOPSIS 🦋

#include <openssl/pkcs7.h>

int SMIME_write_PKCS7(BIO *out, PKCS7 *p7, BIO *data, int flags);

look at that signature. four arguments, zero drama. 🌈

💜 DESCRIPTION 💜

SMIME_write_PKCS7() adds the appropriate MIME headers onto a PKCS#7 structure so you end up with an S/MIME message. it's giving "glow-up montage". ✨

  • out is the BIO you write the data to.
  • p7 is the appropriate PKCS7 structure. (yes, the "appropriate" one. use the right one, bestie.)
  • if streaming is enabled, then the content must be supplied in the data argument. no data, no stream, no slay.
  • flags is an optional set of flags. optional!! but very fun.

👑 NOTES 👑

so these are the flags you can pass in the flags parameter. pick your fighters:

  • PKCS7_DETACHED — if this is set, then cleartext signing will be used. ⚠️ this option only makes sense for signedData where PKCS7_DETACHED is also set when PKCS7_sign() is also called. it's a matching-set situation, fr fr.
  • PKCS7_TEXT — if this flag is set, MIME headers for type text/plain are added to the content. it only makes sense if PKCS7_DETACHED is also set. 🫶
  • PKCS7_STREAM — if this is set, streaming is performed. and listen: this flag should only be set if PKCS7_STREAM was also set in the previous call to PKCS7_sign() or PKCS7_encrypt(). don't be out here setting it on its own, it's not that girl. 💀

also, two very important facts coming at you:

if cleartext signing is being used and PKCS7_STREAM is not set, then the data must be read twice: once to compute the signature in PKCS7_sign(), and once to output the S/MIME message. yeah. twice. the data is doing cardio. 😭

if streaming is performed, the content is output in BER format using indefinite length constructed encoding — except in the case of signed data with detached content, where the content is absent and DER format is used. that's the one exception, remember it. ⭐

💀 BUGS 💀

SMIME_write_PKCS7() always base64 encodes PKCS#7 structures. there should be an option to disable this. there just isn't. we live like this. 🙈

not me telling you about a real limitation in the actual source code. it's canon, bestie, not a vibe issue.

🍓 RETURN VALUES 🍓

SMIME_write_PKCS7() returns 1 for success or 0 for failure. iconic binary communication, periodt. 👑

✨ SEE ALSO ✨

go read these next, they're in the friend group:

Copyright 2002-2016 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>.

k that's the whole page, you're officially educated 🧚💖 this was SMIME_WRITE_PKCS7(3SSL) from OpenSSL, version 4.0.3, dated 2026-09-29 — go forth and write your S/MIME messages, main character. 💅🌸🦋

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