The ts command is a basic Time
Stamping Authority (TSA) client and server application as specified
in RFC 3161 (Time-Stamp Protocol, TSP). A TSA can be part of a PKI
deployment and its role is to provide long term proof of the
existence of a certain datum before a particular time. Here is a
brief description of the protocol:
The TSA client computes a one-way hash value for a data file
and sends the hash to the TSA.
The TSA attaches the current date and time to the received hash
value, signs them and sends the time stamp token back to the
client. By creating this token the TSA certifies the existence
of the original data file at the time of response generation.
The TSA client receives the time stamp token and verifies the
signature on it. It also checks if the token contains the same
hash value that it had sent to the TSA.
There is one DER encoded protocol data unit defined for transporting
a time stamp request to the TSA and one for sending the time stamp
response back to the client. The ts
command has three main functions: creating a time stamp request based
on a data file, creating a time stamp response based on a request,
verifying if a response corresponds to a particular request or a data
file.
There is no support for sending the requests/responses automatically
over HTTP or TCP yet as suggested in RFC 3161. The users must send
the requests either by ftp or e-mail.
OPTIONS
Time Stamp Request generation
The -query switch can be used for
creating and printing a time stamp request with the following
options:
-rand file:file...
The files containing random data for seeding the random
number generator. Multiple files can be specified, the
separator is ; for
MS-Windows, , for VMS and
: for all other platforms.
(Optional)
-config configfile
The configuration file to use, this option overrides the
OPENSSL_CONF environment
variable. Only the OID section of the config file is used
with the -query command.
(Optional)
-data file_to_hash
The data file for which the time stamp request needs to be
created. stdin is the default if neither the -data nor the -digest parameter is specified.
(Optional)
-digest digest_bytes
It is possible to specify the message imprint explicitly
without the data file. The imprint must be specified in a
hexadecimal format, two characters per byte, the bytes
optionally separated by colons (e.g. 1A:F6:01:... or
1AF601...). The number of bytes must match the message
digest algorithm in use. (Optional)
-md2|-md4|-md5|-sha|-sha1|-mdc2|-ripemd160|...
The message digest to apply to the data file, it supports
all the message digest algorithms that are supported by the
openssl dgst command. The
default is SHA-1. (Optional)
-policy object_id
The policy that the client expects the TSA to use for
creating the time stamp token. Either the dotted OID
notation or OID names defined in the config file can be
used. If no policy is requested the TSA will use its own
default policy. (Optional)
-no_nonce
No nonce is specified in the request if this option is
given. Otherwise a 64 bit long pseudo-random none is
included in the request. It is recommended to use nonce to
protect against replay-attacks. (Optional)
-cert
The TSA is expected to include its signing certificate in
the response. (Optional)
-in request.tsq
This option specifies a previously created time stamp
request in DER format that will be printed into the output
file. Useful when you need to examine the content of a
request in human-readable
format. (Optional)
-out request.tsq
Name of the output file to which the request will be
written. Default is stdout. (Optional)
-text
If this option is specified the output is human-readable
text format instead of DER. (Optional)
Time Stamp Response generation
A time stamp response (TimeStampResp) consists of a response status
and the time stamp token itself (ContentInfo), if the token
generation was successful. The -reply command is for creating a time stamp
response or time stamp token based on a request and printing the
response/token in human-readable format. If -token_out is not specified the output is
always a time stamp response (TimeStampResp), otherwise it is a
time stamp token (ContentInfo).
-config configfile
The configuration file to use, this option overrides the
OPENSSL_CONF environment
variable. See CONFIGURATION FILE
OPTIONS for configurable variables. (Optional)
-section tsa_section
The name of the config file section conatining the settings
for the response generation. If not specified the default
TSA section is used, see CONFIGURATION FILE OPTIONS for
details. (Optional)
-queryfile request.tsq
The name of the file containing a DER encoded time stamp
request. (Optional)
-passin password_src
Specifies the password source for the private key of the
TSA. See PASS PHRASE
ARGUMENTS in openssl(1). (Optional)
-signer tsa_cert.pem
The signer certificate of the TSA in PEM format. The TSA
signing certificate must have exactly one extended key
usage assigned to it: timeStamping. The extended key usage
must also be critical, otherwise the certificate is going
to be refused. Overrides the signer_cert variable of the config
file. (Optional)
-inkey private.pem
The signer private key of the TSA in PEM format. Overrides
the signer_key config file
option. (Optional)
-chain certs_file.pem
The collection of certificates in PEM format that will all
be included in the response in addition to the signer
certificate if the -cert
option was used for the request. This file is supposed to
contain the certificate chain for the signer certificate
from its issuer upwards. The -reply command does not build a
certificate chain automatically. (Optional)
-policy object_id
The default policy to use for the response unless the
client explicitly requires a particular TSA policy. The OID
can be specified either in dotted notation or with its
name. Overrides the default_policy config file option.
(Optional)
-in response.tsr
Specifies a previously created time stamp response or time
stamp token (if -token_in
is also specified) in DER format that will be written to
the output file. This option does not require a request, it
is useful e.g. when you need to examine the content of a
response or token or you want to extract the time stamp
token from a response. If the input is a token and the
output is a time stamp response a default 'granted' status
info is added to the token. (Optional)
-token_in
This flag can be used together with the -in option and indicates that the
input is a DER encoded time stamp token (ContentInfo)
instead of a time stamp response (TimeStampResp).
(Optional)
-out response.tsr
The response is written to this file. The format and
content of the file depends on other options (see -text, -token_out). The default is stdout.
(Optional)
-token_out
The output is a time stamp token (ContentInfo) instead of
time stamp response (TimeStampResp). (Optional)
-text
If this option is specified the output is human-readable
text format instead of DER. (Optional)
-engine id
Specifying an engine (by its unique id string) will cause ts to attempt to obtain a functional
reference to the specified engine, thus initialising it if
needed. The engine will then be set as the default for all
available algorithms. Default is builtin. (Optional)
Time Stamp Response verification
The -verify command is for
verifying if a time stamp response or time stamp token is valid and
matches a particular time stamp request or data file. The -verify command does not use the
configuration file.
-data file_to_hash
The response or token must be verified against
file_to_hash. The file is hashed with the message digest
algorithm specified in the token. The -digest and -queryfile options must not be
specified with this one. (Optional)
-digest digest_bytes
The response or token must be verified against the message
digest specified with this option. The number of bytes must
match the message digest algorithm specified in the token.
The -data and -queryfile options must not be
specified with this one. (Optional)
-queryfile request.tsq
The original time stamp request in DER format. The
-data and -digest options must not be
specified with this one. (Optional)
-in response.tsr
The time stamp response that needs to be verified in DER
format. (Mandatory)
-token_in
This flag can be used together with the -in option and indicates that the
input is a DER encoded time stamp token (ContentInfo)
instead of a time stamp response (TimeStampResp).
(Optional)
-CApath trusted_cert_path
The name of the directory containing the trused CA
certificates of the client. See the similar option of verify(1) for additional
details. Either this option or -CAfile must be specified.
(Optional)
-CAfile trusted_certs.pem
The name of the file containing a set of trusted
self-signed CA certificates in PEM format. See the similar
option of verify(1)
for additional details. Either this option or -CApath must be specified.
(Optional)
-untrusted cert_file.pem
Set of additional untrusted certificates in PEM format
which may be needed when building the certificate chain for
the TSA's signing certificate. This file must contain the
TSA signing certificate and all intermediate CA
certificates unless the response includes them. (Optional)
CONFIGURATION FILE OPTIONS
The -query and -reply commands make use of a configuration
file defined by the OPENSSL_CONF
environment variable. See config(5) for a general description
of the syntax of the config file. The -query command uses only the symbolic OID
names section and it can work without it. However, the -reply command needs the config file for its
operation.
When there is a command line switch equivalent of a variable the
switch always overrides the settings in the config file.
tsa section, default_tsa
This is the main section and it specifies the name of another
section that contains all the options for the -reply command. This default section
can be overriden with the -section command line switch.
(Optional)
The name of the file containing the hexadecimal serial number
of the last time stamp response created. This number is
incremented by 1 for each response. If the file does not
exist at the time of response generation a new file is
created with serial number 1. (Mandatory)
crypto_device
Specifies the OpenSSL engine that will be set as the default
for all available algorithms. The default value is builtin,
you can specify any other engines supported by OpenSSL (e.g.
use chil for the NCipher HSM). (Optional)
signer_cert
TSA signing certificate in PEM format. The same as the
-signer command line option.
(Optional)
certs
A file containing a set of PEM encoded certificates that need
to be included in the response. The same as the -chain command line option. (Optional)
signer_key
The private key of the TSA in PEM format. The same as the
-inkey command line option.
(Optional)
default_policy
The default policy to use when the request does not mandate
any policy. The same as the -policy command line option.
(Optional)
other_policies
Comma separated list of policies that are also acceptable by
the TSA and used only if the request explicitly specifies one
of them. (Optional)
digests
The list of message digest algorithms that the TSA accepts.
At least one algorithm must be specified. (Mandatory)
accuracy
The accuracy of the time source of the TSA in seconds,
milliseconds and microseconds. E.g. secs:1, millisecs:500,
microsecs:100. If any of the components is missing zero is
assumed for that field. (Optional)
clock_precision_digits
Specifies the maximum number of digits, which represent the
fraction of seconds, that need to be included in the time
field. The trailing zeroes must be removed from the time, so
there might actually be fewer digits, or no fraction of
seconds at all. Supported only on UNIX platforms. The maximum
value is 6, default is 0. (Optional)
ordering
If this option is yes the responses generated by this TSA can
always be ordered, even if the time difference between two
responses is less than the sum of their accuracies. Default
is no. (Optional)
tsa_name
Set this option to yes if the subject name of the TSA must be
included in the TSA name field of the response. Default is
no. (Optional)
ess_cert_id_chain
The SignedData objects created by the TSA always contain the
certificate identifier of the signing certificate in a signed
attribute (see RFC 2634, Enhanced Security Services). If this
option is set to yes and either the certs variable or the -chain option is specified then the
certificate identifiers of the chain will also be included in
the SigningCertificate signed attribute. If this variable is
set to no, only the signing certificate identifier is
included. Default is no. (Optional)
ENVIRONMENT VARIABLES
OPENSSL_CONF contains the path of
the configuration file and can be overriden by the -config command line option.
EXAMPLES
All the examples below presume that OPENSSL_CONF is set to a proper configuration
file, e.g. the example configuration file openssl/apps/openssl.cnf
will do.
Time Stamp Request
To create a time stamp request for design1.txt with SHA-1 without
nonce and policy and no certificate is required in the response:
To print the content of the previous request in human readable
format:
openssl ts -query -in design1.tsq -text
To create a time stamp request which includes the MD-5 digest of
design2.txt, requests the signer certificate and nonce, specifies a
policy id (assuming the tsa_policy1 name is defined in the OID
section of the config file):
Before generating a response a signing certificate must be created
for the TSA that contains the timeStamping critical extended key usage
extension without any other key usage extensions. You can add the
'extendedKeyUsage = critical,timeStamping' line to the user
certificate section of the config file to generate a proper
certificate. See req(1), ca(1), x509(1) for instructions. The
examples below assume that cacert.pem contains the certificate of
the CA, tsacert.pem is the signing certificate issued by cacert.pem
and tsakey.pem is the private key of the TSA.
To verify a time stamp token against the original data file:
openssl ts -verify -data design2.txt -in design2.tsr \ -CAfile
cacert.pem
To verify a time stamp token against a message imprint: openssl ts
-verify -digest b7e5d3f93198b38379852f2c04e78d73abdd0f4b \ -in
design2.tsr -CAfile cacert.pem
You could also look at the 'test' directory for more examples.
BUGS
If you find any bugs or you have suggestions please write to Zoltan
Glozik <zglozik@opentsa.org>. Known issues:
* No support for time stamps over SMTP, though it is quite easy
to implement an automatic e-mail based TSA with procmail(1)
and perl(1). HTTP server support is provided in the form of
a separate apache module. HTTP client support is provided by
tsget(1). Pure TCP/IP protocol is not supported.
* The file containing the last serial number of the TSA is not
locked when being read or written. This is a problem if more than one
instance of openssl(1) is trying to create a time stamp
response at the same time. This is not an issue when using the apache
server module, it does proper locking.
* Look for the FIXME word in the source files.
* The source code should really be reviewed by somebody else, too.
* More testing is needed, I have done only some basic tests (see
test/testtsa).
