Michael Chihlas
f1be3abcc5
Co-authored-by: Michael Chihlas <michael@resolutionflow.com> Co-committed-by: Michael Chihlas <michael@resolutionflow.com>
62 lines
2.3 KiB
TypeScript
62 lines
2.3 KiB
TypeScript
/**
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* UTF-8-safe base64url encoding for OAuth `state` payloads.
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*
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* The /accept-invite flow round-trips an invite code + invited email through
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* the OAuth provider's `state` parameter. Internationalized email addresses
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* (e.g., `user@münchen.de`) contain code points > 255, which raw `btoa` /
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* `atob` cannot represent — they throw `DOMException: The string to be
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* encoded contains characters outside of the Latin1 range`.
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*
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* The classic `unescape(encodeURIComponent(...))` trick maps a UTF-16 string
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* through its UTF-8 byte representation into a Latin-1 string that `btoa`
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* accepts. The decode side reverses the transformation.
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*/
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export interface OAuthStatePayload {
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csrf: string
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accountInviteCode: string
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invitedEmail: string
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}
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export interface DecodedOAuthState {
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csrf: string
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accountInviteCode?: string
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invitedEmail?: string
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}
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/** Encode an OAuth state payload as URL-safe base64. UTF-8 safe. */
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export function encodeOAuthState(payload: OAuthStatePayload): string {
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const json = JSON.stringify(payload)
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// unescape(encodeURIComponent(...)) converts UTF-16 -> UTF-8 -> Latin-1
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// string so btoa can encode it without throwing on non-Latin-1 chars.
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const b64 = btoa(unescape(encodeURIComponent(json)))
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return b64.replace(/\+/g, '-').replace(/\//g, '_').replace(/=+$/, '')
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}
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/** Best-effort base64url-decode. Returns null on legacy random-hex states or
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* malformed input so the caller can fall back to a simple equality check. */
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export function decodeOAuthState(raw: string | null): DecodedOAuthState | null {
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if (!raw) return null
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try {
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const padded = raw.replace(/-/g, '+').replace(/_/g, '/')
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const b64 = padded + '='.repeat((4 - (padded.length % 4)) % 4)
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// decodeURIComponent(escape(...)) reverses the encode-side transform.
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const json = decodeURIComponent(escape(atob(b64)))
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const parsed = JSON.parse(json) as Partial<DecodedOAuthState>
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if (typeof parsed?.csrf === 'string') {
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return {
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csrf: parsed.csrf,
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accountInviteCode:
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typeof parsed.accountInviteCode === 'string'
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? parsed.accountInviteCode
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: undefined,
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invitedEmail:
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typeof parsed.invitedEmail === 'string' ? parsed.invitedEmail : undefined,
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}
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}
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return null
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} catch {
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return null
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}
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}
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