PKCS7_verify(3)             OpenSSL             PKCS7_verify(3)





NAME
       PKCS7_verify - verify a PKCS#7 signedData structure

SYNOPSIS
       int PKCS7_verify(PKCS7 *p7, STACK_OF(X509) *certs,
       X509_STORE *store, BIO *indata, BIO *out, int flags);

       int PKCS7_get0_signers(PKCS7 *p7, STACK_OF(X509) *certs,
       int flags);

DESCRIPTION
       PKCS7_verify() verifies a PKCS#7 signedData structure.
       p7 is the PKCS7 structure to verify. certs is a set of
       certificates in which to search for the signer's cer-
       tificate. store is a trusted certficate store (used for
       chain verification). indata is the signed data if the
       content is not present in p7 (that is it is detached).
       The content is written to out if it is not NULL.

       flags is an optional set of flags, which can be used to
       modify the verify operation.

       PKCS7_get0_signers() retrieves the signer's certificates
       from p7, it does not check their validity or whether any
       signatures are valid. The certs and flags parameters
       have the same meanings as in PKCS7_verify().

VERIFY PROCESS
       Normally the verify process proceeds as follows.

       Initially some sanity checks are performed on p7. The
       type of p7 must be signedData. There must be at least
       one signature on the data and if the content is detached
       indata cannot be NULL.

       An attempt is made to locate all the signer's certifi-
       cates, first looking in the certs parameter (if it is
       not NULL) and then looking in any certificates contained
       in the p7 structure itself. If any signer's certificates
       cannot be located the operation fails.

       Each signer's certificate is chain verified using the
       smimesign purpose and the supplied trusted certificate
       store. Any internal certificates in the message are used
       as untrusted CAs. If any chain verify fails an error
       code is returned.

       Finally the signed content is read (and written to out
       is it is not NULL) and the signature's checked.

       If all signature's verify correctly then the function is
       successful.

       Any of the following flags (ored together) can be passed
       in the flags parameter to change the default verify be-
       haviour. Only the flag PKCS7_NOINTERN is meaningful to
       PKCS7_get0_signers().

       If PKCS7_NOINTERN is set the certificates in the message
       itself are not searched when locating the signer's cer-
       tificate. This means that all the signers certificates
       must be in the certs parameter.

       If the PKCS7_TEXT flag is set MIME headers for type
       text/plain are deleted from the content. If the content
       is not of type text/plain then an error is returned.

       If PKCS7_NOVERIFY is set the signer's certificates are
       not chain verified.

       If PKCS7_NOCHAIN is set then the certificates contained
       in the message are not used as untrusted CAs. This means
       that the whole verify chain (apart from the signer's
       certificate) must be contained in the trusted store.

       If PKCS7_NOSIGS is set then the signatures on the data
       are not checked.

NOTES
       One application of PKCS7_NOINTERN is to only accept mes-
       sages signed by a small number of certificates. The
       acceptable certificates would be passed in the certs
       parameter. In this case if the signer is not one of the
       certificates supplied in certs then the verify will fail
       because the signer cannot be found.

       Care should be taken when modifying the default verify
       behaviour, for example setting PKCS7_NOVER-
       IFY|PKCS7_NOSIGS will totally disable all verification
       and any signed message will be considered valid. This
       combination is however useful if one merely wishes to
       write the content to out and its validity is not consid-
       ered important.

       Chain verification should arguably be performed  using
       the signing time rather than the current time. However
       since the signing time is supplied by the signer it can-
       not be trusted without additional evidence (such as a
       trusted timestamp).

RETURN VALUES
       PKCS7_verify() returns 1 for a successful verification
       and zero or a negative value if an error occurs.

       PKCS7_get0_signers() returns all signers or NULL if an
       error occurred.

       The error can be obtained from ERR_get_error(3)

BUGS
       The trusted certificate store is not searched for the
       signers certificate, this is primarily due to the inade-
       quacies of the current X509_STORE functionality.

       The lack of single pass processing and need to hold all
       data in memory as mentioned in PKCS7_sign() also applies
       to PKCS7_verify().

SEE ALSO
       ERR_get_error(3), PKCS7_sign(3)

HISTORY
       PKCS7_verify() was added to OpenSSL 0.9.5



0.9.7c                     2002-10-09           PKCS7_verify(3)
