Custom PasswordHasher in ASP.NET Core Identity

 1public class PortalUserManager : UserManager<PortalUser>
 2{
 3    private readonly IUserPasswordStore<PortalUser> _passwordStore;
 4
 5    public PortalUserManager(
 6        IUserStore<PortalUser> store,
 7        IOptions<IdentityOptions> optionsAccessor,
 8        IPasswordHasher<PortalUser> passwordHasher,
 9        IEnumerable<IUserValidator<PortalUser>> userValidators,
10        IEnumerable<IPasswordValidator<PortalUser>> passwordValidators,
11        ILookupNormalizer keyNormalizer, IdentityErrorDescriber errors,
12        IServiceProvider services, ILogger<UserManager<PortalUser>> logger) : base(store, optionsAccessor, passwordHasher, userValidators, passwordValidators, keyNormalizer, errors, services, logger)
13    {
14        _passwordStore = Store as IUserPasswordStore<PortalUser>;
15    }
16
17    public override async Task<bool> CheckPasswordAsync(PortalUser user, string password)
18    {
19        if (user is null) { return false; }
20
21        // Verify users password
22        PasswordVerificationResult result = await VerifyPasswordAsync(_passwordStore, user, password);
23
24        // if reshash is required, automatically rehash the password
25        if (result == PasswordVerificationResult.SuccessRehashNeeded)
26        {
27            await UpdatePasswordHash(user, password, validatePassword: false);
28            await UpdateUserAsync(user);
29        }
30
31        bool success = result != PasswordVerificationResult.Failed;
32        if (!success)
33        {
34                Logger.LogWarning(0, $"Invalid password for user {user.Id}.");
35        }
36        return success;
37    }
38}

 1public class PortalUserPasswordHasher : PasswordHasher<PortalUser>, IPasswordHasher<PortalUser>
 2{
 3    public PortalUserPasswordHasher(
 4        IOptions<PasswordHasherOptions> optionsAccessor = null) 
 5        : base(optionsAccessor) { }
 6
 7    /// </summary>
 8    public override PasswordVerificationResult VerifyHashedPassword(
 9        PortalUser user, string hashedPassword, string providedPassword)
10    {
11        // pass as bytes
12        byte[] decodedHashedPassword = Convert.FromBase64String(hashedPassword);
13
14        // we check the first byte
15        //    this byte indicates which hash algorithm is used
16        switch (decodedHashedPassword[0])
17        {
18            // if it's old (old PHP platform), request rehash on success
19            case PortalUserHashHelper.PhpBBFormatMarker:
20                if (LegacyPhpBBPasswordProvider.VerifyHashedPassword(
21                                    decodedHashedPassword, providedPassword))
22                {
23                    return PasswordVerificationResult.SuccessRehashNeeded;
24                }
25                else
26                {
27                    return PasswordVerificationResult.Failed;
28                }
29
30            // otherwise we use the default ASP.NET Core Identity behavior
31            default:
32                return base.VerifyHashedPassword(user, hashedPassword, providedPassword);
33        }
34    }
35}