PKCS7_encrypt - create a PKCS#7 envelopedData structure
PKCS7 *PKCS7_encrypt(STACK_OF(X509) *certs, BIO *in, const EVP_CIPHER *cipher, int flags);
creates and returns a PKCS#7 envelopedData structure.
is a list of recipient certificates. in
is the content to
be encrypted. cipher
is the symmetric cipher to use. flags
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.
(triple DES) is the algorithm of choice for S/MIME use
because most clients will support it.
Some old "export grade" clients may only support weak encryption using
40 or 64 bit RC2. These can be used by passing EVP_rc2_40_cbc()
The algorithm passed in the cipher
parameter must support ASN1 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
The following flags can be passed in the flags
If the PKCS7_TEXT
flag is set MIME headers for type text/plain
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
is set then PKCS7_TEXT
If the PKCS7_STREAM
flag is set a partial PKCS7
output suitable for streaming I/O: no data is read from the BIO in
If the flag PKCS7_STREAM
is set the returned PKCS7
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()
the structure. Alternatively finalization can be performed by obtaining the
streaming ASN1 BIO
directly using BIO_new_PKCS7()
returns either a PKCS7 structure or NULL if an error
occurred. The error can be obtained from ERR_get_error(3)
was added to OpenSSL 0.9.5 The PKCS7_STREAM
was first supported in OpenSSL 1.0.0.