/usr/man/cat.3/PKCS7_verify.3(/usr/man/cat.3/PKCS7_verify.3)

PKCS7_verify(3)              OpenSSL              PKCS7_verify(3)

NAME

     PKCS7_verify, PKCS7_get0_signers - verify a PKCS#7
     signedData structure

SYNOPSIS

      #include <openssl/pkcs7.h>

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

      STACK_OF(X509) *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
     certificate. 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 certificates,
     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.

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PKCS7_verify(3)              OpenSSL              PKCS7_verify(3)

     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 behaviour.
     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
     certificate. 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 messages
     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_NOVERIFY|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 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

     PKCS7_verify() returns one for a successful verification and
     zero if an error occurs.

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PKCS7_verify(3)              OpenSSL              PKCS7_verify(3)

     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
     inadequacies 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

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See also PKCS7_get0_signers(3)