NAME
    smime - S/MIME utility

SYNOPSIS
    openssl smime [-encrypt] [-decrypt] [-sign] [-verify] [-pk7out] [-des]
    [-des3] [-rc2-40] [-rc2-64] [-rc2-128] [-in file] [-certfile file]
    [-signer file] [-recip file] [-inform SMIME|PEM|DER] [-passin arg]
    [-inkey file] [-out file] [-outform SMIME|PEM|DER] [-content file] [-to
    addr] [-from ad] [-subject s] [-text] [-rand file(s)] [cert.pem]...

DESCRIPTION
    The smime command handles S/MIME mail. It can encrypt, decrypt, sign
    and verify S/MIME messages.

COMMAND OPTIONS
    There are five 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 out-
   puts the signed data. Both clear text and opaque signing is sup-
   ported.

    -pk7out
   takes an input message and writes out a PEM encoded PKCS#7 struc-
   ture.

    -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 exam-
   ple with -verify or -decrypt) this option has no effect.

    -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 sup-
   plied 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.

    -des -des3 -rc2-40 -rc2-64 -rc2-128
   the encryption algorithm to use. DES (56 bits), triple DES (168
   bits) or 40, 64 or 128 bit RC2 respectively 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 resis-
   tant 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
   the signers certificate when signing a message. 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 certifi-
   cate 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.

    -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 num-
   ber generator, or an EGD socket (see RAND_egd(3)). Multiple files
   can be specified separated by a OS-dependent character. The sepa-
   rator is ; for MS-Windows, , for OpenVMS, and : for all others.

    cert.pem...
   one or more certificates of message recipients: used when encrypt-
   ing 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.

NOTES
    The MIME message must be sent without any blank lines between the head-
    ers and the output. Some mail programs will automatically add a blank
    line. Piping the mail directly to sendmail is one way to achieve the
    correct format.

    The supplied message to be signed or encrypted must include the neces-
    sary MIME headers or many S/MIME clients wont display it properly (if
    at all). You can use the -text option to automatically add plain text
    headers.

    A "signed and encrypted" message is one where a signed message is then
    encrypted. This can be produced by encrypting an already signed mes-
    sage: see the examples section.

    This version of the program only allows one signer per message but it
    will verify multiple signers on received messages. Some S/MIME clients
    choke if a message contains multiple signers. It is possible to sign
    messages "in parallel" by signing an already signed message.

    The options -encrypt and -decrypt reflect common usage in S/MIME
    clients. Strictly speaking these process PKCS#7 enveloped data: PKCS#7
    encrypted data is used for other purposes.

EXIT CODES
    0  the operation was completely successfully.

    1  an error occurred parsing the command options.

    2  one of the input files could not be read.

    3  an error occurred creating the PKCS#7 file or when reading the MIME
   message.

    4  an error occurred decrypting or verifying the message.

    5  the message was verified correctly but an error occurred writing
   out the signers certificates.

EXAMPLES
    Create a cleartext signed message:

 openssl smime -sign -in message.txt -text -out mail.msg \
     -signer mycert.pem

    Create and opaque signed message

 openssl smime -sign -in message.txt -text -out mail.msg -nodetach \
     -signer mycert.pem

    Create a signed message, include some additional certificates and read
    the private key from another file:

 openssl smime -sign -in in.txt -text -out mail.msg \
     -signer mycert.pem -inkey mykey.pem -certfile mycerts.pem

    Send a signed message under Unix directly to sendmail, including head-
    ers:

 openssl smime -sign -in in.txt -text -signer mycert.pem \
     -from steve@openssl.org -to someone@somewhere \
     -subject "Signed message" | sendmail someone@somewhere

    Verify a message and extract the signer's certificate if successful:

 openssl smime -verify -in mail.msg -signer user.pem -out signedtext.txt

    Send encrypted mail using triple DES:

 openssl smime -encrypt -in in.txt -from steve@openssl.org \
     -to someone@somewhere -subject "Encrypted message" \
     -des3 user.pem -out mail.msg

    Sign and encrypt mail:

 openssl smime -sign -in ml.txt -signer my.pem -text \
     | openssl smime -encrypt -out mail.msg \
     -from steve@openssl.org -to someone@somewhere \
     -subject "Signed and Encrypted message" -des3 user.pem

    Note: the encryption command does not include the -text option because
    the message being encrypted already has MIME headers.

    Decrypt mail:

 openssl smime -decrypt -in mail.msg -recip mycert.pem -inkey key.pem

    The output from Netscape form signing is a PKCS#7 structure with the
    detached signature format. You can use this program to verify the sig-
    nature by line wrapping the base64 encoded structure and surrounding it
    with:

 -----BEGIN PKCS7-----
 -----END PKCS7-----

    and using the command,

 openssl smime -verify -inform PEM -in signature.pem -content content.txt

    alternatively you can base64 decode the signature and use

 openssl smime -verify -inform DER -in signature.der -content content.txt

BUGS
    The MIME parser isn't very clever: it seems to handle most messages
    that I've thrown at it but it may choke on others.

    The code currently will only write out the signer's certificate to a
    file: if the signer has a separate encryption certificate this must be
    manually extracted. There should be some heuristic that determines the
    correct encryption certificate.

    Ideally a database should be maintained of a certificates for each
    email address.

    The code doesn't currently take note of the permitted symmetric encryp-
    tion algorithms as supplied in the SMIMECapabilities signed attribute.
    this means the user has to manually include the correct encryption
    algorithm. It should store the list of permitted ciphers in a database
    and only use those.

    No revocation checking is done on the signer's certificate.

    The current code can only handle S/MIME v2 messages, the more complex
    S/MIME v3 structures may cause parsing errors.