FA-26806 / HTTP ranges / Open access

Part headers end at the first double CRLF · case 01

Part headers end at the first double CRLF.

Verified by executionVariant 1 · 6 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

The multipart-client-header-terminator decision uses p=data.rfind("\r\n\r\n") return [data[:p],data[p+4:]] if p>=0 else None.

VERIFIED REPAIR

Apply the bounded decision exactly: p=data.find("\r\n\r\n") return [data[:p],data[p+4:]] if p>=0 else None

Unsuccessful approach: The partial repair uses p=data.find("\r\n") return [data[:p],data[p+2:]] if p>=0 else None, which still violates the stated contract.

Case contract

Split buffered part at the first CRLFCRLF into [header,body], or None if incomplete. Body may contain additional double CRLF sequences.

Why this case matters

Range responses combine representation identity, conditional requests, framing, and partial-object state.

1 / The failure

Exit 1

"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(data):
    p=data.rfind("\r\n\r\n")
    return [data[:p],data[p+4:]] if p>=0 else None
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('multipart-client-header-terminator fixture 0', solve("H\r\n\r\n"+"p"*N+"\r\n\r\nX"), ["H","p"*N+"\r\n\r\nX"])
check('multipart-client-header-terminator fixture 1', solve("H\r\nX"), None)
check('multipart-client-header-terminator fixture 2', solve("H\r\n\r\nP"), ["H","P"])
check('multipart-client-header-terminator fixture 3', solve("\r\n\r\n"), ["",""])
check('multipart-client-header-terminator fixture 4', solve(""), None)
check('multipart-client-header-terminator fixture 5', solve("A\r\nB\r\n\r\nP"), ["A\r\nB","P"])
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)

Boundary fixture	Actual	Expected	Outcome
multipart-client-header-terminator fixture 0	`['H\r\n\r\np', 'X']`	`['H', 'p\r\n\r\nX']`	Failed
multipart-client-header-terminator fixture 1	`None`	`None`	Passed
multipart-client-header-terminator fixture 2	`['H', 'P']`	`['H', 'P']`	Passed
multipart-client-header-terminator fixture 3	`['', '']`	`['', '']`	Passed
multipart-client-header-terminator fixture 4	`None`	`None`	Passed
multipart-client-header-terminator fixture 5	`['A\r\nB', 'P']`	`['A\r\nB', 'P']`	Passed

SHA-256 / 7cadbfd6b544dd2be21bf49ffcae306a49ca0d550044e95f6ddd95d735c697d1

2 / The unsuccessful fix

Exit 1

"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(data):
    p=data.find("\r\n")
    return [data[:p],data[p+2:]] if p>=0 else None
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('multipart-client-header-terminator fixture 0', solve("H\r\n\r\n"+"p"*N+"\r\n\r\nX"), ["H","p"*N+"\r\n\r\nX"])
check('multipart-client-header-terminator fixture 1', solve("H\r\nX"), None)
check('multipart-client-header-terminator fixture 2', solve("H\r\n\r\nP"), ["H","P"])
check('multipart-client-header-terminator fixture 3', solve("\r\n\r\n"), ["",""])
check('multipart-client-header-terminator fixture 4', solve(""), None)
check('multipart-client-header-terminator fixture 5', solve("A\r\nB\r\n\r\nP"), ["A\r\nB","P"])
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)

Boundary fixture	Actual	Expected	Outcome
multipart-client-header-terminator fixture 0	`['H', '\r\np\r\n\r\nX']`	`['H', 'p\r\n\r\nX']`	Failed
multipart-client-header-terminator fixture 1	`['H', 'X']`	`None`	Failed
multipart-client-header-terminator fixture 2	`['H', '\r\nP']`	`['H', 'P']`	Failed
multipart-client-header-terminator fixture 3	`['', '\r\n']`	`['', '']`	Failed
multipart-client-header-terminator fixture 4	`None`	`None`	Passed
multipart-client-header-terminator fixture 5	`['A', 'B\r\n\r\nP']`	`['A\r\nB', 'P']`	Failed

SHA-256 / 416db51a2d4f4cca5b382a14ae298ee6d4ce2743a3135e947ad2a2f1b993c44a

3 / The verified repair

Exit 0

"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(data):
    p=data.find("\r\n\r\n")
    return [data[:p],data[p+4:]] if p>=0 else None
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('multipart-client-header-terminator fixture 0', solve("H\r\n\r\n"+"p"*N+"\r\n\r\nX"), ["H","p"*N+"\r\n\r\nX"])
check('multipart-client-header-terminator fixture 1', solve("H\r\nX"), None)
check('multipart-client-header-terminator fixture 2', solve("H\r\n\r\nP"), ["H","P"])
check('multipart-client-header-terminator fixture 3', solve("\r\n\r\n"), ["",""])
check('multipart-client-header-terminator fixture 4', solve(""), None)
check('multipart-client-header-terminator fixture 5', solve("A\r\nB\r\n\r\nP"), ["A\r\nB","P"])
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)

Boundary fixture	Actual	Expected	Outcome
multipart-client-header-terminator fixture 0	`['H', 'p\r\n\r\nX']`	`['H', 'p\r\n\r\nX']`	Passed
multipart-client-header-terminator fixture 1	`None`	`None`	Passed
multipart-client-header-terminator fixture 2	`['H', 'P']`	`['H', 'P']`	Passed
multipart-client-header-terminator fixture 3	`['', '']`	`['', '']`	Passed
multipart-client-header-terminator fixture 4	`None`	`None`	Passed
multipart-client-header-terminator fixture 5	`['A\r\nB', 'P']`	`['A\r\nB', 'P']`	Passed

SHA-256 / 9c94f225a99d8d3d2af93f5f7d31cd1ca9e1e298704bd0a24718c5143da9f5a9

Verification & scope

Deterministic simplified range service, with stipulated local policies and already parsed trusted inputs; not a complete HTTP implementation. This reproducer isolates one failure mechanism. Results cover the supplied fixtures. Variants within a family share a test contract and should remain grouped when constructing evaluation splits. Related mechanisms with a shared evaluation_group must also remain together; these controlled models are not independent production incidents.

Observations recorded using Python 3.12.14 at 2026-09-29T14:41:19.344771+00:00.

Case digest / 1492f9fe179eab3cc3b4783189239b845dd75cc2c3608a65a8f9af493bfa0a8b