golang.org/x/crypto v0.21.0: 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@v0.21.0
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/golang.org/x/crypto@v0.21.0
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:sha256:687e50f85d9e9b5c76263e88c7848b09696c19f7c1fc7a9c5440808b6f0b4ec5","contract":["bcrypt.DefaultCost is defined with value 10","bcrypt.DefaultCost is within MinCost and MaxCost inclusive","bcrypt.GenerateFromPassword with DefaultCost yields hash with DefaultCost","bcrypt.GenerateFromPassword with zero cost defaults to DefaultCost","bcrypt.GenerateFromPassword with cost below MinCost defaults to DefaultCost","bcrypt.CompareHashAndPassword successfully validates hash produced with DefaultCost"],"goal":"verify golang.org/x/crypto/bcrypt.DefaultCost in pkg:golang/golang.org/x/crypto@v0.21.0","kind":"HOW","packages":["pkg:golang/golang.org/x/crypto@v0.21.0"],"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@v0.21.0"],"schemaVersion":1,"subject":"pkg:golang/golang.org/x/crypto@v0.21.0","symbols":["golang.org/x/crypto/bcrypt.DefaultCost"],"verifierAdapter":"golang@1"}

module example.com/sample

go 1.22

require golang.org/x/crypto v0.21.0

golang.org/x/crypto v0.21.0 h1:X31++rzVUdKhX5sWmSOFZxx8UW/ldWx55cbf08iNAMA=
golang.org/x/crypto v0.21.0/go.mod h1:0BP7YvVV9gBbVKyeTG0Gyn+gZm94bibOW5BjDEYAOMs=

package main

import (
	"fmt"
	"log"

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

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

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

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

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

	if err := bcrypt.CompareHashAndPassword(hash, password); err != nil {
		log.Fatalf("password verification failed: %v", err)
	}
	fmt.Println("Password verified successfully.")
}

{
  "schemaVersion": 1,
  "goal": "verify golang.org/x/crypto/bcrypt.DefaultCost in pkg:golang/golang.org/x/crypto@v0.21.0",
  "kind": "HOW",
  "packages": [
    "pkg:golang/golang.org/x/crypto@v0.21.0"
  ],
  "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 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 not in range [%d, %d]\n", bcrypt.DefaultCost, bcrypt.MinCost, bcrypt.MaxCost)
		os.Exit(1)
	}

	// 3. bcrypt.GenerateFromPassword with DefaultCost yields hash with 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 zero cost defaults to DefaultCost
	hashZero, err := bcrypt.GenerateFromPassword(password, 0)
	if err != nil {
		fmt.Fprintf(os.Stderr, "assertion 4 failed: %v\n", err)
		os.Exit(1)
	}
	costZero, err := bcrypt.Cost(hashZero)
	if err != nil {
		fmt.Fprintf(os.Stderr, "assertion 4 failed reading cost: %v\n", err)
		os.Exit(1)
	}
	if costZero != bcrypt.DefaultCost {
		fmt.Fprintf(os.Stderr, "assertion 4 failed: expected cost %d, got %d\n", bcrypt.DefaultCost, costZero)
		os.Exit(1)
	}

	// 5. bcrypt.GenerateFromPassword with cost below MinCost defaults to DefaultCost
	hashBelowMin, err := bcrypt.GenerateFromPassword(password, 1)
	if err != nil {
		fmt.Fprintf(os.Stderr, "assertion 5 failed: %v\n", err)
		os.Exit(1)
	}
	costBelowMin, err := bcrypt.Cost(hashBelowMin)
	if err != nil {
		fmt.Fprintf(os.Stderr, "assertion 5 failed reading cost: %v\n", err)
		os.Exit(1)
	}
	if costBelowMin != bcrypt.DefaultCost {
		fmt.Fprintf(os.Stderr, "assertion 5 failed: expected cost %d, got %d\n", bcrypt.DefaultCost, costBelowMin)
		os.Exit(1)
	}

	// 6. bcrypt.CompareHashAndPassword successfully validates hash produced with DefaultCost
	if err := bcrypt.CompareHashAndPassword(hashDefault, password); err != nil {
		fmt.Fprintf(os.Stderr, "assertion 6 failed: %v\n", err)
		os.Exit(1)
	}

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