hclsyntax: helpers for fuzz testing with go-fuzz

hcl/hclsyntax/fuzz/.gitignore

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+fuzz*-fuzz.zip

hcl/hclsyntax/fuzz/Makefile

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+
+ifndef FUZZ_WORK_DIR
+$(error FUZZ_WORK_DIR is not set)
+endif
+
+default:
+	@echo "See README.md for usage instructions"
+
+fuzz-config: fuzz-exec-config
+fuzz-expr: fuzz-exec-expr
+fuzz-template: fuzz-exec-template
+fuzz-traversal: fuzz-exec-traversal
+
+fuzz-exec-%: fuzz%-fuzz.zip
+	go-fuzz -bin=./fuzz$*-fuzz.zip -workdir=$(FUZZ_WORK_DIR)
+
+fuzz%-fuzz.zip: %/fuzz.go
+	go-fuzz-build github.com/hashicorp/hcl2/hcl/hclsyntax/fuzz/$*
+
+tools:
+	go get -u github.com/dvyukov/go-fuzz/go-fuzz
+	go get -u github.com/dvyukov/go-fuzz/go-fuzz-build
+
+clean:
+	rm fuzz*-fuzz.zip
+
+.PHONY: tools clean fuzz-config fuzz-expr fuzz-template fuzz-traversal
+.PRECIOUS: fuzzconfig-fuzz.zip fuzzexpr-fuzz.zip fuzztemplate-fuzz.zip fuzztraversal-fuzz.zip

hcl/hclsyntax/fuzz/README.md

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+# hclsyntax fuzzing utilities
+
+This directory contains helper functions and corpuses that can be used to
+fuzz-test the `hclsyntax` parsers using [go-fuzz](https://github.com/dvyukov/go-fuzz).
+
+To fuzz, first install go-fuzz and its build tool in your `GOPATH`:
+
+```
+$ make tools
+```
+
+Now you can fuzz one or all of the parsers:
+
+```
+$ make fuzz-config FUZZ_WORK_DIR=/tmp/hcl2-fuzz-config
+$ make fuzz-expr  FUZZ_WORK_DIR=/tmp/hcl2-fuzz-expr
+$ make fuzz-template  FUZZ_WORK_DIR=/tmp/hcl2-fuzz-template
+$ make fuzz-traversal FUZZ_WORK_DIR=/tmp/hcl2-fuzz-traversal
+```
+
+In all cases, set `FUZZ_WORK_DIR` to a directory where `go-fuzz` can keep state
+as it works. This should ideally be in a ramdisk for efficiency, and should
+probably _not_ be on an SSD to avoid thrashing it.
+
+## Understanding the result
+
+A small number of subdirectories will be created in the work directory.
+
+If you let `go-fuzz` run for a few minutes (the more minutes the better) it
+may detect "crashers", which are inputs that caused the parser to panic. Details
+about these are written to `$FUZZ_WORK_DIR/crashers`:
+
+```
+$ ls /tmp/hcl2-fuzz-config/crashers
+7f5e9ec80c89da14b8b0b238ec88969f658f5a2d
+7f5e9ec80c89da14b8b0b238ec88969f658f5a2d.output
+7f5e9ec80c89da14b8b0b238ec88969f658f5a2d.quoted
+```
+
+The base file above (with no extension) is the input that caused a crash. The
+`.output` file contains the panic stack trace, which you can use as a clue to
+figure out what caused the crash.
+
+A good first step to fixing a detected crasher is to copy the failing input
+into one of the unit tests in the `hclsyntax` package and see it crash there
+too. After that, it's easy to re-run the test as you try to fix it. The
+file with the `.quoted` extension contains a form of the input that is quoted
+in Go syntax for easy copy-paste into a test case, even if the input contains
+non-printable characters or other inconvenient symbols.
+
+## Rebuilding for new Upstream Code
+
+An archive file is created for `go-fuzz` to use on the first run of each
+of the above, as a `.zip` file created in this directory. If upstream code
+is changed these will need to be deleted to cause them to be rebuilt with
+the latest code:
+
+```
+$ make clean
+```

hcl/hclsyntax/fuzz/config/corpus/attr-expr.hcl

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+foo = upper(bar + baz[1])

hcl/hclsyntax/fuzz/config/corpus/attr-literal.hcl

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+foo = "bar"

hcl/hclsyntax/fuzz/config/corpus/block-attrs.hcl

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+block {
+  foo = true
+}

hcl/hclsyntax/fuzz/config/corpus/block-empty.hcl

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+block {
+}

hcl/hclsyntax/fuzz/config/corpus/block-nested.hcl

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+block {
+  another_block {
+    foo = bar
+  }
+}

hcl/hclsyntax/fuzz/config/corpus/utf8.hcl

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+foo = "föo ${föo("föo")}"

hcl/hclsyntax/fuzz/config/fuzz.go

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+package fuzzconfig
+
+import (
+	"github.com/hashicorp/hcl2/hcl"
+	"github.com/hashicorp/hcl2/hcl/hclsyntax"
+)
+
+func Fuzz(data []byte) int {
+	_, diags := hclsyntax.ParseConfig(data, "<fuzz-conf>", hcl.Pos{Line: 1, Column: 1})
+
+	if diags.HasErrors() {
+		return 0
+	}
+
+	return 1
+}

hcl/hclsyntax/fuzz/expr/corpus/empty.hcle

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+""

hcl/hclsyntax/fuzz/expr/corpus/escape-dollar.hcle

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+"hi $${var.foo}"

hcl/hclsyntax/fuzz/expr/corpus/escape-newline.hcle

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+"bar\nbaz"

hcl/hclsyntax/fuzz/expr/corpus/function-call.hcle

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+title(var.name)

hcl/hclsyntax/fuzz/expr/corpus/int.hcle

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+42

hcl/hclsyntax/fuzz/expr/corpus/literal.hcle

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+foo

hcl/hclsyntax/fuzz/expr/corpus/splat-attr.hcle

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+foo.bar.*.baz

hcl/hclsyntax/fuzz/expr/corpus/splat-full.hcle

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+foo.bar[*].baz

hcl/hclsyntax/fuzz/expr/corpus/utf8.hcle

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+föo("föo") + föo

hcl/hclsyntax/fuzz/expr/corpus/var.hcle

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+var.bar

hcl/hclsyntax/fuzz/expr/fuzz.go

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+package fuzzexpr
+
+import (
+	"github.com/hashicorp/hcl2/hcl"
+	"github.com/hashicorp/hcl2/hcl/hclsyntax"
+)
+
+func Fuzz(data []byte) int {
+	_, diags := hclsyntax.ParseExpression(data, "<fuzz-expr>", hcl.Pos{Line: 1, Column: 1})
+
+	if diags.HasErrors() {
+		return 0
+	}
+
+	return 1
+}

hcl/hclsyntax/fuzz/template/corpus/escape-dollar.tmpl

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+hi $${var.foo}

hcl/hclsyntax/fuzz/template/corpus/escape-newline.tmpl

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+foo ${"bar\nbaz"}

hcl/hclsyntax/fuzz/template/corpus/function-call.tmpl

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+hi ${title(var.name)}

hcl/hclsyntax/fuzz/template/corpus/int.tmpl

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+foo ${42}

hcl/hclsyntax/fuzz/template/corpus/just-interp.tmpl

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+${var.bar}

hcl/hclsyntax/fuzz/template/corpus/literal.tmpl

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+foo

hcl/hclsyntax/fuzz/template/corpus/utf8.tmpl

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+föo ${föo("föo")}

hcl/hclsyntax/fuzz/template/fuzz.go

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+package fuzztemplate
+
+import (
+	"github.com/hashicorp/hcl2/hcl"
+	"github.com/hashicorp/hcl2/hcl/hclsyntax"
+)
+
+func Fuzz(data []byte) int {
+	_, diags := hclsyntax.ParseTemplate(data, "<fuzz-tmpl>", hcl.Pos{Line: 1, Column: 1})
+
+	if diags.HasErrors() {
+		return 0
+	}
+
+	return 1
+}

hcl/hclsyntax/fuzz/traversal/corpus/attr.hclt

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+foo.bar

hcl/hclsyntax/fuzz/traversal/corpus/complex.hclt

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+foo.bar[1].baz["foo"].pizza

hcl/hclsyntax/fuzz/traversal/corpus/index.hclt

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+foo[1]

hcl/hclsyntax/fuzz/traversal/corpus/root.hclt

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+foo

hcl/hclsyntax/fuzz/traversal/fuzz.go

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+package fuzztraversal
+
+import (
+	"github.com/hashicorp/hcl2/hcl"
+	"github.com/hashicorp/hcl2/hcl/hclsyntax"
+)
+
+func Fuzz(data []byte) int {
+	_, diags := hclsyntax.ParseTraversalAbs(data, "<fuzz-trav>", hcl.Pos{Line: 1, Column: 1})
+
+	if diags.HasErrors() {
+		return 0
+	}
+
+	return 1
+}