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PKCS7_ENCRYPT(3) Library Functions Manual PKCS7_ENCRYPT(3)

PKCS7_encrypt
create a PKCS#7 envelopedData structure

#include <openssl/pkcs7.h>
PKCS7 *
PKCS7_encrypt(STACK_OF(X509) *certs, BIO *in, const EVP_CIPHER *cipher, int flags);

PKCS7_encrypt() creates and returns a PKCS#7 envelopedData structure. certs is a list of recipient certificates. in is the content to be encrypted. cipher is the symmetric cipher to use. flags is an optional set of flags.
Only RSA keys are supported in PKCS#7 and envelopedData so the recipient certificates supplied to this function must all contain RSA public keys, though they do not have to be signed using the RSA algorithm.
The algorithm passed in the cipher parameter must support ASN.1 encoding of its parameters.
Many browsers implement a "sign and encrypt" option which is simply an S/MIME envelopedData containing an S/MIME signed message. This can be readily produced by storing the S/MIME signed message in a memory BIO and passing it to PKCS7_encrypt().
The following flags can be passed in the flags parameter.
If the PKCS7_TEXT flag is set, MIME headers for type text/plain are prepended to the data.
Normally the supplied content is translated into MIME canonical format (as required by the S/MIME specifications). If PKCS7_BINARY is set, no translation occurs. This option should be used if the supplied data is in binary format; otherwise, the translation will corrupt it. If PKCS7_BINARY is set, then PKCS7_TEXT is ignored.
If the PKCS7_STREAM flag is set, a partial PKCS7 structure is output suitable for streaming I/O: no data is read from in.
If the flag PKCS7_STREAM is set, the returned PKCS7 structure is not complete and outputting its contents via a function that does not properly finalize the PKCS7 structure will give unpredictable results.
Several functions, including SMIME_write_PKCS7(3), i2d_PKCS7_bio_stream(3), and PEM_write_bio_PKCS7_stream(3), finalize the structure. Alternatively finalization can be performed by obtaining the streaming ASN.1 BIO directly using BIO_new_PKCS7().

PKCS7_encrypt() returns either a PKCS7 structure or NULL if an error occurred. The error can be obtained from ERR_get_error(3).

ERR_get_error(3), PKCS7_decrypt(3), PKCS7_new(3)

PKCS7_encrypt() first appeared in OpenSSL 0.9.5 and has been available since OpenBSD 2.7.
The PKCS7_STREAM flag was first supported in OpenSSL 1.0.0.
March 23, 2018 OpenBSD-current