There are six operation options that set the type of operation to be performed. The meaning of the other options varies according to the operation type.
-encrypt
encrypt mail for the given recipient certificates. Input file is the message to be encrypted. The output file is the encrypted mail in MIME format.
-decrypt
decrypt mail using the supplied certificate and private key. Expects an encrypted mail message in MIME format for the input file. The decrypted mail is written to the output file.
-sign
sign mail using the supplied certificate and private key. Input file is the message to be signed. The signed message in MIME format is written to the output file.
-verify
verify signed mail. Expects a signed mail message on input and outputs the signed data. Both clear text and opaque signing is supported.
-pk7out
takes an input message and writes out a PEM encoded PKCS#7 structure.
-resign
resign a message: take an existing message and one or more new signers.
-in filename
the input message to be encrypted or signed or the MIME message to be decrypted or verified.
-inform SMIME|PEM|DER
this specifies the input format for the PKCS#7 structure. The default is SMIME which reads an S/MIME format message. PEM and DER format change this to expect PEM and DER format PKCS#7 structures instead. This currently only affects the input format of the PKCS#7 structure, if no PKCS#7 structure is being input (for example with -encrypt or -sign) this option has no effect.
-out filename
the message text that has been decrypted or verified or the output MIME format message that has been signed or verified.
-outform SMIME|PEM|DER
this specifies the output format for the PKCS#7 structure. The default is SMIME which write an S/MIME format message. PEM and DER format change this to write PEM and DER format PKCS#7 structures instead. This currently only affects the output format of the PKCS#7 structure, if no PKCS#7 structure is being output (for example with -verify or -decrypt) this option has no effect.
-stream -indef -noindef
the -stream and -indef options are equivalent and enable streaming I/O for encoding operations. This permits single pass processing of data without the need to hold the entire contents in memory, potentially supporting very large files. Streaming is automatically set for S/MIME signing with detached data if the output format is SMIME it is currently off by default for all other operations.
-noindef
disable streaming I/O where it would produce and indefinite length constructed encoding. This option currently has no effect. In future streaming will be enabled by default on all relevant operations and this option will disable it.
-content filename
This specifies a file containing the detached content, this is only useful with the -verify command. This is only usable if the PKCS#7 structure is using the detached signature form where the content is not included. This option will override any content if the input format is S/MIME and it uses the multipart/signed MIME content type.
-text
this option adds plain text (text/plain) MIME headers to the supplied message if encrypting or signing. If decrypting or verifying it strips off text headers: if the decrypted or verified message is not of MIME type text/plain then an error occurs.
-CAfile file
a file containing trusted CA certificates, only used with -verify.
-CApath dir
a directory containing trusted CA certificates, only used with -verify. This directory must be a standard certificate directory: that is a hash of each subject name (using x509 -hash) should be linked to each certificate.
-md digest
digest algorithm to use when signing or resigning. If not present then the default digest algorithm for the signing key will be used (usually SHA1).
-[cipher]
the encryption algorithm to use. For example DES (56 bits) -
-des, triple DES (168 bits) - -des3, EVP_get_cipherbyname() function) can also be used preceded by a dash, for example -aes_128_cbc. See enc for list of ciphers supported by your version of OpenSSL.
If not specified 40 bit RC2 is used. Only used with
-encrypt.
-nointern
when verifying a message normally certificates (if any) included in the message are searched for the signing certificate. With this option only the certificates specified in the -certfile option are used. The supplied certificates can still be used as untrusted CAs however.
-noverify
do not verify the signers certificate of a signed message.
-nochain
do not do chain verification of signers certificates: that is don't use the certificates in the signed message as untrusted CAs.
-nosigs
don't try to verify the signatures on the message.
-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 -certfile option for example).
-noattr
normally when a message is signed a set of attributes are included which include the signing time and supported symmetric algorithms. With this option they are not included.
-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 option is present no translation occurs. This is useful when handling binary data which may not be in MIME format.
-nodetach
when signing a message use opaque signing: this form is more resistant to translation by mail relays but it cannot be read by mail agents that do not support S/MIME. Without this option cleartext signing with the MIME type multipart/signed is used.
-certfile file
allows additional certificates to be specified. When signing these will be included with the message. When verifying these will be searched for the signers certificates. The certificates should be in PEM format.
-signer file
a signing certificate when signing or resigning a message, this option can be used multiple times if more than one signer is required. If a message is being verified then the signers certificates will be written to this file if the verification was successful.
-recip file
the recipients certificate when decrypting a message. This certificate must match one of the recipients of the message or an error occurs.
-inkey file
the private key to use when signing or decrypting. This must match the corresponding certificate. If this option is not specified then the private key must be included in the certificate file specified with the -recip or -signer file. When signing this option can be used multiple times to specify successive keys.
-passin arg
the private key password source. For more information about the format of arg see the PASS PHRASE ARGUMENTS section in openssl(1).
-rand file(s)
a file or files containing random data used to seed the random number generator, or an EGD socket (see RAND_egd(3)). Multiple files can be specified separated by a OS-dependent character. The separator is ; for MS-Windows, , for OpenVMS, and : for all others.
cert.pem...
one or more certificates of message recipients: used when encrypting a message.
-to, -from, -subject
the relevant mail headers. These are included outside the signed portion of a message so they may be included manually. If signing then many S/MIME mail clients check the signers certificate's email address matches that specified in the From: address.
-purpose, -ignore_critical, -issuer_checks, -crl_check, -crl_check_all, -policy_check, -extended_crl, -x509_strict, -policy -check_ss_sig
Set various options of certificate chain verification. See verify manual page for details.