golang.org/x/crypto v0.0.0-20190426145343-a29dc8fdc734: bcrypt.InvalidCostError

Clean-room public code sample — generation instructions

Write a brand-new, minimal, self-contained code sample in this clean-room directory.
Do not copy, paraphrase, or reference any existing project source. Work only from this spec.

A csx.json manifest scaffold already exists. Do not recreate it from memory. Preserve its case.goal, packages and symbols; fill its empty case.contract with exact assertions and correct its environment, commands and verifierAdapter for the files you generate.

Goal: verify golang.org/x/crypto/bcrypt.InvalidCostError in pkg:golang/golang.org/x/crypto@v0.0.0-20190426145343-a29dc8fdc734
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/golang.org/x/crypto@v0.0.0-20190426145343-a29dc8fdc734
Demonstrate these symbols/APIs:
  - golang.org/x/crypto/bcrypt.InvalidCostError

Rules:
  - One focused purpose; the smallest project that proves the goal.
  - Include a contract test (test/contract.*) that runs OFFLINE and exits 0 exactly when the goal behavior works.
  - Pin every dependency with a lockfile so resolution is reproducible.
  - No secrets, credentials, or tokens. No real URLs (only example.com or localhost). No absolute paths.
  - No personal names, emails, company names, or project identifiers of any kind.
  - No binaries and no generated output (node_modules, dist, target, venv, .git, .env).
  - Keep it under 200 files and 256KB packed.

{"case":{"caseId":"case:sha256:6cf403a3c6431f735414b880dafb5bd7b99fd2c919586aa2ad80b19d0159712b","contract":["bcrypt.InvalidCostError is an int type representing an out-of-range cost","bcrypt.InvalidCostError.Error() formats the cost and allowed range (MinCost, MaxCost)","bcrypt.GenerateFromPassword returns InvalidCostError when cost exceeds bcrypt.MaxCost","bcrypt.Cost returns InvalidCostError when hash cost is below bcrypt.MinCost","bcrypt.Cost returns InvalidCostError when hash cost exceeds bcrypt.MaxCost","bcrypt.CompareHashAndPassword returns InvalidCostError when given a hash with invalid cost"],"goal":"verify golang.org/x/crypto/bcrypt.InvalidCostError in pkg:golang/golang.org/x/crypto@v0.0.0-20190426145343-a29dc8fdc734","kind":"HOW","packages":["pkg:golang/golang.org/x/crypto@v0.0.0-20190426145343-a29dc8fdc734"],"schemaVersion":1,"symbols":["golang.org/x/crypto/bcrypt.InvalidCostError"]},"contractCommand":["go","run","./test"],"environment":{"arch":"x64","distro":"ubuntu","ecosystem":"golang","libc":"glibc","libcVersion":"2.39","os":"linux","osVersionBucket":"24","packageManager":"go","schemaVersion":1},"license":"MIT-0","packages":["pkg:golang/golang.org/x/crypto@v0.0.0-20190426145343-a29dc8fdc734"],"schemaVersion":1,"subject":"pkg:golang/golang.org/x/crypto@v0.0.0-20190426145343-a29dc8fdc734","symbols":["golang.org/x/crypto/bcrypt.InvalidCostError"],"verifierAdapter":"golang@1"}

module example.com/sample

go 1.24

require golang.org/x/crypto v0.0.0-20190426145343-a29dc8fdc734

golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
golang.org/x/crypto v0.0.0-20190426145343-a29dc8fdc734 h1:p/H982KKEjUnLJkM3tt/LemDnOc1GiZL5FCVlORJ5zo=
golang.org/x/crypto v0.0.0-20190426145343-a29dc8fdc734/go.mod h1:yigFU9vqHzYiE8UmvKecakEJjdnWj3jj499lnFckfCI=
golang.org/x/net v0.0.0-20190404232315-eb5bcb51f2a3/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
golang.org/x/sys v0.0.0-20190412213103-97732733099d/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=

package main

import (
	"errors"
	"fmt"

	"golang.org/x/crypto/bcrypt"
)

func main() {
	_, err := bcrypt.GenerateFromPassword([]byte("sample-secret"), bcrypt.MaxCost+1)
	var costErr bcrypt.InvalidCostError
	if errors.As(err, &costErr) {
		fmt.Printf("Invalid cost rejected: %d (%v)\n", int(costErr), costErr.Error())
	}
}

{
  "schemaVersion": 1,
  "goal": "verify golang.org/x/crypto/bcrypt.InvalidCostError in pkg:golang/golang.org/x/crypto@v0.0.0-20190426145343-a29dc8fdc734",
  "kind": "HOW",
  "packages": [
    "pkg:golang/golang.org/x/crypto@v0.0.0-20190426145343-a29dc8fdc734"
  ],
  "symbols": [
    "golang.org/x/crypto/bcrypt.InvalidCostError"
  ]
}

package main

import (
	"errors"
	"fmt"
	"os"

	"golang.org/x/crypto/bcrypt"
)

func main() {
	// 1. bcrypt.InvalidCostError is an int type representing an out-of-range cost
	directErr := bcrypt.InvalidCostError(2)
	if int(directErr) != 2 {
		fmt.Fprintf(os.Stderr, "expected InvalidCostError int value 2, got %d\n", int(directErr))
		os.Exit(1)
	}

	// 2. bcrypt.InvalidCostError.Error() formats the cost and allowed range (MinCost, MaxCost)
	expectedMsg := fmt.Sprintf("crypto/bcrypt: cost 35 is outside allowed range (%d,%d)", bcrypt.MinCost, bcrypt.MaxCost)
	if bcrypt.InvalidCostError(35).Error() != expectedMsg {
		fmt.Fprintf(os.Stderr, "expected error message %q, got %q\n", expectedMsg, bcrypt.InvalidCostError(35).Error())
		os.Exit(1)
	}

	// 3. bcrypt.GenerateFromPassword returns InvalidCostError when cost > bcrypt.MaxCost
	secret := []byte("verification-secret")
	_, err := bcrypt.GenerateFromPassword(secret, bcrypt.MaxCost+1)
	var invalidCost bcrypt.InvalidCostError
	if !errors.As(err, &invalidCost) || int(invalidCost) != bcrypt.MaxCost+1 {
		fmt.Fprintf(os.Stderr, "expected InvalidCostError(%d) from GenerateFromPassword, got %v\n", bcrypt.MaxCost+1, err)
		os.Exit(1)
	}

	// 4. bcrypt.Cost returns InvalidCostError when hash cost < bcrypt.MinCost
	hashBelowMin := []byte("$2a$03$usesomesillystringfore2uDLvp1AK2Q68Lp7FI0d5BOmvnoZZGW")
	_, err = bcrypt.Cost(hashBelowMin)
	if !errors.As(err, &invalidCost) || int(invalidCost) != 3 {
		fmt.Fprintf(os.Stderr, "expected InvalidCostError(3) from Cost, got %v\n", err)
		os.Exit(1)
	}

	// 5. bcrypt.Cost returns InvalidCostError when hash cost > bcrypt.MaxCost
	hashAboveMax := []byte("$2a$32$usesomesillystringfore2uDLvp1AK2Q68Lp7FI0d5BOmvnoZZGW")
	_, err = bcrypt.Cost(hashAboveMax)
	if !errors.As(err, &invalidCost) || int(invalidCost) != 32 {
		fmt.Fprintf(os.Stderr, "expected InvalidCostError(32) from Cost, got %v\n", err)
		os.Exit(1)
	}

	// 6. bcrypt.CompareHashAndPassword returns InvalidCostError when given hash with invalid cost
	err = bcrypt.CompareHashAndPassword(hashBelowMin, secret)
	if !errors.As(err, &invalidCost) || int(invalidCost) != 3 {
		fmt.Fprintf(os.Stderr, "expected InvalidCostError(3) from CompareHashAndPassword, got %v\n", err)
		os.Exit(1)
	}
}