fix(sender/email): don't log email body, log size instead#285
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The verify provider sends one-shot magic-link tokens by email; the
Email sender's debug log dumped the full body verbatim:
[DEBUG] send "Confirmation token: <jwt>" to victim@example.com
Anyone with log access (centralized logging, crash bundles, support
tools, mail-gateway-adjacent observability) could redeem that token
within its TTL — independently of the legitimate recipient. The
verify-replay PR (#281) limits reuse to one consumption, but the
log-reader can still race the user for that one consumption.
Log only the recipient and the body length:
[DEBUG] send 142-byte message to victim@example.com
Same fix in v1 (provider/sender/email.go:84) and v2
(v2/provider/sender/email.go:84), single PR.
Test: TestEmail_SendDoesNotLogBody captures logger output, sends a
known-secret body to a non-existent SMTP host, and asserts the body
substring is absent while the recipient is present. Added in both
modules.
Coverage Report for CI Build 25572603805Coverage increased (+0.4%) to 84.66%Details
Uncovered ChangesNo uncovered changes found. Coverage RegressionsNo coverage regressions found. Coverage Stats
💛 - Coveralls |
umputun
approved these changes
May 8, 2026
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umputun
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lgtm.
one small nit: the new test uses func(format string, args ...interface{}) for the capturing logger, but #283 (just merged) modernized all existing interface{} to any across the codebase. Worth swapping the new test's signature to args ...any here too, otherwise it's a tiny regression on the modernization. Not blocking.
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Summary
The verify provider sends one-shot magic-link tokens via email. The Email sender's debug log dumped the full body verbatim:
Anyone with log access (centralized logging, crash bundles, support tools, mail-gateway observability) could redeem that token within its TTL — independently of the legitimate recipient. PR #281 (verify replay) limits reuse to one consumption, but the log reader can still race the user for that one consumption. This PR closes the leak at the source.
Change
Log the recipient and body length only:
Same redaction in v1 (
provider/sender/email.go:84) and v2 (v2/provider/sender/email.go:84), single PR.Test
TestEmail_SendDoesNotLogBodycaptures logger output, sends a known-secret body to a non-existent SMTP host (Send fails fast — that's fine, we only assert on the log line), and verifies:Added in both modules. Full
go test -race ./...green;golangci-lint run --new-from-rev=master0 issues.