NAME¶
PKCS7_encrypt - create a PKCS#7 envelopedData structure
SYNOPSIS¶
#include <openssl/pkcs7.h>
PKCS7 *PKCS7_encrypt(STACK_OF(X509) *certs, BIO *in, const EVP_CIPHER *cipher, int flags);
DESCRIPTION¶
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.
NOTES¶
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.
EVP_des_ede3_cbc() (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() and
EVP_rc2_64_cbc() respectively.
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
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 the BIO
in.
NOTES¶
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(),
i2d_PKCS7_bio_stream(),
PEM_write_bio_PKCS7_stream() finalize
the structure. Alternatively finalization can be performed by obtaining the
streaming ASN1
BIO directly using
BIO_new_PKCS7().
RETURN VALUES¶
PKCS7_encrypt() returns either a PKCS7 structure or NULL if an error
occurred. The error can be obtained from
ERR_get_error(3).
SEE ALSO¶
ERR_get_error(3),
PKCS7_decrypt(3)
HISTORY¶
PKCS7_decrypt() was added to OpenSSL 0.9.5 The
PKCS7_STREAM flag
was first supported in OpenSSL 1.0.0.