Metadata-Version: 1.1
Name: caucase
Version: 0.9.8
Summary: Certificate Authority.
Home-page: https://lab.nexedi.com/nexedi/caucase
Author: Vincent Pelletier
Author-email: vincent@nexedi.com
License: GPLv3+ with wide exception for FOSS
Description: ..  Note to the editor: beware of implicit inline
            targets aliasing, keep global title different from all commands
        
        =============================================================================
        caucase - Certificate Authority for Users, Certificate Authority for SErvices
        =============================================================================
        
        Overview
        ========
        
        The goal of caucase is to automate certificate issuance and renewal without
        constraining how the certificate will be used.
        
        For example, there is no assumption that the certificate will be used to
        secure HTTP, nor to serve anything at all: you may need certificates to
        authenticate users, or sign your mails, or secure an SQL server socket.
        
        As an unfortunate consequence, it is not possible for caucase to automatically
        validate a signing request content against a service (ex: as one could check
        the certificate for an HTTPS service was requested by someone with the ability
        to make it serve a special file).
        
        This also means that, while caucase imposes RFC-recommended constraints on many
        certificate fields and extensions to be worthy of trust, it imposes no
        constraint at all on subject and alternate subject certificate fields.
        
        To still allow certificates to be used, caucase uses itself to authenticate
        users (humans or otherwise) who implement the validation procedure: they tell
        caucase what certificates to emit. Once done, any certificate can be
        prolonged at a simple request of the key holder while the to-renew
        certificate is still valid (not expired, not revoked).
        
        Bootstrapping the system (creating the first service certificate for
        `caucased`_ to operate on HTTPS, and creating the first user certificate to
        control further certificate issuance) works by caucase automatically signing a
        set number of certificates upon submission.
        
        Vocabulary
        ==========
        
        Caucase manipulates the following asymmetric cryptography concepts.
        
        - Key pair: A private key and corresponding public key. The public key can be
          derived from the private key, but not the other way around. As a consequence,
          the private key is itself considered to be a key pair.
        
        - Certificate: A certificate is the assurante, by a certificate authority,
          that a given public key and set of attributes belong to an authorised entity.
          Abbreviated cert or crt. A certificate is by definition signed by a CA.
        
        - Certificate Authority: An entry, arbitrarily trusted (but worthy of trust by
          its actions and decision) which can issue certificates. Abbreviated CA.
        
        - Certificate signing request: A document produced by an entity desiring to get
          certified, which they send to a certificate authority. The certificate signing
          request contains the public key and desired set of attributes that the CA
          should pronounce itself on. The CA has all liberty to issue a different set
          of attributes, or to not issue a certificate.
        
        - Certificate revocation list: Lists the certificates which were issued by a CA
          but which should not be trusted anymore. This can happen for a variety of
          reasons: the private key was compromised, or its owning entity should not be
          trusted anymore (ex: entity's permission to access to protected service was
          revoked).
        
        - PEM: A serialisation mechanism commonly used for various cryptographic data
          pieces. It relies on base64 so it is 7-bits-safe (unlike DER), and is very
          commonly supported. Caucase exclusively uses PEM format.
        
        Validity period
        ===============
        
        Cryptographic keys wear out as are used and as they age.
        
        Of course, they do not bit-rot nor become thinner with use. But each time one
        uses a key and each minute an attacker had access to a public key, fractions
        of the private key bits are inevitably leaked, weakening it overall.
        
        So keys must be renewed periodically to preserve intended security level. So
        there is a limited life span to each certificate, including the ones emitted by
        caucase.
        
        The unit duration for caucase-emitted certificates is the "normal" certificate
        life span. It default to 93 days from the moment the certificate was signed,
        or about 3 months.
        
        Then the CA certificate has a default life span of 4 "normal" certificate
        validity periods. As CA renewal happens in caucase without x509-level cross
        signing (by decision, to avoid relying on intermediate CA support on
        certificate presenter side and instead rely on more widespread
        multi-CA-certificate support on verifier side), there is a hard lower bound of
        3 validity periods, under which the CA certificate cannot be reliably renewed
        without risking certificate validation issues for emitted "normal"
        certificates. CA certificate renewal is composed of 2 phases:
        
        - Passive distribution phase: current CA certificate has a remaining life span
          of less than 2 "normal" certificate life spans: a new CA certificate is
          generated and distributed on-demand (on "normal" certificate renewal and
          issuance, on CRL retrieval with caucase tools...), but not used to sign
          anything.
        - Active use phase: new CA certificate is valid for more than one "normal"
          certificate life span. This means that all existing certificates which are
          still in active use had to be renewed at least once since the new CA
          certificate exists. This means all the certificate holders had the
          opportunity to learn about the new CA certificate. So the new CA certificate
          starts being used to sign new certificates, and the old CA certificate falls
          out of use as its signed "normal" certificates expire.
        
        By default, all caucase tools will generate a new private key unrelated to the
        previous one on each certificate renewal.
        
        Lastly, there is another limited validity period, although not for the same
        reasons: the list of revoked certificates also has a maximum life span. In
        caucase, the CRL is re-generated whenever it is requested and:
        
        - there is no previous CRL
        - previous CRL expired
        - any revocation happened since previous CRL was created
        
        Commands
        ========
        
        Caucase provides several commands to work with certificates.
        
        caucase
        +++++++
        
        Reference caucase "one-shot" client.
        
        This command is intended to be used for isolated actions:
        
        - listing and signing pending certificate signature requests
        
        - revoking certificates
        
        It is also able to submit certificate signing requests, retrieve signed
        certificates, requesting certificate renewals and updating both
        CA certificates and revocation lists, but you may be interested in using
        `caucase-updater`_ for this instead.
        
        caucase-updater
        +++++++++++++++
        
        Reference caucase certificate renewal daemon.
        
        Monitors a key pair, corresponding CA certificate and CRL, and renew them
        before expiration.
        
        When the key-pair lacks a signed certificate, issues a pre-existing CSR to
        caucase server and waits for the certificate to be issued.
        
        caucase-probe
        +++++++++++++
        
        Caucase server availability tester.
        
        Performs minimal checks to verify a caucase server is available at given URL.
        
        caucase-rerequest
        +++++++++++++++++
        
        Utility allowing to re-issue a CSR using a locally-generated private key.
        
        Intended to be used in conjunction with `caucase-updater`_ when user cannot
        generate the CSR on the system where the certificate is desired (ex: automated
        HTTPS server deployment), where user is not the intended audience for
        caucase-produced certificate:
        
        - User generates a CSR on their own system, and signs it with any key (it will
          not be needed later
        - User sends the CSR to the system where the certificate is desired
        - User gets caucase-rerequest to run on this CSR, producing a new private key
          and a CSR similar to issued one, but signed with this new private key
        - From then on, caucase-updater can take over
        
        This way, no private key left their original system, and user could still
        freely customise certificate extensions.
        
        caucase-key-id
        ++++++++++++++
        
        Utility displaying the identifier of given key, or the identifier of keys
        involved in given backup file.
        
        Allows identifying users which hold a private key candidate for restoring a
        caucased backup (see `Restoration procedure`_).
        
        caucased
        ++++++++
        
        Reference caucase server daemon.
        
        This daemon provides access to both CAU and CAS services over both HTTP and
        HTTPS.
        
        It handles its own certificate issuance and renewal, so there is no need to use
        `caucase-updater`_ for this service.
        
        CORS
        ----
        
        caucased implements CORS protection: when receiving a cross-origin request,
        it will respond with 401 Unauthorized, with the WWW-Authenticate header set to
        a custom scheme ("cors") with an "url" parameter containing an URI template
        with one variable field: "return" (more on it later).
        
        Upon receiving this response, the application is expected to render the URL
        template and redirect the user to resulting URL. There, the user will be
        informed of the cross-origin access attempt, and offered the choice to grant or
        deny access to given origin.
        
        Once their decision is made, their browser will receive a cookie remembering
        this decision, and they will be redirected to the URL received in the "return"
        field received upon above-described redirection.
        
        Then, the application should retry the original request, which will be
        accompanied by that cookie.
        
        Backups
        -------
        
        Loosing the CA private key prevents issuing any new certificate trusted by
        services which trusted the CA. Also, it prevents issuing any new CRL.
        Recovering from such total loss requires starting a new CA and rolling it out
        to all services which used the previous one. This is very time-costly.
        
        So backups are required.
        
        On the other hand, if someone gets their hand on the CA private key, they can
        issue certificates for themselves, allowing them to authenticate with services
        trusting the CA managed by caucase - including caucased itself if they issue a
        user certificate: they can then revoke existing certificates and cause a lot of
        damage.
        
        So backups cannot happen in clear text, they must be encrypted.
        
        But the danger of encrypted backups is that by definition they become worthless
        if they cannot be decrypted. So as many (trusted) entities as possible should
        be granted the ability to decrypt the backups.
        
        The solution proposed by caucased is to encrypt produced backups in a way which
        allows any of the caucase users to decrypt the archive.
        
        As these users are already entrusted with issuing certificates, this puts
        only a little more power in their hands than they already have. The little
        extra power they get is that by having unrestricted access to the CA private
        key they can issue certificates bypassing all caucase restrictions. The
        proposed parade is to only make the backups available to a limited subset of
        caucase users when there is an actual disaster, and otherwise keep it out of
        their reach. This mechanism is not handled by caucase.
        
        As there are few trusted users, caucase can keep their still-valid certificates
        in its database for the duration of their validity with minimal size cost.
        
        Backup procedure
        ----------------
        
        Backups happen periodically as long as caucased is running. See
        `--backup-period` and `--backup-directory`.
        
        As discussed above, produced files should be kept out of reach of caucase
        users until a disaster happens.
        
        Restoration procedure
        ---------------------
        
        See `caucased-manage --restore-backup`.
        
        To restore, one of the trusted users must voluntarily compromise their own
        private key, providing it to the administrator in charge of the restoration
        procedure. Restoration procedure will hence immediately revoke their
        certificate. They must also provide a CSR generated with a different private
        key, so that caucase can provide them with a new certificate, so they keep
        their access only via different credentials.
        
        - admin identifies the list of keys which can decipher a backup, and broadcasts
          that list to key holders
        
        - key holders manifest themselves
        
        - admin picks a key holder, requests them to provide their existing private key
          and to generate a new key and accompanying CSR
        
        - key holder provide requested items
        
        - admin initiates restoration with `--restore-backup` and provides key holder
          with replacement certificate
        
        - admin starts caucased, service is back online.
        
        Backup file format
        ------------------
        
        - 64bits: 'caucase\0' magic string
        
        - 32bits LE: header length
        
        - header: json-encoded header (see below)
        
        - encrypted byte stream (aka payload)
        
        Header schema (inspired from s/mime, but s/mime tools available do not
        support at least iterative production or iterative generation)::
        
          {
            "description": "Caucase backup header",
            "required": ["algorithm", "key_list"],
            "properties": {
              "cipher": {
                "description": "Symetric ciher used for payload",
                "required": ["name"],
                "properties": {
                  "name":
                    "enum": ["aes256_cbc_pkcs7_hmac_10M_sha256"],
                    "type": "string"
                  },
                  "parameter": {
                    "description": "Name-dependend clear cipher parameter (ex: IV)",
                    "type": "string"
                  }
                }
                "type": "object"
              },
              "key_list": {
                "description": "Content key, encrypted with public keys",
                "minItems": 1,
                "items": {
                  "required": ["id", "cipher", "key"],
                  "properties": {
                    "id": {
                      "description": "Hex-encoded sha1 hash of the public key",
                      "type": "string"
                    },
                    "cipher": {
                      "description": "Asymetric cipher used for symetric key",
                      "required": ["name"],
                      "properties": {
                        "name": {
                          "enum": ["rsa_oaep_sha1_mgf1_sha1"],
                          "type": "string"
                        }
                      },
                      "type": "object"
                    }
                    "key": {
                      "description": "Hex-encoded encrypted concatenation of signing and symetric encryption keys",
                      "type": "string"
                    }
                  },
                  "type": "object"
                },
                "type": "array"
              }
            },
            "type": "object"
          }
        
        0.9.8 (2020-06-29)
        ==================
        * Add support for python3.
        * Add support for one-CA-cert-per-file layout. For services which do not support loading multiple CA certificates from a single file.
        * Fix caucase.sh authenticated usage (was broken by 0.9.4 "Make caucased https CA certificate safer").
        * Avoid busy-loop in caucase-updater when it thinks a renewal is due but caucased does not offer a newer version.
        * Fix tests timeouts on slower machined. Anything faster than a Raspberry Pi 1 should now pass.
        
        0.9.7 (2020-06-04)
        ==================
        * Fix CRL renewal:
          * teach caucased to renew CRLs ahead of their expirations.
          * make caucase-updater check CRL expiration date.
        * Grant extra permissions in license.
        
        0.9.6 (2019-05-27)
        ==================
        * Do not use a 128bits OID arc for caucase internal use, as it is not widely supported.
        * Assorted CLI usability improvements.
        
        0.9.5 (2019-01-24)
        ==================
        * Add --version support.
        * Logging is reworked to reduce verbosity (especially in tests).
        * Fix caucased sometimes crashing when renewing its https certificate.
        * Make caucased logs more apache-like.
        * Make caucased responses more standard-compliant ("Allow" header in 405 response and "Date" header in all responses).
        * Fix unintended dependency on system timezone.
        
        0.9.4 (2018-11-14)
        ==================
        * Improved documentation.
        * Tentative web-friendliness (not used in real life yet, so practicality is still uncertain):
          * Make caucased https CA certificate safer for adding in a trust store (ex: browser) by constraining the certificates it can sign.
          * cookie-based CORS access control with crude UI.
          * API is self-documenting using application/hal+json format.
        * Tentative python3 friendliness, there may still be file IO encoding issues.
        
        0.9.3 (2018-09-21)
        ==================
        * Add support for listening to multiple specific addresses in caucased.
        * shell implementation does not rely on an external file anymore.
        * Do not start listening on https port before wrapping sockets with an ssl context
        * Make caucase-updater usable by anonymous services (ex: they only need to connect to a caucase-certified service, without authenticating themselves using caucase)
        * Use stricter file permissions for caucased sqlite database.
        * Include caucase version in user agent header.
        * Make caucased logging format more similar to apache's default.
        * Fix caucased https certificate renewal. Fixes a crash which happens every 2 months.
        * Make caucase-updater retry on network errors. Fixes crashes on transient network error.
        
        0.9.2 (2017-11-03)
        ==================
        * Add support for migrating an existing CA to caucase: import CA cert and CRLs.
        * Require CRL signature checks (bumps cryptography module version requirements).
        * Provide CRL distribution point extension in CA certificates.
        * Play nicer with http:
          * Catch more errors to provide nice status codes
          * Add support for "Transfer-Encoding: chunked"
          * Add support for "Expect: 100-continue"
        * Produce TLS-compliant certificates (domain name must be in an alternative name extension, subject is not enough).
        * Reduce speed requirements in tests.
        * Add shell implementation of "caucase" command.
        * Certificate renewal bypasses pending CSR limits.
        * caucase-manage: new command for offline database maintenance.
        
        0.9.1 (2017-09-21)
        ==================
        * Documentation improvements
        * Packaging improvements
        
        0.9.0 (2017-08-02)
        ==================
        * implement the "cau" half of "caucase"
        * massive rework: removal of flask dependency, removal of HTML UI, rework of
          the REST API, rework of the CLI tools, rework of the WGSI application,
          incomatible redesign of the database.
        
        0.1.4 (2017-07-21)
        ==================
        * caucase web parameter 'auto-sign-csr-amount' can be used to set how many csr must be signed automatically.
        
        0.1.3 (2017-06-30)
        ==================
        
        * add support for backup caucase database to cli
        * serial is a random unique formatted hexadecimal number get from the csr_id
        * allow to set custom subject (X509Name) when signing a certificate
        * add new cliweb command which when required will download/update crl file from caucase web
        
        0.1.2 (2017-05-12)
        ==================
        * cliweb: renew now takes threshold option to check if renew is required and optional on-renew script to run after certificate renewal
        
        0.1.1 (2017-04-27)
        ==================
        
         * initial implementation of certificate authority
        
        
Keywords: certificate authority
Platform: UNKNOWN
Classifier: Environment :: Console
Classifier: Environment :: Web Environment
Classifier: Intended Audience :: System Administrators
Classifier: Intended Audience :: Information Technology
Classifier: License :: OSI Approved :: GNU General Public License v3 or later (GPLv3+)
Classifier: Topic :: Security :: Cryptography
Classifier: Topic :: System :: Systems Administration :: Authentication/Directory
Classifier: Topic :: Internet :: WWW/HTTP :: WSGI :: Application
