| 1 | =pod
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| 2 |
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| 3 | =head1 NAME
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| 4 |
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| 5 | CMS_encrypt_ex, CMS_encrypt - create a CMS envelopedData structure
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| 6 |
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| 7 | =head1 SYNOPSIS
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| 8 |
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| 9 | #include <openssl/cms.h>
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| 10 |
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| 11 | CMS_ContentInfo *CMS_encrypt_ex(STACK_OF(X509) *certs, BIO *in,
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| 12 | const EVP_CIPHER *cipher, unsigned int flags,
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| 13 | OSSL_LIB_CTX *libctx, const char *propq);
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| 14 | CMS_ContentInfo *CMS_encrypt(STACK_OF(X509) *certs, BIO *in,
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| 15 | const EVP_CIPHER *cipher, unsigned int flags);
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| 16 |
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| 17 | =head1 DESCRIPTION
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| 18 |
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| 19 | CMS_encrypt_ex() creates and returns a CMS EnvelopedData or
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| 20 | AuthEnvelopedData structure. I<certs> is a list of recipient certificates.
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| 21 | I<in> is the content to be encrypted. I<cipher> is the symmetric cipher to use.
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| 22 | I<flags> is an optional set of flags. The library context I<libctx> and the
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| 23 | property query I<propq> are used internally when retrieving algorithms from
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| 24 | providers.
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| 25 |
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| 26 | Only certificates carrying RSA, Diffie-Hellman or EC keys are supported by this
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| 27 | function.
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| 28 |
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| 29 | EVP_des_ede3_cbc() (triple DES) is the algorithm of choice for S/MIME use
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| 30 | because most clients will support it.
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| 31 |
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| 32 | The algorithm passed in the B<cipher> parameter must support ASN1 encoding of
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| 33 | its parameters. If the cipher mode is GCM, then an AuthEnvelopedData structure
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| 34 | containing MAC is used. Otherwise an EnvelopedData structure is used. Currently
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| 35 | the AES variants with GCM mode are the only supported AEAD algorithms.
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| 36 |
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| 37 | Many browsers implement a "sign and encrypt" option which is simply an S/MIME
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| 38 | envelopedData containing an S/MIME signed message. This can be readily produced
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| 39 | by storing the S/MIME signed message in a memory BIO and passing it to
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| 40 | CMS_encrypt().
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| 41 |
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| 42 | The following flags can be passed in the B<flags> parameter.
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| 43 |
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| 44 | If the B<CMS_TEXT> flag is set MIME headers for type B<text/plain> are
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| 45 | prepended to the data.
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| 46 |
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| 47 | Normally the supplied content is translated into MIME canonical format (as
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| 48 | required by the S/MIME specifications) if B<CMS_BINARY> is set no translation
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| 49 | occurs. This option should be used if the supplied data is in binary format
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| 50 | otherwise the translation will corrupt it. If B<CMS_BINARY> is set then
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| 51 | B<CMS_TEXT> is ignored.
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| 52 |
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| 53 | OpenSSL will by default identify recipient certificates using issuer name
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| 54 | and serial number. If B<CMS_USE_KEYID> is set it will use the subject key
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| 55 | identifier value instead. An error occurs if all recipient certificates do not
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| 56 | have a subject key identifier extension.
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| 57 |
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| 58 | If the B<CMS_STREAM> flag is set a partial B<CMS_ContentInfo> structure is
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| 59 | returned suitable for streaming I/O: no data is read from the BIO B<in>.
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| 60 |
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| 61 | If the B<CMS_PARTIAL> flag is set a partial B<CMS_ContentInfo> structure is
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| 62 | returned to which additional recipients and attributes can be added before
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| 63 | finalization.
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| 64 |
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| 65 | The data being encrypted is included in the CMS_ContentInfo structure, unless
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| 66 | B<CMS_DETACHED> is set in which case it is omitted. This is rarely used in
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| 67 | practice and is not supported by SMIME_write_CMS().
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| 68 |
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| 69 | If the flag B<CMS_STREAM> is set the returned B<CMS_ContentInfo> structure is
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| 70 | B<not> complete and outputting its contents via a function that does not
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| 71 | properly finalize the B<CMS_ContentInfo> structure will give unpredictable
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| 72 | results.
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| 73 |
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| 74 | Several functions including SMIME_write_CMS(), i2d_CMS_bio_stream(),
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| 75 | PEM_write_bio_CMS_stream() finalize the structure. Alternatively finalization
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| 76 | can be performed by obtaining the streaming ASN1 B<BIO> directly using
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| 77 | BIO_new_CMS().
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| 78 |
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| 79 | The recipients specified in B<certs> use a CMS KeyTransRecipientInfo info
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| 80 | structure. KEKRecipientInfo is also supported using the flag B<CMS_PARTIAL>
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| 81 | and CMS_add0_recipient_key().
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| 82 |
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| 83 | The parameter B<certs> may be NULL if B<CMS_PARTIAL> is set and recipients
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| 84 | added later using CMS_add1_recipient_cert() or CMS_add0_recipient_key().
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| 85 |
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| 86 | CMS_encrypt() is similar to CMS_encrypt_ex() but uses default values
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| 87 | of NULL for the library context I<libctx> and the property query I<propq>.
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| 88 |
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| 89 | =head1 RETURN VALUES
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| 90 |
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| 91 | CMS_encrypt_ex() and CMS_encrypt() return either a CMS_ContentInfo
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| 92 | structure or NULL if an error occurred. The error can be obtained from
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| 93 | ERR_get_error(3).
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| 94 |
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| 95 | =head1 SEE ALSO
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| 96 |
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| 97 | L<ERR_get_error(3)>, L<CMS_decrypt(3)>
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| 98 |
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| 99 | =head1 HISTORY
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| 100 |
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| 101 | The function CMS_encrypt_ex() was added in OpenSSL 3.0.
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| 102 |
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| 103 | The B<CMS_STREAM> flag was first supported in OpenSSL 1.0.0.
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| 104 |
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| 105 | =head1 COPYRIGHT
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| 106 |
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| 107 | Copyright 2008-2020 The OpenSSL Project Authors. All Rights Reserved.
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| 108 |
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| 109 | Licensed under the Apache License 2.0 (the "License"). You may not use
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| 110 | this file except in compliance with the License. You can obtain a copy
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| 111 | in the file LICENSE in the source distribution or at
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| 112 | L<https://www.openssl.org/source/license.html>.
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| 113 |
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| 114 | =cut
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