SMIME_READ_CMS(3)

💖 SMIME_READ_CMS(3) — extract CMS ContentInfo from an S/MIME message 💖

okay so bestie, welcome to the SMIME_READ_CMS(3) page from the Library Functions Manual. it's giving “extract CMS ContentInfo from an S/MIME message,” and honestly? iconic. no cap, that's the whole vibe. 🎀

🌸 NAME 🌸

SMIME_read_CMS — extract CMS ContentInfo from an S/MIME message. literally the main character function name. 💅

✨ SYNOPSIS ✨

This one lives in libcrypto — the synopsis literally says library “libcrypto” — and the header you need is #include <openssl/cms.h>. The signature is exactly:

#include <openssl/cms.h>

CMS_ContentInfo *
SMIME_read_CMS(BIO *in, BIO **bcont);

🦋 DESCRIPTION 🦋

Okay so SMIME_read_CMS() parses a message in S/MIME format from in. the way that it just does that? main character energy, honestly. 💫

If the message uses cleartext signing, the content is saved in a memory BIO which is written to *bcont and which can then be passed to CMS_verify(3) with the CMS_DETACHED flag set. periodt. Otherwise, *bcont is set to NULL, and the type of the returned structure can be determined using CMS_get0_type(3). iykyk. 🔥

To support future functionality if bcont is not NULL, *bcont should be initialized to NULL, for example:

BIO *cont = NULL;
CMS_ContentInfo *cms = SMIME_read_CMS(in, &cont);

That's the exact little ritual, bestie — don't skip it. 🫶

🎀 RETURN VALUES 🎀

SMIME_read_CMS() returns a valid CMS_ContentInfo structure or NULL if an error occurred. If it's NULL, the error can be obtained from ERR_get_error(3). no cap, that's your diagnostics hook. 😭

🌈 SEE ALSO 🌈

• BIO_f_base64(3)
• BIO_new(3)
• CMS_ContentInfo_new(3)
• CMS_decrypt(3)
• CMS_get0_type(3)
• CMS_verify(3)
• d2i_CMS_ContentInfo(3)
• SMIME_read_PKCS7(3)
• SMIME_text(3)
• SMIME_write_CMS(3)

all the linked lore, bestie. go read them if you want the full extended universe. iykyk. 💜

🧚 HISTORY 🧚

SMIME_read_CMS() first appeared in OpenSSL 0.9.8h and has been available since OpenBSD 6.7. old enough to have lore, still relevant. periodt. 👑

💀 BUGS 💀

The MIME parser used by SMIME_read_CMS() is somewhat primitive. While it will handle most S/MIME messages, more complex compound formats may not work. lowkey important, so don't expect it to eat every weird format. 🙈

The parser assumes that the CMS_ContentInfo structure is always base64 encoded and will not handle the case where it is in binary format or uses quoted printable format. fr fr, that's a hard limit. 🚫

The use of a memory BIO to hold the signed content limits the size of the message which can be processed due to memory restraints: a streaming single pass option should be available. big sigh, but that's what the page says. 😮‍💨

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mwah 💋 — this page came from Debian, dated June 11, 2025. SMIME_READ_CMS(3) out. 🫶