cli for password hashing using dotnetcore identity with no user

GenerateSql.ps1

# this is actually just output from running in powershell,
#  but I'll just add my comments in here along with the output

## First of all, I am going to set an alias to the compiled exe
└[C:\git\h]> set-alias h "C:\git\h\bin\Release\netcoreapp3.1\win-x64\h.exe"

## Generate a users file, I'm using a tab here because if you
##  select this from a database query window, it'll be tab seperated
##  `t is a tab character in powershell
## This first line puts a header row in there
└[C:\git\h]> "Username`tPassword" > users.txt

## Add a value for users 0-5
└[C:\git\h]> 0..5 | %{"User$_`tPassword$_">>users.txt}

## show the file
└[C:\git\h]> type users.txt
Username        Password
User0   Password0
User1   Password1
User2   Password2
User3   Password3
User4   Password4
User5   Password5

## Import the file, noting the delimiter is a `t, by default it's ,
└[C:\git\h]> $users = ipcsv users.txt -Delimiter "`t"

## Now generate hashes for each password, note the call to the 'h.exe' here
└[C:\git\h]> $hashes = $users | select Username, @{n="Hash";e={h $_.Password}}

## Show them, note these will be different each time due to how the hasher
##  works, but they will still match, also due to how the hasher works
└[C:\git\h]> $hashes

Username Hash
-------- ----
User0    AQAAAAEAACcQAAAAEMEKg+0ZBbN5yrU61QwLjLmGtfqz9rxeI/JE+yh50b8MUSQ5ZP9jTnBo03Rgqjxinw==
User1    AQAAAAEAACcQAAAAEOITU5VLDv09PxDS0Srlx3fBfN/ESW8kcCDLvZWMA7MoiI+FaJxAEjTgowP0v8bkHw==
User2    AQAAAAEAACcQAAAAEDtt5KDzMHns6HAxu+BRVBC9fx4p+sbp7C865vBQ55FkEzwis4r0KZEVXF1tf68vkA==
User3    AQAAAAEAACcQAAAAEGl8rdnq7w32QMxprJvyhQm5c+uPStmvz+xWqC1h0KsufB9I2tfwjQB66BnoRmWm2A==
User4    AQAAAAEAACcQAAAAEICrchmblaQio2cGyDtuNKVoosNZBDYOpSlu/otk5ZlTICVGeIpGdY0hMxRZgGcnbA==
User5    AQAAAAEAACcQAAAAELZbMaqVlXex8t40fXlpyXpaW4PClcVrxqjTuIMP4rp7v6OCJy6CC0wnNQlmB4tGgw==

## Now we will generate some sql that holds the users and hashes.
##  This will be wrapped with the actual statements needed to insert
##  You'll see the output in the following lines, but just to provide
##  some info on what is happening, I'm taking the hashes and then
##  creating a new object with a property called sql that has a
##  select statement for each value, then i use the join command
##  for each of those sql values to put a new line and a union all
##  sql command between them. What this basically will do is make
##  a big select statement that will merge all of these values
└[C:\git\h]> $UsersAndHashes = ($hashes | select @{n="sql";e={"select '{0}','{1}'" -f $_.UserName,$_.Hash}} ).sql -join "`nunion all "

## This will actually generate the sql to run. You can see that the
##  sql generated above is just placed into the middle of the value below
## Note: just in case you are not a powershell person, note that the >> at
##  the front of the line is part of the way the shell shows commands that
##  span a line, if you were running this at the command line, you would not
##  have the >> characters at the front. This is what it looks like
##  typed or pasted into the command line.
└[C:\git\h]> $SqlToRun = @"
>> ;with a(UserName,Hash) as (
>> $UsersAndHashes
>> )
>> insert into [dbo].[AspNetUsers] ([Id],[SecurityStamp],UserName,[NormalizedUserName],[EmailConfirmed],[PasswordHash],[TwoFactorEnabled],[LockoutEnabled],AccessFailedCount,PhoneNumberConfirmed)
>> select newid(),newid(),UserName, UPPER(UserName),1,[Hash],0,0,0,0 from a
>> "@

## And here is the Sql you'll actually paste into a sql window with the
##  aspnet identity tables in it. when i was working on this, i wrapped it
##  in a tran so i could check it before and after. you should probably
##  do the same just to be safe =).
## In case this sql is not clear, what is happening is we are using a CTE
##  to basically serve as a temp table for the values we generated for
##  users and passwordhashes, that is then getting used along with some
##  default values with an insert statement to put the users into the
##  required table. You have to add a value for the security stamp and
##  the id, but these are just guids so newid works fine. you also have
##  to add the 0 and 1 values as those are non null fields. Obviously,
##  if you are wanting to set some different values, do so. This is just
##  what I used for testing. I normalized to uppercase as that seemed
##  to be what was in there when I created some users the normal way,
##  although the 'normal' way had email addresses in there. This worked
##  just fine with usernames though.
└[C:\git\h]> $SqlToRun
;with a(UserName,Hash) as (
select 'User0','AQAAAAEAACcQAAAAEMEKg+0ZBbN5yrU61QwLjLmGtfqz9rxeI/JE+yh50b8MUSQ5ZP9jTnBo03Rgqjxinw=='
union all select 'User1','AQAAAAEAACcQAAAAEOITU5VLDv09PxDS0Srlx3fBfN/ESW8kcCDLvZWMA7MoiI+FaJxAEjTgowP0v8bkHw=='
union all select 'User2','AQAAAAEAACcQAAAAEDtt5KDzMHns6HAxu+BRVBC9fx4p+sbp7C865vBQ55FkEzwis4r0KZEVXF1tf68vkA=='
union all select 'User3','AQAAAAEAACcQAAAAEGl8rdnq7w32QMxprJvyhQm5c+uPStmvz+xWqC1h0KsufB9I2tfwjQB66BnoRmWm2A=='
union all select 'User4','AQAAAAEAACcQAAAAEICrchmblaQio2cGyDtuNKVoosNZBDYOpSlu/otk5ZlTICVGeIpGdY0hMxRZgGcnbA=='
union all select 'User5','AQAAAAEAACcQAAAAELZbMaqVlXex8t40fXlpyXpaW4PClcVrxqjTuIMP4rp7v6OCJy6CC0wnNQlmB4tGgw=='
)
insert into [dbo].[AspNetUsers] ([Id],[SecurityStamp],UserName,[NormalizedUserName],[EmailConfirmed],[PasswordHash],[TwoFactorEnabled],[LockoutEnabled],AccessFailedCount,PhoneNumberConfirmed)
select newid(),newid(),UserName, UPPER(UserName),1,[Hash],0,0,0,0 from a

InitialProjectSetup.ps1

# make the base project
dotnet new console -o h

# switch to project dir
cd h

# add a couple of packages we'll need
dotnet add package Microsoft.AspNetCore.Identity
dotnet add package Microsoft.AspNetCore.Cryptography.KeyDerivation

# get the source file we'll tweak from github
$uri = "https://raw.githubusercontent.com/aspnet/Identity/master/src/Core/"
"PasswordHasher.cs" | %{iwr $uri$_ -o .\$_}

Output.txt

[C:\git\h]> dotnet build
Microsoft (R) Build Engine version 16.6.0+5ff7b0c9e for .NET Core
Copyright (C) Microsoft Corporation. All rights reserved.

  Determining projects to restore...
  All projects are up-to-date for restore.
  h -> C:\git\h\bin\Debug\netcoreapp3.1\h.dll

Build succeeded.
    0 Warning(s)
    0 Error(s)

Time Elapsed 00:00:01.51
└[C:\git\h]> $passwordHash = dotnet run password
└[C:\git\h]> $password1Hash = dotnet run password1
└[C:\git\h]> $passwordHash
AQAAAAEAACcQAAAAEKBC6Tb5klZXeE51B8GwBssJWHVyqAy4O3BWPEVkaNzYx6XttTBXNuUYlI6Bu4sGFQ==
└[C:\git\h]> $password1Hash
AQAAAAEAACcQAAAAEEO6oT/nnLhprMbx2TwFhaM3WLdylwAS5bNVwAeWI9t0jD1BBLgL0+gcYmFS5y+7og==
└[C:\git\h]> dotnet run password $passwordHash
True
└[C:\git\h]> dotnet run password $password1Hash
False
└[C:\git\h]> dotnet run password1 $password1Hash
True
└[C:\git\h]> dotnet run password1 $passwordHash
False

PasswordHasherChanges.cs

//change this:
public class PasswordHasher<TUser> : IPasswordHasher<TUser> where TUser : class

//to this, or just remove everything after the comment below
public class PasswordHasher//<TUser> : IPasswordHasher<TUser> where TUser : class

//next, simply add some default values for these private vars

//these...
private readonly PasswordHasherCompatibilityMode _compatibilityMode;
private readonly int _iterCount;
private readonly RandomNumberGenerator _rng;

//become these...
//Note these are the default values from the PasswordHasherOptions.cs file
// you can see that here if you want:
//https://github.com/aspnet/Identity/blob/master/src/Core/PasswordHasherOptions.cs
private readonly PasswordHasherCompatibilityMode _compatibilityMode = PasswordHasherCompatibilityMode.IdentityV3;
private readonly int _iterCount = 10000;
private readonly RandomNumberGenerator _rng = RandomNumberGenerator.Create();

//next we are going to, basically, wipe out the constructor
// as we don't need to pass in any information

//replace this...
public PasswordHasher(IOptions<PasswordHasherOptions> optionsAccessor = null)
{
  var options = optionsAccessor?.Value ?? new PasswordHasherOptions();

  _compatibilityMode = options.CompatibilityMode;
  switch (_compatibilityMode)
  {
    case PasswordHasherCompatibilityMode.IdentityV2:
      // nothing else to do
      break;

    case PasswordHasherCompatibilityMode.IdentityV3:
      _iterCount = options.IterationCount;
      if (_iterCount < 1)
      {
        throw new InvalidOperationException(Resources.InvalidPasswordHasherIterationCount);
      }
      break;

    default:
      throw new InvalidOperationException(Resources.InvalidPasswordHasherCompatibilityMode);
  }

  _rng = options.Rng;
}

// with just this one line:
public PasswordHasher(){}

// and finally, we need to remove the user var from these two function calls
// so these lines...
public virtual string HashPassword(TUser user, string password)
public virtual PasswordVerificationResult VerifyHashedPassword(TUser user, string hashedPassword, string providedPassword)
  
//become these lines...
public virtual string HashPassword(string password)
public virtual PasswordVerificationResult VerifyHashedPassword(string hashedPassword, string providedPassword)

Program.cs

using System;

namespace h
{
    class Program
    {
        static void Main(string[] args)
        {
            string result = "Syntax: hash <password> or hash <password> <hash>";
            if (args.Length==1 || args.Length==2){
                var passwordHasher = new Microsoft.AspNetCore.Identity.PasswordHasher();
                if(args.Length == 1)
                    result = passwordHasher.HashPassword(args[0]);
                if(args.Length == 2)
                    result = (passwordHasher.VerifyHashedPassword(args[1],args[0]).ToString() == "Success").ToString();
            }
            Console.WriteLine(result);
        }
    }
}