PKCS7_sign.pod 4.3 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, BIO *data, int flags);
  7. =head1 DESCRIPTION
  8. PKCS7_sign() creates and returns a PKCS#7 signedData structure. B<signcert> is
  9. the certificate to sign with, B<pkey> is the corresponsding private key.
  10. B<certs> is an optional additional set of certificates to include in the PKCS#7
  11. structure (for example any intermediate CAs in the chain).
  12. The data to be signed is read from BIO B<data>.
  13. B<flags> is an optional set of flags.
  14. =head1 NOTES
  15. Any of the following flags (ored together) can be passed in the B<flags>
  16. parameter.
  17. Many S/MIME clients expect the signed content to include valid MIME headers. If
  18. the B<PKCS7_TEXT> flag is set MIME headers for type B<text/plain> are prepended
  19. to the data.
  20. If B<PKCS7_NOCERTS> is set the signer's certificate will not be included in the
  21. PKCS7 structure, the signer's certificate must still be supplied in the
  22. B<signcert> parameter though. This can reduce the size of the signature if the
  23. signers certificate can be obtained by other means: for example a previously
  24. signed message.
  25. The data being signed is included in the PKCS7 structure, unless
  26. B<PKCS7_DETACHED> is set in which case it is omitted. This is used for PKCS7
  27. detached signatures which are used in S/MIME plaintext signed messages for
  28. example.
  29. Normally the supplied content is translated into MIME canonical format (as
  30. required by the S/MIME specifications) if B<PKCS7_BINARY> is set no translation
  31. occurs. This option should be used if the supplied data is in binary format
  32. otherwise the translation will corrupt it.
  33. The signedData structure includes several PKCS#7 autenticatedAttributes
  34. including the signing time, the PKCS#7 content type and the supported list of
  35. ciphers in an SMIMECapabilities attribute. If B<PKCS7_NOATTR> is set then no
  36. authenticatedAttributes will be used. If B<PKCS7_NOSMIMECAP> is set then just
  37. the SMIMECapabilities are omitted.
  38. If present the SMIMECapabilities attribute indicates support for the following
  39. algorithms: triple DES, 128 bit RC2, 64 bit RC2, DES and 40 bit RC2. If any of
  40. these algorithms is disabled then it will not be included.
  41. If the flags B<PKCS7_STREAM> is set then the returned B<PKCS7> structure is
  42. just initialized ready to perform the signing operation. The signing is however
  43. B<not> performed and the data to be signed is not read from the B<data>
  44. parameter. Signing is deferred until after the data has been written. In this
  45. way data can be signed in a single pass.
  46. If the B<PKCS7_PARTIAL> flag is set a partial B<PKCS7> structure is output to
  47. which additional signers and capabilities can be added before finalization.
  48. =head1 NOTES
  49. If the flag B<PKCS7_STREAM> is set the returned B<PKCS7> structure is B<not>
  50. complete and outputting its contents via a function that does not properly
  51. finalize the B<PKCS7> structure will give unpredictable results.
  52. Several functions including SMIME_write_PKCS7(), i2d_PKCS7_bio_stream(),
  53. PEM_write_bio_PKCS7_stream() finalize the structure. Alternatively finalization
  54. can be performed by obtaining the streaming ASN1 B<BIO> directly using
  55. BIO_new_PKCS7().
  56. If a signer is specified it will use the default digest for the signing
  57. algorithm. This is B<SHA1> for both RSA and DSA keys.
  58. In OpenSSL 1.0.0 the B<certs>, B<signcert> and B<pkey> parameters can all be
  59. B<NULL> if the B<PKCS7_PARTIAL> flag is set. One or more signers can be added
  60. using the function B<PKCS7_sign_add_signer()>. B<PKCS7_final()> must also be
  61. called to finalize the structure if streaming is not enabled. Alternative
  62. signing digests can also be specified using this method.
  63. In OpenSSL 1.0.0 if B<signcert> and B<pkey> are NULL then a certificates only
  64. PKCS#7 structure is output.
  65. In versions of OpenSSL before 1.0.0 the B<signcert> and B<pkey> parameters must
  66. B<NOT> be NULL.
  67. =head1 BUGS
  68. Some advanced attributes such as counter signatures are not supported.
  69. =head1 RETURN VALUES
  70. PKCS7_sign() returns either a valid PKCS7 structure or NULL if an error
  71. occurred. The error can be obtained from ERR_get_error(3).
  72. =head1 SEE ALSO
  73. L<ERR_get_error(3)|ERR_get_error(3)>, L<PKCS7_verify(3)|PKCS7_verify(3)>
  74. =head1 HISTORY
  75. PKCS7_sign() was added to OpenSSL 0.9.5
  76. The B<PKCS7_PARTIAL> flag was added in OpenSSL 1.0.0
  77. The B<PKCS7_STREAM> flag was added in OpenSSL 1.0.0
  78. =cut