CMS(1) OpenSSL CMS(1)
NAME
cms - CMS utility
SYNOPSIS
openssl cms [-encrypt] [-decrypt] [-sign] [-verify] [-cmsout] [-resign]
[-data_create] [-data_out] [-digest_create] [-digest_verify]
[-compress] [-uncompress] [-EncryptedData_encrypt] [-sign_receipt]
[-verify_receipt receipt] [-in filename] [-inform SMIME|PEM|DER]
[-rctform SMIME|PEM|DER] [-out filename] [-outform SMIME|PEM|DER]
[-stream -indef -noindef] [-noindef] [-content filename] [-text]
[-noout] [-print] [-CAfile file] [-CApath dir] [-trusted_first]
[-no_alt_chains] [-md digest] [-[cipher]] [-nointern]
[-no_signer_cert_verify] [-nocerts] [-noattr] [-nosmimecap] [-binary]
[-nodetach] [-certfile file] [-certsout file] [-signer file] [-recip
file] [-keyid] [-receipt_request_all -receipt_request_first]
[-receipt_request_from emailaddress] [-receipt_request_to emailaddress]
[-receipt_request_print] [-secretkey key] [-secretkeyid id]
[-econtent_type type] [-inkey file] [-keyopt name:parameter] [-passin
arg] [-rand file(s)] [cert.pem...] [-to addr] [-from addr] [-subject
subj] [cert.pem]...
DESCRIPTION
The cms command handles S/MIME v3.1 mail. It can encrypt, decrypt, sign
and verify, compress and uncompress S/MIME messages.
COMMAND OPTIONS
There are fourteen 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. The actual CMS type is <B>EnvelopedData<B>.
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.
-debug_decrypt
this option sets the CMS_DEBUG_DECRYPT flag. This option should be
used with caution: see the notes section below.
-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.
-cmsout
takes an input message and writes out a PEM encoded CMS structure.
-resign
resign a message: take an existing message and one or more new
signers.
-data_create
Create a CMS Data type.
-data_out
Data type and output the content.
-digest_create
Create a CMS DigestedData type.
-digest_verify
Verify a CMS DigestedData type and output the content.
-compress
Create a CMS CompressedData type. OpenSSL must be compiled with
zlib support for this option to work, otherwise it will output an
error.
-uncompress
Uncompress a CMS CompressedData type and output the content.
OpenSSL must be compiled with zlib support for this option to work,
otherwise it will output an error.
-EncryptedData_encrypt
Encrypt content using supplied symmetric key and algorithm using a
CMS EncrytedData type and output the content.
-sign_receipt
Generate and output a signed receipt for the supplied message. The
input message must contain a signed receipt request. Functionality
is otherwise similar to the -sign operation.
-verify_receipt receipt
Verify a signed receipt in filename receipt. The input message must
contain the original receipt request. Functionality is otherwise
similar to the -verify operation.
-in filename
the input message to be encrypted or signed or the message to be
decrypted or verified.
-inform SMIME|PEM|DER
this specifies the input format for the CMS structure. The default
is SMIME which reads an S/MIME format message. PEM and DER format
change this to expect PEM and DER format CMS structures instead.
This currently only affects the input format of the CMS structure,
if no CMS structure is being input (for example with -encrypt or
-sign) this option has no effect.
-rctform SMIME|PEM|DER
specify the format for a signed receipt for use with the
-receipt_verify operation.
-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 CMS structure. The default
is SMIME which writes an S/MIME format message. PEM and DER format
change this to write PEM and DER format CMS structures instead.
This currently only affects the output format of the CMS structure,
if no CMS 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 CMS
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.
-noout
for the -cmsout operation do not output the parsed CMS structure.
This is useful when combined with the -print option or if the
syntax of the CMS structure is being checked.
-print
for the -cmsout operation print out all fields of the CMS
structure. This is mainly useful for testing purposes.
-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 before untrusted
certificates from the message when building the trust chain to
verify certificates. 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 triple DES (168 bits)
- -des3 or 256 bit AES - -aes256. Any standard algorithm name (as
used by the EVP_get_cipherbyname() function) can also be used
preceded by a dash, for example -aes_128_cbc. See enc for a list of
ciphers supported by your version of OpenSSL.
If not specified triple DES is used. Only used with -encrypt and
-EncryptedData_create commands.
-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.
-no_signer_cert_verify
do not verify the signers certificate of a signed 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.
-nosmimecap
exclude the list of supported algorithms from signed attributes,
other options such as signing time and content type are still
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.
-certsout file
any certificates contained in the message are written to file.
-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
when decrypting a message this specifies the recipients
certificate. The certificate must match one of the recipients of
the message or an error occurs.
When encrypting a message this option may be used multiple times to
specify each recipient. This form must be used if customised
parameters are required (for example to specify RSA-OAEP).
-keyid
use subject key identifier to identify certificates instead of
issuer name and serial number. The supplied certificate must
include a subject key identifier extension. Supported by -sign and
-encrypt options.
-receipt_request_all -receipt_request_first
for -sign option include a signed receipt request. Indicate
requests should be provided by all receipient or first tier
recipients (those mailed directly and not from a mailing list).
Ignored it -receipt_request_from is included.
-receipt_request_from emailaddress
for -sign option include a signed receipt request. Add an explicit
email address where receipts should be supplied.
-receipt_request_to emailaddress
Add an explicit email address where signed receipts should be sent
to. This option must but supplied if a signed receipt it requested.
-receipt_request_print
For the -verify operation print out the contents of any signed
receipt requests.
-secretkey key
specify symmetric key to use. The key must be supplied in hex
format and be consistent with the algorithm used. Supported by the
-EncryptedData_encrypt -EncrryptedData_decrypt, -encrypt and
-decrypt options. When used with -encrypt or -decrypt the supplied
key is used to wrap or unwrap the content encryption key using an
AES key in the KEKRecipientInfo type.
-secretkeyid id
the key identifier for the supplied symmetric key for
KEKRecipientInfo type. This option must be present if the
-secretkey option is used with -encrypt. With -decrypt operations
the id is used to locate the relevant key if it is not supplied
then an attempt is used to decrypt any KEKRecipientInfo structures.
-econtent_type type
set the encapsulated content type to type if not supplied the Data
type is used. The type argument can be any valid OID name in either
text or numerical format.
-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.
-keyopt name:opt
for signing and encryption this option can be used multiple times
to set customised parameters for the preceding key or certificate.
It can currently be used to set RSA-PSS for signing, RSA-OAEP for
encryption or to modify default parameters for ECDH.
-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 certificate chain valiadition option. See the 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 CMS enveloped data: CMS
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 CMS structure the encoding
remains DER.
If the -decrypt option is used without a recipient certificate then an
attempt is made to locate the recipient by trying each potential
recipient in turn using the supplied private key. To thwart the MMA
attack (Bleichenbacher's attack on PKCS #1 v1.5 RSA padding) all
recipients are tried whether they succeed or not and if no recipients
match the message is "decrypted" using a random key which will
typically output garbage. The -debug_decrypt option can be used to
disable the MMA attack protection and return an error if no recipient
can be found: this option should be used with caution. For a fuller
description see CMS_decrypt(3)).
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 CMS 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.
COMPATIBILITY WITH PKCS#7 format.
The smime utility can only process the older PKCS#7 format. The cms
utility supports Cryptographic Message Syntax format. Use of some
features will result in messages which cannot be processed by
applications which only support the older format. These are detailed
below.
The use of the -keyid option with -sign or -encrypt.
The -outform PEM option uses different headers.
The -compress option.
The -secretkey option when used with -encrypt.
The use of PSS with -sign.
The use of OAEP or non-RSA keys with -encrypt.
Additionally the -EncryptedData_create and -data_create type cannot be
processed by the older smime command.
EXAMPLES
Create a cleartext signed message:
openssl cms -sign -in message.txt -text -out mail.msg \
-signer mycert.pem
Create an opaque signed message
openssl cms -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 cms -sign -in in.txt -text -out mail.msg \
-signer mycert.pem -inkey mykey.pem -certfile mycerts.pem
Create a signed message with two signers, use key identifier:
openssl cms -sign -in message.txt -text -out mail.msg \
-signer mycert.pem -signer othercert.pem -keyid
Send a signed message under Unix directly to sendmail, including
headers:
openssl cms -sign -in in.txt -text -signer mycert.pem \
-from steve AT openssl.org -to someone@somewhere \
-subject "Signed message" | sendmail someone@somewhere
Verify a message and extract the signer's certificate if successful:
openssl cms -verify -in mail.msg -signer user.pem -out signedtext.txt
Send encrypted mail using triple DES:
openssl cms -encrypt -in in.txt -from steve AT openssl.org \
-to someone@somewhere -subject "Encrypted message" \
-des3 user.pem -out mail.msg
Sign and encrypt mail:
openssl cms -sign -in ml.txt -signer my.pem -text \
| openssl cms -encrypt -out mail.msg \
-from steve AT 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 cms -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 cms -verify -inform PEM -in signature.pem -content content.txt
alternatively you can base64 decode the signature and use
openssl cms -verify -inform DER -in signature.der -content content.txt
Create an encrypted message using 128 bit Camellia:
openssl cms -encrypt -in plain.txt -camellia128 -out mail.msg cert.pem
Add a signer to an existing message:
openssl cms -resign -in mail.msg -signer newsign.pem -out mail2.msg
Sign mail using RSA-PSS:
openssl cms -sign -in message.txt -text -out mail.msg \
-signer mycert.pem -keyopt rsa_padding_mode:pss
Create encrypted mail using RSA-OAEP:
openssl cms -encrypt -in plain.txt -out mail.msg \
-recip cert.pem -keyopt rsa_padding_mode:oaep
Use SHA256 KDF with an ECDH certificate:
openssl cms -encrypt -in plain.txt -out mail.msg \
-recip ecdhcert.pem -keyopt ecdh_kdf_md:sha256
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.
HISTORY
The use of multiple -signer options and the -resign command were first
added in OpenSSL 1.0.0
The keyopt option was first added in OpenSSL 1.1.0
The use of -recip to specify the recipient when encrypting mail was
first added to OpenSSL 1.1.0
Support for RSA-OAEP and RSA-PSS was first added to OpenSSL 1.1.0.
The use of non-RSA keys with -encrypt and -decrypt was first added to
OpenSSL 1.1.0.
The -no_alt_chains options was first added to OpenSSL 1.0.2b.
1.0.2k 2023-11-13 CMS(1)
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