PKCS7_DECRYPT(3ossl)

📦
version 3.5.9 · 8 versions
, in fedora 43, fedora 44

💖 PKCS7_DECRYPT(3ossl) 💖

ok so bestie, welcome to PKCS7_decrypt — it's a page from the OpenSSL manuals, section 3ossl, and it's literally all about pulling the actual content back out of a PKCS#7 envelopedData structure. 🎀

✨ NAME ✨

PKCS7_decrypt — decrypt content from a PKCS#7 envelopedData structure 🦋

✨ SYNOPSIS ✨

#include <openssl/pkcs7.h>

int PKCS7_decrypt(PKCS7 *p7, EVP_PKEY *pkey, X509 *cert, BIO *data, int flags);

✨ DESCRIPTION ✨

ok so here's the vibe. PKCS7_decrypt() extracts and decrypts the content from a PKCS#7 envelopedData structure. the way it works is:

  • pkey — this is the private key of the recipient 🔑
  • cert — this is the recipient's certificate 🪪
  • data — a BIO that the content gets written to ✍️
  • flags — an optional set of flags 🚩

periodt. that's the whole signature.

✨ NOTES ✨

ok so plot twist: even though the recipient's certificate is not needed to actually decrypt the data, it IS needed to locate the appropriate recipient — and yeah, there can be several of them in the PKCS#7 structure. so like, bring the cert anyway bestie. 💅

when RSA PKCS#1 v1.5 Key Transport is in use, the invoked EVP_PKEY_decrypt() will use an implicit rejection mechanism. it always returns the result of RSA decryption of the symmetric key, specifically to avoid the Marvin attack. 🛡️

this result is deterministic and can happen to match the symmetric cipher used for the content encryption. so if the certificate is not provided, the last RecipientInfo producing the key that looks valid will be used. 🙈

⚠️ and heads up: that can cause you to get garbage content on decryption. no cap.

the following flags can be passed in the flags parameter 👇

  • PKCS7_TEXT — if this flag is set, MIME headers for type text/plain are deleted from the content. and if the content is not of type text/plain, then an error is returned. 😭

✨ RETURN VALUES ✨

PKCS7_decrypt() returns either 1 for success or 0 for failure. 💀 and the error can be obtained from ERR_get_error(3).

✨ BUGS ✨

ngl, PKCS7_decrypt() must be passed the correct recipient key and certificate. it would be better if it could look up the correct key and certificate from a database. 🥲 but it does not. it cannot. it's giving "you do it yourself."

✨ SEE ALSO ✨

Copyright 2002-2026 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>. 🌈

ok that's the whole page bestie, ily, go decrypt something responsibly 🫶✨

version 3.5.9 · dated 2026-09-29 · from the OpenSSL crew 💖

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