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Removes WithWorkDirFS and "." resolution (#660)

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This removes WithWorkDirFS and any other attempts to resolve the current directory (".") in host functions. This is a reaction to reality of compilers who track this inside wasm (not via host functions). One nice side effect is substantially simpler internal implementation of file-systems.

This also allows experimental.WithFS to block file access via passing nil.

Signed-off-by: Adrian Cole <adrian@tetrate.io>
This commit is contained in:
Crypt Keeper
2022-06-27 13:29:35 +08:00
committed by GitHub
parent fb911b811c
commit 798ff20f81
24 changed files with 473 additions and 514 deletions
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58
config.go
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@@ -394,10 +394,10 @@ type ModuleConfig interface {
// See https://linux.die.net/man/3/environ and https://en.wikipedia.org/wiki/Null-terminated_string
WithEnv(key, value string) ModuleConfig
// WithFS assigns the file system to use for any paths beginning at "/". Defaults to not found.
// Note: This sets WithWorkDirFS to the same file-system unless already set.
// WithFS assigns the file system to use for any paths beginning at "/".
// Defaults return fs.ErrNotExist.
//
// Ex. This sets a read-only, embedded file-system to serve files under the root ("/") and working (".") directories:
// Ex. This sets a read-only, embedded file-system:
//
// //go:embed testdata/index.html
// var testdataIndex embed.FS
@@ -405,9 +405,24 @@ type ModuleConfig interface {
// rooted, err := fs.Sub(testdataIndex, "testdata")
// require.NoError(t, err)
//
// // "index.html" is accessible as both "/index.html" and "./index.html" because we didn't use WithWorkDirFS.
// // "index.html" is accessible as "/index.html".
// config := wazero.NewModuleConfig().WithFS(rooted)
//
// Ex. This sets a mutable file-system:
//
// // Files relative to "/work/appA" are accessible as "/".
// config := wazero.NewModuleConfig().WithFS(os.DirFS("/work/appA"))
//
// Isolation
//
// os.DirFS documentation includes important notes about isolation, which
// also applies to fs.Sub. As of Go 1.19, the built-in file-systems are not
// jailed (chroot). See https://github.com/golang/go/issues/42322
//
// Working Directory "."
//
// Relative path resolution, such as "./config.yml" to "/config.yml" or
// otherwise, is compiler-specific. See /RATIONALE.md for notes.
WithFS(fs.FS) ModuleConfig
// WithName configures the module name. Defaults to what was decoded or overridden via CompileConfig.WithModuleName.
@@ -531,20 +546,6 @@ type ModuleConfig interface {
//
// Note: The caller is responsible to close any io.Reader they supply: It is not closed on api.Module Close.
WithRandSource(io.Reader) ModuleConfig
// WithWorkDirFS indicates the file system to use for any paths beginning at "./". Defaults to the same as WithFS.
//
// Ex. This sets a read-only, embedded file-system as the root ("/"), and a mutable one as the working directory ("."):
//
// //go:embed appA
// var rootFS embed.FS
//
// // Files relative to this source under appA are available under "/" and files relative to "/work/appA" under ".".
// config := wazero.NewModuleConfig().WithFS(rootFS).WithWorkDirFS(os.DirFS("/work/appA"))
//
// Note: os.DirFS documentation includes important notes about isolation, which also applies to fs.Sub. As of Go 1.18,
// the built-in file-systems are not jailed (chroot). See https://github.com/golang/go/issues/42322
WithWorkDirFS(fs.FS) ModuleConfig
}
type moduleConfig struct {
@@ -564,7 +565,8 @@ type moduleConfig struct {
environ []string
// environKeys allow overwriting of existing values.
environKeys map[string]int
fs *internalsys.FSConfig
// fs is the file system to open files with
fs fs.FS
}
// NewModuleConfig returns a ModuleConfig that can be used for configuring module instantiation.
@@ -572,7 +574,6 @@ func NewModuleConfig() ModuleConfig {
return &moduleConfig{
startFunctions: []string{"_start"},
environKeys: map[string]int{},
fs: internalsys.NewFSConfig(),
}
}
@@ -583,7 +584,6 @@ func (c *moduleConfig) clone() *moduleConfig {
for key, value := range c.environKeys {
ret.environKeys[key] = value
}
ret.fs = c.fs.Clone()
return &ret
}
@@ -610,7 +610,7 @@ func (c *moduleConfig) WithEnv(key, value string) ModuleConfig {
// WithFS implements ModuleConfig.WithFS
func (c *moduleConfig) WithFS(fs fs.FS) ModuleConfig {
ret := c.clone()
ret.fs = ret.fs.WithFS(fs)
ret.fs = fs
return ret
}
@@ -698,13 +698,6 @@ func (c *moduleConfig) WithRandSource(source io.Reader) ModuleConfig {
return ret
}
// WithWorkDirFS implements ModuleConfig.WithWorkDirFS
func (c *moduleConfig) WithWorkDirFS(fs fs.FS) ModuleConfig {
ret := c.clone()
ret.fs = ret.fs.WithWorkDirFS(fs)
return ret
}
// toSysContext creates a baseline wasm.Context configured by ModuleConfig.
func (c *moduleConfig) toSysContext() (sysCtx *internalsys.Context, err error) {
var environ []string // Intentionally doesn't pre-allocate to reduce logic to default to nil.
@@ -724,11 +717,6 @@ func (c *moduleConfig) toSysContext() (sysCtx *internalsys.Context, err error) {
environ = append(environ, key+"="+value)
}
preopens, err := c.fs.Preopens()
if err != nil {
return nil, err
}
return internalsys.NewContext(
math.MaxUint32,
c.args,
@@ -740,6 +728,6 @@ func (c *moduleConfig) toSysContext() (sysCtx *internalsys.Context, err error) {
c.walltime, c.walltimeResolution,
c.nanotime, c.nanotimeResolution,
c.nanosleep,
preopens,
c.fs,
)
}