smime - S/MIME utility


   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]...


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


   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 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 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 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 signed mail. Expects a signed mail message on input and
       outputs the signed data. Both clear text and opaque signing is

       takes an input message and writes out a PEM encoded PKCS#7

       resign a message: take an existing message and one or more new

   -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.

       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

       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).

       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.

       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

       do not verify the signers certificate of a signed message.

       do not do chain verification of signers certificates: that is don't
       use the certificates in the signed message as untrusted CAs.

       don't try to verify the signatures on the message.

       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).

       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.

       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.

       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

   -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.

       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.


   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 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

   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

   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.


   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

   4   an error occurred decrypting or verifying the message.

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


   Create a cleartext signed message:

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

   Create an 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

   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

    openssl smime -sign -in in.txt -text -signer mycert.pem \
           -from -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 \
           -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 -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:

    -----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


   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.


   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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