SMIME_WRITE_CMS(3ossl)

📦 version 3.5.0, in opensuse-leap 16.0

🌸 NAME 🌸

SMIME_write_CMS — convert CMS structure to S/MIME format. This is the SMIME_WRITE_CMS(3ossl) page, bestie, and it's all about turning a CMS structure into an S/MIME message with the right MIME headers. Slay. 💌

✨ SYNOPSIS ✨

#include <openssl/cms.h>

int SMIME_write_CMS(BIO *out, CMS_ContentInfo *cms, BIO *data, int flags);

💖 DESCRIPTION 💖

okay so SMIME_write_CMS() adds the appropriate MIME headers to a CMS structure to produce an S/MIME message. That's the whole vibe. 💅

  • out is the BIO to write the data to.
  • cms is the appropriate CMS_ContentInfo structure.
  • If streaming is enabled, then the content must be supplied in the data argument.
  • flags is an optional set of flags.

🎀 NOTES 🎀

The following flags can be passed in the flags parameter. Yes bestie, these are the little switches that change the behavior. 👑

  • CMS_DETACHED — if this is set, then cleartext signing will be used. This option only makes sense for SignedData where CMS_DETACHED is also set when CMS_sign() is called. iykyk. 💫
  • CMS_TEXT — if this flag is set, MIME headers for type text/plain are added to the content. This only makes sense if CMS_DETACHED is also set.
  • CMS_STREAM — if this flag is set, streaming is performed. This flag should only be set if CMS_STREAM was also set in the previous call to a CMS_ContentInfo creation function. no cap, it's a matching-set situation. 🔥

If cleartext signing is being used and CMS_STREAM not set, then the data must be read twice: once to compute the signature in CMS_sign() and once to output the S/MIME message. Yes, 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 exact format tea. 🍵

💀 BUGS 💀

SMIME_write_CMS() always base64 encodes CMS structures. There should be an option to disable this. That's the bug note, bestie — not me making it up. 🙈

🌈 RETURN VALUES 🌈

SMIME_write_CMS() returns 1 for success or 0 for failure. That's it. Success slays, failure is a zero. 💅

🦋 SEE ALSO 🦋

Copyright 2008-2016 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>.

✨ cute sign-off: this is OpenSSL 3.5.0, dated 2026-09-25 — mwah, bestie 💋🫶

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