diff mbox

gnu: Add Kerberos client service.

Message ID 1480768049-18696-1-git-send-email-jmd@gnu.org
State New
Headers show

Commit Message

John Darrington Dec. 3, 2016, 12:27 p.m. UTC
* doc/guix.texi (Kerberos Services)[Krb5 Service]: New subsubheading.
* gnu/services/kerberos.scm (krb5-service-type): New variable.
* gnu/services/configuration.scm (configuration-field-serializer,
  configuration-field-getter): Export variables.
---
 doc/guix.texi                  |  93 ++++++++++
 gnu/services/configuration.scm |   2 +
 gnu/services/kerberos.scm      | 377 ++++++++++++++++++++++++++++++++++++++++-
 3 files changed, 470 insertions(+), 2 deletions(-)

Comments

Ludovic Courtès Dec. 3, 2016, 3:13 p.m. UTC | #1
John Darrington <jmd@gnu.org> skribis:

> * doc/guix.texi (Kerberos Services)[Krb5 Service]: New subsubheading.
> * gnu/services/kerberos.scm (krb5-service-type): New variable.
> * gnu/services/configuration.scm (configuration-field-serializer,
>   configuration-field-getter): Export variables.

[...]

> +@subsubheading Krb5 Service
> +
> +Programs using Kerberos client library packages normally

s/Kerberos client library packages/a Kerberos client library/

> +No keytab filea are provided by this service.  You must explicitly create these.
                 ^
Typo.

Also ``keytab'', since we don't know what that is.

> +(define (serialize-string/unset field-name val)
> +  (if (not (eq? val unset-field))
> +      (serialize-field* field-name val)))
> +
> +(define (serialize-integer/unset field-name val)
> +  (if (not (eq? val unset-field))
> +      (serialize-field* field-name val)))
> +
> +(define (serialize-boolean/unset field-name val)
> +  (if (not (eq? val unset-field))
> +      (serialize-field* field-name
> +                        (if val "true" "false"))))
> +

Please use ‘when’ or ‘unless’ for single-arm ‘if’ (there are other
occurrences of this further down in this file.)  It makes it clear that
this is for effect.

(At some point we should add an explicit ‘port’ parameter for these
serialize procedures.)

> +;; An end-point is an address such as "192.168.0.1"
> +;; or an address port pair ("string/unset.example.com" . 109)
> +(define (end-point? val)
> +  (or (string? val)
> +      (and (pair? val)
> +           (string? (car val))
> +           (integer? (cdr val)))))

See <https://lists.gnu.org/archive/html/guix-devel/2016-11/msg01252.html>.

> +(define (serialize-end-point field-name val)
> +  (serialize-field* field-name
> +                   (if (string? val)
> +                       ;; The [] are needed in the case of IPv6 addresses
> +                       (format #f "[~a]" val)
> +                       (format #f "[~a]:~a" (car val) (cdr val)))))

See <https://lists.gnu.org/archive/html/guix-devel/2016-11/msg01252.html>.

> +(define (serialize-space-separated-string-list/unset field-name val)
> +  (if (not (eq? val unset-field))
> +      (serialize-field* field-name (string-join val " "))))

‘unless’.

OK with all these changes.

In the future, could you write a short summary of the changes when you
submit a new revision of a patch, to make it easier to keep track of it?

Thanks,
Ludo’.
diff mbox

Patch

diff --git a/doc/guix.texi b/doc/guix.texi
index 3b4ba48..a214354 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -11542,6 +11542,99 @@  remote servers.  Run @command{man smtpd.conf} for more information.
 The @code{(gnu services kerberos)} module provides services relating to
 the authentication protocol @dfn{Kerberos}.
 
+@subsubheading Krb5 Service
+
+Programs using Kerberos client library packages normally
+expect a configuration file in @file{/etc/krb5.conf}.
+This service generates such a file from a definition provided in the
+operating system declaration.
+It does not cause any daemon to be started.
+
+No keytab filea are provided by this service.  You must explicitly create these.
+This service is known to work with the MIT client library, @code{mit-krb5}.
+Other implementations have not been tested.
+
+@defvr {Scheme Variable} krb5-service-type
+A service type for Kerberos 5 clients.
+@end defvr
+
+@noindent
+Here is an example of its use:
+@lisp
+(service krb5-service-type
+         (krb5-configuration
+          (default-realm "EXAMPLE.COM")
+          (allow-weak-crypto? #t)
+          (realms (list
+                   (krb5-realm
+                    (name "EXAMPLE.COM")
+                    (admin-server "groucho.example.com")
+                    (kdc "karl.example.com"))
+                   (krb5-realm
+                    (name "ARGRX.EDU")
+                    (admin-server "kerb-admin.argrx.edu")
+                    (kdc "keys.argrx.edu"))))))
+@end lisp
+
+@noindent
+This example provides a Kerberos@tie{}5 client configuration which:
+@itemize
+@item Recognizes two realms, @i{viz:} ``EXAMPLE.COM'' and ``ARGRX.EDU'', both
+of which have distinct administration servers and key distribution centers;
+@item Will default to the realm ``EXAMPLE.COM'' if the realm is not explicitly
+specified by clients;
+@item Accepts services which only support encryption types known to be weak.
+@end itemize
+
+The @code{krb5-realm} and @code{krb5-configuration} types have many fields.
+Only the most commonly used ones are described here.
+For a full list, and more detailed explanation of each, see the MIT
+@uref{http://web.mit.edu/kerberos/krb5-devel/doc/admin/conf_files/krb5_conf.html,,krb5.conf}
+documentation.
+
+
+@deftp {Data Type} krb5-realm
+@cindex realm, kerberos
+@table @asis
+@item @code{name}
+This field is a string identifying the name of the realm.
+A common convention is to use the fully qualified DNS name of your organization,
+converted to upper case.
+
+@item @code{admin-server}
+This field is a string identifying the host where the administration server is
+running.
+
+@item @code{kdc}
+This field is a string identifying the key distribution center
+for the realm.
+@end table
+@end deftp
+
+@deftp {Data Type} krb5-configuration
+
+@table @asis
+@item @code{allow-weak-crypto?} (default: @code{#f})
+If this flag is @code{#t} then services which only offer encryption algorithms
+known to be weak will be accepted.
+
+@item @code{default-realm} (default: @code{#f})
+This field should be a string identifying the default Kerberos
+realm for the client.
+You should set this field to the name of your Kerberos realm.
+If this value is @code{#f}
+then a realm must be specified with every Kerberos principal when invoking programs
+such as @command{kinit}.
+
+@item @code{realms}
+This should be a non-empty list of @code{krb5-realm} objects, which clients may
+access.
+Normally, one of them will have a @code{name} field matching the @code{default-realm}
+field.
+@end table
+@end deftp
+
+
 @subsubheading PAM krb5 Service
 @cindex pam-krb5
 
diff --git a/gnu/services/configuration.scm b/gnu/services/configuration.scm
index 9f28aab..94c5f21 100644
--- a/gnu/services/configuration.scm
+++ b/gnu/services/configuration.scm
@@ -30,6 +30,8 @@ 
             configuration-field-name
             configuration-missing-field
             configuration-field-error
+            configuration-field-serializer
+            configuration-field-getter
             serialize-configuration
             define-configuration
             validate-configuration
diff --git a/gnu/services/kerberos.scm b/gnu/services/kerberos.scm
index a56f630..b23085d 100644
--- a/gnu/services/kerberos.scm
+++ b/gnu/services/kerberos.scm
@@ -17,14 +17,387 @@ 
 ;;; along with GNU Guix.  If not, see <http://www.gnu.org/licenses/>.
 
 (define-module (gnu services kerberos)
-  #:use-module (gnu packages admin)
   #:use-module (gnu services)
+  #:use-module (gnu services configuration)
   #:use-module (gnu system pam)
   #:use-module (guix gexp)
   #:use-module (guix records)
+  #:use-module (srfi srfi-1)
+  #:use-module (srfi srfi-34)
+  #:use-module (srfi srfi-35)
+  #:use-module (ice-9 match)
   #:export (pam-krb5-configuration
             pam-krb5-configuration?
-            pam-krb5-service-type))
+            pam-krb5-service-type
+
+            krb5-realm
+            krb5-realm?
+
+            krb5-configuration
+            krb5-configuration?
+            krb5-service-type))
+
+
+
+(define unset-field (list 'unset-field))
+
+(define (predicate/unset pred)
+  (lambda (x) (or (eq? x unset-field) (pred x))))
+
+(define string/unset? (predicate/unset string?))
+(define boolean/unset? (predicate/unset boolean?))
+(define integer/unset? (predicate/unset integer?))
+
+(define (uglify-field-name field-name)
+  "Return FIELD-NAME with all instances of '-' replaced by '_' and any
+trailing '?' removed."
+  (let ((str (symbol->string field-name)))
+    (string-join (string-split (if (string-suffix? "?" str)
+                                   (substring str 0 (1- (string-length str)))
+                                   str)
+                               #\-)
+                 "_")))
+
+(define (serialize-field* field-name val)
+  (format #t "~a = ~a\n" (uglify-field-name field-name) val))
+
+(define (serialize-string/unset field-name val)
+  (if (not (eq? val unset-field))
+      (serialize-field* field-name val)))
+
+(define (serialize-integer/unset field-name val)
+  (if (not (eq? val unset-field))
+      (serialize-field* field-name val)))
+
+(define (serialize-boolean/unset field-name val)
+  (if (not (eq? val unset-field))
+      (serialize-field* field-name
+                        (if val "true" "false"))))
+
+
+;; An end-point is an address such as "192.168.0.1"
+;; or an address port pair ("string/unset.example.com" . 109)
+(define (end-point? val)
+  (or (string? val)
+      (and (pair? val)
+           (string? (car val))
+           (integer? (cdr val)))))
+
+(define (serialize-end-point field-name val)
+  (serialize-field* field-name
+                   (if (string? val)
+                       ;; The [] are needed in the case of IPv6 addresses
+                       (format #f "[~a]" val)
+                       (format #f "[~a]:~a" (car val) (cdr val)))))
+
+
+(define (serialize-space-separated-string-list/unset field-name val)
+  (if (not (eq? val unset-field))
+      (serialize-field* field-name (string-join val " "))))
+
+(define space-separated-string-list/unset?
+  (predicate/unset space-separated-string-list?))
+
+(define comma-separated-integer-list/unset?
+  (predicate/unset (lambda (val)
+                     (and (list? val)
+                          (and-map (lambda (x) (integer? x))
+                                   val)))))
+
+(define (serialize-comma-separated-integer-list/unset field-name val)
+  (if (not (eq? val unset-field))
+      (serialize-field* field-name
+                       (string-drop ; Drop the leading comma
+                        (fold
+                         (lambda (i prev)
+                           (string-append prev "," (number->string i)))
+                         "" val) 1))))
+
+(define file-name? (predicate/unset
+                    (lambda (val)
+                      (string-prefix? "/" val))))
+
+(define (serialize-file-name field-name val)
+  (if (not (eq? val unset-field))
+      (serialize-string field-name val)))
+
+(define (non-negative-integer? val)
+  (and (exact-integer? val) (not (negative? val))))
+
+(define (serialize-non-negative-integer/unset field-name val)
+  (if (not (eq? val unset-field))
+      (serialize-field* field-name val)))
+
+(define (free-form-fields? val)
+  (match val
+    (() #t)
+    ((((? symbol?) . (? string)) . val) (free-form-fields? val))
+    (_ #f)))
+
+(define (serialize-free-form-fields field-name val)
+  (for-each (match-lambda ((k . v) (serialize-field* k v))) val))
+
+(define non-negative-integer/unset? (predicate/unset non-negative-integer?))
+
+(define (realm-list? val)
+  (and (list? val)
+       (and-map (lambda (x) (krb5-realm? x)) val)))
+
+(define (serialize-realm-list field-name val)
+  (format #t "\n[~a]\n" field-name)
+  (for-each (lambda (realm)
+              (format #t "\n~a = {\n" (krb5-realm-name realm))
+              (for-each (lambda (field)
+                          (unless (eq? 'name (configuration-field-name field))
+                            ((configuration-field-serializer field)
+                             (configuration-field-name field)
+                             ((configuration-field-getter field)
+                              realm)))) krb5-realm-fields)
+
+              (format #t "}\n")) val))
+
+
+
+;; For a more detailed explanation of these fields see man 5 krb5.conf
+(define-configuration krb5-realm
+  (name
+   (string/unset unset-field)
+   "The name of the realm.")
+
+  (kdc
+   (end-point unset-field)
+   "The host and port on which the realm's Key Distribution Server listens.")
+
+  (admin-server
+   (string/unset unset-field)
+   "The Host running the administration server for the realm.")
+
+  (master-kdc
+   (string/unset unset-field)
+   "If an attempt to get credentials fails because of an invalid password, 
+the client software will attempt to contact the master KDC.")
+
+  (kpasswd-server
+   (string/unset unset-field)
+   "The server where password changes are performed.")
+
+  (auth-to-local
+   (free-form-fields '())
+   "Rules to map between principals and local users.")
+
+  (auth-to-local-names
+   (free-form-fields '())
+   "Explicit mappings between principal names and local user names.")
+
+  (http-anchors
+   (free-form-fields '())
+   "Useful only when http proxy is used to access KDC or KPASSWD.")
+
+  ;; The following are useful only for working with V4 services
+  (default-domain
+    (string/unset unset-field)
+    "The domain used to expand host names when translating Kerberos 4 service
+principals to Kerberos 5 principals")
+
+  (v4-instance-convert
+   (free-form-fields '())
+   "Exceptions to the default-domain mapping rule.")
+
+  (v4-realm
+   (string/unset unset-field)
+   "Used  when the V4 realm name and the V5 realm name are not the same, but
+still share the same principal names and passwords"))
+
+
+
+;; For a more detailed explanation of these fields see man 5 krb5.conf
+(define-configuration krb5-configuration
+  (allow-weak-crypto?
+   (boolean/unset unset-field)
+   "If true, permits access to services which only offer weak encryption.")
+
+  (ap-req-checksum-type
+   (non-negative-integer/unset unset-field)
+   "The type of the AP-REQ checksum.")
+
+  (canonicalize?
+   (boolean/unset unset-field)
+   "Should principals in initial ticket requests be canonicalized?")
+
+  (ccache-type
+   (non-negative-integer/unset unset-field)
+   "The format of the credential cache type.")
+
+  (clockskew
+   (non-negative-integer/unset unset-field)
+   "Maximum allowable clock skew in seconds (default 300).")
+
+  (default-ccache-name
+    (file-name unset-field)
+    "The name of the default credential cache.")
+
+  (default-client-keytab-name
+    (file-name unset-field)
+    "The name of the default keytab for client credentials.")
+
+  (default-keytab-name
+    (file-name unset-field)
+    "The name of the default keytab file.")
+
+  (default-realm
+    (string/unset unset-field)
+    "The realm to be accessed if not explicitly specified by clients.")
+
+  (default-tgs-enctypes
+    (free-form-fields '())
+    "Session key encryption types when making TGS-REQ requests.")
+
+  (default-tkt-enctypes
+    (free-form-fields '())
+    "Session key encryption types when making AS-REQ requests.")
+
+  (dns-canonicalize-hostname?
+   (boolean/unset  unset-field)
+   "Whether name lookups will be used to canonicalize host names for use in 
+service principal names.")
+
+  (dns-lookup-kdc?
+   (boolean/unset unset-field)
+ "Should DNS SRV records should be used to locate the KDCs and other servers 
+not appearing in the realm specification")
+
+  (err-fmt
+   (string/unset unset-field)
+   "Custom error message formatting. If not #f error messages will be formatted 
+by substituting a normal error message for %M and an error code for %C in the 
+value.")
+
+  (forwardable?
+   (boolean/unset unset-field)
+   "Should initial tickets be forwardable by default?")
+
+  (ignore-acceptor-hostname?
+   (boolean/unset unset-field)
+   "When accepting GSSAPI or krb5 security contexts for host-based service 
+principals, ignore any hostname passed by the calling application, and allow 
+clients to authenticate to any service principal in the keytab matching the 
+service name and realm name.")
+
+  (k5login-authoritative?
+   (boolean/unset unset-field)
+   "If this flag is true, principals must be listed in a local user's k5login
+file to be granted login access, if a ~/.k5login file exists.")
+
+  (k5login-directory
+   (string/unset unset-field)
+   "If not #f, the library will look for a local user's @file{k5login} file 
+within the named directory (instead of the user's home directory), with a 
+file name corresponding to the local user name.")
+
+  (kcm-mach-service
+   (string/unset unset-field)
+   "The name of the bootstrap service used to contact the KCM daemon for the 
+KCM credential cache type.")
+
+  (kcm-socket
+   (file-name unset-field)
+ "Path to the Unix domain socket used to access the KCM daemon for the KCM 
+credential cache type.")
+
+  (kdc-default-options
+   (non-negative-integer/unset unset-field)
+   "Default KDC options (logored for multiple values) when requesting initial 
+tickets.")
+
+  (kdc-timesync
+   (non-negative-integer/unset unset-field)
+   "Attempt to compensate for clock skew between the KDC and client.")
+
+  (kdc-req-checksum-type
+   (non-negative-integer/unset unset-field)
+   "The type of checksum to use for the KDC requests. Relevant only for DES 
+keys")
+
+  (noaddresses?
+   (boolean/unset unset-field)
+   "If true, initial ticket requests will not be made with address restrictions.
+This enables their use across NATs.")
+
+  (permitted-enctypes
+   (space-separated-string-list/unset unset-field)
+   "All encryption types that are permitted for use in session key encryption.")
+
+  (plugin-base-dir
+   (file-name unset-field)
+   "The directory where krb5 plugins are located.")
+
+  (preferred-preauth-types
+   (comma-separated-integer-list/unset unset-field)
+   "The preferred pre-authentication types which the client will attempt before 
+others.")
+
+  (proxiable?
+   (boolean/unset unset-field)
+   "Should initial tickets be proxiable by default?")
+
+  (rdns?
+   (boolean/unset unset-field)
+   "Should reverse DNS lookup be used in addition to forward name lookup to 
+canonicalize host names for use in service principal names.")
+
+  (realm-try-domains
+   (integer/unset unset-field)
+   "Should a host's domain components should be used to determine the Kerberos 
+realm of the host.")
+
+  (renew-lifetime
+   (non-negative-integer/unset unset-field)
+   "The default renewable lifetime for initial ticket requests.")
+
+  (safe-checksum-type
+   (non-negative-integer/unset unset-field)
+   "The type of checksum to use for the KRB-SAFE requests.")
+
+  (ticket-lifetime
+   (non-negative-integer/unset unset-field)
+   "The default lifetime for initial ticket requests.")
+
+  (udp-preference-limit
+   (non-negative-integer/unset unset-field)
+   "When sending messages to the KDC, the library will try using TCP
+before UDP if the size of the message greater than this limit.")
+
+  (verify-ap-rereq-nofail?
+   (boolean/unset unset-field)
+ "If true, then attempts to verify initial credentials will fail if the client
+machine does not have a keytab.")
+
+  (realms
+   (realm-list '())
+   "The list of realms which clients may access."))
+
+
+(define (krb5-configuration-file config)
+  "Create a Kerberos 5 configuration file based on CONFIG"
+  (mixed-text-file "krb5.conf"
+                   "[libdefaults]\n\n"
+                   (with-output-to-string
+                     (lambda ()
+                       (serialize-configuration config
+                                                krb5-configuration-fields)))))
+
+(define (krb5-etc-service config)
+  (list `("krb5.conf" ,(krb5-configuration-file config))))
+
+
+(define krb5-service-type
+  (service-type (name 'krb5)
+                (extensions
+                 (list (service-extension etc-service-type
+                                          krb5-etc-service)))))
+
+
+
 
 (define-record-type* <pam-krb5-configuration>
   pam-krb5-configuration  make-pam-krb5-configuration