SMIME 1 2008-05-09 0.9.9-dev OpenSSL
NAME
smime - S/MIME utility
LIBRARY
libcrypto, -lcrypto
SYNOPSIS
ooppeennssssll ssmmiimmee
[--eennccrryypptt]
[--ddeeccrryypptt]
[--ssiiggnn]
[--rreessiiggnn]
[--vveerriiffyy]
[--ppkk77oouutt]
[--ddeess]
[--ddeess33]
[--rrcc22--4400]
[--rrcc22--6644]
[--rrcc22--112288]
[--aaeess112288]
[--aaeess119922]
[--aaeess225566]
[--ccaammeelllliiaa112288]
[--ccaammeelllliiaa119922]
[--ccaammeelllliiaa225566]
[--iinn ffiillee]
[--cceerrttffiillee ffiillee]
[--ssiiggnneerr ffiillee]
[--rreecciipp ffiillee]
[--iinnffoorrmm SSMMIIMMEE||PPEEMM||DDEERR]
[--ppaassssiinn aarrgg]
[--iinnkkeeyy ffiillee]
[--oouutt ffiillee]
[--oouuttffoorrmm SSMMIIMMEE||PPEEMM||DDEERR]
[--ccoonntteenntt ffiillee]
[--ttoo aaddddrr]
[--ffrroomm aadd]
[--ssuubbjjeecctt ss]
[--tteexxtt]
[--iinnddeeff]
[--nnooiinnddeeff]
[--ssttrreeaamm]
[--rraanndd ffiillee((ss))]
[--mmdd ddiiggeesstt]
[cert.pem]...
DESCRIPTION
The ssmmiimmee 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.
-
--eennccrryypptt
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.
-
--ddeeccrryypptt
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.
-
--ssiiggnn
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.
-
--vveerriiffyy
verify signed mail. Expects a signed mail message on input and outputs
-
the signed data. Both clear text and opaque signing is supported.
-
--ppkk77oouutt
takes an input message and writes out a PEM encoded PKCS#7 structure.
-
-
--rreessiiggnn
resign a message: take an existing message and one or more new signers.
-
-
--iinn ffiilleennaammee
the input message to be encrypted or signed or the MIME message to
-
be decrypted or verified.
-
--iinnffoorrmm SSMMIIMMEE||PPEEMM||DDEERR
this specifies the input format for the PKCS#7 structure. The default
-
is SSMMIIMMEE which reads an S/MIME format message. PPEEMM and DDEERR
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
--eennccrryypptt or --ssiiggnn) this option has no effect.
-
--oouutt ffiilleennaammee
the message text that has been decrypted or verified or the output MIME
-
format message that has been signed or verified.
-
--oouuttffoorrmm SSMMIIMMEE||PPEEMM||DDEERR
this specifies the output format for the PKCS#7 structure. The default
-
is SSMMIIMMEE which write an S/MIME format message. PPEEMM and DDEERR
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
--vveerriiffyy or --ddeeccrryypptt) this option has no effect.
-
--ssttrreeaamm --iinnddeeff --nnooiinnddeeff
the --ssttrreeaamm and --iinnddeeff 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 SSMMIIMMEE it is currently off by default for all
other operations.
-
--nnooiinnddeeff
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.
-
--ccoonntteenntt ffiilleennaammee
This specifies a file containing the detached content, this is only
-
useful with the --vveerriiffyy 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.
-
--tteexxtt
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.
-
--CCAAffiillee ffiillee
a file containing trusted CA certificates, only used with --vveerriiffyy.
-
-
--CCAAppaatthh ddiirr
a directory containing trusted CA certificates, only used with
-
--vveerriiffyy. This directory must be a standard certificate directory: that
is a hash of each subject name (using xx550099 --hhaasshh) should be linked
to each certificate.
-
--mmdd ddiiggeesstt
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).
-
--ddeess --ddeess33 --rrcc22--4400 --rrcc22--6644 --rrcc22--112288 --aaeess112288 --aaeess119922 --aaeess225566 --ccaammeelllliiaa112288 --ccaammeelllliiaa119922 --ccaammeelllliiaa225566
the encryption algorithm to use. DES (56 bits), triple DES (168 bits), 40, 64
-
or 128 bit RC2, 128, 192 or 256 bit AES, or 128, 192 or 256 bit Camellia
respectively. Any other cipher name (as recognized by the
_E_V_P___g_e_t___c_i_p_h_e_r_b_y_n_a_m_e_(_) function) can also be used preceded by a dash, for
example --aaeess__112288__ccbbcc.
If not specified 40 bit RC2 is used. Only used with --eennccrryypptt.
-
--nnooiinntteerrnn
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 --cceerrttffiillee option are used.
The supplied certificates can still be used as untrusted CAs however.
-
--nnoovveerriiffyy
do not verify the signers certificate of a signed message.
-
-
--nnoocchhaaiinn
do not do chain verification of signers certificates: that is don't
-
use the certificates in the signed message as untrusted CAs.
-
--nnoossiiggss
don't try to verify the signatures on the message.
-
-
--nnoocceerrttss
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 --cceerrttffiillee option for example).
-
--nnooaattttrr
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.
-
--bbiinnaarryy
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.
-
--nnooddeettaacchh
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.
-
--cceerrttffiillee ffiillee
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.
-
--ssiiggnneerr ffiillee
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.
-
--rreecciipp ffiillee
the recipients certificate when decrypting a message. This certificate
-
must match one of the recipients of the message or an error occurs.
-
--iinnkkeeyy ffiillee
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 --rreecciipp or --ssiiggnneerr file. When signing this option can be used
multiple times to specify successive keys.
-
--ppaassssiinn aarrgg
the private key password source. For more information about the format of aarrgg
-
see the PPAASSSS PPHHRRAASSEE AARRGGUUMMEENNTTSS section in _o_p_e_n_s_s_l(1).
-
--rraanndd ffiillee((ss))
a file or files containing random data used to seed the random number
-
generator, or an EGD socket (see _R_A_N_D___e_g_d(3)).
Multiple files can be specified separated by a OS-dependent character.
The separator is ;; for MS-Windows, ,, for OpenVMS, and :: for
all others.
-
cceerrtt..ppeemm......
one or more certificates of message recipients: used when encrypting
-
a message.
-
--ttoo,, --ffrroomm,, --ssuubbjjeecctt
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.
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 --tteexxtt 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 --eennccrryypptt and --ddeeccrryypptt 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 --rreessiiggnn 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 --ssttrreeaamm and --iinnddeeff 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 --eennccrryypptt operation and the
--ssiiggnn operation if the content is not detached.
Streaming is always used for the --ssiiggnn 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 --tteexxtt 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 --ssiiggnneerr options and the --rreessiiggnn command were first
added in OpenSSL 0.9.9