$NetBSD: PKCS7_encrypt.3,v 1.7 2013/02/12 19:52:13 christos Exp $

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Title "PKCS7_encrypt 3" For nroff, turn off justification. Always turn off hyphenation; it makes
way too many mistakes in technical documents.
PKCS7_encrypt - create a PKCS#7 envelopedData structure libcrypto, -lcrypto Header "SYNOPSIS" .Vb 1 #include <openssl/pkcs7.h> \& PKCS7 *PKCS7_encrypt(STACK_OF(X509) *certs, BIO *in, const EVP_CIPHER *cipher, int flags); .Ve Header "DESCRIPTION" \fIPKCS7_encrypt() creates and returns a PKCS#7 envelopedData structure. certs is a list of recipient certificates. in is the content to be encrypted. \fBcipher is the symmetric cipher to use. flags is an optional set of flags. Header "NOTES" Only \s-1RSA\s0 keys are supported in PKCS#7 and envelopedData so the recipient certificates supplied to this function must all contain \s-1RSA\s0 public keys, though they do not have to be signed using the \s-1RSA\s0 algorithm.

\fIEVP_des_ede3_cbc() (triple \s-1DES\s0) is the algorithm of choice for S/MIME use because most clients will support it.

Some old \*(L"export grade\*(R" clients may only support weak encryption using 40 or 64 bit \s-1RC2\s0. 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 \s-1ASN1\s0 encoding of its parameters.

Many browsers implement a \*(L"sign and encrypt\*(R" 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 \s-1BIO\s0 and passing it to \fIPKCS7_encrypt().

The following flags can be passed in the flags parameter.

If the \s-1PKCS7_TEXT\s0 flag is set \s-1MIME\s0 headers for type text/plain are prepended to the data.

Normally the supplied content is translated into \s-1MIME\s0 canonical format (as required by the S/MIME specifications) if \s-1PKCS7_BINARY\s0 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 \s-1PKCS7_BINARY\s0 is set then \fB\s-1PKCS7_TEXT\s0 is ignored.

If the \s-1PKCS7_STREAM\s0 flag is set a partial \s-1PKCS7\s0 structure is output suitable for streaming I/O: no data is read from the \s-1BIO\s0 in.

Header "NOTES" If the flag \s-1PKCS7_STREAM\s0 is set the returned \s-1PKCS7\s0 structure is not complete and outputting its contents via a function that does not properly finalize the \s-1PKCS7\s0 structure will give unpredictable results.

Several functions including SMIME_write_PKCS7(), i2d_PKCS7_bio_stream(), \fIPEM_write_bio_PKCS7_stream() finalize the structure. Alternatively finalization can be performed by obtaining the streaming \s-1ASN1\s0 \s-1BIO\s0 directly using \fIBIO_new_PKCS7().

Header "RETURN VALUES" \fIPKCS7_encrypt() returns either a \s-1PKCS7\s0 structure or \s-1NULL\s0 if an error occurred. The error can be obtained from ERR_get_error\|(3). Header "SEE ALSO" \fIERR_get_error\|(3), PKCS7_decrypt\|(3) Header "HISTORY" \fIPKCS7_decrypt() was added to OpenSSL 0.9.5 The \s-1PKCS7_STREAM\s0 flag was first supported in OpenSSL 1.0.0.