c53ee5f6ad
Subsystem to monitor IMAP mailbox for new messages. Introduces: - intake: worker that uses IDLE or polling to detect new emails. - imap: client wrapper for connection management and IMAP commands. - filter: logic for IMAP search and sender allow-list. - tracker: concurrency control to prevent processing the same UID twice. - backoff: for handling connection retries with jitter.
53 lines
1.8 KiB
Go
53 lines
1.8 KiB
Go
// Package filter provides message filtering configuration.
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// It is used to restrict which messages are processed by the answer workers.
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//
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// NOTE: IMAP Search Limitations
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// IMAP SEARCH (RFC 3501 §6.4.4) uses case-insensitive substring matching for
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// text fields.
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// A filter like From: "alice@example.com" would match:
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// - alice@example.com
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// - malice@example.com
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// - alice@example.com.evil.org
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//
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// For this reason, server-side IMAP filters should be considered
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// performance optimizations only, not security controls. Use the
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// [Filters.Senders] allowlist for exact sender matching.
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//
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// [RFC 3501 §6.4.4]:
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// https://datatracker.ietf.org/doc/html/rfc3501#section-6.4.4
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package filter
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import "strings"
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// Filters holds message filtering configuration for IMAP searches
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// and sender verification.
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type Filters struct {
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// Body contains keywords that must appear in the message body.
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Body []string `yaml:"body"`
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// From filters messages by the From header field.
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From string `yaml:"from"`
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// Senders is an allowlist of email addresses permitted to receive
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// replies. If empty, all senders are allowed.
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Senders []string `yaml:"allowed_senders"`
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// Subject filters messages by the Subject header field.
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Subject string `yaml:"subject"`
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// To filters messages by the To header field.
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To string `yaml:"to"`
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}
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// MatchSender checks if the sender is in the allowed list.
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// Returns true if the allowlist is empty (allow all) or if the sender matches.
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// Comparison is case-insensitive and ignores leading/trailing whitespace.
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func (f *Filters) MatchSender(sender string) bool {
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if len(f.Senders) == 0 {
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return true
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}
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sender = strings.ToLower(strings.TrimSpace(sender))
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for _, allowed := range f.Senders {
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if strings.ToLower(strings.TrimSpace(allowed)) == sender {
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return true
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}
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}
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return false
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}
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