SMIME(1)			    OpenSSL			      SMIME(1)



NAME
       smime - S/MIME utility

SYNOPSIS
       openssl smime [-encrypt] [-decrypt] [-sign] [-resign] [-verify]
       [-pk7out] [-[cipher]] [-in file] [-CAfile file] [-CApath dir]
       [-trusted_first] [-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 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.

       -trusted_first
	   Use certificates in CA file or CA directory over certificates
	   provided in the message when building the trust chain to verify a
	   certificate.	 This is mainly useful in environments with Bridge CA
	   or Cross-Certified CAs.

       -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
	   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
       -no_alt_chains
	   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 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:

	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:

	-----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.



1.0.2k				  2023-11-15			      SMIME(1)