libopendkim: don't error on missing CRLF when l= body length tag is used#339
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thegushi merged 2 commits intoMay 25, 2026
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When a DKIM signature includes the l= body length tag, the MTA delivers only that many bytes of body and OpenDKIM returns SMFIS_SKIP. The truncated body may not end with CRLF, which is expected: RFC 6376 section 3.7 specifies that body canonicalization appends CRLF to a non-empty body that doesn't already end with one. Treating this as a syntax error was a false positive. When canon_remain != -1 (i.e. l= was used), always take the append-CRLF path in dkim_canon_closebody() rather than erroring. The error is still raised when no body length limit was in use, consistent with the original intent. Fixes trusteddomainproject#45
…fix t-test149 uses SIG2 which has l=340. After the fix in dkim-canon.c, missing CRLF is no longer a syntax error when a body length tag is present, so the first run no longer returns DKIM_STAT_SYNTAX. The regression test that confirms DKIM_STAT_SYNTAX is still raised without l= is covered by the new t-test207.
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Summary
When a DKIM signature includes
l=, the MTA delivers only that many body bytes and replies withSMFIS_SKIP. The truncated body may not end with CRLF - which is expected per RFC 6376 §3.7: both simple and relaxed canonicalization append a CRLF to any non-empty body that doesn't already end with one.The bug:
dkim_canon_closebody()returnedDKIM_STAT_SYNTAX("CRLF at end of body missing") whenever there was buffered content without a trailing CRLF, unlessDKIM_LIBFLAGS_FIXCRLFwas set. Withl=this was a false positive.Fix: when
canon_remain != -1(i.e.l=was present and set a body length limit), always take the append-CRLF path.canon_remainis set from thel=value during signature parsing and decrements to 0 after the body bytes are processed - it is never -1 whenl=is in use. The error path is preserved for signatures withoutl=, consistent with mskucherawy's comment in the original thread.Tests added:
t-test206: sign with explicit body length and body without CRLF; verify that both sign and verify succeedt-test207: regression - withoutl=, body without CRLF still raisesDKIM_STAT_SYNTAXFixes #45
Test plan
make checkpasses including t-test206 and t-test207