golang.org/x/crypto v0.0.0-20190313024323-a1f597ede03a: bcrypt.DefaultCost

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.DefaultCost in pkg:golang/golang.org/x/crypto@v0.0.0-20190313024323-a1f597ede03a
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/golang.org/x/crypto@v0.0.0-20190313024323-a1f597ede03a
Demonstrate these symbols/APIs:
  - golang.org/x/crypto/bcrypt.DefaultCost

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:e64243b172ca9596719c300358090e3cd97e675d3f9623d9877db38dd7142087","contract":["bcrypt.DefaultCost is defined with value 10","bcrypt.DefaultCost is within MinCost and MaxCost inclusive","bcrypt.GenerateFromPassword with DefaultCost produces a hash whose cost equals DefaultCost","bcrypt.GenerateFromPassword with cost below MinCost falls back to DefaultCost","bcrypt.CompareHashAndPassword validates the hash generated with DefaultCost"],"goal":"verify golang.org/x/crypto/bcrypt.DefaultCost in pkg:golang/golang.org/x/crypto@v0.0.0-20190313024323-a1f597ede03a","kind":"HOW","packages":["pkg:golang/golang.org/x/crypto@v0.0.0-20190313024323-a1f597ede03a"],"schemaVersion":1,"symbols":["golang.org/x/crypto/bcrypt.DefaultCost"]},"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@v0.0.0-20190313024323-a1f597ede03a"],"schemaVersion":1,"subject":"pkg:golang/golang.org/x/crypto@v0.0.0-20190313024323-a1f597ede03a","symbols":["golang.org/x/crypto/bcrypt.DefaultCost"],"verifierAdapter":"golang@1"}

module example.com/sample

go 1.24

require golang.org/x/crypto v0.0.0-20190313024323-a1f597ede03a

golang.org/x/crypto v0.0.0-20190313024323-a1f597ede03a h1:YX8ljsm6wXlHZO+aRz9Exqr0evNhKRNe5K/gi+zKh4U=
golang.org/x/crypto v0.0.0-20190313024323-a1f597ede03a/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=

package main

import (
	"fmt"
	"log"

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

func main() {
	password := []byte("sample-password")

	fmt.Printf("bcrypt.DefaultCost: %d\n", bcrypt.DefaultCost)

	hash, err := bcrypt.GenerateFromPassword(password, bcrypt.DefaultCost)
	if err != nil {
		log.Fatalf("GenerateFromPassword failed: %v", err)
	}

	cost, err := bcrypt.Cost(hash)
	if err != nil {
		log.Fatalf("Cost failed: %v", err)
	}
	fmt.Printf("Hash cost: %d\n", cost)

	if err := bcrypt.CompareHashAndPassword(hash, password); err != nil {
		log.Fatalf("CompareHashAndPassword failed: %v", err)
	}
	fmt.Println("Verified password against hash with DefaultCost.")
}

{
  "schemaVersion": 1,
  "goal": "verify golang.org/x/crypto/bcrypt.DefaultCost in pkg:golang/golang.org/x/crypto@v0.0.0-20190313024323-a1f597ede03a",
  "kind": "HOW",
  "packages": [
    "pkg:golang/golang.org/x/crypto@v0.0.0-20190313024323-a1f597ede03a"
  ],
  "symbols": [
    "golang.org/x/crypto/bcrypt.DefaultCost"
  ]
}

package main

import (
	"fmt"
	"os"

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

func main() {
	password := []byte("contract-test-password")

	// 1. bcrypt.DefaultCost is defined with value 10
	if bcrypt.DefaultCost != 10 {
		fmt.Fprintf(os.Stderr, "assertion 1 failed: expected DefaultCost 10, got %d\n", bcrypt.DefaultCost)
		os.Exit(1)
	}

	// 2. bcrypt.DefaultCost is within MinCost and MaxCost inclusive
	if bcrypt.DefaultCost < bcrypt.MinCost || bcrypt.DefaultCost > bcrypt.MaxCost {
		fmt.Fprintf(os.Stderr, "assertion 2 failed: DefaultCost %d outside [%d, %d]\n", bcrypt.DefaultCost, bcrypt.MinCost, bcrypt.MaxCost)
		os.Exit(1)
	}

	// 3. bcrypt.GenerateFromPassword with DefaultCost produces a hash whose cost equals DefaultCost
	hashDefault, err := bcrypt.GenerateFromPassword(password, bcrypt.DefaultCost)
	if err != nil {
		fmt.Fprintf(os.Stderr, "assertion 3 failed: %v\n", err)
		os.Exit(1)
	}
	costDefault, err := bcrypt.Cost(hashDefault)
	if err != nil {
		fmt.Fprintf(os.Stderr, "assertion 3 failed reading cost: %v\n", err)
		os.Exit(1)
	}
	if costDefault != bcrypt.DefaultCost {
		fmt.Fprintf(os.Stderr, "assertion 3 failed: expected cost %d, got %d\n", bcrypt.DefaultCost, costDefault)
		os.Exit(1)
	}

	// 4. bcrypt.GenerateFromPassword with cost below MinCost falls back to DefaultCost
	hashBelowMin, err := bcrypt.GenerateFromPassword(password, bcrypt.MinCost-1)
	if err != nil {
		fmt.Fprintf(os.Stderr, "assertion 4 failed: %v\n", err)
		os.Exit(1)
	}
	costBelowMin, err := bcrypt.Cost(hashBelowMin)
	if err != nil {
		fmt.Fprintf(os.Stderr, "assertion 4 failed reading cost: %v\n", err)
		os.Exit(1)
	}
	if costBelowMin != bcrypt.DefaultCost {
		fmt.Fprintf(os.Stderr, "assertion 4 failed: expected fallback cost %d, got %d\n", bcrypt.DefaultCost, costBelowMin)
		os.Exit(1)
	}

	// 5. bcrypt.CompareHashAndPassword validates the hash generated with DefaultCost
	if err := bcrypt.CompareHashAndPassword(hashDefault, password); err != nil {
		fmt.Fprintf(os.Stderr, "assertion 5 failed: %v\n", err)
		os.Exit(1)
	}

	fmt.Println("All contract assertions passed.")
}