| 1 | package client |
| 2 | |
| 3 | import ( |
| 4 | "encoding/binary" |
| 5 | "encoding/json" |
| 6 | "fmt" |
| 7 | "io" |
| 8 | "net/http" |
| 9 | "strings" |
| 10 | "time" |
| 11 | |
| 12 | "lchat/internal/e2ee" |
| 13 | ) |
| 14 | |
| 15 | // The home server (home.elevenmessenger.com, home/) is the passkey-gated |
| 16 | // backup store: a member's saved spaces — each with its credentials — live in |
| 17 | // one client-encrypted blob there. This file is the Go half of that contract, |
| 18 | // byte-compatible with home/web/static/crypto.js (and the Swift HomeCrypto): |
| 19 | // open the EHB1 envelope with a DEK, and unwrap the {token, dek} session the |
| 20 | // restore page hands a CLI after the passkey ceremony. The CLI never sees a |
| 21 | // PRF or KEK — the browser did the ceremony; it arrives holding the DEK. |
| 22 | |
| 23 | // HomeSession is what the restore page hands over after a passkey unlock |
| 24 | // (restore.js's app/cli handoff): ongoing bearer auth to the vault plus the |
| 25 | // key that opens it. Holding this file IS holding every saved space's |
| 26 | // credentials — same trust profile as the native apps' Keychain copy. |
| 27 | type HomeSession struct { |
| 28 | V int `json:"v"` |
| 29 | Base string `json:"base,omitempty"` // home server URL (CLI bookkeeping) |
| 30 | Token string `json:"token"` |
| 31 | CredID string `json:"credId"` |
| 32 | DEK string `json:"dek"` // raw AES-256 key, base64url |
| 33 | } |
| 34 | |
| 35 | // Vault is the decrypted backup: the member's saved spaces in master order |
| 36 | // (ios/LChatCore HomeVault.Contents / home/web/static/serverlist.js). |
| 37 | type Vault struct { |
| 38 | V int `json:"v"` |
| 39 | Servers []VaultServer `json:"servers"` |
| 40 | } |
| 41 | |
| 42 | // VaultServer is one saved space. Credentials is nil for a bare saved URL |
| 43 | // (home.js can save a space by URL alone); Archived entries are hidden from |
| 44 | // the native rail and home's list, so a restore skips them too. |
| 45 | type VaultServer struct { |
| 46 | URL string `json:"url"` |
| 47 | Name string `json:"name,omitempty"` |
| 48 | Starred bool `json:"starred,omitempty"` |
| 49 | Archived bool `json:"archived,omitempty"` |
| 50 | Credentials *VaultCredentials `json:"credentials,omitempty"` |
| 51 | } |
| 52 | |
| 53 | // VaultCredentials is a space session in vault clothing — the same fields as |
| 54 | // Session, keyed the same way (home's blob JSON and the session file share |
| 55 | // the userPub/userPriv naming on purpose). |
| 56 | type VaultCredentials struct { |
| 57 | Token string `json:"token"` |
| 58 | UserPub string `json:"userPub"` |
| 59 | UserPriv string `json:"userPriv"` |
| 60 | Name string `json:"name,omitempty"` |
| 61 | } |
| 62 | |
| 63 | // Session converts a vault entry into a live space session. |
| 64 | func (s VaultServer) Session() *Session { |
| 65 | if s.Credentials == nil { |
| 66 | return nil |
| 67 | } |
| 68 | name := s.Credentials.Name |
| 69 | if name == "" { |
| 70 | name = s.Name |
| 71 | } |
| 72 | return &Session{ |
| 73 | Base: strings.TrimRight(s.URL, "/"), |
| 74 | Token: s.Credentials.Token, |
| 75 | Name: name, |
| 76 | UserPub: s.Credentials.UserPub, |
| 77 | UserPriv: s.Credentials.UserPriv, |
| 78 | // The roster label already exists server-side for a member restored |
| 79 | // from backup — this is an existing identity, not a fresh join. |
| 80 | LabelPublished: true, |
| 81 | SpaceName: s.Name, |
| 82 | Starred: s.Starred, |
| 83 | } |
| 84 | } |
| 85 | |
| 86 | // OpenHandoff decodes what the restore page returned (the base64url "back" |
| 87 | // payload — a loopback ?d= value or a pasted code), verifies the nonce is the |
| 88 | // one this process minted, and unwraps the home session with the ephemeral |
| 89 | // private key that never left this process. |
| 90 | func OpenHandoff(backB64, nonce, ephPrivB64 string) (*HomeSession, error) { |
| 91 | raw, err := e2ee.B64uDecode(strings.TrimSpace(backB64)) |
| 92 | if err != nil { |
| 93 | return nil, fmt.Errorf("client: that doesn't look like a sign-in code") |
| 94 | } |
| 95 | var back struct { |
| 96 | Nonce string `json:"nonce"` |
| 97 | Wrapped string `json:"wrapped"` |
| 98 | } |
| 99 | if json.Unmarshal(raw, &back) != nil || back.Wrapped == "" { |
| 100 | return nil, fmt.Errorf("client: that doesn't look like a sign-in code") |
| 101 | } |
| 102 | if back.Nonce != nonce { |
| 103 | return nil, fmt.Errorf("client: sign-in code is from a different signin attempt — run signin again and use the fresh code") |
| 104 | } |
| 105 | var hs HomeSession |
| 106 | if err := e2ee.OpenSealed(back.Wrapped, ephPrivB64, &hs); err != nil { |
| 107 | return nil, fmt.Errorf("client: couldn't unlock the sign-in code: %w", err) |
| 108 | } |
| 109 | if hs.Token == "" || hs.DEK == "" { |
| 110 | return nil, fmt.Errorf("client: sign-in code is missing its session") |
| 111 | } |
| 112 | return &hs, nil |
| 113 | } |
| 114 | |
| 115 | // FetchVault pulls the encrypted backup from home and opens it with the |
| 116 | // session's DEK. A member with no backup yet returns an empty vault, not an |
| 117 | // error. An expired/revoked token returns ErrHomeAuth so callers can rerun |
| 118 | // the ceremony. |
| 119 | func FetchVault(hs *HomeSession) (*Vault, error) { |
| 120 | req, err := http.NewRequest("GET", strings.TrimRight(hs.Base, "/")+"/api/blob", nil) |
| 121 | if err != nil { |
| 122 | return nil, err |
| 123 | } |
| 124 | req.Header.Set("Authorization", "Bearer "+hs.Token) |
| 125 | hc := &http.Client{Timeout: 30 * time.Second} |
| 126 | resp, err := hc.Do(req) |
| 127 | if err != nil { |
| 128 | return nil, err |
| 129 | } |
| 130 | defer resp.Body.Close() |
| 131 | switch resp.StatusCode { |
| 132 | case http.StatusOK: |
| 133 | case http.StatusNotFound: |
| 134 | return &Vault{V: 1}, nil |
| 135 | case http.StatusUnauthorized, http.StatusForbidden: |
| 136 | return nil, ErrHomeAuth |
| 137 | default: |
| 138 | return nil, fmt.Errorf("client: home server: HTTP %d", resp.StatusCode) |
| 139 | } |
| 140 | envelope, err := io.ReadAll(io.LimitReader(resp.Body, 1<<20)) |
| 141 | if err != nil { |
| 142 | return nil, err |
| 143 | } |
| 144 | dek, err := e2ee.B64uDecode(hs.DEK) |
| 145 | if err != nil { |
| 146 | return nil, fmt.Errorf("client: bad home session key: %w", err) |
| 147 | } |
| 148 | return OpenHomeBlob(envelope, dek) |
| 149 | } |
| 150 | |
| 151 | // ErrHomeAuth: the stored home session no longer authenticates (token revoked |
| 152 | // or expired) — the caller should run the passkey ceremony again. |
| 153 | var ErrHomeAuth = fmt.Errorf("client: home sign-in has expired — run `eleven signin` again") |
| 154 | |
| 155 | // OpenHomeBlob opens an EHB1 envelope with an already-unwrapped DEK, |
| 156 | // mirroring home/web/static/crypto.js unpackBlob + openBlob: |
| 157 | // |
| 158 | // "EHB1"(4) || u32 BE headerLen || header JSON || iv(12) || ciphertext |
| 159 | // |
| 160 | // The header (per-passkey wrapped DEKs) is skipped — the DEK is in hand. The |
| 161 | // plaintext is padded (4-byte BE length prefix, zeros to 16 KiB) so ciphertext |
| 162 | // length leaks nothing; unpad recovers the JSON. |
| 163 | func OpenHomeBlob(envelope, dek []byte) (*Vault, error) { |
| 164 | if len(envelope) < 8 || string(envelope[:4]) != "EHB1" { |
| 165 | return nil, fmt.Errorf("client: not a home backup blob") |
| 166 | } |
| 167 | headerLen := binary.BigEndian.Uint32(envelope[4:8]) |
| 168 | if int(headerLen) > len(envelope)-8 { |
| 169 | return nil, fmt.Errorf("client: corrupt home backup blob") |
| 170 | } |
| 171 | body := envelope[8+headerLen:] |
| 172 | padded, err := e2ee.DecryptBytes(dek, body) |
| 173 | if err != nil { |
| 174 | return nil, fmt.Errorf("client: couldn't open the backup (wrong key?): %w", err) |
| 175 | } |
| 176 | if len(padded) < 4 { |
| 177 | return nil, fmt.Errorf("client: corrupt home backup blob") |
| 178 | } |
| 179 | ptLen := binary.BigEndian.Uint32(padded[:4]) |
| 180 | if int(ptLen) > len(padded)-4 { |
| 181 | return nil, fmt.Errorf("client: corrupt home backup blob") |
| 182 | } |
| 183 | var v Vault |
| 184 | if err := json.Unmarshal(padded[4:4+ptLen], &v); err != nil { |
| 185 | return nil, fmt.Errorf("client: corrupt home backup blob: %w", err) |
| 186 | } |
| 187 | return &v, nil |
| 188 | } |
| 189 | |
| 190 | // SealHomeBlob is OpenHomeBlob's inverse (crypto.js sealBlob) — the envelope a |
| 191 | // browser would PUT. Used by tests to prove byte-compatibility both ways; a |
| 192 | // future write-back (starring a space from the CLI) would go through here. |
| 193 | // keys is the per-passkey wrapped-DEK header, passed through untouched. |
| 194 | func SealHomeBlob(v *Vault, dek []byte, keys map[string]string) ([]byte, error) { |
| 195 | pt, err := json.Marshal(v) |
| 196 | if err != nil { |
| 197 | return nil, err |
| 198 | } |
| 199 | const pad = 16384 // crypto.js BLOB_PAD |
| 200 | if len(pt) > pad-4 { |
| 201 | return nil, fmt.Errorf("client: backup contents too large") |
| 202 | } |
| 203 | padded := make([]byte, pad) |
| 204 | binary.BigEndian.PutUint32(padded, uint32(len(pt))) |
| 205 | copy(padded[4:], pt) |
| 206 | body, err := e2ee.EncryptBytes(dek, padded) |
| 207 | if err != nil { |
| 208 | return nil, err |
| 209 | } |
| 210 | header, err := json.Marshal(map[string]any{"keys": keys}) |
| 211 | if err != nil { |
| 212 | return nil, err |
| 213 | } |
| 214 | out := make([]byte, 0, 8+len(header)+len(body)) |
| 215 | out = append(out, "EHB1"...) |
| 216 | out = binary.BigEndian.AppendUint32(out, uint32(len(header))) |
| 217 | out = append(out, header...) |
| 218 | out = append(out, body...) |
| 219 | return out, nil |
| 220 | } |
| 221 | |
amadan