golang.org/x/crypto v0.48.0: bcrypt.MinCost

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.MinCost in pkg:golang/golang.org/x/crypto@v0.48.0
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/golang.org/x/crypto@v0.48.0
Demonstrate these symbols/APIs:
  - golang.org/x/crypto/bcrypt.MinCost

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:sha256:9b6ef2aa02408585d499c366f0ea0c28e9f703e8a15990bca661d6d26036469c","contract":["bcrypt.MinCost constant equals 4","bcrypt.GenerateFromPassword succeeds when cost is set to bcrypt.MinCost","bcrypt.Cost returns bcrypt.MinCost for hash generated with bcrypt.MinCost","bcrypt.CompareHashAndPassword returns nil when verifying correct password against hash generated with bcrypt.MinCost","bcrypt.CompareHashAndPassword returns ErrMismatchedHashAndPassword when verifying incorrect password against hash generated with bcrypt.MinCost","bcrypt.GenerateFromPassword defaults to bcrypt.DefaultCost when passed a cost below bcrypt.MinCost"],"goal":"verify golang.org/x/crypto/bcrypt.MinCost in pkg:golang/golang.org/x/crypto@v0.48.0","kind":"HOW","packages":["pkg:golang/golang.org/x/crypto@v0.48.0"],"schemaVersion":1,"symbols":["golang.org/x/crypto/bcrypt.MinCost"]},"contractCommand":["go","run","./test"],"environment":{"arch":"x64","distro":"ubuntu","ecosystem":"golang","language":"go","libc":"glibc","libcVersion":"2.39","os":"linux","osVersionBucket":"24","packageManager":"go","packageManagerVersion":"1.26.6","runtime":"go","runtimeVersion":"1.26.6","schemaVersion":1},"license":"MIT-0","packages":["pkg:golang/golang.org/x/crypto@v0.48.0"],"schemaVersion":1,"subject":"pkg:golang/golang.org/x/crypto@v0.48.0","symbols":["golang.org/x/crypto/bcrypt.MinCost"],"verifierAdapter":"golang@1"}

module example.com/sample

go 1.26.6

require golang.org/x/crypto v0.48.0

golang.org/x/crypto v0.48.0 h1:/VRzVqiRSggnhY7gNRxPauEQ5Drw9haKdM0jqfcCFts=
golang.org/x/crypto v0.48.0/go.mod h1:r0kV5h3qnFPlQnBSrULhlsRfryS2pmewsg+XfMgkVos=

package main

import (
	"fmt"
	"log"

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

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

	// Generate a bcrypt hash using the minimum allowable cost
	hash, err := bcrypt.GenerateFromPassword(password, bcrypt.MinCost)
	if err != nil {
		log.Fatalf("failed to generate hash: %v", err)
	}
	fmt.Printf("Generated bcrypt hash with MinCost (%d): %s\n", bcrypt.MinCost, string(hash))

	// Verify the hash against the original password
	if err := bcrypt.CompareHashAndPassword(hash, password); err != nil {
		log.Fatalf("password comparison failed: %v", err)
	}
	fmt.Println("Password comparison succeeded.")
}

{
  "schemaVersion": 1,
  "goal": "verify golang.org/x/crypto/bcrypt.MinCost in pkg:golang/golang.org/x/crypto@v0.48.0",
  "kind": "HOW",
  "packages": [
    "pkg:golang/golang.org/x/crypto@v0.48.0"
  ],
  "symbols": [
    "golang.org/x/crypto/bcrypt.MinCost"
  ]
}

package main

import (
	"errors"
	"fmt"
	"os"

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

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

	// 1. bcrypt.MinCost constant equals 4
	if bcrypt.MinCost != 4 {
		fmt.Fprintf(os.Stderr, "assertion 1 failed: expected MinCost to be 4, got %d\n", bcrypt.MinCost)
		os.Exit(1)
	}

	// 2. bcrypt.GenerateFromPassword succeeds when cost is set to bcrypt.MinCost
	hash, err := bcrypt.GenerateFromPassword(password, bcrypt.MinCost)
	if err != nil {
		fmt.Fprintf(os.Stderr, "assertion 2 failed: %v\n", err)
		os.Exit(1)
	}

	// 3. bcrypt.Cost returns bcrypt.MinCost for hash generated with bcrypt.MinCost
	cost, err := bcrypt.Cost(hash)
	if err != nil {
		fmt.Fprintf(os.Stderr, "assertion 3 failed: %v\n", err)
		os.Exit(1)
	}
	if cost != bcrypt.MinCost {
		fmt.Fprintf(os.Stderr, "assertion 3 failed: expected cost %d, got %d\n", bcrypt.MinCost, cost)
		os.Exit(1)
	}

	// 4. bcrypt.CompareHashAndPassword returns nil when verifying correct password against hash generated with bcrypt.MinCost
	if err := bcrypt.CompareHashAndPassword(hash, password); err != nil {
		fmt.Fprintf(os.Stderr, "assertion 4 failed: %v\n", err)
		os.Exit(1)
	}

	// 5. bcrypt.CompareHashAndPassword returns ErrMismatchedHashAndPassword when verifying incorrect password against hash generated with bcrypt.MinCost
	if err := bcrypt.CompareHashAndPassword(hash, wrongPassword); !errors.Is(err, bcrypt.ErrMismatchedHashAndPassword) {
		fmt.Fprintf(os.Stderr, "assertion 5 failed: expected ErrMismatchedHashAndPassword, got %v\n", err)
		os.Exit(1)
	}

	// 6. bcrypt.GenerateFromPassword defaults to bcrypt.DefaultCost when passed a cost below bcrypt.MinCost
	hashBelow, err := bcrypt.GenerateFromPassword(password, bcrypt.MinCost-1)
	if err != nil {
		fmt.Fprintf(os.Stderr, "assertion 6 failed: %v\n", err)
		os.Exit(1)
	}
	costBelow, err := bcrypt.Cost(hashBelow)
	if err != nil {
		fmt.Fprintf(os.Stderr, "assertion 6 failed: %v\n", err)
		os.Exit(1)
	}
	if costBelow != bcrypt.DefaultCost {
		fmt.Fprintf(os.Stderr, "assertion 6 failed: expected cost %d, got %d\n", bcrypt.DefaultCost, costBelow)
		os.Exit(1)
	}

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