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Diffstat (limited to 'doc/safe.n')
| -rw-r--r-- | doc/safe.n | 128 |
1 files changed, 69 insertions, 59 deletions
@@ -3,15 +3,13 @@ '\" '\" See the file "license.terms" for information on usage and redistribution '\" of this file, and for a DISCLAIMER OF ALL WARRANTIES. -'\" -'\" RCS: @(#) $Id: safe.n,v 1.7 2004/09/06 09:44:57 dkf Exp $ -'\" -.so man.macros +'\" .TH "Safe Tcl" n 8.0 Tcl "Tcl Built-In Commands" +.so man.macros .BS '\" Note: do not modify the .SH NAME line immediately below! .SH NAME -Safe\ Base \- A mechanism for creating and manipulating safe interpreters +safe \- Creating and manipulating safe interpreters .SH SYNOPSIS \fB::safe::interpCreate\fR ?\fIslave\fR? ?\fIoptions...\fR? .sp @@ -26,28 +24,27 @@ Safe\ Base \- A mechanism for creating and manipulating safe interpreters \fB::safe::interpFindInAccessPath\fR \fIslave\fR \fIdirectory\fR .sp \fB::safe::setLogCmd\fR ?\fIcmd arg...\fR? -.SH OPTIONS +.SS OPTIONS .PP ?\fB\-accessPath\fR \fIpathList\fR? ?\fB\-statics\fR \fIboolean\fR? ?\fB\-noStatics\fR? ?\fB\-nested\fR \fIboolean\fR? ?\fB\-nestedLoadOk\fR? ?\fB\-deleteHook\fR \fIscript\fR? .BE - .SH DESCRIPTION Safe Tcl is a mechanism for executing untrusted Tcl scripts safely and for providing mediated access by such scripts to potentially dangerous functionality. .PP -The Safe Base ensures that untrusted Tcl scripts cannot harm the +Safe Tcl ensures that untrusted Tcl scripts cannot harm the hosting application. -The Safe Base prevents integrity and privacy attacks. Untrusted Tcl +It prevents integrity and privacy attacks. Untrusted Tcl scripts are prevented from corrupting the state of the hosting application or computer. Untrusted scripts are also prevented from disclosing information stored on the hosting computer or in the hosting application to any party. .PP -The Safe Base allows a master interpreter to create safe, restricted +Safe Tcl allows a master interpreter to create safe, restricted interpreters that contain a set of predefined aliases for the \fBsource\fR, \fBload\fR, \fBfile\fR, \fBencoding\fR, and \fBexit\fR commands and are able to use the auto-loading and package mechanisms. @@ -56,22 +53,21 @@ No knowledge of the file system structure is leaked to the safe interpreter, because it has access only to a virtualized path containing tokens. When the safe interpreter requests to source a file, it uses the token in the virtual path as part of the file name to source; the -master interpreter transparently -translates the token into a real directory name and executes the +master interpreter transparently +translates the token into a real directory name and executes the requested operation (see the section \fBSECURITY\fR below for details). Different levels of security can be selected by using the optional flags of the commands described below. .PP -All commands provided in the master interpreter by the Safe Base reside in -the \fBsafe\fR namespace: - +All commands provided in the master interpreter by Safe Tcl reside in +the \fBsafe\fR namespace. .SH COMMANDS The following commands are provided in the master interpreter: .TP \fB::safe::interpCreate\fR ?\fIslave\fR? ?\fIoptions...\fR? Creates a safe interpreter, installs the aliases described in the section \fBALIASES\fR and initializes the auto-loading and package mechanism as -specified by the supplied \fBoptions\fR. +specified by the supplied \fIoptions\fR. See the \fBOPTIONS\fR section below for a description of the optional arguments. If the \fIslave\fR argument is omitted, a name will be generated. @@ -80,12 +76,12 @@ If the \fIslave\fR argument is omitted, a name will be generated. \fB::safe::interpInit\fR \fIslave\fR ?\fIoptions...\fR? This command is similar to \fBinterpCreate\fR except it that does not create the safe interpreter. \fIslave\fR must have been created by some -other means, like \fBinterp create \-safe\fR. +other means, like \fBinterp create\fR \fB\-safe\fR. .TP \fB::safe::interpConfigure\fR \fIslave\fR ?\fIoptions...\fR? If no \fIoptions\fR are given, returns the settings for all options for the named safe interpreter as a list of options and their current values -for that \fIslave\fR. +for that \fIslave\fR. If a single additional argument is provided, it will return a list of 2 elements \fIname\fR and \fIvalue\fR where \fIname\fR is the full name of that option and \fIvalue\fR the current value @@ -95,19 +91,22 @@ safe interpreter and change each and only the provided options. See the section on \fBOPTIONS\fR below for options description. Example of use: .RS +.PP .CS -# Create a new interp with the same configuration as "$i0" : -set i1 [eval safe::interpCreate [safe::interpConfigure $i0]] +# Create new interp with the same configuration as "$i0": +set i1 [safe::interpCreate {*}[safe::interpConfigure $i0]] + # Get the current deleteHook set dh [safe::interpConfigure $i0 \-del] -# Change (only) the statics loading ok attribute of an interp -# and its deleteHook (leaving the rest unchanged) : -safe::interpConfigure $i0 \-delete {foo bar} \-statics 0 ; + +# Change (only) the statics loading ok attribute of an +# interp and its deleteHook (leaving the rest unchanged): +safe::interpConfigure $i0 \-delete {foo bar} \-statics 0 .CE .RE .TP \fB::safe::interpDelete\fR \fIslave\fR -Deletes the safe interpreter and cleans up the corresponding +Deletes the safe interpreter and cleans up the corresponding master interpreter data structures. If a \fIdeleteHook\fR script was specified for this interpreter it is evaluated before the interpreter is deleted, with the name of the @@ -119,8 +118,10 @@ This command finds and returns the token for the real directory It generates an error if the directory is not found. Example of use: .RS +.PP .CS -$slave eval [list set tk_library [::safe::interpFindInAccessPath $name $tk_library]] +$slave eval [list set tk_library \e + [::safe::interpFindInAccessPath $name $tk_library]] .CE .RE .TP @@ -132,8 +133,10 @@ If the directory is already in the virtual path, it only returns the token without adding the directory to the virtual path again. Example of use: .RS +.PP .CS -$slave eval [list set tk_library [::safe::interpAddToAccessPath $name $tk_library]] +$slave eval [list set tk_library \e + [::safe::interpAddToAccessPath $name $tk_library]] .CE .RE .TP @@ -152,14 +155,18 @@ This prevents a safe interpreter from seeing messages about failures and other events that might contain sensitive information such as real directory names. .RS +.PP Example of use: +.PP .CS ::safe::setLogCmd puts stderr .CE +.PP Below is the output of a sample session in which a safe interpreter attempted to source a file not found in its virtual access path. Note that the safe interpreter only received an error message saying that the file was not found: +.PP .CS NOTICE for slave interp10 : Created NOTICE for slave interp10 : Setting accessPath=(/foo/bar) staticsok=1 nestedok=0 deletehook=() @@ -167,47 +174,46 @@ NOTICE for slave interp10 : auto_path in interp10 has been set to {$p(:0:)} ERROR for slave interp10 : /foo/bar/init.tcl: no such file or directory .CE .RE - -.SH OPTIONS -The following options are common to -\fB::safe::interpCreate\fR, \fB::safe::interpInit\fR, +.SS OPTIONS +The following options are common to +\fB::safe::interpCreate\fR, \fB::safe::interpInit\fR, and \fB::safe::interpConfigure\fR. -Any option name can be abbreviated to its minimal +Any option name can be abbreviated to its minimal non-ambiguous name. Option names are not case sensitive. -.TP +.TP \fB\-accessPath\fR \fIdirectoryList\fR This option sets the list of directories from which the safe interpreter can \fBsource\fR and \fBload\fR files. If this option is not specified, or if it is given as the empty list, the safe interpreter will use the same directories as its master for auto-loading. -See the section \fBSECURITY\fR below for more detail about virtual paths, +See the section \fBSECURITY\fR below for more detail about virtual paths, tokens and access control. .TP \fB\-statics\fR \fIboolean\fR This option specifies if the safe interpreter will be allowed to load statically linked packages (like \fBload {} Tk\fR). -The default value is \fBtrue\fR : +The default value is \fBtrue\fR : safe interpreters are allowed to load statically linked packages. .TP \fB\-noStatics\fR -This option is a convenience shortcut for \fB-statics false\fR and +This option is a convenience shortcut for \fB\-statics false\fR and thus specifies that the safe interpreter will not be allowed to load statically linked packages. .TP \fB\-nested\fR \fIboolean\fR This option specifies if the safe interpreter will be allowed to load packages into its own sub-interpreters. -The default value is \fBfalse\fR : +The default value is \fBfalse\fR : safe interpreters are not allowed to load packages into their own sub-interpreters. .TP \fB\-nestedLoadOk\fR -This option is a convenience shortcut for \fB-nested true\fR and +This option is a convenience shortcut for \fB\-nested true\fR and thus specifies the safe interpreter will be allowed to load packages into its own sub-interpreters. -.TP +.TP \fB\-deleteHook\fR \fIscript\fR When this option is given a non-empty \fIscript\fR, it will be evaluated in the master with the name of @@ -254,15 +260,14 @@ the system encoding, but allows all other subcommands including \fBexit\fR The calling interpreter is deleted and its computation is stopped, but the Tcl process in which this interpreter exists is not terminated. - .SH SECURITY -The Safe Base does not attempt to completely prevent annoyance and +Safe Tcl does not attempt to completely prevent annoyance and denial of service attacks. These forms of attack prevent the application or user from temporarily using the computer to perform useful work, for example by consuming all available CPU time or all available screen real estate. These attacks, while aggravating, are deemed to be of lesser importance -in general than integrity and privacy attacks that the Safe Base +in general than integrity and privacy attacks that Safe Tcl is to prevent. .PP The commands available in a safe interpreter, in addition to @@ -281,17 +286,17 @@ This virtual path system is maintained in the master interpreter for each safe interpreter created by \fB::safe::interpCreate\fR or initialized by \fB::safe::interpInit\fR and the path maps tokens accessible in the safe interpreter into real path -names on the local file system thus preventing safe interpreters +names on the local file system thus preventing safe interpreters from gaining knowledge about the structure of the file system of the host on which the interpreter is executing. The only valid file names arguments for the \fBsource\fR and \fBload\fR aliases provided to the slave -are path in the form of -\fB[file join \fR\fItoken filename\fR\fB]\fR (i.e. when using the -native file path formats: \fItoken\fR\fB/\fR\fIfilename\fR -on Unix and \fItoken\fR\fB\\\fIfilename\fR on Windows), -where \fItoken\fR is representing one of the directories +are path in the form of +\fB[file join \fItoken filename\fB]\fR (i.e. when using the +native file path formats: \fItoken\fB/\fIfilename\fR +on Unix and \fItoken\fB\e\fIfilename\fR on Windows), +where \fItoken\fR is representing one of the directories of the \fIaccessPath\fR list and \fIfilename\fR is one file in that directory (no sub directories access are allowed). .PP @@ -306,33 +311,37 @@ To further prevent potential information leakage from sensitive files that are accidentally included in the set of files that can be sourced by a safe interpreter, the \fBsource\fR alias restricts access to files meeting the following constraints: the file name must -fourteen characters or shorter, must not contain more than one dot ("\fB.\fR"), -must end up with the extension \fB.tcl\fR or be called \fBtclIndex\fR. +fourteen characters or shorter, must not contain more than one dot +.PQ \fB.\fR "" , +must end up with the extension +.PQ \fB.tcl\fR +or be called +.PQ \fBtclIndex\fR . .PP Each element of the initial access path list will be assigned a token that will be set in the slave \fBauto_path\fR and the first element of that list will be set as the \fBtcl_library\fR for that slave. .PP -If the access path argument is not given or is the empty list, +If the access path argument is not given or is the empty list, the default behavior is to let the slave access the same packages -as the master has access to (Or to be more precise: -only packages written in Tcl (which by definition can't be dangerous +as the master has access to (Or to be more precise: +only packages written in Tcl (which by definition cannot be dangerous as they run in the slave interpreter) and C extensions that -provides a Safe_Init entry point). For that purpose, the master's -\fBauto_path\fR will be used to construct the slave access path. +provides a _SafeInit entry point). For that purpose, the master's +\fBauto_path\fR will be used to construct the slave access path. In order that the slave successfully loads the Tcl library files (which includes the auto-loading mechanism itself) the \fBtcl_library\fR will be -added or moved to the first position if necessary, in the +added or moved to the first position if necessary, in the slave access path, so the slave \fBtcl_library\fR will be the same as the master's (its real -path will still be invisible to the slave though). +path will still be invisible to the slave though). In order that auto-loading works the same for the slave and the master in this by default case, the first-level sub directories of each directory in the master \fBauto_path\fR will also be added (if not already included) to the slave access path. You can always specify a more -restrictive path for which sub directories will never be searched by +restrictive path for which sub directories will never be searched by explicitly specifying your directory list with the \fB\-accessPath\fR flag instead of relying on this default mechanism. .PP @@ -340,10 +349,11 @@ When the \fIaccessPath\fR is changed after the first creation or initialization (i.e. through \fBinterpConfigure -accessPath \fR\fIlist\fR), an \fBauto_reset\fR is automatically evaluated in the safe interpreter to synchronize its \fBauto_index\fR with the new token list. - .SH "SEE ALSO" interp(n), library(n), load(n), package(n), source(n), unknown(n) - .SH KEYWORDS alias, auto\-loading, auto_mkindex, load, master interpreter, safe interpreter, slave interpreter, source +'\" Local Variables: +'\" mode: nroff +'\" End: |