PKCS7verify(3) OpenSSL PKCS7verify(3)

NAME
       PKCS7verify - verify a PKCS#7 signedData structure

SYNOPSIS
       int PKCS7verify(PKCS7 *p7, STACKOF(X509) *certs, X509STORE *store,
       BIO *indata, BIO *out, int flags);

       STACKOF(X509) *PKCS7get0signers(PKCS7 *p7, STACKOF(X509) *certs,
       int flags);

DESCRIPTION
       PKCS7verify() verifies a PKCS#7 signedData structure. pp77 is the PKCS7
       structure to verify. cceerrttss is a set of certificates in which to search
       for the signer's certificate. ssttoorree is a trusted certficate store (used
       for chain verification). iinnddaattaa is the signed data if the content is
       not present in pp77 (that is it is detached). The content is written to
       oouutt if it is not NULL.

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

       PKCS7get0signers() retrieves the signer's certificates from pp77, it
       does nnoott check their validity or whether any signatures are valid. The
       cceerrttss and ffllaaggss parameters have the same meanings as in PKCS7verify().

VVEERRIIFFYY PPRROOCCEESSSS
       Normally the verify process proceeds as follows.

       Initially some sanity checks are performed on pp77. The type of pp77 must
       be signedData. There must be at least one signature on the data and if
       the content is detached iinnddaattaa cannot be NNUULLLL.

       An attempt is made to locate all the signer's certificates, first
       looking in the cceerrttss parameter (if it is not NNUULLLL) and then looking in
       any certificates contained in the pp77 structure itself. If any signer's
       certificates cannot be located the operation fails.

       Each signer's certificate is chain verified using the ssmmiimmeessiiggnn 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 oouutt 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 ffllaaggss
       parameter to change the default verify behaviour. Only the flag
       PPKKCCSS77NNOOIINNTTEERRNN is meaningful to PKCS7get0signers().

       If PPKKCCSS77NNOOIINNTTEERRNN is set the certificates in the message itself are not
       searched when locating the signer's certificate. This means that all
       the signers certificates must be in the cceerrttss parameter.

       If the PPKKCCSS77TTEEXXTT flag is set MIME headers for type tteexxtt//ppllaaiinn are
       deleted from the content. If the content is not of type tteexxtt//ppllaaiinn then
       an error is returned.

       If PPKKCCSS77NNOOVVEERRIIFFYY is set the signer's certificates are not chain
       verified.

       If PPKKCCSS77NNOOCCHHAAIINN 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 PPKKCCSS77NNOOSSIIGGSS is set then the signatures on the data are not checked.

NNOOTTEESS
       One application of PPKKCCSS77NNOOIINNTTEERRNN is to only accept messages signed by
       a small number of certificates. The acceptable certificates would be
       passed in the cceerrttss parameter. In this case if the signer is not one of
       the certificates supplied in cceerrttss then the verify will fail because
       the signer cannot be found.

       Care should be taken when modifying the default verify behaviour, for
       example setting PPKKCCSS77NNOOVVEERRIIFFYY||PPKKCCSS77NNOOSSIIGGSS 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 oouutt and its validity is not considered 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 cannot be trusted without additional evidence
       (such as a trusted timestamp).

RETURN VALUES
       PKCS7verify() returns 1 for a successful verification and zero or a
       negative value if an error occurs.

       PKCS7get0signers() returns all signers or NNUULLLL if an error occurred.

       The error can be obtained from ERRgeterror(3)

BUGS
       The trusted certificate store is not searched for the signers
       certificate, this is primarily due to the inadequacies of the current
       XX550099SSTTOORREE functionality.

       The lack of single pass processing and need to hold all data in memory
       as mentioned in PKCS7sign() also applies to PKCS7verify().

SEE ALSO
       ERRgeterror(3), PKCS7sign(3)

HISTORY       PKCS7verify() was added to OpenSSL 0.9.5



0.9.7l                            2006-01-15                   PKCS7verify(3)