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feat: prevent path expansion using host context #158

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Merged
merged 1 commit into from
Jun 27, 2025
Merged

feat: prevent path expansion using host context #158

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40 changes: 40 additions & 0 deletions init.go
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Original file line number Diff line number Diff line change
@@ -0,0 +1,40 @@
package preview

import (
"github.com/aquasecurity/trivy/pkg/iac/scanners/terraform/parser/funcs"
"github.com/zclconf/go-cty/cty"
"github.com/zclconf/go-cty/cty/function"
"golang.org/x/xerrors"
)

// init intends to override some of the default functions afforded by terraform.
// Specifically, any functions that require the context of the host.
//
// This is really unfortunate, but all the functions are globals, and this
// is the only way to override them.
func init() {
// PathExpandFunc looks for references to a home directory on the host. The
// preview rendering should not have access to the host's home directory path,
// and will return an error if it is used.
funcs.PathExpandFunc = function.New(&function.Spec{
Params: []function.Parameter{
{
Name: "path",
Type: cty.String,
},
},
Type: function.StaticReturnType(cty.String),
Impl: func(args []cty.Value, retType cty.Type) (cty.Value, error) {
path := args[0].AsString()
if len(path) == 0 {
return cty.StringVal(path), nil
}

if path[0] != '~' {
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Suggested change
if path[0] != '~' {
if strings.HasPrefix(path, "~") {

nit but I think this is easier to read, says what it's doing a little more loudly

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I copied this code directly from the homedir package. Just going leave it.

I made an issue to follow up: #159

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could you leave a comment with a permalink to the original source to make that clearer?

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My bad
#161

return cty.StringVal(path), nil
}

return cty.NilVal, xerrors.Errorf("not allowed to expand paths starting with '~' in this context")
},
})
}
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