Supported on Linux; FreeBSD needs a `setkey(8)` SAD entry

RFC 2385 - Protection of BGP Sessions via the TCP MD5 Signature Option

Every requirement this repository extracted from RFC 2385, the tests bound to it, and what a reader has verified about them. This summary is enrolled and gated by ./le rfc check.

Overview

Positive

what Ze has

Tested both ways66.7%6 of 9 binding obligations

a positive test proves Ze does what the requirement demands and a negative one proves it refuses what the requirement forbids

One polarity plus reason33.3%3 of 9 binding obligations

the requirement admits no counter-case, so one polarity plus a recorded reason is the whole proof available for it

One polarity, unexcused0.0%0 of 9 binding obligations

one direction is tested, the other is neither tested nor excused, and nothing states which

No test at all0.0%0 of 9 binding obligations

no test carries the requirement id, whether or not a gap states why

Proven by a recorded break100.0%15 of 15 tagged units

a red was observed once under a recorded procedure, and the unit, the claim and the producer it rested on still hash to what was recorded. The break is not re-run. A test pair is not a proof until one has been observed

Neutral

measures that are neither good news nor bad

Gated MUSTs9of 10 this summary declares

MUST-level requirements the gate HOLDS. A population, not a result: the shares beside it are what says how Ze stands

Out of scope0of 9 gated MUSTs

a {not-applicable} annotation says the obligation does not bind Ze. Scope, not coverage: it is in no share below

The 4 shares marked as a part above are the whole of the 9 obligations that bind Ze: they add to 100%. Proven by a recorded break is a share of TAGGED UNITS, a different population, so it is not one of them.

How to read the colors

A color names what the measure MEANS, not how well Ze scores on it. Green is a good outcome at any value, red is a bad one, and neither a population nor a scope count is an outcome, so both take no color. The number under the label is what says how far Ze has got.

Card	Tone here	Why that color
Gated MUSTs	neutral	no color: a population is a scale, and a larger one is neither good news nor bad. It is the accounting total
Out of scope	neutral	no color: an obligation that never bound Ze is neither an achievement nor a failure, and counting it either way would be a claim
Tested both ways	ok	green at every value: a test pair is the outcome this gate exists to produce, and the share under the label is what says how far Ze has got
One polarity plus reason	ok	green at every value: where no counter-case exists, one polarity IS the complete answer, and a recorded reason is what the gate demands beside it
One polarity, unexcused	ok	green at zero, RED above it: half a proof with no reason for the other half
No test at all	ok	green at zero, RED above it: a binding obligation nothing exercises is a claim with nothing behind it, whether or not a reason is stated
Proven by a recorded break	ok	green at every value: an observed break is the outcome the discrimination gate exists to produce. The denominator is TAGGED UNITS, not obligations, so this share is not one of the parts above
Audit verdicts	warn	RED on the first weak, wrong or unimplemented verdict, amber while a verdict is no longer current or a gated MUST is unjudged, green when every one is judged sound and current

At a glance

Field	Value
Public status	Supported on Linux; FreeBSD needs a `setkey(8)` SAD entry
Enrolment	Enrolled
Requirements	10
Gated MUST-level	9
Obligations that bind Ze	9
Not applicable, so out of scope	0
Declared gaps	0
Gated with no test	0
Nightly-only evidence	0
Test tags	15
Tagged units	15
Recorded audit verdicts	0
Discrimination records	15
Summary	`rfc/short/rfc2385.md`
Requirement shard	`rfc/requirements/rfc2385.md`
RFC text	`rfc/full/rfc2385.txt`

Enrolment

Enrolled: Protection of BGP Sessions via the TCP MD5 Signature Option: nine gated requirements, every one written in lowercase by a document that predates RFC 2119, so the extraction sign-off derives register 'prose' (rfc/extraction/rfc2385.json, 8 sites, 1 excluded). Ze computes no digest: it installs the operator's key with TCP_MD5SIG and the kernel signs and validates every segment, which is the whole-stack ruling in ai/rules/rfc-compliance.md. The proof runs at the boundary ze owns and reads what the stack answers on loopback (internal/core/network/md5_rfc2385_linux_test.go): one key installed on both sockets carries a 256 KiB payload (RFC2385-2.0-1, -2.0-2, -2.0-6, -3.0-1, -4.3-1 and -4.3-2 positive, RFC2385-2.0-3 negative); a mismatched key is dropped with no answer at all, so the dial times out instead of being refused or reset (RFC2385-2.0-2, -2.0-6 and -3.0-1 negative, RFC2385-2.0-3 positive); and a key held by only one end carries no session (RFC2385-2.0-1 negative). The application-control rows are proven over the config path (internal/component/bgp/reactor/rfc2385_test.go): a peer carrying md5 { password } gets that key on the dialer and in the listener's key set (RFC2385-2.0-5 positive), a peer without one gets none on either (RFC2385-2.0-5 negative), and a failed connection attempt leaves the key in place (RFC2385-2.0-4 positive). Three rows are single-polarity positive because ze holds no rejecting branch for them: RFC2385-2.0-4, and the two section 4.3 rows, whose MSS and option list are assembled by the kernel. RFC2385-4.5-1 is SHOULD-level and met exactly at its floor: setTCPMD5Sig refuses a key above 80 octets (internal/core/network/md5_linux.go), which is Linux's TCP_MD5SIG_MAXKEYLEN. Enrolled 2026-09-01.

What the public ledger says

Status: Supported on Linux; FreeBSD needs a `setkey(8)` SAD entry

What the ledger says is covered

Per-peer TCP MD5 through connection { md5 { password; ip; } }. parsePeer (internal/component/bgp/reactor/config.go) reads the key, NewSession puts it on the dialing socket and md5PeersForListener puts it in the listening socket's key set (internal/component/bgp/reactor/session.go, reactor.go), and setTCPMD5Sig installs it with TCP_MD5SIG before connect and before bind (internal/core/network/md5_linux.go), so the kernel signs and validates every segment of the peering. Ze computes no digest of its own
conformance is judged on what the whole stack produces, and every requirement row is proven at the boundary ze owns. The nine gated rows of rfc/short/rfc2385.md each carry both polarities or a single-polarity annotation: a loopback session under one shared key carries 256 KiB, a mismatched key is dropped with no answer at all, and a key held by one end only carries no session (internal/core/network/md5_rfc2385_linux_test.go). An FRR peer configured with the same password establishes with ze in the nightly interop lab, where the scenario's assertion is FRR's own view of the session (test/interop/scenarios/bgp-md5-auth-frr, scenarioOperations in internal/le/interoplab/bgp/checkers.go). The key is capped at 80 octets, which is the floor Section 4.5 recommends and Linux's own TCP_MD5SIG_MAXKEYLEN.

What the ledger says remains

No conformance gap is tracked.

One platform limit: on FreeBSD setTCPMD5Sig (internal/core/network/md5_freebsd.go) enables the socket flag only and takes the key from the Security Association Database, so a configured password installs nothing there until setkey(8) carries it (plan/journal/silent-fall-through.md, 2026-09-01). macOS and every other platform refuse the socket option, so the connection fails rather than falling back to an unsigned session.

Coverage

Bucket	Count	What it counts
Positive and negative tests	6	one part of the gated population
Annotated instead of tested	3	one part of the gated population
One polarity only	0	one part of the gated population
No test and no annotation	0	one part of the gated population
Evidence that runs nightly only	0	an overlay: each of these is also counted by the part it falls in
Gated MUST-level requirements	9	every gated MUST falls in exactly one bucket above

Positive and negative tests (6): RFC2385-2.0-1, RFC2385-2.0-2, RFC2385-2.0-3, RFC2385-2.0-5, RFC2385-2.0-6, RFC2385-3.0-1

Annotated instead of tested (3): RFC2385-2.0-4, RFC2385-4.3-1, RFC2385-4.3-2

Requirements

Requirement	Level	Section	Tests
`RFC2385-2.0-1`	The key must be known by both ends of the connection, so the same configured key is installed for the peer on the outbound socket and on the listening socket (§2.0)
	MUST	2.0 - Proposal	positive`unit/verifyTestRFC2385MatchingKeysCarryASignedSession` negative`unit/verifyTestRFC2385KeyOnOneEndOnlyCarriesNoSession`
`RFC2385-2.0-2`	Upon receiving a signed segment, the receiver must validate it by calculating its own digest from the same data using its own key and comparing the two digests (§2.0)
	MUST	2.0 - Proposal	positive`unit/verifyTestRFC2385MatchingKeysCarryASignedSession` negative`unit/verifyTestRFC2385MismatchedKeyIsDroppedWithNoResponse`
`RFC2385-2.0-3`	A failing comparison must result in the segment being dropped, and must not produce any response back to the sender (§2.0)
	MUST	2.0 - Proposal	positive`unit/verifyTestRFC2385MismatchedKeyIsDroppedWithNoResponse` negative`unit/verifyTestRFC2385MatchingKeysCarryASignedSession`
`RFC2385-2.0-4`	The absence of the option in the SYN,ACK segment must not cause the sender to disable its sending of signatures (§2.0)
	MUST NOT	2.0 - Proposal	positive`unit/verifyTestRFC2385FailedConnectDoesNotDisableSigning` negative`no test`no negative test {single-polarity}: ze holds no code path that stops signing: the key is installed from the peer's settings on every dial attempt and is never cleared by anything the remote host does or fails to do, so there is no rejecting branch a negative test could reach
`RFC2385-2.0-5`	The sending of signatures must be under the complete control of the application, not at the mercy of the remote host not understanding the option (§2.0)
	MUST	2.0 - Proposal	positive`unit/verifyTestRFC2385ConfiguredKeyReachesBothSockets` negative`unit/verifyTestRFC2385NoKeyWithoutConfiguration`
`RFC2385-2.0-6`	Every segment sent on a protected connection carries the 16-byte MD5 digest of the TCP pseudo-header, the TCP header with a zero checksum, the segment data and the key, in that order (§2.0)
	MUST	2.0 - Proposal	positive`unit/verifyTestRFC2385MatchingKeysCarryASignedSession` negative`unit/verifyTestRFC2385MismatchedKeyIsDroppedWithNoResponse`
`RFC2385-3.0-1`	The option is Kind 19, Length 18, carrying a 16-byte digest, and it appears in every segment of the connection (§3.0)
	MUST	3.0 - Syntax	positive`unit/verifyTestRFC2385MatchingKeysCarryASignedSession` negative`unit/verifyTestRFC2385MismatchedKeyIsDroppedWithNoResponse`
`RFC2385-4.3-1`	The size of the MD5 option must be factored into the MSS offered to the other side during connection negotiation (§4.3)
	MUST	4.3 - TCP Header Size	positive`unit/verifyTestRFC2385MatchingKeysCarryASignedSession` negative`no test`no negative test {single-polarity}: the MSS is chosen by the kernel that signs the segments, and ze holds no code that lowers, rejects or recomputes an MSS, so there is no rejecting branch a negative test could reach
`RFC2385-4.3-2`	The total size of the TCP header plus its options must be less than or equal to 60 bytes, leaving 40 bytes for options (§4.3)
	MUST	4.3 - TCP Header Size	positive`unit/verifyTestRFC2385MatchingKeysCarryASignedSession` negative`no test`no negative test {single-polarity}: the option list is assembled by the kernel and ze contributes no TCP option of its own, so there is no rejecting branch a negative test could reach
`RFC2385-4.5-1`	It is strongly recommended that an implementation support at minimum a key composed of a string of printable ASCII of 80 bytes or less (§4.5)
	SHOULD	4.5 - Key configuration	positive`no test`no positive test negative`no test`no negative test

Gaps and untested MUSTs

RFC 2385 declares no gap, and every gated MUST it carries has a test bound to it.

Proof state

A tagged unit reads unproven where no discrimination record exists for it: nothing in this tree has been observed to break it, so the claim its tag makes is unproven.

`RFC2385-2.0-1`

The key must be known by both ends of the connection, so the same configured key is installed for the peer on the outbound socket and on the listening socket (§2.0)