winauth-go/internal/authenticator/steam_enroll.go

package authenticator

import (
	"context"
	"crypto/rsa"
	"encoding/base64"
	"encoding/hex"
	"encoding/json"
	"errors"
	"fmt"
	"math/big"
	"net/http"
	"net/url"
	"strconv"
	"strings"
	"time"

	"git.wxccs.org/iceking2nd/winauth-go/internal/global"
)

// EnrollState carries the cross-call state of a Steam enrollment. The
// caller (UI) creates one, fills in Username/Password (and optionally
// CaptchaText / EmailAuthText / ActivationCode on retries), and calls
// SteamAuthenticator.Enroll repeatedly until Success == true or Error
// is set to a fatal message.
type EnrollState struct {
	// Inputs supplied by the caller across multiple calls.
	Username       string
	Password       string
	CaptchaID      string
	CaptchaURL     string
	CaptchaText    string
	EmailDomain    string
	EmailAuthText  string
	ActivationCode string

	// Session state carried across calls. The cookie jar is internal to
	// the http client; we cache it here so retries reuse it.
	jar        http.CookieJar
	SteamID    string
	OAuthToken string

	// Flags the caller inspects after each Enroll call to decide which
	// extra input is needed next.
	RequiresLogin      bool
	RequiresCaptcha    bool
	Requires2FA        bool
	RequiresEmailAuth  bool
	RequiresActivation bool

	// Outputs populated once enrollment succeeds. RevocationCode MUST
	// be displayed to the user — losing it locks them out of the
	// authenticator removal flow.
	RevocationCode string
	SecretKey      string // hex form, for convenience; raw is on the authenticator
	Success        bool

	// Error is the last user-facing message. Cleared at the start of
	// every Enroll call.
	Error string
}

// enrollActivateRetries matches the C# ENROLL_ACTIVATE_RETRIES constant.
const enrollActivateRetries = 30

// invalidActivationCode is the response.status value Steam returns when
// the SMS code the user typed is wrong. Mirrors the C# constant.
const invalidActivationCode = 89

// rsaKeyResponse models the /mobilelogin/getrsakey response.
type rsaKeyResponse struct {
	Success      bool   `json:"success"`
	PublicKeyMod string `json:"publickey_mod"`
	PublicKeyExp string `json:"publickey_exp"`
	Timestamp    string `json:"timestamp"`
}

// Enroll drives one step of the Steam mobile-authenticator enrollment
// state machine. Call it repeatedly with the same EnrollState until it
// returns (true, nil) or sets state.Error.
//
// Return value:
//   - (true, nil)   → enrollment fully complete; this authenticator now
//     holds the new secret/serial/deviceid/steamdata.
//   - (false, nil)  → caller must inspect state.Requires* and supply the
//     missing input (captcha text, email code, 2FA
//     activation code) then call Enroll again.
//   - (false, err)  → unrecoverable transport / parse error.
//
// SECURITY: state.Password is wiped from the struct after a successful
// RSA-encrypted login round, so a subsequent retry (e.g. for activation
// code) does not keep the cleartext password resident.
func (s *SteamAuthenticator) Enroll(ctx context.Context, state *EnrollState) (bool, error) {
	const fn = "internal.authenticator.SteamAuthenticator.Enroll"
	logger := global.Log.WithField("func", fn)

	state.Error = ""

	if state.jar == nil {
		jar, err := newSteamCookieJar()
		if err != nil {
			return false, err
		}
		state.jar = jar
	}
	client := steamHTTPClient(state.jar)

	if state.OAuthToken == "" {
		// One-time GET so the jar gets the sessionid cookie. Mirrors
		// the C# "if cookies.Count == 0" branch.
		if !steamJarHasSessionID(state.jar) {
			headers := http.Header{"X-Requested-With": []string{"com.valvesoftware.android.steam.community"}}
			_, err := steamRequest(ctx, client, http.MethodGet,
				steamCommunityBase+"/mobilelogin?oauth_client_id="+steamOAuthClientID+
					"&oauth_scope="+url.QueryEscape(steamOAuthScope), nil, headers)
			if err != nil {
				return false, fmt.Errorf("mobilelogin GET: %w", err)
			}
		}

		state.Username = stripNonASCII(state.Username)
		state.Password = stripNonASCII(state.Password)

		rsaResp, err := steamRequest(ctx, client, http.MethodPost,
			steamCommunityBase+"/mobilelogin/getrsakey",
			url.Values{"username": {state.Username}}, nil)
		if err != nil {
			return false, fmt.Errorf("getrsakey: %w", err)
		}
		var rsaJSON rsaKeyResponse
		if err := json.Unmarshal([]byte(rsaResp), &rsaJSON); err != nil {
			return false, fmt.Errorf("getrsakey parse: %w", err)
		}
		if !rsaJSON.Success {
			return false, errors.New("steam: cannot fetch RSA key for user")
		}

		encPw, err := steamRSAEncryptPassword(state.Password, rsaJSON.PublicKeyMod, rsaJSON.PublicKeyExp)
		if err != nil {
			return false, fmt.Errorf("rsa encrypt: %w", err)
		}

		captchaID := state.CaptchaID
		if captchaID == "" {
			captchaID = "-1"
		}
		captchaText := state.CaptchaText
		if captchaText == "" {
			captchaText = "enter above characters"
		}
		emailSteamID := ""
		if state.EmailAuthText != "" {
			emailSteamID = state.SteamID
		}
		loginForm := url.Values{
			"password":          {base64.StdEncoding.EncodeToString(encPw)},
			"username":          {state.Username},
			"twofactorcode":     {""},
			"emailauth":         {state.EmailAuthText},
			"loginfriendlyname": {"#login_emailauth_friendlyname_mobile"},
			"captchagid":        {captchaID},
			"captcha_text":      {captchaText},
			"emailsteamid":      {emailSteamID},
			"rsatimestamp":      {rsaJSON.Timestamp},
			"remember_login":    {"false"},
			"oauth_client_id":   {steamOAuthClientID},
			"oauth_scope":       {steamOAuthScope},
			"donotache":         {strconv.FormatInt(time.Now().UnixMilli(), 10)},
		}
		loginResp, err := steamRequest(ctx, client, http.MethodPost,
			steamCommunityBase+"/mobilelogin/dologin/", loginForm, nil)
		if err != nil {
			return false, fmt.Errorf("dologin: %w", err)
		}

		// Wipe the plaintext password from memory now that it has been
		// RSA-encrypted and sent.
		state.Password = ""

		var login map[string]any
		if err := json.Unmarshal([]byte(loginResp), &login); err != nil {
			return false, fmt.Errorf("dologin parse: %w", err)
		}

		if v, ok := login["emailsteamid"].(string); ok {
			state.SteamID = v
		}

		if b, _ := login["captcha_needed"].(bool); b {
			state.RequiresCaptcha = true
			if id, ok := login["captcha_gid"].(string); ok {
				state.CaptchaID = id
				state.CaptchaURL = steamCommunityBase + "/public/captcha.php?gid=" + id
			}
		} else {
			state.RequiresCaptcha = false
			state.CaptchaID = ""
			state.CaptchaURL = ""
			state.CaptchaText = ""
		}

		if b, _ := login["emailauth_needed"].(bool); b {
			if d, ok := login["emaildomain"].(string); ok && d != "" {
				state.EmailDomain = d
			}
			state.RequiresEmailAuth = true
		} else {
			state.EmailDomain = ""
			state.RequiresEmailAuth = false
		}

		if b, _ := login["requires_twofactor"].(bool); b {
			state.Requires2FA = true
		} else {
			state.Requires2FA = false
		}

		complete, _ := login["login_complete"].(bool)
		oauthStr, _ := login["oauth"].(string)
		if !complete || oauthStr == "" {
			if oauthStr == "" {
				state.Error = "Invalid response from Steam (No OAuth token)"
			}
			if msg, ok := login["message"].(string); ok && msg != "" {
				state.Error = msg
			}
			return false, nil
		}

		// oauth is a JSON-stringified inner object.
		var oauth struct {
			OAuthToken string `json:"oauth_token"`
			SteamID    string `json:"steamid"`
		}
		if err := json.Unmarshal([]byte(oauthStr), &oauth); err != nil {
			return false, fmt.Errorf("oauth parse: %w", err)
		}
		state.OAuthToken = oauth.OAuthToken
		if oauth.SteamID != "" {
			state.SteamID = oauth.SteamID
		}
	}

	// Logon to WebAPI (needed for the ITwoFactorService calls below).
	if _, err := steamRequest(ctx, client, http.MethodPost,
		steamWebAPIBase+"/ISteamWebUserPresenceOAuth/Logon/v0001",
		url.Values{"access_token": {state.OAuthToken}}, nil); err != nil {
		return false, fmt.Errorf("ISteamWebUserPresenceOAuth/Logon: %w", err)
	}

	sessionID := steamJarSessionID(state.jar)

	if !state.RequiresActivation {
		// Phone check. No phone → cannot enroll.
		phoneResp, err := steamRequest(ctx, client, http.MethodPost,
			steamCommunityBase+"/steamguard/phoneajax",
			url.Values{"op": {"has_phone"}, "arg": {"null"}, "sessionid": {sessionID}}, nil)
		if err != nil {
			return false, fmt.Errorf("phoneajax: %w", err)
		}
		var phoneJSON struct {
			HasPhone bool `json:"has_phone"`
		}
		if err := json.Unmarshal([]byte(phoneResp), &phoneJSON); err != nil {
			return false, fmt.Errorf("phoneajax parse: %w", err)
		}
		if !phoneJSON.HasPhone {
			state.OAuthToken = ""
			state.RequiresLogin = true
			state.jar = nil
			state.Error = "Your Steam account must have a SMS-capable phone number attached. Go into Account Details of the Steam client or Steam website and click Add a Phone Number."
			return false, nil
		}

		deviceID := buildRandomDeviceID()
		addResp, err := steamRequest(ctx, client, http.MethodPost,
			steamWebAPIBase+"/ITwoFactorService/AddAuthenticator/v0001",
			url.Values{
				"access_token":       {state.OAuthToken},
				"steamid":            {state.SteamID},
				"authenticator_type": {"1"},
				"device_identifier":  {deviceID},
				"sms_phone_id":       {"1"},
			}, nil)
		if err != nil {
			return false, fmt.Errorf("AddAuthenticator: %w", err)
		}

		// The C# branch on response.status == 84 = "SMS send failed".
		var addJSON struct {
			Response struct {
				Status         int             `json:"status"`
				SharedSecret   string          `json:"shared_secret"`
				SerialNumber   string          `json:"serial_number"`
				RevocationCode string          `json:"revocation_code"`
				ServerTime     json.Number     `json:"server_time"`
				Raw            json.RawMessage `json:"-"`
			} `json:"response"`
		}
		if err := json.Unmarshal([]byte(addResp), &addJSON); err != nil {
			return false, fmt.Errorf("AddAuthenticator parse: %w", err)
		}
		if addJSON.Response.Status == 84 {
			state.OAuthToken = ""
			state.RequiresLogin = true
			state.jar = nil
			state.Error = "Unable to send SMS. Check your phone is registered on your Steam account."
			return false, nil
		}
		if addJSON.Response.SharedSecret == "" {
			state.OAuthToken = ""
			state.RequiresLogin = true
			state.jar = nil
			state.Error = "Invalid response from Steam"
			return false, nil
		}

		secretRaw, err := base64.StdEncoding.DecodeString(addJSON.Response.SharedSecret)
		if err != nil {
			return false, fmt.Errorf("shared_secret decode: %w", err)
		}
		s.SecretKey = secretRaw
		s.Serial = addJSON.Response.SerialNumber
		s.DeviceID = deviceID
		state.RevocationCode = addJSON.Response.RevocationCode

		// Re-parse the response.* sub-object so we can preserve every
		// field Steam returned and just inject steamid / steamguard_scheme
		// if missing, matching the C# behaviour.
		var envelope map[string]json.RawMessage
		_ = json.Unmarshal([]byte(addResp), &envelope)
		var steamDataMap map[string]any
		if raw, ok := envelope["response"]; ok {
			_ = json.Unmarshal(raw, &steamDataMap)
		}
		if steamDataMap == nil {
			steamDataMap = map[string]any{}
		}
		if _, ok := steamDataMap["steamid"]; !ok {
			steamDataMap["steamid"] = state.SteamID
		}
		if _, ok := steamDataMap["steamguard_scheme"]; !ok {
			steamDataMap["steamguard_scheme"] = "2"
		}
		steamDataBytes, _ := json.Marshal(steamDataMap)
		s.SteamData = string(steamDataBytes)

		if addJSON.Response.ServerTime != "" {
			if sec, err := strconv.ParseInt(string(addJSON.Response.ServerTime), 10, 64); err == nil {
				s.ServerTimeDiff = sec*1000 - NowMillis()
				s.LastServerTime = NowMillis()
			}
		}

		state.RequiresActivation = true
		logger.Info("authenticator added; awaiting SMS activation code")
		return false, nil
	}

	// Activation: try up to ENROLL_ACTIVATE_RETRIES times. Between
	// retries we slide ServerTimeDiff forward by one TOTP period to
	// align with whichever step Steam is expecting.
	retries := 0
	for state.RequiresActivation && retries < enrollActivateRetries {
		form := url.Values{
			"access_token":       {state.OAuthToken},
			"steamid":            {state.SteamID},
			"activation_code":    {state.ActivationCode},
			"authenticator_code": {s.steamCode()},
			"authenticator_time": {strconv.FormatInt(s.ServerTime()/1000, 10)},
		}
		finResp, err := steamRequest(ctx, client, http.MethodPost,
			steamWebAPIBase+"/ITwoFactorService/FinalizeAddAuthenticator/v0001", form, nil)
		if err != nil {
			return false, fmt.Errorf("FinalizeAddAuthenticator: %w", err)
		}
		var fin struct {
			Response struct {
				Status     int         `json:"status"`
				Success    bool        `json:"success"`
				WantMore   bool        `json:"want_more"`
				ServerTime json.Number `json:"server_time"`
			} `json:"response"`
		}
		if err := json.Unmarshal([]byte(finResp), &fin); err != nil {
			return false, fmt.Errorf("FinalizeAddAuthenticator parse: %w", err)
		}
		if fin.Response.Status == invalidActivationCode {
			state.Error = "Invalid activation code"
			return false, nil
		}
		if fin.Response.ServerTime != "" {
			if sec, err := strconv.ParseInt(string(fin.Response.ServerTime), 10, 64); err == nil {
				s.ServerTimeDiff = sec*1000 - NowMillis()
				s.LastServerTime = NowMillis()
			}
		}
		if fin.Response.Success {
			if fin.Response.WantMore {
				s.advanceServerTime()
				retries++
				continue
			}
			state.RequiresActivation = false
			break
		}
		s.advanceServerTime()
		retries++
	}
	if state.RequiresActivation {
		state.Error = "There was a problem activating. There might be an issue with the Steam servers. Please try again later."
		return false, nil
	}

	state.Success = true
	state.SecretKey = strings.ToUpper(hex.EncodeToString(s.SecretKey))

	// Best-effort confirmation email; failures are non-fatal because
	// the authenticator is already activated.
	_, _ = steamRequest(ctx, client, http.MethodPost,
		steamWebAPIBase+"/ITwoFactorService/SendEmail/v0001",
		url.Values{
			"access_token": {state.OAuthToken},
			"steamid":      {state.SteamID},
			"email_type":   {"2"},
		}, nil)

	logger.WithField("serial", s.Serial).Info("steam authenticator enrolled")
	return true, nil
}

// advanceServerTime nudges ServerTimeDiff forward by one TOTP period so
// the next FinalizeAddAuthenticator call submits a code for the next
// step. Matches the C# loop.
func (s *SteamAuthenticator) advanceServerTime() {
	period := s.Period
	if period <= 0 {
		period = DefaultPeriod
	}
	s.ServerTimeDiff += int64(period) * 1000
}

// steamRSAEncryptPassword RSA-encrypts the password using the hex
// modulus / exponent returned by getrsakey. The original WinAuth uses
// RSACryptoServiceProvider.Encrypt(_, false) which is PKCS#1 v1.5.
func steamRSAEncryptPassword(password, hexMod, hexExp string) ([]byte, error) {
	modBytes, err := hex.DecodeString(hexMod)
	if err != nil {
		return nil, fmt.Errorf("modulus hex: %w", err)
	}
	expBytes, err := hex.DecodeString(hexExp)
	if err != nil {
		return nil, fmt.Errorf("exponent hex: %w", err)
	}
	n := new(big.Int).SetBytes(modBytes)
	e := new(big.Int).SetBytes(expBytes)
	pub := &rsa.PublicKey{N: n, E: int(e.Int64())}
	// PKCS#1 v1.5 is required by the Steam mobile-login endpoint;
	// OAEP would be rejected. The deprecation warning is acknowledged.
	return rsa.EncryptPKCS1v15(nil, pub, []byte(password))
}

// steamJarSessionID returns the "sessionid" cookie set by Steam on the
// community domain, or "" if it has not been issued yet.
func steamJarSessionID(jar http.CookieJar) string {
	u, _ := url.Parse(steamCommunityBase + "/")
	for _, c := range jar.Cookies(u) {
		if c.Name == "sessionid" {
			return c.Value
		}
	}
	return ""
}

func steamJarHasSessionID(jar http.CookieJar) bool {
	return steamJarSessionID(jar) != ""
}