PKCS7 Flags/Constants

The S/MIME functions make use of flags which are specified using a bitfield which can include one or more of the following values:

PKCS7 CONSTANTS

Constant	Description
PKCS7_TEXT	Adds text/plain content type headers to encrypted/signed message. If decrypting or verifying, it strips those headers from the output - if the decrypted or verified message is not of MIME type text/plain then an error will occur.
PKCS7_BINARY	Normally the input message is converted to "canonical" format which is effectively using CR and LF as end of line: as required by the S/MIME specification. When this options is present, no translation occurs. This is useful when handling binary data which may not be in MIME format.
PKCS7_NOINTERN	When verifying a message, certificates (if any) included in the message are normally searched for the signing certificate. With this option only the certificates specified in the extracerts parameter of openssl_pkcs7_verify() are used. The supplied certificates can still be used as untrusted CAs however.
PKCS7_NOVERIFY	Do not verify the signers certificate of a signed message.
PKCS7_NOCHAIN	Do not chain verification of signers certificates: that is don't use the certificates in the signed message as untrusted CAs.
PKCS7_NOCERTS	When signing a message the signer's certificate is normally included - with this option it is excluded. This will reduce the size of the signed message but the verifier must have a copy of the signers certificate available locally (passed using the extracerts to openssl_pkcs7_verify() for example).
PKCS7_NOATTR	Normally when a message is signed, a set of attributes are included which include the signing time and the supported symmetric algorithms. With this option they are not included.
PKCS7_DETACHED	When signing a message, use cleartext signing with the MIME type multipart/signed. This is the default if you do not specify any flags to openssl_pkcs7_sign(). If you turn this option off, the message will be signed using opaque signing, which is more resistant to translation by mail relays but cannot be read by mail agents that do not support S/MIME.
PKCS7_NOSIGS	Don't try and verify the signatures on a message

Note: These constants were added in 4.0.6.