PKCS7_verify.pod 5.0 KB

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  1. =pod
  2. =head1 NAME
  3. PKCS7_verify, PKCS7_get0_signers - verify a PKCS#7 signedData structure
  4. =head1 SYNOPSIS
  5. #include <openssl/pkcs7.h>
  6. int PKCS7_verify(PKCS7 *p7, STACK_OF(X509) *certs, X509_STORE *store,
  7. BIO *indata, BIO *out, int flags);
  8. STACK_OF(X509) *PKCS7_get0_signers(PKCS7 *p7, STACK_OF(X509) *certs, int flags);
  9. =head1 DESCRIPTION
  10. PKCS7_verify() verifies a PKCS#7 signedData structure. B<p7> is the PKCS7
  11. structure to verify. B<certs> is a set of certificates in which to search for
  12. the signer's certificate. B<store> is a trusted certificate store (used for
  13. chain verification). B<indata> is the signed data if the content is not
  14. present in B<p7> (that is it is detached). The content is written to B<out>
  15. if it is not NULL.
  16. B<flags> is an optional set of flags, which can be used to modify the verify
  17. operation.
  18. PKCS7_get0_signers() retrieves the signer's certificates from B<p7>, it does
  19. B<not> check their validity or whether any signatures are valid. The B<certs>
  20. and B<flags> parameters have the same meanings as in PKCS7_verify().
  21. =head1 VERIFY PROCESS
  22. Normally the verify process proceeds as follows.
  23. Initially some sanity checks are performed on B<p7>. The type of B<p7> must
  24. be signedData. There must be at least one signature on the data and if
  25. the content is detached B<indata> cannot be B<NULL>. If the content is
  26. not detached and B<indata> is not B<NULL>, then the structure has both
  27. embedded and external content. To treat this as an error, use the flag
  28. B<PKCS7_NO_DUAL_CONTENT>.
  29. The default behavior allows this, for compatibility with older
  30. versions of OpenSSL.
  31. An attempt is made to locate all the signer's certificates, first looking in
  32. the B<certs> parameter (if it is not B<NULL>) and then looking in any certificates
  33. contained in the B<p7> structure itself. If any signer's certificates cannot be
  34. located the operation fails.
  35. Each signer's certificate is chain verified using the B<smimesign> purpose and
  36. the supplied trusted certificate store. Any internal certificates in the message
  37. are used as untrusted CAs. If any chain verify fails an error code is returned.
  38. Finally the signed content is read (and written to B<out> is it is not NULL) and
  39. the signature's checked.
  40. If all signature's verify correctly then the function is successful.
  41. Any of the following flags (ored together) can be passed in the B<flags> parameter
  42. to change the default verify behaviour. Only the flag B<PKCS7_NOINTERN> is
  43. meaningful to PKCS7_get0_signers().
  44. If B<PKCS7_NOINTERN> is set the certificates in the message itself are not
  45. searched when locating the signer's certificate. This means that all the signers
  46. certificates must be in the B<certs> parameter.
  47. If the B<PKCS7_TEXT> flag is set MIME headers for type B<text/plain> are deleted
  48. from the content. If the content is not of type B<text/plain> then an error is
  49. returned.
  50. If B<PKCS7_NOVERIFY> is set the signer's certificates are not chain verified.
  51. If B<PKCS7_NOCHAIN> is set then the certificates contained in the message are
  52. not used as untrusted CAs. This means that the whole verify chain (apart from
  53. the signer's certificate) must be contained in the trusted store.
  54. If B<PKCS7_NOSIGS> is set then the signatures on the data are not checked.
  55. =head1 NOTES
  56. One application of B<PKCS7_NOINTERN> is to only accept messages signed by
  57. a small number of certificates. The acceptable certificates would be passed
  58. in the B<certs> parameter. In this case if the signer is not one of the
  59. certificates supplied in B<certs> then the verify will fail because the
  60. signer cannot be found.
  61. Care should be taken when modifying the default verify behaviour, for example
  62. setting C<PKCS7_NOVERIFY|PKCS7_NOSIGS> will totally disable all verification
  63. and any signed message will be considered valid. This combination is however
  64. useful if one merely wishes to write the content to B<out> and its validity
  65. is not considered important.
  66. Chain verification should arguably be performed using the signing time rather
  67. than the current time. However, since the signing time is supplied by the
  68. signer it cannot be trusted without additional evidence (such as a trusted
  69. timestamp).
  70. =head1 RETURN VALUES
  71. PKCS7_verify() returns one for a successful verification and zero
  72. if an error occurs.
  73. PKCS7_get0_signers() returns all signers or B<NULL> if an error occurred.
  74. The error can be obtained from L<ERR_get_error(3)>
  75. =head1 BUGS
  76. The trusted certificate store is not searched for the signers certificate,
  77. this is primarily due to the inadequacies of the current B<X509_STORE>
  78. functionality.
  79. The lack of single pass processing and need to hold all data in memory as
  80. mentioned in PKCS7_sign() also applies to PKCS7_verify().
  81. =head1 SEE ALSO
  82. L<ERR_get_error(3)>, L<PKCS7_sign(3)>
  83. =head1 COPYRIGHT
  84. Copyright 2002-2020 The OpenSSL Project Authors. All Rights Reserved.
  85. Licensed under the Apache License 2.0 (the "License"). You may not use
  86. this file except in compliance with the License. You can obtain a copy
  87. in the file LICENSE in the source distribution or at
  88. L<https://www.openssl.org/source/license.html>.
  89. =cut