dev-npgsql/npgsql: Npgsql is the .NET data provider for PostgreSQL.

src/Npgsql/NpgsqlConnector.Auth.cs
390 строк17 KB
Shay Rojansky
Stop requiring users to specify Integrated Security (#5687)
30 апр 2024, 01:34
30 апр 2024, 01:34337acb3
using System;
using System.Collections.Generic;
using System.IO;
using System.Net;
using System.Net.Security;
using System.Security.Cryptography;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using Npgsql.BackendMessages;
using Npgsql.Util;
using static Npgsql.Util.Statics;

namespace Npgsql
{
    partial class NpgsqlConnector
    {
        async Task Authenticate(string username, NpgsqlTimeout timeout, bool async)
        {
            Log.Trace("Authenticating...", Id);

            var msg = Expect<AuthenticationRequestMessage>(await ReadMessage(async), this);
            timeout.Check();
            switch (msg.AuthRequestType)
            {
            case AuthenticationRequestType.AuthenticationOk:
                return;

            case AuthenticationRequestType.AuthenticationCleartextPassword:
                await AuthenticateCleartext(username, async);
                return;

            case AuthenticationRequestType.AuthenticationMD5Password:
                await AuthenticateMD5(username, ((AuthenticationMD5PasswordMessage)msg).Salt, async);
                return;

            case AuthenticationRequestType.AuthenticationSASL:
                await AuthenticateSASL(((AuthenticationSASLMessage)msg).Mechanisms, username, async);
                return;

            case AuthenticationRequestType.AuthenticationGSS:
            case AuthenticationRequestType.AuthenticationSSPI:
                await AuthenticateGSS(async);
                return;

            case AuthenticationRequestType.AuthenticationGSSContinue:
                throw new NpgsqlException("Can't start auth cycle with AuthenticationGSSContinue");

            default:
                throw new NotSupportedException($"Authentication method not supported (Received: {msg.AuthRequestType})");
            }
        }

        async Task AuthenticateCleartext(string username, bool async)
        {
            var passwd = GetPassword(username);
            if (passwd == null)
                throw new NpgsqlException("No password has been provided but the backend requires one (in cleartext)");

            var encoded = new byte[Encoding.UTF8.GetByteCount(passwd) + 1];
            Encoding.UTF8.GetBytes(passwd, 0, passwd.Length, encoded, 0);

            await WritePassword(encoded, async);
            await Flush(async);
            Expect<AuthenticationRequestMessage>(await ReadMessage(async), this);
        }

        async Task AuthenticateSASL(List<string> mechanisms, string username, bool async)
        {
            // At the time of writing PostgreSQL only supports SCRAM-SHA-256
            if (!mechanisms.Contains("SCRAM-SHA-256"))
                throw new NpgsqlException("No supported SASL mechanism found (only SCRAM-SHA-256 is supported for now). " +
                                          "Mechanisms received from server: " + string.Join(", ", mechanisms));
            var mechanism = "SCRAM-SHA-256";

            var passwd = GetPassword(username) ??
                         throw new NpgsqlException($"No password has been provided but the backend requires one (in SASL/{mechanism})");

            // Assumption: the write buffer is big enough to contain all our outgoing messages
            var clientNonce = GetNonce();

            await WriteSASLInitialResponse(mechanism, PGUtil.UTF8Encoding.GetBytes("n,,n=*,r=" + clientNonce), async);
            await Flush(async);

            var saslContinueMsg = Expect<AuthenticationSASLContinueMessage>(await ReadMessage(async), this);
            if (saslContinueMsg.AuthRequestType != AuthenticationRequestType.AuthenticationSASLContinue)
                throw new NpgsqlException("[SASL] AuthenticationSASLContinue message expected");
            var firstServerMsg = AuthenticationSCRAMServerFirstMessage.Load(saslContinueMsg.Payload);
            if (!firstServerMsg.Nonce.StartsWith(clientNonce))
                throw new InvalidOperationException("[SCRAM] Malformed SCRAMServerFirst message: server nonce doesn't start with client nonce");

            var saltBytes = Convert.FromBase64String(firstServerMsg.Salt);
            var saltedPassword = Hi(passwd.Normalize(NormalizationForm.FormKC), saltBytes, firstServerMsg.Iteration);

            var clientKey = HMAC(saltedPassword, "Client Key");
            byte[] storedKey;
            using (var sha256 = SHA256.Create())
                storedKey = sha256.ComputeHash(clientKey);

            var clientFirstMessageBare = "n=*,r=" + clientNonce;
            var serverFirstMessage = $"r={firstServerMsg.Nonce},s={firstServerMsg.Salt},i={firstServerMsg.Iteration}";
            var clientFinalMessageWithoutProof = "c=biws,r=" + firstServerMsg.Nonce;

            var authMessage = $"{clientFirstMessageBare},{serverFirstMessage},{clientFinalMessageWithoutProof}";

            var clientSignature = HMAC(storedKey, authMessage);
            var clientProofBytes = Xor(clientKey, clientSignature);
            var clientProof = Convert.ToBase64String(clientProofBytes);

            var serverKey = HMAC(saltedPassword, "Server Key");
            var serverSignature = HMAC(serverKey, authMessage);

            var messageStr = $"{clientFinalMessageWithoutProof},p={clientProof}";

            await WriteSASLResponse(Encoding.UTF8.GetBytes(messageStr), async);
            await Flush(async);

            var saslFinalServerMsg = Expect<AuthenticationSASLFinalMessage>(await ReadMessage(async), this);
            if (saslFinalServerMsg.AuthRequestType != AuthenticationRequestType.AuthenticationSASLFinal)
                throw new NpgsqlException("[SASL] AuthenticationSASLFinal message expected");

            var scramFinalServerMsg = AuthenticationSCRAMServerFinalMessage.Load(saslFinalServerMsg.Payload);
            if (scramFinalServerMsg.ServerSignature != Convert.ToBase64String(serverSignature))
                throw new NpgsqlException("[SCRAM] Unable to verify server signature");

            var okMsg = Expect<AuthenticationRequestMessage>(await ReadMessage(async), this);
            if (okMsg.AuthRequestType != AuthenticationRequestType.AuthenticationOk)
                throw new NpgsqlException("[SASL] Expected AuthenticationOK message");

            static string GetNonce()
            {
                using var rncProvider = RandomNumberGenerator.Create();
                var nonceBytes = new byte[18];

                rncProvider.GetBytes(nonceBytes);
                return Convert.ToBase64String(nonceBytes);
            }

            static byte[] Hi(string str, byte[] salt, int count)
            {
                using var hmac = new HMACSHA256(Encoding.UTF8.GetBytes(str));
                var salt1 = new byte[salt.Length + 4];
                byte[] hi, u1;

                Buffer.BlockCopy(salt, 0, salt1, 0, salt.Length);
                salt1[salt1.Length - 1] = 1;

                hi = u1 = hmac.ComputeHash(salt1);

                for (var i = 1; i < count; i++)
                {
                    var u2 = hmac.ComputeHash(u1);
                    Xor(hi, u2);
                    u1 = u2;
                }

                return hi;
            }

            static byte[] Xor(byte[] buffer1, byte[] buffer2)
            {
                for (var i = 0; i < buffer1.Length; i++)
                    buffer1[i] ^= buffer2[i];
                return buffer1;
            }

            static byte[] HMAC(byte[] data, string key)
            {
                using var hmacsha256 = new HMACSHA256(data);
                return hmacsha256.ComputeHash(Encoding.UTF8.GetBytes(key));
            }
        }

        async Task AuthenticateMD5(string username, byte[] salt, bool async)
        {
            var passwd = GetPassword(username);
            if (passwd == null)
                throw new NpgsqlException("No password has been provided but the backend requires one (in MD5)");

            byte[] result;
            using (var md5 = MD5.Create())
            {
                // First phase
                var passwordBytes = PGUtil.UTF8Encoding.GetBytes(passwd);
                var usernameBytes = PGUtil.UTF8Encoding.GetBytes(username);
                var cryptBuf = new byte[passwordBytes.Length + usernameBytes.Length];
                passwordBytes.CopyTo(cryptBuf, 0);
                usernameBytes.CopyTo(cryptBuf, passwordBytes.Length);

                var sb = new StringBuilder();
                var hashResult = md5.ComputeHash(cryptBuf);
                foreach (var b in hashResult)
                    sb.Append(b.ToString("x2"));

                var prehash = sb.ToString();

                var prehashbytes = PGUtil.UTF8Encoding.GetBytes(prehash);
                cryptBuf = new byte[prehashbytes.Length + 4];

                Array.Copy(salt, 0, cryptBuf, prehashbytes.Length, 4);

                // 2.
                prehashbytes.CopyTo(cryptBuf, 0);

                sb = new StringBuilder("md5");
                hashResult = md5.ComputeHash(cryptBuf);
                foreach (var b in hashResult)
                    sb.Append(b.ToString("x2"));

                var resultString = sb.ToString();
                result = new byte[Encoding.UTF8.GetByteCount(resultString) + 1];
                Encoding.UTF8.GetBytes(resultString, 0, resultString.Length, result, 0);
                result[result.Length - 1] = 0;
            }

            await WritePassword(result, async);
            await Flush(async);
            Expect<AuthenticationRequestMessage>(await ReadMessage(async), this);
        }

#pragma warning disable CA1801 // Review unused parameters
        async Task AuthenticateGSS(bool async)
        {
            using (var negotiateStream = new NegotiateStream(new GSSPasswordMessageStream(this), true))
            {
                try
                {
                    var targetName = $"{KerberosServiceName}/{Host}";
                    if (async)
                        await negotiateStream.AuthenticateAsClientAsync(CredentialCache.DefaultNetworkCredentials, targetName);
                    else
                        negotiateStream.AuthenticateAsClient(CredentialCache.DefaultNetworkCredentials, targetName);
                }
                catch (AuthenticationCompleteException)
                {
                    return;
                }
                catch (IOException e) when (e.InnerException is AuthenticationCompleteException)
                {
                    return;
                }
                catch (IOException e) when (e.InnerException is PostgresException)
                {
                    throw e.InnerException;
                }
            }
            throw new NpgsqlException("NegotiateStream.AuthenticateAsClient completed unexpectedly without signaling success");
        }
#pragma warning restore CA1801 // Review unused parameters

        /// <summary>
        /// This Stream is placed between NegotiateStream and the socket's NetworkStream (or SSLStream). It intercepts
        /// traffic and performs the following operations:
        /// * Outgoing messages are framed in PostgreSQL's PasswordMessage, and incoming are stripped of it.
        /// * NegotiateStream frames payloads with a 5-byte header, which PostgreSQL doesn't understand. This header is
        /// stripped from outgoing messages and added to incoming ones.
        /// </summary>
        /// <remarks>
        /// See https://referencesource.microsoft.com/#System/net/System/Net/_StreamFramer.cs,16417e735f0e9530,references
        /// </remarks>
        class GSSPasswordMessageStream : Stream
        {
            readonly NpgsqlConnector _connector;
            int _leftToWrite;
            int _leftToRead, _readPos;
            byte[]? _readBuf;

            internal GSSPasswordMessageStream(NpgsqlConnector connector)
            {
                _connector = connector;
            }

            public override Task WriteAsync(byte[] buffer, int offset, int count, CancellationToken cancellationToken)
                => Write(buffer, offset, count, true);

            public override void Write(byte[] buffer, int offset, int count)
                => Write(buffer, offset, count, false).GetAwaiter().GetResult();

            async Task Write(byte[] buffer, int offset, int count, bool async)
            {
                if (_leftToWrite == 0)
                {
                    // We're writing the frame header, which contains the payload size.
                    _leftToWrite = (buffer[3] << 8) | buffer[4];

                    buffer[0] = 22;
                    if (buffer[1] != 1)
                        throw new NotSupportedException($"Received frame header major v {buffer[1]} (different from 1)");
                    if (buffer[2] != 0)
                        throw new NotSupportedException($"Received frame header minor v {buffer[2]} (different from 0)");

                    // In case of payload data in the same buffer just after the frame header
                    if (count == 5)
                        return;
                    count -= 5;
                    offset += 5;
                }

                if (count > _leftToWrite)
                    throw new NpgsqlException($"NegotiateStream trying to write {count} bytes but according to frame header we only have {_leftToWrite} left!");
                await _connector.WritePassword(buffer, offset, count, async);
                await _connector.Flush(async);
                _leftToWrite -= count;
            }

            public override Task<int> ReadAsync(byte[] buffer, int offset, int count, CancellationToken cancellationToken)
                => Read(buffer, offset, count, true);

            public override int Read(byte[] buffer, int offset, int count)
                => Read(buffer, offset, count, false).GetAwaiter().GetResult();

            async Task<int> Read(byte[] buffer, int offset, int count, bool async)
            {
                if (_leftToRead == 0)
                {
                    var response = Expect<AuthenticationRequestMessage>(await _connector.ReadMessage(async), _connector);
                    if (response.AuthRequestType == AuthenticationRequestType.AuthenticationOk)
                        throw new AuthenticationCompleteException();
                    var gssMsg = response as AuthenticationGSSContinueMessage;
                    if (gssMsg == null)
                        throw new NpgsqlException($"Received unexpected authentication request message {response.AuthRequestType}");
                    _readBuf = gssMsg.AuthenticationData;
                    _leftToRead = gssMsg.AuthenticationData.Length;
                    _readPos = 0;
                    buffer[0] = 22;
                    buffer[1] = 1;
                    buffer[2] = 0;
                    buffer[3] = (byte)((_leftToRead >> 8) & 0xFF);
                    buffer[4] = (byte)(_leftToRead & 0xFF);
                    return 5;
                }

                if (count > _leftToRead)
                    throw new NpgsqlException($"NegotiateStream trying to read {count} bytes but according to frame header we only have {_leftToRead} left!");
                count = Math.Min(count, _leftToRead);
                Array.Copy(_readBuf!, _readPos, buffer, offset, count);
                _leftToRead -= count;
                return count;
            }

            public override void Flush() { }

            public override long Seek(long offset, SeekOrigin origin) => throw new NotSupportedException();
            public override void SetLength(long value) => throw new NotSupportedException();

            public override bool CanRead => true;
            public override bool CanWrite => true;
            public override bool CanSeek => false;
            public override long Length => throw new NotSupportedException();

            public override long Position
            {
                get => throw new NotSupportedException();
                set => throw new NotSupportedException();
            }
        }

        class AuthenticationCompleteException : Exception { }

        string? GetPassword(string username)
        {
            var passwd = Settings.Password;
            if (passwd != null)
                return passwd;

            // No password was provided. Attempt to pull the password from the pgpass file.
            var matchingEntry = PgPassFile.Load(Settings.Passfile)?.GetFirstMatchingEntry(Host, Port, Settings.Database!, username);
            if (matchingEntry != null)
            {
                Log.Trace("Taking password from pgpass file");
                return matchingEntry.Password;
            }

            if (ProvidePasswordCallback != null)
            {
                Log.Trace($"Taking password from {nameof(ProvidePasswordCallback)} delegate");
                try
                {
                    return ProvidePasswordCallback(Host, Port, Settings.Database!, username);
                }
                catch (Exception e)
                {
                    throw new NpgsqlException($"Obtaining password using {nameof(NpgsqlConnection)}.{nameof(ProvidePasswordCallback)} delegate failed", e);
                }
            }

            return null;
        }
    }
}