golang.org/x/crypto v0.0.0-20210616213533-5ff15b29337e: bcrypt.InvalidHashPrefixError

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.InvalidHashPrefixError in pkg:golang/golang.org/x/crypto@v0.0.0-20210616213533-5ff15b29337e
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/golang.org/x/crypto@v0.0.0-20210616213533-5ff15b29337e
Demonstrate these symbols/APIs:
  - golang.org/x/crypto/bcrypt.InvalidHashPrefixError

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:d3f79b1efd0c7e549fa8e336f74b9975d1551c7c3f83a4ba8f7f6d57e7beb5e0","contract":["bcrypt.InvalidHashPrefixError('#').Error() returns \"crypto/bcrypt: bcrypt hashes must start with '$', but hashedSecret started with '#'\"","bcrypt.CompareHashAndPassword returns bcrypt.InvalidHashPrefixError('#') when given a full-length hash starting with '#' instead of '$'","bcrypt.Cost returns bcrypt.InvalidHashPrefixError('!') when given a full-length hash starting with '!'"],"goal":"verify golang.org/x/crypto/bcrypt.InvalidHashPrefixError in pkg:golang/golang.org/x/crypto@v0.0.0-20210616213533-5ff15b29337e","kind":"HOW","packages":["pkg:golang/golang.org/x/crypto@v0.0.0-20210616213533-5ff15b29337e"],"schemaVersion":1,"symbols":["golang.org/x/crypto/bcrypt.InvalidHashPrefixError"]},"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@v0.0.0-20210616213533-5ff15b29337e"],"schemaVersion":1,"subject":"pkg:golang/golang.org/x/crypto@v0.0.0-20210616213533-5ff15b29337e","symbols":["golang.org/x/crypto/bcrypt.InvalidHashPrefixError"],"verifierAdapter":"golang@1"}

module example.com/sample

go 1.21

require golang.org/x/crypto v0.0.0-20210616213533-5ff15b29337e

golang.org/x/crypto v0.0.0-20210616213533-5ff15b29337e h1:gsTQYXdTw2Gq7RBsWvlQ91b+aEQ6bXFUngBGuR8sPpI=
golang.org/x/crypto v0.0.0-20210616213533-5ff15b29337e/go.mod h1:GvvjBRRGRdwPK5ydBHafDWAxML/pGHZbMvKqRZ5+Abc=

package main

import (
	"fmt"
	"golang.org/x/crypto/bcrypt"
)

func main() {
	err := bcrypt.InvalidHashPrefixError('#')
	fmt.Println(err.Error())

	cmpErr := bcrypt.CompareHashAndPassword([]byte("#2a$10$abcdefghijklmnopqrstuuABCDEFGHIJKLMNOPQRSTUVWXYZ01234"), []byte("password"))
	if prefixErr, ok := cmpErr.(bcrypt.InvalidHashPrefixError); ok {
		fmt.Printf("prefix=%c msg=%s\n", byte(prefixErr), prefixErr.Error())
	}
}

{
  "schemaVersion": 1,
  "goal": "verify golang.org/x/crypto/bcrypt.InvalidHashPrefixError in pkg:golang/golang.org/x/crypto@v0.0.0-20210616213533-5ff15b29337e",
  "kind": "HOW",
  "packages": [
    "pkg:golang/golang.org/x/crypto@v0.0.0-20210616213533-5ff15b29337e"
  ],
  "symbols": [
    "golang.org/x/crypto/bcrypt.InvalidHashPrefixError"
  ]
}

package main

import (
	"errors"
	"os"

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

func main() {
	directErr := bcrypt.InvalidHashPrefixError('#')
	expectedMsg := "crypto/bcrypt: bcrypt hashes must start with '$', but hashedSecret started with '#'"
	if directErr.Error() != expectedMsg {
		os.Exit(1)
	}

	var asErr error = directErr
	if byte(directErr) != '#' || asErr.Error() != expectedMsg {
		os.Exit(1)
	}

	cmpErr := bcrypt.CompareHashAndPassword([]byte("#2a$10$abcdefghijklmnopqrstuuABCDEFGHIJKLMNOPQRSTUVWXYZ01234"), []byte("password"))
	if cmpErr == nil {
		os.Exit(1)
	}

	var target bcrypt.InvalidHashPrefixError
	if !errors.As(cmpErr, &target) {
		os.Exit(1)
	}
	if target != bcrypt.InvalidHashPrefixError('#') {
		os.Exit(1)
	}
	if target.Error() != expectedMsg {
		os.Exit(1)
	}

	costErr, err := bcrypt.Cost([]byte("!2a$10$abcdefghijklmnopqrstuuABCDEFGHIJKLMNOPQRSTUVWXYZ01234"))
	if costErr != 0 || err != bcrypt.InvalidHashPrefixError('!') {
		os.Exit(1)
	}
}