On Thu, Mar 04, 2021 at 06:10:12PM +0000, Daniel P. Berrangé wrote:
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com> --- docs/auth.html.in | 368 ---------------------------------------------- docs/auth.rst | 350 +++++++++++++++++++++++++++++++++++++++++++ docs/meson.build | 2 +- 3 files changed, 351 insertions(+), 369 deletions(-) delete mode 100644 docs/auth.html.in create mode 100644 docs/auth.rst
diff --git a/docs/auth.html.in b/docs/auth.html.in deleted file mode 100644 index 9b940a8598..0000000000 --- a/docs/auth.html.in +++ /dev/null @@ -1,368 +0,0 @@ -<?xml version="1.0" encoding="UTF-8"?> -<!DOCTYPE html> -<html xmlns="http://www.w3.org/1999/xhtml"> - <body> - <h1>Connection authentication</h1> - <p> - When connecting to libvirt, some connections may require client - authentication before allowing use of the APIs. The set of possible - authentication mechanisms is administrator controlled, independent - of applications using libvirt. Once authenticated, libvirt can apply - fine grained <a href="acl.html">access control</a> to the operations - performed by a client. - </p> - - <ul id="toc"></ul> - - <h2><a id="Auth_client_config">Client configuration</a></h2> - - <p> - When connecting to a remote hypervisor which requires authentication, -most libvirt applications will prompt the user for the credentials. It is -also possible to provide a client configuration file containing all the -authentication credentials, avoiding any interaction. Libvirt will look -for the authentication file using the following sequence: - </p> - <ol> - <li>The file path specified by the $LIBVIRT_AUTH_FILE environment - variable.</li> - <li>The file path specified by the "authfile=/some/file" URI - query parameter</li> - <li>The file $XDG_CONFIG_HOME/libvirt/auth.conf</li> - <li>The file /etc/libvirt/auth.conf</li> - </ol> - - <p> - The auth configuration file uses the traditional <code>".ini"</code> - style syntax. There are two types of groups that can be present in - the config. First there are one or more <strong>credential</strong> - sets, which provide the actual authentication credentials. The keys - within the group may be: - </p> - - <ul> - <li><code>username</code>: the user login name to act as. This - is relevant for ESX, Xen, HyperV and SSH, but probably not - the one you want to libvirtd with SASL.</li> - <li><code>authname</code>: the name to authorize as. This is - what is commonly required for libvirtd with SASL.</li> - <li><code>password</code>: the secret password</li> - <li><code>realm</code>: the domain realm for SASL, mostly - unused</li> - </ul> - - <p> - Each set of credentials has a name, which is part of the group - entry name. Overall the syntax is - </p> - - <pre> -[credentials-$NAME] -credname1=value1 -credname2=value2</pre> - - <p> - For example, to define two sets of credentials used for production - and test machines, using libvirtd, and a further ESX server for dev: - </p> -<pre> -[credentials-test] -authname=fred -password=123456 - -[credentials-prod] -authname=bar -password=letmein - -[credentials-dev] -username=joe -password=hello - -[credentials-defgrp] -username=defuser -password=defpw</pre> - - <p> - The second set of groups provide mappings of credentials to - specific machine services. The config file group names compromise - the service type and host: - </p> - - <pre> -[auth-$SERVICE-$HOSTNAME] -credentials=$CREDENTIALS</pre> - - <p> - For example, following the previous example, here is how to - map some machines. For convenience libvirt supports a default - mapping of credentials to machines: - </p> - - <pre> -[auth-libvirt-test1.example.com] -credentials=test - -[auth-libvirt-test2.example.com] -credentials=test - -[auth-libvirt-demo3.example.com] -credentials=test - -[auth-libvirt-prod1.example.com] -credentials=prod - -[auth-libvirt-default] -credentials=defgrp - -[auth-esx-dev1.example.com] -credentials=dev - -[auth-esx-default] -credentials=defgrp</pre> - - - <p> - The following service types are known to libvirt: - </p> - - <ul> - <li><code>esx</code> - used for connections to an ESX or - VirtualCenter server</li> - <li><code>hyperv</code> - used for connections to an HyperV - server</li> - <li><code>libvirt</code> - used for connections to a libvirtd - server, which is configured with SASL auth</li> - <li><code>ssh</code> - used for connections to a remote QEMU driver - over SSH</li> - </ul> - - <p> - Applications using libvirt are free to use this same configuration - file for storing other credentials. For example, it can be used - to storage VNC or SPICE login credentials - </p> - - <h2><a id="ACL_server_config">Server configuration</a></h2> - <p> -The libvirt daemon allows the administrator to choose the authentication -mechanisms used for client connections on each network socket independently. -This is primarily controlled via the libvirt daemon master config file in -<code>/etc/libvirt/libvirtd.conf</code>. Each of the libvirt sockets can -have its authentication mechanism configured independently. There is -currently a choice of <code>none</code>, <code>polkit</code>, and <code>sasl</code>. -The SASL scheme can be further configured to choose between a large -number of different mechanisms. -</p> - <h2><a id="ACL_server_unix_perms">UNIX socket permissions/group</a></h2> - <p> -If libvirt does not contain support for PolicyKit, then access control for -the UNIX domain socket is done using traditional file user/group ownership -and permissions. There are 2 sockets, one for full read-write access, the -other for read-only access. The RW socket will be restricted (mode 0700) to -only allow the <code>root</code> user to connect. The read-only socket will -be open access (mode 0777) to allow any user to connect. -</p> - <p> -To allow non-root users greater access, the <code>libvirtd.conf</code> file -can be edited to change the permissions via the <code>unix_sock_rw_perms</code>, -config parameter and to set a user group via the <code>unix_sock_group</code> -parameter. For example, setting the former to mode <code>0770</code> and the -latter <code>wheel</code> would let any user in the wheel group connect to -the libvirt daemon. -</p> - <h2><a id="ACL_server_polkit">UNIX socket PolicyKit auth</a></h2> - <p> -If libvirt contains support for PolicyKit, then access control options are -more advanced. The <code>auth_unix_rw</code> parameter will default to -<code>polkit</code>, and the file permissions will default to <code>0777</code> -even on the RW socket. Upon connecting to the socket, the client application -will be required to identify itself with PolicyKit. The default policy for the -RW daemon socket will require any application running in the current desktop -session to authenticate using the user's password. This is akin to <code>sudo</code> -auth, but does not require that the client application ultimately run as root. -Default policy will still allow any application to connect to the RO socket. -</p> - <p> -The default policy can be overridden by creating a new policy file in the -<code>/etc/polkit-1/rules.d</code> directory. Information on the options -available can be found by reading the <code>polkit(8)</code> man page. The -two libvirt actions are named <code>org.libvirt.unix.manage</code> for full -management access, and <code>org.libvirt.unix.monitor</code> for read-only -access. -</p> - <p> -As an example, creating <code>/etc/polkit-1/rules.d/80-libvirt-manage.rules</code> -with the following gives the user <code>fred</code> full management access -when accessing from an active local session: - </p> -<pre>polkit.addRule(function(action, subject) { - if (action.id == "org.libvirt.unix.manage" && - subject.local && subject.active && subject.user == "fred") { - return polkit.Result.YES; - } -});</pre> - <p> -Older versions of PolicyKit used policy files ending with .pkla in the -local override directory <code>/etc/polkit-1/localauthority/50-local.d/</code>. -Compatibility with this older format is provided by <a -href="https://pagure.io/polkit-pkla-compat">polkit-pkla-compat</a>. As an -example, this gives the user <code>fred</code> full management access: - </p> -<pre>[Allow fred libvirt management permissions] -Identity=unix-user:fred -Action=org.libvirt.unix.manage -ResultAny=yes -ResultInactive=yes -ResultActive=yes</pre> - <h2><a id="ACL_server_sasl">SASL pluggable authentication</a></h2> - - <p> -Libvirt integrates with the cyrus-sasl library to provide a pluggable authentication -system using the SASL protocol. SASL can be used in combination with libvirtd's TLS -or TCP socket listeners. When used with the TCP listener, the SASL mechanism is -rqeuired to provide session encryption in addition to authentication. Only a very -few SASL mechanisms are able to do this, and of those that can do it, only the -GSSAPI plugin is considered acceptably secure by modern standards: - </p> - - <dl> - <dt>GSSAPI</dt> - <dd><strong>This is the current default mechanism to use with libvirtd</strong>. - It uses the Kerberos v5 authentication protocol underneath, and assuming - the Kerberos client/server are configured with modern ciphers (AES), - it provides strong session encryption capabilities.</dd> - - <dt>DIGEST-MD5</dt> - <dd>This was previously set as the default mechanism to use with libvirtd. - It provides a simple username/password based authentication mechanism - that includes session encryption. - <a href="https://tools.ietf.org/html/rfc6331">RFC 6331</a>, however, - documents a number of serious security flaws with DIGEST-MD5 and as a - result marks it as <code>OBSOLETE</code>. Specific concerns are that - it is vulnerable to MITM attacks and the MD5 hash can be brute-forced - to reveal the password. A replacement is provided via the SCRAM mechanism, - however, note that this does not provide encryption, so the SCRAM - mechanism can only be used on the libvirtd TLS listener. - </dd> - - <dt>PASSDSS-3DES-1</dt> - <dd>This provides a simple username/password based authentication - mechanism that includes session encryption. The current cyrus-sasl - implementation does not provide a way to validate the server's - public key identity, thus it is susceptible to a MITM attacker - impersonating the server. It is also not enabled in many OS - distros when building SASL libraries.</dd> - - <dt>KERBEROS_V4</dt> - <dd>This uses the obsolete Kerberos v4 protocol to provide both authentication - and session encryption. Kerberos v4 protocol has been obsolete since the - early 1990's and has known security vulnerabilities so this will never be - used in practice.</dd> - </dl> - - <p> - Other SASL mechanisms, not listed above, can only be used when the libvirtd - TLS or UNIX socket listeners. - </p> - - <h3><a id="ACL_server_username">Username/password auth</a></h3> - <p> -As noted above, the DIGEST-MD5 mechanism is considered obsolete and should -not be used anymore. To provide a simple username/password auth scheme on -the libvirt UNIX socket or TLS listeners, however, it is possible to use -the SCRAM mechanism. The <code>auth_unix_ro</code>, <code>auth_unix_rw</code>, -<code>auth_tls</code> config params in <code>libvirt.conf</code> can be used -to turn on SASL auth in these listeners. - </p> - <p> -Since the libvirt SASL config file defaults to using GSSAPI (Kerberos), a -config change is required to enable plain password auth. This is done by -editing <code>/etc/sasl2/libvirt.conf</code> to set the <code>mech_list</code> -parameter to <code>scram-sha-1</code>. - </p> - <p> -Out of the box, no user accounts are defined, so no clients will be able to authenticate -on the TCP socket. Adding users and setting their passwords is done with the <code>saslpasswd2</code> -command. When running this command it is important to tell it that the appname is <code>libvirt</code>. -As an example, to add a user <code>fred</code>, run -</p> - <pre> -# saslpasswd2 -a libvirt fred -Password: xxxxxx -Again (for verification): xxxxxx -</pre> - <p> -To see a list of all accounts the <code>sasldblistusers2</code> command can be used. -This command expects to be given the path to the libvirt user database, which is kept -in <code>/etc/libvirt/passwd.db</code> -</p> - <pre> -# sasldblistusers2 -f /etc/libvirt/passwd.db -fred@t60wlan.home.berrange.com: userPassword -</pre> - <p> -Finally, to disable a user's access, the <code>saslpasswd2</code> command can be used -again: -</p> - <pre> -# saslpasswd2 -a libvirt -d fred -</pre> - <h3><a id="ACL_server_kerberos">GSSAPI/Kerberos auth</a></h3> - <p> -The plain TCP listener of the libvirt daemon defaults to using SASL for authentication. -The libvirt SASL config also defaults to GSSAPI, so there is no need to edit the -SASL config when using GSSAPI. If the libvirtd TLS or UNIX listeners are used, -then the Kerberos session encryption will be disabled since it is not required -in these scenarios - only the plain TCP listener needs encryption -</p> - <p> -Some operating systems do not install the SASL kerberos plugin by default. It -may be necessary to install a sub-package such as <code>cyrus-sasl-gssapi</code>. -To check whether the Kerberos plugin is installed run the <code>pluginviewer</code> -program and verify that <code>gssapi</code> is listed, e.g.: -</p> - <pre> -# pluginviewer -...snip... -Plugin "gssapiv2" [loaded], API version: 4 - SASL mechanism: GSSAPI, best SSF: 56 - security flags: NO_ANONYMOUS|NO_PLAINTEXT|NO_ACTIVE|PASS_CREDENTIALS|MUTUAL_AUTH - features: WANT_CLIENT_FIRST|PROXY_AUTHENTICATION|NEED_SERVER_FQDN -</pre> - <p> -Next it is necessary for the administrator of the Kerberos realm to -issue a principal for the libvirt server. There needs to be one -principal per host running the libvirt daemon. The principal should be -named <code>libvirt/full.hostname@KERBEROS.REALM</code>. This is -typically done by running the <code>kadmin.local</code> command on the -Kerberos server, though some Kerberos servers have alternate ways of -setting up service principals. Once created, the principal should be -exported to a keytab, copied to the host running the libvirt daemon -and placed in <code>/etc/libvirt/krb5.tab</code> -</p> - <pre> -# kadmin.local -kadmin.local: add_principal libvirt/foo.example.com -Enter password for principal "libvirt/foo.example.com@EXAMPLE.COM": -Re-enter password for principal "libvirt/foo.example.com@EXAMPLE.COM": -Principal "libvirt/foo.example.com@EXAMPLE.COM" created. - -kadmin.local: ktadd -k /root/libvirt-foo-example.tab libvirt/foo.example.com@EXAMPLE.COM -Entry for principal libvirt/foo.example.com@EXAMPLE.COM with kvno 4, encryption type Triple DES cbc mode with HMAC/sha1 added to keytab WRFILE:/root/libvirt-foo-example.tab. -Entry for principal libvirt/foo.example.com@EXAMPLE.COM with kvno 4, encryption type ArcFour with HMAC/md5 added to keytab WRFILE:/root/libvirt-foo-example.tab. -Entry for principal libvirt/foo.example.com@EXAMPLE.COM with kvno 4, encryption type DES with HMAC/sha1 added to keytab WRFILE:/root/libvirt-foo-example.tab. -Entry for principal libvirt/foo.example.com@EXAMPLE.COM with kvno 4, encryption type DES cbc mode with RSA-MD5 added to keytab WRFILE:/root/libvirt-foo-example.tab. - -kadmin.local: quit - -# scp /root/libvirt-foo-example.tab root@foo.example.com:/etc/libvirt/krb5.tab -# rm /root/libvirt-foo-example.tab -</pre> - <p> -Any client application wishing to connect to a Kerberos enabled libvirt server -merely needs to run <code>kinit</code> to gain a user principal. This may well -be done automatically when a user logs into a desktop session, if PAM is set up -to authenticate against Kerberos. -</p> - </body> -</html> diff --git a/docs/auth.rst b/docs/auth.rst new file mode 100644 index 0000000000..506e6b5c13 --- /dev/null +++ b/docs/auth.rst @@ -0,0 +1,350 @@ +========================= +Connection authentication +========================= + +.. contents:: + +When connecting to libvirt, some connections may require client +authentication before allowing use of the APIs. The set of possible +authentication mechanisms is administrator controlled, independent +of applications using libvirt. Once authenticated, libvirt can apply +fine grained `access control <acl.html>`_ to the operations +performed by a client. + +Client configuration +==================== + +When connecting to a remote hypervisor which requires authentication, +most libvirt applications will prompt the user for the credentials. It is +also possible to provide a client configuration file containing all the +authentication credentials, avoiding any interaction. Libvirt will look +for the authentication file using the following sequence: + +* The file path specified by the ``$LIBVIRT_AUTH_FILE`` environment + variable. +* The file path specified by the ``authfile=/some/file`` URI + query parameter +* The file ``$XDG_CONFIG_HOME/libvirt/auth.conf`` +* The file ``/etc/libvirt/auth.conf`` + +The auth configuration file uses the traditional ``.ini`` +style syntax. There are two types of groups that can be present in +the config. First there are one or more ``credential`` +sets, which provide the actual authentication credentials. The keys +within the group may be: + +* ``username``: the user login name to act as. This + is relevant for ESX, Xen, HyperV and SSH, but probably not + the one you want to libvirtd with SASL.
s/want to/want for ...
+For example, to define two sets of credentials used for production +and test machines, using libvirtd, and a further ESX server for dev:
s/dev/development/ ...
+ polkit.addRule(function(action, subject) { + if (action.id == "org.libvirt.unix.manage" && + subject.local && subject.active &&; subject.user == "fred") {
s/amp;//g s/; subject/ subject/ ...
+ +As noted above, the DIGEST-MD5 mechanism is considered obsolete and should +not be used anymore. To provide a simple username/password auth scheme on +the libvirt UNIX socket or TLS listeners, however, it is possible to use +the SCRAM mechanism. The ``auth_unix_ro``, ``auth_unix_rw``, +``auth_tls`` config params in ``libvirt.conf`` can be used
s/libvirt.conf/libvirtd.conf/ All of the nits are pre-existing...please fix them in a trivial patch before pushing. Reviewed-by: Erik Skultety <eskultet@redhat.com>