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487 lines
14 KiB
ReStructuredText
487 lines
14 KiB
ReStructuredText
===================
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The Signer Protocol
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===================
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Communication with the signer is performed via a serial connection. That
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connection has to be established by the client before speaking the protocol
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defined here.
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.. _signer-request-data-format:
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Signer request data format specification
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========================================
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Protocol request data is encoded in the following format:
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.. table:: signer request message format
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======= ==============================================================
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Byte Data
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======= ==============================================================
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0-2 length of header + data in network byte order
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3-5 length of header network byte order
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6-14 action specific header
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15-17 length of first action specific content in network byte order
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18-N fist action specific content string
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N+1-N+3 length of second action specific content in network byte order
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N+4-M second action specific content string
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M+1-M+3 lenght of third action specific content in network byte order
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M+4-End third action specific content string
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======= ==============================================================
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Due to the length encoding in 3 bytes the messages can have a maximum length
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of 8\ :sup:`3` = 2\ :sup:`24` Bytes which is around 16 MiB.
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General request header format
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-----------------------------
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Every protocol request header (bytes 3-12 of protocol request message) follows
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the same 9 byte structure. The content of bytes 3-8 are protocol action
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specific.
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.. table:: general request header format
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==== ===========================
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Byte Value
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==== ===========================
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0 Version (``0x01``)
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1 Action
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2 System (used crypto system)
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3 8 bits root
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4 8 bits configuration
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5 8 bits parameter
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6-7 16 bits parameter
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8 8 bits parameter
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==== ===========================
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.. _signer-nul-request-format:
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Format of NUL requests
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----------------------
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NUL requests are sent at the end of each iteration in
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:sourcefile:`client.pl <CommModule/client.pl>`'s main loop.
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.. table:: NUL request header format
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==== ==================
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Byte Value
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==== ==================
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0 Version (``0x01``)
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1 Action (``0x00``)
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2 System (``0x00``)
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3 ``0x00``
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4 ``0x00``
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5 ``0x00``
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6-7 ``0x0000``
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8 ``0x00``
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==== ==================
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**NUL Request Payload:**
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- GMT timestamp in %m%d%H%M%Y.%S format
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- ""
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- ""
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.. note::
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The timestamp sent with the NUL request is used to create a
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script to synchronize the time on the signer using :program:`date` and
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:program:`hwclock`.
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.. _signer-x509-request-format:
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Format of X.509 signing request messages
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----------------------------------------
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X.509 signing request messages are sent in
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:sourcefile:`client.pl <CommModule/client.pl>`'s main loop for each requested
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certificate.
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.. table:: X.509 certificate signing request header format
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==== ===================================================================
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Byte Value
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==== ===================================================================
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0 Version (``0x01``)
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1 Action (``0x01``)
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2 System (``0x01`` for X.509)
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3 Root (see table :ref:`table-cert-roots`)
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4 Profile (see table :ref:`table-cert-profiles`)
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5 Message Digest Id (see table :ref:`table-md-ids`)
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6-7 Days in big-endian format
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8 Key type [#unused-server]_
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==== ===================================================================
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The key type is stored in the column *keytype* of the certificate request
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table which is one of
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- *domaincerts*
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- *emailcerts*
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- *orgdomaincerts*
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- *orgemailcerts*
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**X.509 Signing Request Payload:**
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- PEM encoded PKCS#10 / :rfc:`2986` certifcate signing request or SPKAC
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(Netscape) signed public key and challenge (i.e. generated from a
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`\<keygen\> HTML form element <keygen>`_)
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- comma separated list of SubjectAlternative names in a format that is
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accepted by openssl configuration file directive ``subjectAltName`` (see
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https://www.openssl.org/docs/man1.0.2/apps/x509v3_config.html#Subject-Alternative-Name)
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- The requested subject DN in openssl format (parts separated by ``/``)
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.. _keygen: https://developer.mozilla.org/en-US/docs/Web/HTML/Element/keygen
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.. _table-cert-roots:
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.. table:: CA root certificate identifiers
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== =================================================
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Id CA root
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== =================================================
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0 CAcert root (aka CAcert class 1 root)
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1 CAcert class3
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2 CAcert class3s
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x root{}
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== =================================================
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.. note::
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The CA root identifier is retrieved from the database by
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:sourcefile:`client.pl <CommModule/client.pl>` the value that is found there is
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decremented by 1 before it is sent to the server.
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The server in :sourcefile:`server.pl <CommModule/server.pl>` restricts the
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allowed root id in its ``CheckSystem`` function.
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.. _table-cert-profiles:
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.. table:: Certificate profile ids
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== ======================
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Id Profile
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== ======================
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0 Client (personal)
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1 Client (Organization)
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2 Client (Code signing)
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3 Client (Machine)
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4 Client (ADS)
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5 Server (personal)
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6 Server (Organization)
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7 Server (Jabber)
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8 Server (OCSP)
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9 Server (Timestamp)
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10 Proxy
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11 SubCA
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== ======================
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.. note::
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:sourcefile:`client.pl <CommModule/client.pl>` supports profiles 0, 1, 2, 4,
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5, 6, 8 and 9 only.
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.. _table-md-ids:
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.. table:: Message digest ids
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== ==========
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Id Algorithm
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== ==========
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1 MD5
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2 SHA-1
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3 RIPE-MD160
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8 SHA-256
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9 SHA-384
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10 SHA-512
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== ==========
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.. _signer-openpgp-request-format:
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Format of OpenPGP key signing request messages
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----------------------------------------------
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OpenPGP key signing request messages are sent in
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:sourcefile:`client.pl <CommModule/client.pl>`'s main loop for each requested
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OpenPGP key.
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.. table:: OpenPGP key signing request header format
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==== =============================
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Byte Value
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==== =============================
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0 Version (``0x01``)
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1 Action (``0x01``)
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2 System (``0x02`` for OpenPGP)
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3 ``0x00``
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4 ``0x00``
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5 ``0x02`` [#unused-server]_
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6-7 366 encoded as ``0x016e``
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8 ``0x00``
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==== =============================
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**OpenPGP Signing Request Payload:**
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- OpenPGP public keyring in binary format (see :rfc:`4880`)
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- ""
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- ""
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.. [#unused-server] the field is unused in
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:sourcefile:`server.pl <CommModule/server.pl>`
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.. _signer-csr-request-format:
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Format of X.509 certificate revocation request messages
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-------------------------------------------------------
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X.509 certificate revocation request messages are sent in
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:sourcefile:`client.pl <Commmodule/client.pl>`'s main loop for each requested
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X.509 certificate revocation.
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==== ===========================
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Byte Value
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==== ===========================
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0 Version (``0x01``)
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1 Action (``0x02``)
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2 System (``0x01`` for X.509)
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3 Root
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4 ``0x00``
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5 ``0x00``
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6-7 365 encoded as ``0x016d``
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8 ``0x00``
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==== ===========================
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**X.509 Certificate Revocation Request Payload:**
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- PEM encoded certificate data of the certificate to be revoked
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- ""
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- hexadecimal encoded SHA-1 hash of the CRL known CRL file of the requested
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CA Root (header byte 3)
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.. _signer-response-data-format:
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Signer response data format specification
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=========================================
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Protocol response data is encoded in the following format:
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.. table:: signer response message format:
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======= =======================================================
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Byte Data
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======= =======================================================
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0-2 length of header + data in network byte order
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3-5 length of header network byte order
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6-9 header data
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10-12 length of payload data 1 in network byte order
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13-N payload data 1
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N+1-N+3 length of payload data 2 network byte order
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N+4-M payload data 2
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M+1-M+3 length of payload data 3 network byte order
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M+4-End payload data 3
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======= =======================================================
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General response header format
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------------------------------
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Every protocol response header (bytes 6-9 of protocol response message)
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follows the same 4 byte structure. The content of bytes 3 and 4 are not used
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yet.
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.. table:: general response header format
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==== ==================
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Byte Value
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==== ==================
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0 Version (``0x01``)
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1 Action
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2 ``0x00`` unused
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3 ``0x00`` unused
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==== ==================
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.. _signer-nul-response-format:
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Format of NUL Responses
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-----------------------
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NUL responses are sent in response to
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:ref:`NUL requests <signer-nul-request-format>`.
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.. table:: NUL response header format
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==== ==================
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Byte Value
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==== ==================
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0 Version (``0x01``)
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1 Action (``0x00``)
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2 ``0x00`` unused
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3 ``0x00`` unused
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==== ==================
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**NUL Response Payload:**
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- ""
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- ""
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- ""
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Format of X.509 certificate response messages
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---------------------------------------------
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X.509 certificate response messages are sent in response to
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:ref:`X.509 certificate signing request messages <signer-x509-request-format>`.
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.. table:: X.509 certificate response header format
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==== ==================
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Byte Value
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==== ==================
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0 Version (``0x01``)
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1 Action (``0x01``)
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2 ``0x00`` unused
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3 ``0x00`` unused
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==== ==================
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**X.509 certificate response payload:**
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- PEM encoded X.509 certificate
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- ""
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- ""
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.. _signer-openpgp-response-format:
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Format of OpenPGP key signature response messages
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-------------------------------------------------
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OpenPGP key signature response messages are sent in response to
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:ref:`OpenPGP key signing request messages <signer-openpgp-request-format>`.
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.. table:: OpenPGP key signature response header format
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==== ==================
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Byte Value
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==== ==================
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0 Version (``0x01``)
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1 Action (``0x02``)
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2 ``0x00`` unused
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3 ``0x00`` unused
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==== ==================
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**OpenPGP key signature response payload:**
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- ASCII armored PGP public key block
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- ""
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- ""
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Format of X.509 certificate revocation response messages
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--------------------------------------------------------
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X.509 certificate revocation response messages are sent in response to
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:ref:`X.509 certificate revocation request messages
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<signer-csr-request-format>`.
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.. table:: X.509 certificate revocation response header format
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==== =====================================
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Byte Value
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==== =====================================
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0 Version (``0x01``)
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1 Action (``0x02``) [#overlap-openpgp]_
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2 ``0x00`` unused
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3 ``0x00`` unused
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==== =====================================
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.. [#overlap-openpgp] this response type uses the same action byte as the
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:ref:`OpenPGP key signature response message <signer-openpgp-response-format>`
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**X.509 certificate revocation response payload:**
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- CRL diff in :program:`xdelta` format or "" if the original CRL specified
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by the SHA-1 hash in the third payload field of the request is not
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available
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- ""
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- ""
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Protocol messages
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=================
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.. _signer-message-handshake:
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Handshake
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---------
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#. client sends 1 byte ``0x02`` to serial port
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#. client reads 1 byte from serial port (with a 20 second timeout)
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#. client checks whether the byte is ``0x10``
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.. seqdiag::
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seqdiag handhake {
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client -> server [label = "0x02"];
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client <-- server [label = "0x10"];
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}
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If anything different is received there was a protocol error and no further
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messages should be sent over the serial connection.
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.. _signer-message-senddata:
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Send data
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---------
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:Preconditions:
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successful :ref:`Handshake <signer-message-handshake>`,
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data is encoded according to the :ref:`signer-request-data-format`
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#. client builds byte wise xor of all data bytes into 1 byte $xor
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#. client sends concatenated $data string + xor-Byte + "rie4Ech7"
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#. client reads 1 byte (with a 5 second timeout)
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#. if received byte is ``0x11`` try again
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#. if received byte is ``0x10`` the message has been sent successfully
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.. seqdiag::
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seqdiag request_with_retry {
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client -> client [label = "xor $data"];
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client -> server [label = "$data . $xor . \"rie4Ech7\""];
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server -> server [label = "detect corruption"];
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client <-- server [label = "0x11"];
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client -> server [label = "$data . $xor . \"rie4Ech7\""];
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client <-- server [label = "0x10"];
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}
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If anything different is received there was a protocol error and no further
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messages should be sent over the serial connection.
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Receive data
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------------
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:Preconditions:
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client :ref:`sent data <signer-message-senddata>`
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#. client waits for a response (with a 120 second timeout)
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#. server builds byte wise xor of all data bytes in 1 byte $xor
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#. server sends ``0x02`` to start transmission
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#. client sends ``0x10`` to confirm receipt (server timeout 1 second)
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#. server sends concatenated $data string + xor-Byte + "rie4Ech7"
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#. client reads data in 100 byte segments (5 second timeout)
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#. client sends ``0x11`` in case of corrupted data and retries reading
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#. client sends ``0x10`` if successful
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#. server waits for response for 5 seconds
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#. server sends concatenated $data string + xor-Byte + "rie4Ech7" if client
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response is ``0x11``
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.. seqdiag::
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seqdiag response_with_retry {
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client -> server [label = "wait"];
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server -> server [label = "xor $data"];
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client <- server [label = "0x02"];
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client --> server [label = "0x10"];
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client <- server [label = "$data . $xor . \"rie4Ech7\""];
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client -> client [label = "detect corruption"];
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client --> server [label = "0x11"];
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client <- server [label = "$data . $xor . \"rie4Ech7\""];
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client --> server [label = "0x10"];
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}
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