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SMIME(1)                     OpenSSL                     SMIME(1)


NAME

     openssl-smime, smime - S/MIME utility


SYNOPSIS

     openssl smime [-encrypt] [-decrypt] [-sign] [-resign]
     [-verify] [-pk7out] [-[cipher]] [-in file] [-no_alt_chains]
     [-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] [-indef] [-noindef] [-stream]
     [-rand file(s)] [-md digest] [cert.pem]...


DESCRIPTION

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


COMMAND OPTIONS

     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.

         Note that no revocation check is done for the recipient
         cert, so if that key has been compromised, others may be
         able to decrypt the text.

     -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

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SMIME(1)                     OpenSSL                     SMIME(1)

         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

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SMIME(1)                     OpenSSL                     SMIME(1)

         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 triple DES 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

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SMIME(1)                     OpenSSL                     SMIME(1)

         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

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SMIME(1)                     OpenSSL                     SMIME(1)

         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.


-crl_check_all, -policy_check, -extended_crl, -x509_strict,


-policy -check_ss_sig -no_alt_chains

     -purpose, -ignore_critical, -issuer_checks, -crl_check,
         Set various options of certificate chain verification.
         See verify manual page for details.


NOTES

     The MIME message must be sent without any blank lines
     between the headers 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 necessary 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

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SMIME(1)                     OpenSSL                     SMIME(1)

     encrypting an already signed message: 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.

     The -resign option uses an existing message digest when
     adding a new signer. This means that attributes must be
     present in at least one existing signer using the same
     message digest or this operation will fail.

     The -stream and -indef options enable experimental streaming
     I/O support.  As a result the encoding is BER using
     indefinite length constructed encoding and no longer DER.
     Streaming is supported for the -encrypt operation and the
     -sign operation if the content is not detached.

     Streaming is always used for the -sign operation with
     detached data but since the content is no longer part of the
     PKCS#7 structure the encoding remains DER.


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 an opaque signed message:

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SMIME(1)                     OpenSSL                     SMIME(1)

      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

     Create a signed message with two signers:

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

     Send a signed message under Unix directly to sendmail,
     including headers:

      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 signature by line wrapping the base64 encoded
     structure and surrounding it with:

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SMIME(1)                     OpenSSL                     SMIME(1)

      -----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

     Create an encrypted message using 128 bit Camellia:

      openssl smime -encrypt -in plain.txt -camellia128 -out mail.msg cert.pem

     Add a signer to an existing message:

      openssl smime -resign -in mail.msg -signer newsign.pem -out mail2.msg


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 encryption 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.


HISTORY

     The use of multiple -signer options and the -resign command
     were first added in OpenSSL 1.0.0

     The -no_alt_chains options was first added to OpenSSL
     1.0.2b.

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See also smime(1)

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