| 1 | package auth |
| 2 | |
| 3 | import ( |
| 4 | "context" |
| 5 | "crypto/rand" |
| 6 | "crypto/sha256" |
| 7 | "encoding/base64" |
| 8 | "encoding/hex" |
| 9 | "errors" |
| 10 | "net/http" |
| 11 | "strings" |
| 12 | "time" |
| 13 | |
| 14 | "gorm.io/gorm" |
| 15 | |
| 16 | "github.com/carlosframework/rastrillo/sessions" |
| 17 | |
| 18 | "github.com/carlosframework/contra/internal/contra/model" |
| 19 | "github.com/carlosframework/contra/internal/contra/store" |
| 20 | ) |
| 21 | |
| 22 | // Signup in three steps: prove the address, choose a passphrase, then |
| 23 | // optionally add a passkey. |
| 24 | // |
| 25 | // It replaced a single screen that did everything between one button press |
| 26 | // and one result. That screen was wrong for two reasons and both matter. |
| 27 | // |
| 28 | // The small one: it took six seconds and could fail in a dozen places, and |
| 29 | // when it did the person got one sentence from whichever operation happened |
| 30 | // to throw. Steps that each report their own outcome are diagnosable. |
| 31 | // |
| 32 | // The large one: nothing proved the address. Anyone could claim any address's |
| 33 | // blind index, and the person who owned it could then never register. This is |
| 34 | // the direction AGENTS.md decision 3 already committed to — "email + magic |
| 35 | // link for signup, then passkey for quick sign-in thereafter, is intended to |
| 36 | // become the CARLOS default. CONTRA is where it gets built first." |
| 37 | // |
| 38 | // # What the server learns |
| 39 | // |
| 40 | // Nothing new. The address is used to address one message and is not written |
| 41 | // down; the row holds the blind index and a hash of the emailed token. A |
| 42 | // database-plus-bucket leak yields nothing anyone can click. |
| 43 | |
| 44 | // SignupTTL is how long a link is good for. Long enough to walk to another |
| 45 | // device and open the mail, short enough that an old message in an archive is |
| 46 | // not a way in. |
| 47 | const SignupTTL = 30 * time.Minute |
| 48 | |
| 49 | // signupSubject prefixes the session Subject of somebody who has proved an |
| 50 | // address but has no account yet. |
| 51 | // |
| 52 | // Deliberately not a bare hex id: every other subject in this app is an |
| 53 | // account id, and vault.accountID decodes exactly 16 bytes — so a signup |
| 54 | // session cannot reach a vault route by accident. It fails the length check |
| 55 | // and answers 404, which is the correct answer to "show me the vault of an |
| 56 | // account that does not exist". |
| 57 | const signupSubject = "signup:" |
| 58 | |
| 59 | var ErrNoSignupSession = errors.New("auth: no verified signup in progress") |
| 60 | |
| 61 | func newToken() (token string, hash []byte, err error) { |
| 62 | raw := make([]byte, 32) |
| 63 | if _, err := rand.Read(raw); err != nil { |
| 64 | return "", nil, err |
| 65 | } |
| 66 | sum := sha256.Sum256(raw) |
| 67 | return base64.RawURLEncoding.EncodeToString(raw), sum[:], nil |
| 68 | } |
| 69 | |
| 70 | func hashToken(token string) ([]byte, error) { |
| 71 | raw, err := base64.RawURLEncoding.DecodeString(token) |
| 72 | if err != nil || len(raw) != 32 { |
| 73 | return nil, errors.New("auth: malformed token") |
| 74 | } |
| 75 | sum := sha256.Sum256(raw) |
| 76 | return sum[:], nil |
| 77 | } |
| 78 | |
| 79 | type beginRequest struct { |
| 80 | Email string `json:"email"` |
| 81 | } |
| 82 | |
| 83 | // Begin takes an address, emails it a link, and says the same thing either |
| 84 | // way. |
| 85 | // |
| 86 | // The response never varies on whether an account exists, whether a signup is |
| 87 | // already in flight, or whether the message was delivered — because all three |
| 88 | // are facts about somebody else's account when the asker is not that person. |
| 89 | // What varies is which message gets sent. |
| 90 | func (a *Auth) Begin(w http.ResponseWriter, r *http.Request) { |
| 91 | var req beginRequest |
| 92 | if !readJSON(w, r, &req) { |
| 93 | return |
| 94 | } |
| 95 | email := NormalizeEmail(req.Email) |
| 96 | if email == "" || !strings.Contains(email, "@") { |
| 97 | writeJSON(w, http.StatusBadRequest, |
| 98 | map[string]string{"error": "that does not look like an email address"}) |
| 99 | return |
| 100 | } |
| 101 | |
| 102 | ctx := r.Context() |
| 103 | index := a.BlindIndex(email) |
| 104 | |
| 105 | // Whatever happens below, the answer is this. |
| 106 | answer := func() { |
| 107 | writeJSON(w, http.StatusOK, map[string]string{ |
| 108 | "status": "sent", |
| 109 | "detail": "If that address can be signed up, a link is on its way.", |
| 110 | }) |
| 111 | } |
| 112 | |
| 113 | var existing model.Account |
| 114 | err := a.db.WithContext(ctx).Where("email_index = ?", index).First(&existing).Error |
| 115 | if err == nil { |
| 116 | // Already registered. Say so to the address itself and nowhere else: |
| 117 | // the person who owns it learns something useful, and a prober learns |
| 118 | // nothing at all. |
| 119 | a.send(ctx, email, "Your CONTRA account", |
| 120 | "Somebody asked to create a CONTRA account with this address, and "+ |
| 121 | "one already exists.\n\nIf that was you, sign in instead:\n\n "+ |
| 122 | a.origin+"/signin\n\nIf it was not you, nothing has happened and "+ |
| 123 | "there is nothing you need to do.\n") |
| 124 | answer() |
| 125 | return |
| 126 | } else if !errors.Is(err, gorm.ErrRecordNotFound) { |
| 127 | writeJSON(w, http.StatusInternalServerError, map[string]string{"error": "lookup failed"}) |
| 128 | return |
| 129 | } |
| 130 | |
| 131 | // One live signup per address: a second request replaces the first, so an |
| 132 | // older link in an inbox stops working. |
| 133 | if err := a.db.WithContext(ctx). |
| 134 | Where("email_index = ?", index).Delete(&model.SignupSession{}).Error; err != nil { |
| 135 | writeJSON(w, http.StatusInternalServerError, map[string]string{"error": "could not start"}) |
| 136 | return |
| 137 | } |
| 138 | |
| 139 | token, hash, err := newToken() |
| 140 | if err != nil { |
| 141 | writeJSON(w, http.StatusInternalServerError, map[string]string{"error": "no randomness"}) |
| 142 | return |
| 143 | } |
| 144 | id, err := store.NewID() |
| 145 | if err != nil { |
| 146 | writeJSON(w, http.StatusInternalServerError, map[string]string{"error": "no randomness"}) |
| 147 | return |
| 148 | } |
| 149 | if err := a.db.WithContext(ctx).Create(&model.SignupSession{ |
| 150 | ID: id, EmailIndex: index, TokenHash: hash, |
| 151 | ExpiresAt: time.Now().UTC().Add(SignupTTL), CreatedAt: time.Now().UTC(), |
| 152 | }).Error; err != nil { |
| 153 | writeJSON(w, http.StatusInternalServerError, map[string]string{"error": "could not start"}) |
| 154 | return |
| 155 | } |
| 156 | |
| 157 | a.send(ctx, email, "Finish setting up CONTRA", |
| 158 | "Open this link to carry on setting up your CONTRA account:\n\n "+ |
| 159 | a.origin+"/signup/verify?t="+token+"\n\nIt works once and expires in "+ |
| 160 | "30 minutes.\n\nIf you did not ask for this, ignore it — nothing has "+ |
| 161 | "been created, and this address has not been stored.\n") |
| 162 | answer() |
| 163 | } |
| 164 | |
| 165 | // send never fails a request. A person who did not get the mail retries; a |
| 166 | // person who did should not be told that delivery worked before it has, and a |
| 167 | // 500 here would tell a prober that this address was the interesting one. |
| 168 | func (a *Auth) send(ctx context.Context, to, subject, body string) { |
| 169 | if a.mailer == nil { |
| 170 | a.logger.Error("auth: no mailer configured; a signup link was not sent") |
| 171 | return |
| 172 | } |
| 173 | ctx, cancel := context.WithTimeout(context.WithoutCancel(ctx), 20*time.Second) |
| 174 | defer cancel() |
| 175 | if err := a.mailer.Send(ctx, to, subject, body); err != nil { |
| 176 | // The address is not logged. Delivery failures are a real operational |
| 177 | // signal and still not worth keeping a list of who we mailed. |
| 178 | a.logger.Error("auth: sending a signup link failed", "err", err) |
| 179 | } |
| 180 | } |
| 181 | |
| 182 | // VerifyLink is the link's landing. It marks the signup verified and mints a |
| 183 | // session that can do exactly one thing: finish signing up. |
| 184 | func (a *Auth) VerifyLink(w http.ResponseWriter, r *http.Request) { |
| 185 | hash, err := hashToken(r.URL.Query().Get("t")) |
| 186 | if err != nil { |
| 187 | http.Redirect(w, r, "/signup?e=badlink", http.StatusSeeOther) |
| 188 | return |
| 189 | } |
| 190 | |
| 191 | ctx := r.Context() |
| 192 | var row model.SignupSession |
| 193 | if err := a.db.WithContext(ctx).Where("token_hash = ?", hash).First(&row).Error; err != nil { |
| 194 | http.Redirect(w, r, "/signup?e=badlink", http.StatusSeeOther) |
| 195 | return |
| 196 | } |
| 197 | if time.Now().UTC().After(row.ExpiresAt) { |
| 198 | a.db.WithContext(ctx).Delete(&model.SignupSession{}, "id = ?", row.ID) |
| 199 | http.Redirect(w, r, "/signup?e=expired", http.StatusSeeOther) |
| 200 | return |
| 201 | } |
| 202 | if err := a.db.WithContext(ctx).Model(&model.SignupSession{}). |
| 203 | Where("id = ?", row.ID).Update("verified", true).Error; err != nil { |
| 204 | http.Redirect(w, r, "/signup?e=failed", http.StatusSeeOther) |
| 205 | return |
| 206 | } |
| 207 | |
| 208 | if err := a.sess.SignIn(w, r, sessions.Session{ |
| 209 | Subject: signupSubject + hex.EncodeToString(row.ID), |
| 210 | Method: "signup-link", |
| 211 | AuthTime: time.Now().UTC(), |
| 212 | }); err != nil { |
| 213 | http.Redirect(w, r, "/signup?e=failed", http.StatusSeeOther) |
| 214 | return |
| 215 | } |
| 216 | http.Redirect(w, r, "/signup/passphrase", http.StatusSeeOther) |
| 217 | } |
| 218 | |
| 219 | // SignupSessionOf returns the verified signup behind this request, if any. |
| 220 | func (a *Auth) SignupSessionOf(r *http.Request) (*model.SignupSession, error) { |
| 221 | sess, ok := sessions.Current(r) |
| 222 | if !ok || !strings.HasPrefix(sess.Subject, signupSubject) { |
| 223 | return nil, ErrNoSignupSession |
| 224 | } |
| 225 | id, err := hex.DecodeString(strings.TrimPrefix(sess.Subject, signupSubject)) |
| 226 | if err != nil || len(id) != 16 { |
| 227 | return nil, ErrNoSignupSession |
| 228 | } |
| 229 | var row model.SignupSession |
| 230 | if err := a.db.WithContext(r.Context()). |
| 231 | Where("id = ? AND verified = ?", id, true).First(&row).Error; err != nil { |
| 232 | return nil, ErrNoSignupSession |
| 233 | } |
| 234 | if time.Now().UTC().After(row.ExpiresAt) { |
| 235 | return nil, ErrNoSignupSession |
| 236 | } |
| 237 | return &row, nil |
| 238 | } |
| 239 | |
| 240 | // Complete is step two: the browser has done all the crypto and posts only |
| 241 | // sealed material. The account is created here, against the address that was |
| 242 | // actually proved, and the signup session is spent. |
| 243 | func (a *Auth) Complete(w http.ResponseWriter, r *http.Request) { |
| 244 | pending, err := a.SignupSessionOf(r) |
| 245 | if err != nil { |
| 246 | writeJSON(w, http.StatusForbidden, map[string]string{ |
| 247 | "error": "That link has expired or was already used. Start again."}) |
| 248 | return |
| 249 | } |
| 250 | |
| 251 | var req signupRequest |
| 252 | if !readJSON(w, r, &req) { |
| 253 | return |
| 254 | } |
| 255 | salt, e1 := hex.DecodeString(req.SaltHex) |
| 256 | accountID, e2 := hex.DecodeString(req.AccountIDHex) |
| 257 | if e1 != nil || e2 != nil || len(salt) != 16 || len(accountID) != 16 { |
| 258 | writeJSON(w, http.StatusBadRequest, map[string]string{"error": "bad account material"}) |
| 259 | return |
| 260 | } |
| 261 | for _, wr := range req.Wraps { |
| 262 | if err := CheckParams(wr.KDFParams); err != nil { |
| 263 | writeJSON(w, http.StatusBadRequest, map[string]string{"error": err.Error()}) |
| 264 | return |
| 265 | } |
| 266 | } |
| 267 | |
| 268 | ctx := r.Context() |
| 269 | acct, err := a.store.CreateAccount(ctx, accountID, pending.EmailIndex, salt) |
| 270 | if err != nil { |
| 271 | // The unique index on email_index is what makes this a conflict |
| 272 | // rather than a second account for one address. |
| 273 | writeJSON(w, http.StatusConflict, |
| 274 | map[string]string{"error": ErrTaken.Error()}) |
| 275 | return |
| 276 | } |
| 277 | if err := a.storeCredentials(ctx, acct.ID, req); err != nil { |
| 278 | writeJSON(w, http.StatusBadRequest, map[string]string{"error": err.Error()}) |
| 279 | return |
| 280 | } |
| 281 | |
| 282 | // Spent. The link cannot be followed again and the row stops being a |
| 283 | // record that this address ever signed up. |
| 284 | a.db.WithContext(ctx).Delete(&model.SignupSession{}, "id = ?", pending.ID) |
| 285 | |
| 286 | if err := a.sess.SignIn(w, r, sessions.Session{ |
| 287 | Subject: hex.EncodeToString(acct.ID), |
| 288 | Method: "signup", |
| 289 | AuthTime: time.Now().UTC(), |
| 290 | }); err != nil { |
| 291 | writeJSON(w, http.StatusInternalServerError, |
| 292 | map[string]string{"error": "the account was created but the session was not"}) |
| 293 | return |
| 294 | } |
| 295 | writeJSON(w, http.StatusCreated, map[string]string{ |
| 296 | "account_id_hex": hex.EncodeToString(acct.ID)}) |
| 297 | } |
| 298 | |
| 299 | // SweepSignups deletes expired rows. |
| 300 | func (a *Auth) SweepSignups(now time.Time) error { |
| 301 | _, err := SweepSignupsIn(context.Background(), a.db, now) |
| 302 | return err |
| 303 | } |
| 304 | |
| 305 | // SweepSignupsIn is the same delete without an Auth to hang it on, so the |
| 306 | // background sweep can run without building the whole ceremony to reach it. |
| 307 | // |
| 308 | // A half-finished signup is already inert — every lookup carries the expiry — |
| 309 | // so this is not about correctness. It is that a table of these that |
| 310 | // accumulated would be a log of who tried to sign up and when. |
| 311 | func SweepSignupsIn(ctx context.Context, db *gorm.DB, now time.Time) (int64, error) { |
| 312 | res := db.WithContext(ctx). |
| 313 | Where("expires_at < ?", now.UTC()).Delete(&model.SignupSession{}) |
| 314 | return res.RowsAffected, res.Error |
| 315 | } |
| 316 | |
amadan