PKCS7_sign.pod 4.7 KB

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  1. =pod
  2. =head1 NAME
  3. PKCS7_sign - create a PKCS#7 signedData structure
  4. =head1 SYNOPSIS
  5. #include <openssl/pkcs7.h>
  6. PKCS7 *PKCS7_sign(X509 *signcert, EVP_PKEY *pkey, STACK_OF(X509) *certs,
  7. BIO *data, int flags);
  8. =head1 DESCRIPTION
  9. PKCS7_sign() creates and returns a PKCS#7 signedData structure. B<signcert> is
  10. the certificate to sign with, B<pkey> is the corresponding private key.
  11. B<certs> is an optional additional set of certificates to include in the PKCS#7
  12. structure (for example any intermediate CAs in the chain).
  13. The data to be signed is read from BIO B<data>.
  14. B<flags> is an optional set of flags.
  15. =head1 NOTES
  16. Any of the following flags (ored together) can be passed in the B<flags>
  17. parameter.
  18. Many S/MIME clients expect the signed content to include valid MIME headers. If
  19. the B<PKCS7_TEXT> flag is set MIME headers for type B<text/plain> are prepended
  20. to the data.
  21. If B<PKCS7_NOCERTS> is set the signer's certificate will not be included in the
  22. PKCS7 structure, the signer's certificate must still be supplied in the
  23. B<signcert> parameter though. This can reduce the size of the signature if the
  24. signers certificate can be obtained by other means: for example a previously
  25. signed message.
  26. The data being signed is included in the PKCS7 structure, unless
  27. B<PKCS7_DETACHED> is set in which case it is omitted. This is used for PKCS7
  28. detached signatures which are used in S/MIME plaintext signed messages for
  29. example.
  30. Normally the supplied content is translated into MIME canonical format (as
  31. required by the S/MIME specifications) if B<PKCS7_BINARY> is set no translation
  32. occurs. This option should be used if the supplied data is in binary format
  33. otherwise the translation will corrupt it.
  34. The signedData structure includes several PKCS#7 authenticatedAttributes
  35. including the signing time, the PKCS#7 content type and the supported list of
  36. ciphers in an SMIMECapabilities attribute. If B<PKCS7_NOATTR> is set then no
  37. authenticatedAttributes will be used. If B<PKCS7_NOSMIMECAP> is set then just
  38. the SMIMECapabilities are omitted.
  39. If present the SMIMECapabilities attribute indicates support for the following
  40. algorithms: triple DES, 128 bit RC2, 64 bit RC2, DES and 40 bit RC2. If any of
  41. these algorithms is disabled then it will not be included.
  42. If the flags B<PKCS7_STREAM> is set then the returned B<PKCS7> structure is
  43. just initialized ready to perform the signing operation. The signing is however
  44. B<not> performed and the data to be signed is not read from the B<data>
  45. parameter. Signing is deferred until after the data has been written. In this
  46. way data can be signed in a single pass.
  47. If the B<PKCS7_PARTIAL> flag is set a partial B<PKCS7> structure is output to
  48. which additional signers and capabilities can be added before finalization.
  49. =head1 NOTES
  50. If the flag B<PKCS7_STREAM> is set the returned B<PKCS7> structure is B<not>
  51. complete and outputting its contents via a function that does not properly
  52. finalize the B<PKCS7> structure will give unpredictable results.
  53. Several functions including SMIME_write_PKCS7(), i2d_PKCS7_bio_stream(),
  54. PEM_write_bio_PKCS7_stream() finalize the structure. Alternatively finalization
  55. can be performed by obtaining the streaming ASN1 B<BIO> directly using
  56. BIO_new_PKCS7().
  57. If a signer is specified it will use the default digest for the signing
  58. algorithm. This is B<SHA1> for both RSA and DSA keys.
  59. The B<certs>, B<signcert> and B<pkey> parameters can all be
  60. B<NULL> if the B<PKCS7_PARTIAL> flag is set. One or more signers can be added
  61. using the function PKCS7_sign_add_signer(). PKCS7_final() must also be
  62. called to finalize the structure if streaming is not enabled. Alternative
  63. signing digests can also be specified using this method.
  64. If B<signcert> and B<pkey> are NULL then a certificates only
  65. PKCS#7 structure is output.
  66. In versions of OpenSSL before 1.0.0 the B<signcert> and B<pkey> parameters must
  67. B<NOT> be NULL.
  68. =head1 BUGS
  69. Some advanced attributes such as counter signatures are not supported.
  70. =head1 RETURN VALUES
  71. PKCS7_sign() returns either a valid PKCS7 structure or NULL if an error
  72. occurred. The error can be obtained from ERR_get_error(3).
  73. =head1 SEE ALSO
  74. L<ERR_get_error(3)>, L<PKCS7_verify(3)>
  75. =head1 HISTORY
  76. The B<PKCS7_PARTIAL> flag, and the ability for B<certs>, B<signcert>,
  77. and B<pkey> parameters to be B<NULL> to be was added in OpenSSL 1.0.0
  78. The B<PKCS7_STREAM> flag was added in OpenSSL 1.0.0
  79. =head1 COPYRIGHT
  80. Copyright 2002-2016 The OpenSSL Project Authors. All Rights Reserved.
  81. Licensed under the OpenSSL license (the "License"). You may not use
  82. this file except in compliance with the License. You can obtain a copy
  83. in the file LICENSE in the source distribution or at
  84. L<https://www.openssl.org/source/license.html>.
  85. =cut