81 lines
2.7 KiB
Plaintext
81 lines
2.7 KiB
Plaintext
=pod
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=head1 NAME
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PKCS7_encrypt - create a PKCS#7 envelopedData structure
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=head1 SYNOPSIS
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#include <openssl/pkcs7.h>
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PKCS7 *PKCS7_encrypt(STACK_OF(X509) *certs, BIO *in, const EVP_CIPHER *cipher, int flags);
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=head1 DESCRIPTION
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PKCS7_encrypt() creates and returns a PKCS#7 envelopedData structure. B<certs>
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is a list of recipient certificates. B<in> is the content to be encrypted.
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B<cipher> is the symmetric cipher to use. B<flags> is an optional set of flags.
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=head1 NOTES
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Only RSA keys are supported in PKCS#7 and envelopedData so the recipient
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certificates supplied to this function must all contain RSA public keys, though
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they do not have to be signed using the RSA algorithm.
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EVP_des_ede3_cbc() (triple DES) is the algorithm of choice for S/MIME use
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because most clients will support it.
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Some old "export grade" clients may only support weak encryption using 40 or 64
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bit RC2. These can be used by passing EVP_rc2_40_cbc() and EVP_rc2_64_cbc()
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respectively.
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The algorithm passed in the B<cipher> parameter must support ASN1 encoding of
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its parameters.
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Many browsers implement a "sign and encrypt" option which is simply an S/MIME
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envelopedData containing an S/MIME signed message. This can be readily produced
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by storing the S/MIME signed message in a memory BIO and passing it to
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PKCS7_encrypt().
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The following flags can be passed in the B<flags> parameter.
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If the B<PKCS7_TEXT> flag is set MIME headers for type B<text/plain> are
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prepended to the data.
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Normally the supplied content is translated into MIME canonical format (as
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required by the S/MIME specifications) if B<PKCS7_BINARY> is set no translation
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occurs. This option should be used if the supplied data is in binary format
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otherwise the translation will corrupt it. If B<PKCS7_BINARY> is set then
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B<PKCS7_TEXT> is ignored.
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If the B<PKCS7_STREAM> flag is set a partial B<PKCS7> structure is output
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suitable for streaming I/O: no data is read from the BIO B<in>.
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=head1 NOTES
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If the flag B<PKCS7_STREAM> is set the returned B<PKCS7> structure is B<not>
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complete and outputting its contents via a function that does not
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properly finalize the B<PKCS7> structure will give unpredictable
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results.
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Several functions including SMIME_write_PKCS7(), i2d_PKCS7_bio_stream(),
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PEM_write_bio_PKCS7_stream() finalize the structure. Alternatively finalization
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can be performed by obtaining the streaming ASN1 B<BIO> directly using
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BIO_new_PKCS7().
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=head1 RETURN VALUES
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PKCS7_encrypt() returns either a PKCS7 structure or NULL if an error occurred.
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The error can be obtained from ERR_get_error(3).
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=head1 SEE ALSO
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L<ERR_get_error(3)|ERR_get_error(3)>, L<PKCS7_decrypt(3)|PKCS7_decrypt(3)>
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=head1 HISTORY
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PKCS7_decrypt() was added to OpenSSL 0.9.5
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The B<PKCS7_STREAM> flag was first supported in OpenSSL 0.9.9.
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=cut
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