mixandClaude Opus 5.5
4dd46ea355
Security review of the DMARC report path (Fable, 2026-10-11), which ran for the first time in 2.0.0. No Critical or High finding. Fixed: - Medium: a report was bounded only as 8 MiB of XML - some 160 000 records or one name of megabytes, all of it rows and table cells. At most 5 000 records (more is ErrRejected, dropped), text fields cut to 255 bytes on a character boundary, a record's count capped. - Medium: the cap of 500 reports was for the whole server, so a stranger filing under one domain's address evicted every other domain's reports. PruneDMARCReports counts per domain. - Low: the pipe service ran up to default_process_limit (100) commands at once against the panel's database; maxproc is 1. - Low: the reason logged for a dropped message carried the sender's bytes (header line, zip entry name) as they came; cut to 200 bytes and reduced to printable ASCII, zip entry names quoted. - Low: SELFPOST_DATA_DIR / SELFPOST_DB_PATH with whitespace or "$" would reach the command through export_environment as another path; refused at start when DMARC ingest is on. Left as they are, told to the owner: the parse-failure count is a lifetime figure shown under "This week"; a report larger than the command reads is dropped as unreadable; nested multipart is not searched. The hub's Retention line follows the design commit before this one. security.md: the review, and the accepted-risk entry says what a stranger can and cannot do now. The roadmap no longer calls the review pending. go vet ./cmd/... ./internal/dmarc/ ./internal/store/: ok go test ./cmd/... ./internal/dmarc/ ./internal/store/ ./internal/web/...: ok make e2e on the test server (with the port-25 scenarios of the next commit): ok Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
94 lines
2.8 KiB
Go
94 lines
2.8 KiB
Go
package main
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import (
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"errors"
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"fmt"
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"io"
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"log"
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"os"
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"path/filepath"
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"strings"
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"time"
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"github.com/mixeme/selfpost/internal/dmarc"
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"github.com/mixeme/selfpost/internal/store"
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)
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const maxIngestStdin = 10 << 20 // 10 MiB
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func runDMARCIngestMode() error {
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cfg := loadConfig()
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if !cfg.dmarcEnabled {
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return fmt.Errorf("dmarc ingest invoked but DMARC_REPORTS_ENABLE is not true")
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}
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st, err := store.Open(cfg.dbPath)
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if err != nil {
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return err
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}
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defer st.Close()
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recipient := ingestRecipient(os.Args[1:])
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if err := dmarc.IngestMessage(st, io.LimitReader(os.Stdin, maxIngestStdin), recipient, time.Now().UTC()); err != nil {
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if !errors.Is(err, dmarc.ErrRejected) {
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return err
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}
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// Not a report this relay keeps. It is dropped: deferring would have
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// Postfix try it again for days, and a bounce would go to an envelope
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// sender anyone can write - the report addresses are public.
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if incrErr := st.IncrDMARCParseFailures(); incrErr != nil {
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log.Printf("dmarc ingest: record failure: %v", incrErr)
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}
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logRejected(err)
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}
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return nil
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}
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// logRejected leaves the reason in the mail log. Postfix puts the start of
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// what a delivery command wrote - about a hundred bytes - into its own line
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// for the message ("status=sent (delivered via dmarc-ingest service (...))"),
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// so the reason goes out first and bare: no prefix, no date, no recipient,
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// all of which that line already has. postlog is no use here: pipe(8) starts
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// the command without the group that may write to Postfix's log socket.
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func logRejected(reason error) {
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fmt.Fprintln(os.Stderr, "dropped: "+logSafe(strings.TrimPrefix(reason.Error(), dmarc.ErrRejected.Error()+": ")))
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}
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// logSafe makes a reason fit for a log line. Parts of it are the sender's own
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// bytes - a header line, a file name inside an archive, a piece of XML - so it
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// is cut short and anything that is not printable ASCII becomes "?", whatever
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// Postfix would have done with it.
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func logSafe(s string) string {
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const max = 200
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if len(s) > max {
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s = s[:max]
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}
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return strings.Map(func(r rune) rune {
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if r < 0x20 || r > 0x7e {
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return '?'
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}
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return r
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}, s)
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}
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// ingestRecipient is the report address the message was delivered to. Postfix's
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// pipe(8) hands it over as an argument (${recipient} in the service's argv,
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// build/postfix-config.sh) - it sets no RECIPIENT variable, that is local(8).
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// Without it the check that a report came to its own domain's address is
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// skipped.
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func ingestRecipient(args []string) string {
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for _, a := range args {
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if a == "-dmarc-ingest" {
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continue
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}
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return strings.ToLower(strings.TrimSpace(a))
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}
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return ""
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}
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func isDMARCIngestInvocation() bool {
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if len(os.Args) > 1 && os.Args[1] == "-dmarc-ingest" {
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return true
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}
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return filepath.Base(os.Args[0]) == "dmarc-ingest"
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}
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