Provided by: openssl_3.0.10-1ubuntu2.3_amd64 
NAME
openssl-smime - S/MIME command
SYNOPSIS
openssl smime [-help] [-encrypt] [-decrypt] [-sign] [-resign] [-verify] [-pk7out]
[-binary] [-crlfeol] [-cipher] [-in file] [-certfile file] [-signer file] [-nointern]
[-noverify] [-nochain] [-nosigs] [-nocerts] [-noattr] [-nodetach] [-nosmimecap] [-recip
file] [-inform DER|PEM|SMIME] [-outform DER|PEM|SMIME] [-keyform DER|PEM|P12|ENGINE]
[-passin arg] [-inkey filename|uri] [-out file] [-content file] [-to addr] [-from ad]
[-subject s] [-text] [-indef] [-noindef] [-stream] [-md digest] [-CAfile file]
[-no-CAfile] [-CApath dir] [-no-CApath] [-CAstore uri] [-no-CAstore] [-engine id] [-rand
files] [-writerand file] [-allow_proxy_certs] [-attime timestamp] [-no_check_time]
[-check_ss_sig] [-crl_check] [-crl_check_all] [-explicit_policy] [-extended_crl]
[-ignore_critical] [-inhibit_any] [-inhibit_map] [-partial_chain] [-policy arg]
[-policy_check] [-policy_print] [-purpose purpose] [-suiteB_128] [-suiteB_128_only]
[-suiteB_192] [-trusted_first] [-no_alt_chains] [-use_deltas] [-auth_level num]
[-verify_depth num] [-verify_email email] [-verify_hostname hostname] [-verify_ip ip]
[-verify_name name] [-x509_strict] [-issuer_checks] [-provider name] [-provider-path path]
[-propquery propq] [-config configfile] recipcert ...
DESCRIPTION
This command handles S/MIME mail. It can encrypt, decrypt, sign and verify S/MIME
messages.
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.
-help
Print out a usage message.
-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.
-out filename
The message text that has been decrypted or verified or the output MIME format message
that has been signed or verified.
-inform DER|PEM|SMIME
The input format of the PKCS#7 (S/MIME) structure (if one is being read); the default
is SMIME. See openssl-format-options(1) for details.
-outform DER|PEM|SMIME
The output format of the PKCS#7 (S/MIME) structure (if one is being written); the
default is SMIME. See openssl-format-options(1) for details.
-keyform DER|PEM|P12|ENGINE
The key format; unspecified by default. See openssl-format-options(1) for details.
-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.
-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 openssl-enc(1) 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, do not 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.
-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.
-nosmimecap
When signing a message, do not include the SMIMECapabilities attribute.
-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.
-crlfeol
Normally the output file uses a single LF as end of line. When this option is present
CRLF is used instead.
-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 input can be in PEM, DER, or PKCS#12 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.
-nocerts
Don't include signers certificate when signing.
-noattr
Don't include any signed attributes when signing.
-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 filename|uri
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
openssl-passphrase-options(1).
-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.
-allow_proxy_certs, -attime, -no_check_time, -check_ss_sig, -crl_check, -crl_check_all,
-explicit_policy, -extended_crl, -ignore_critical, -inhibit_any, -inhibit_map,
-no_alt_chains, -partial_chain, -policy, -policy_check, -policy_print, -purpose,
-suiteB_128, -suiteB_128_only, -suiteB_192, -trusted_first, -use_deltas, -auth_level,
-verify_depth, -verify_email, -verify_hostname, -verify_ip, -verify_name, -x509_strict
-issuer_checks
Set various options of certificate chain verification. See "Verification Options" in
openssl-verification-options(1) for details.
Any verification errors cause the command to exit.
-CAfile file, -no-CAfile, -CApath dir, -no-CApath, -CAstore uri, -no-CAstore
See "Trusted Certificate Options" in openssl-verification-options(1) for details.
-engine id
See "Engine Options" in openssl(1). This option is deprecated.
-rand files, -writerand file
See "Random State Options" in openssl(1) for details.
-provider name
-provider-path path
-propquery propq
See "Provider Options" in openssl(1), provider(7), and property(7).
-config configfile
See "Configuration Option" in openssl(1).
recipcert ...
One or more certificates of message recipients, used when encrypting a message.
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 won't 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 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.
SEE ALSO
ossl_store-file(7)
HISTORY
The use of multiple -signer options and the -resign command were first added in OpenSSL
1.0.0
The -no_alt_chains option was added in OpenSSL 1.1.0.
The -engine option was deprecated in OpenSSL 3.0.
COPYRIGHT
Copyright 2000-2021 The OpenSSL Project Authors. All Rights Reserved.
Licensed under the Apache License 2.0 (the "License"). You may not use this file except
in compliance with the License. You can obtain a copy in the file LICENSE in the source
distribution or at <https://www.openssl.org/source/license.html>.