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86 lines
2.3 KiB
Go
86 lines
2.3 KiB
Go
// Copyright (c) 2018, Daniel Martí <mvdan@mvdan.cc>
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// See LICENSE for licensing information
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package shell
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import (
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"fmt"
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"io"
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"os"
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"mvdan.cc/sh/interp"
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"mvdan.cc/sh/syntax"
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)
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// SourceFile sources a shell file from disk and returns the variables
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// declared in it.
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//
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// A default parser is used; to set custom options, use SourceNode
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// instead.
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func SourceFile(path string) (map[string]interp.Variable, error) {
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f, err := os.Open(path)
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if err != nil {
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return nil, fmt.Errorf("could not open: %v", err)
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}
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defer f.Close()
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p := syntax.NewParser()
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file, err := p.Parse(f, path)
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if err != nil {
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return nil, fmt.Errorf("could not parse: %v", err)
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}
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return SourceNode(file)
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}
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// purePrograms holds a list of common programs that do not have side
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// effects, or otherwise cannot modify or harm the system that runs
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// them.
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var purePrograms = []string{
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// string handling
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"sed", "grep", "tr", "cut", "cat", "head", "tail", "seq", "yes",
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"wc",
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// paths
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"ls", "pwd", "basename", "realpath",
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// others
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"env", "sleep", "uniq", "sort",
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}
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func pureRunner() *interp.Runner {
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r := &interp.Runner{}
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// forbid executing programs that might cause trouble
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r.Exec = func(ctx interp.Ctxt, path string, args []string) error {
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for _, name := range purePrograms {
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if args[0] == name {
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return interp.DefaultExec(ctx, path, args)
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}
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}
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return fmt.Errorf("program not in whitelist: %s", args[0])
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}
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// forbid opening any real files
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r.Open = interp.OpenDevImpls(func(ctx interp.Ctxt, path string, flags int, mode os.FileMode) (io.ReadWriteCloser, error) {
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return nil, fmt.Errorf("cannot open path: %s", ctx.UnixPath(path))
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})
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return r
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}
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// SourceNode sources a shell program from a node and returns the
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// variables declared in it.
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//
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// Any side effects or modifications to the system are forbidden when
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// interpreting the program. This is enforced via whitelists when
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// executing programs and opening paths.
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func SourceNode(node syntax.Node) (map[string]interp.Variable, error) {
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r := pureRunner()
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r.Reset()
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if err := r.Run(node); err != nil {
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return nil, fmt.Errorf("could not run: %v", err)
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}
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// delete the internal shell vars that the user is not
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// interested in
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delete(r.Vars, "PWD")
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delete(r.Vars, "HOME")
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delete(r.Vars, "PATH")
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delete(r.Vars, "IFS")
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delete(r.Vars, "OPTIND")
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return r.Vars, nil
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}
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