X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~ian/git?p=userv.git;a=blobdiff_plain;f=spec.html%2Fch-ipass.html;h=a3a11606c904b7228c1c7eb6ad17409dffd14284;hp=118b3d5d7f4855bf25771b0a40f8a3c5884c39e7;hb=80bd586772a9f17d9235801b4727136d94a96862;hpb=d481e8196cc08ec6761f3a26da16d1e02dbbc712 diff --git a/spec.html/ch-ipass.html b/spec.html/ch-ipass.html index 118b3d5..a3a1160 100644 --- a/spec.html/ch-ipass.html +++ b/spec.html/ch-ipass.html @@ -1,101 +1,185 @@ - + + + + + + + + User service daemon and client specification - Information passed through the client/daemon combination - - + + + + + + +

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-User service daemon and client specification - chapter 5
-Information passed through the client/daemon combination +User service daemon and client specification +
Chapter 5 - Information passed through the client/daemon combination

-The information described below is the only information which passes -between the caller and the service. +

+ + +

+The information described below is the only information which passes between +the caller and the service.

The service name supplied by the caller is available in the -configuration language for deciding whether and which service program -to invoke, in the service parameter, and is used by the -execute-from-directory and execute-from-path -configuration directives. It is usually used to select which service -program to invoke. It is also passed to the service program in the -USERV_SERVICE environment variable. -
File descriptors specified by the client and allowed according to the -configuration language will be connected. Each file descriptor is -opened for reading or writing. Communication is via pipes, one end of -each pipe being open on the appropriate file descriptor in the service -program (when it is invoked) and the other end being held by the -client process, which will read and write files it opens on behalf of -its caller or file descriptors it is passed by its caller.
- -Data may be passed into the service through reading pipes and out of -it through writing pipes. These pipes can remain open only until the -service and client have terminated, or can be made to stay open after -the client has terminated and (if the service program forks) the main -service process has exited; the behaviour is controlled by options -passed to the client by its caller.
- -The caller can arrange that a writing pipe be connected to a pipe or -similar object and cause attempts to write to that descriptor by the -service to generate a SIGPIPE (or EPIPE if -SIGPIPE is caught or ignored) in the service.
- -Likewise, the service can close filedescriptors specified for reading, -which will cause the corresponding filedescriptors passed by the -caller to be closed, so that if these are pipes processes which write -to them will receive SIGPIPE or EPIPE. -
If no-suppress-args is set then arguments passed to the client -by its caller will be passed on, verbatim, to the service. -
Fatal signals and system call failures experienced by the client will -result in the disconnection of the service from the client and -possibly some of the communication file descriptors described above; -if disconnect-hup is set then the service will also be sent a -SIGHUP. -
The value of the LOGNAME (or USER) environment variable -as passed to the client will be used as the login name of the calling -user if the uid of the calling process matches the uid corresponding -to that login name. Otherwise the calling uid's password entry will -be used to determine the calling user's login name.
- -This login name and the calling uid are available in the configuration -language in the calling-user parameter and are passed to the -service program in environment variables USERV_USER and -USERV_UID.
- -The shell corresponding to that login name (according to the password -entry) is available as in the configuration language's -calling-user-shell parameter.
- -If no relevant password entry can be found then no service will be -invoked. -
The numeric values and textual names for calling gid and supplementary -group list are available in the configuration language in the -calling-group parameter and are passed to the service in -environment variables.
- -If no name can be found for a numeric group to which the calling -process belongs then no service will be invoked. -
The name of the current working directory in which the client was -invoked is passed, if available and not hidden using --hidecwd, -to the service program in the USERV_CWD variable. This grants no -special access to that directory unless it is a subdirectory of a -directory which is executable (searchable) but not readable by the -service user. -
Settings specified by the caller using the --defvar -name=value option to the client are available in the -configuration language as the corresponding u-name -parameters and are passed to the service program in environment -variables USERV_U_name. -
If the calling user is root or the same as the service user then -options may be given to the client which bypass the usual security -features; in this case other information may pass between the caller -and the service. -

+The service name supplied by the caller is available in the configuration +language for deciding whether and which service program to invoke, in the +service parameter, and is used by the +execute-from-directory and execute-from-path +configuration directives. It is usually used to select which service program +to invoke. It is also passed to the service program in the +USERV_SERVICE environment variable. +

+ +

+File descriptors specified by the client and allowed according to the +configuration language will be connected. Each file descriptor is opened for +reading or writing. Communication is via pipes, one end of each pipe being +open on the appropriate file descriptor in the service program (when it is +invoked) and the other end being held by the client process, which will read +and write files it opens on behalf of its caller or file descriptors it is +passed by its caller. + +
+Data may be passed into the service through reading pipes and out of it through +writing pipes. These pipes can remain open only until the service and client +have terminated, or can be made to stay open after the client has terminated +and (if the service program forks) the main service process has exited; the +behaviour is controlled by options passed to the client by its caller. + +
+The caller can arrange that a writing pipe be connected to a pipe or similar +object and cause attempts to write to that descriptor by the service to +generate a SIGPIPE (or EPIPE if SIGPIPE +is caught or ignored) in the service. + +
+Likewise, the service can close filedescriptors specified for reading, which +will cause the corresponding filedescriptors passed by the caller to be closed, +so that if these are pipes processes which write to them will receive +SIGPIPE or EPIPE. +

+If no-suppress-args is set then arguments passed to the client by +its caller will be passed on, verbatim, to the service. +

+Fatal signals and system call failures experienced by the client will result in +the disconnection of the service from the client and possibly some of the +communication file descriptors described above; if disconnect-hup +is set then the service will also be sent a SIGHUP. +

+The value of the LOGNAME (or USER) environment +variable as passed to the client will be used as the login name of the calling +user if the uid of the calling process matches the uid corresponding to that +login name. Otherwise the calling uid's password entry will be used to +determine the calling user's login name. + +
+This login name and the calling uid are available in the configuration language +in the calling-user parameter and are passed to the service +program in environment variables USERV_USER and +USERV_UID. + +
+The shell corresponding to that login name (according to the password entry) is +available as in the configuration language's calling-user-shell +parameter. + +
+If no relevant password entry can be found then no service will be invoked. +

+The numeric values and textual names for calling gid and supplementary group +list are available in the configuration language in the +calling-group parameter and are passed to the service in +environment variables. + +
+If no name can be found for a numeric group to which the calling process +belongs then no service will be invoked. +

+The name of the current working directory in which the client was invoked is +passed, if available and not hidden using --hidecwd, to the +service program in the USERV_CWD variable. This grants no special +access to that directory unless it is a subdirectory of a directory which is +executable (searchable) but not readable by the service user. +

+Settings specified by the caller using the --defvar +name=value option to the client are available in +the configuration language as the corresponding u-name +parameters and are passed to the service program in environment variables +USERV_U_name. +

+If the calling user is root or the same as the service user then options may be +given to the client which bypass the usual security features; in this case +other information may pass between the caller and the service. +

+ +[ previous ] +[ Contents ] +[ 1 ] +[ 2 ] +[ 3 ] +[ 4 ] +[ 5 ] +[ 6 ] +[ next ] + +

+ +

User service daemon and client specification -- userv is Copyright 1996-1999 Ian Jackson. -
-Contents; abstract; next; back. -
-

0.61.1
-Ian Jackson ian@davenant.greenend.org.uk

- + +

+1.0.3
+Ian Jackson ian@davenant.greenend.org.uk +

+ +

+ + + + +

-User service daemon and client specification - chapter 5 -Information passed through the client/daemon combination +User service daemon and client specification +Chapter 5 - Information passed through the client/daemon combination

-User service daemon and client specification - chapter 5
-Information passed through the client/daemon combination +User service daemon and client specification +
Chapter 5 - Information passed through the client/daemon combination