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FA-27091 / HTTP ranges / Open access

A bounded Content-Range upload endpoint validates chunk admission: range uploads do not accept retrieval or unframed append methods · case 01

A bounded Content-Range upload endpoint validates chunk admission: range uploads do not accept retrieval or unframed append methods.

Verified by executionVariant 1 · 11 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

The ranged-upload-admission-method-gate decision uses cells=dict(x['cells']) r=x['request'] if False: return ['method',sorted(cells.items())] if r['session']!=x['session']: return ['session',sorted(cells.items())] if r['generation']!=x['generation']: return ['generation',sorted(cells.items())] if r['total']!=x['total']: return ['total',sorted(cells.items())] if r['total']>x['quota']: return ['quota',sorted(cells.items())] if r['start']<0 or r['stop']<r['start'] or r['stop']>r['total']: return ['bounds',sorted(cells.items())] if len(r['body'])!=r['stop']-r['start']: return ['length',sorted(cells.items())] if any(i in cells and cells[i]!=c for i,c in enumerate(r['body'],r['start'])): return ['conflict',sorted(cells.items())] for i,c in enumerate(r['body'],r['start']): cells[i]=c complete=set(cells)==set(range(x['total'])) return ['complete' if complete else 'partial',sorted(cells.items())].

VERIFIED REPAIR

Apply the bounded decision exactly: cells=dict(x['cells']) r=x['request'] if r['method']!='PUT': return ['method',sorted(cells.items())] if r['session']!=x['session']: return ['session',sorted(cells.items())] if r['generation']!=x['generation']: return ['generation',sorted(cells.items())] if r['total']!=x['total']: return ['total',sorted(cells.items())] if r['total']>x['quota']: return ['quota',sorted(cells.items())] if r['start']<0 or r['stop']<r['start'] or r['stop']>r['total']: return ['bounds',sorted(cells.items())] if len(r['body'])!=r['stop']-r['start']: return ['length',sorted(cells.items())] if any(i in cells and cells[i]!=c for i,c in enumerate(r['body'],r['start'])): return ['conflict',sorted(cells.items())] for i,c in enumerate(r['body'],r['start']): cells[i]=c complete=set(cells)==set(range(x['total'])) return ['complete' if complete else 'partial',sorted(cells.items())]

Unsuccessful approach: The partial repair uses cells=dict(x['cells']) r=x['request'] if r['method'] not in ('PUT','POST'): return ['method',sorted(cells.items())] if r['session']!=x['session']: return ['session',sorted(cells.items())] if r['generation']!=x['generation']: return ['generation',sorted(cells.items())] if r['total']!=x['total']: return ['total',sorted(cells.items())] if r['total']>x['quota']: return ['quota',sorted(cells.items())] if r['start']<0 or r['stop']<r['start'] or r['stop']>r['total']: return ['bounds',sorted(cells.items())] if len(r['body'])!=r['stop']-r['start']: return ['length',sorted(cells.items())] if any(i in cells and cells[i]!=c for i,c in enumerate(r['body'],r['start'])): return ['conflict',sorted(cells.items())] for i,c in enumerate(r['body'],r['start']): cells[i]=c complete=set(cells)==set(range(x['total'])) return ['complete' if complete else 'partial',sorted(cells.items())], which still violates the stated contract.

Case contract

This stipulated endpoint accepts PUT chunks against an upload session. Inputs include session ID, generation, declared complete length, [start,stop) byte span, ASCII body, and known committed cells. Return a disposition and updated cells; malformed metadata never mutates stored bytes. Exact duplicate chunks are idempotent, contradicting overlap is conflict, and quota concerns the complete representation rather than chunk size.

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(x):
    cells=dict(x['cells'])
    r=x['request']
    if False: return ['method',sorted(cells.items())]
    if r['session']!=x['session']: return ['session',sorted(cells.items())]
    if r['generation']!=x['generation']: return ['generation',sorted(cells.items())]
    if r['total']!=x['total']: return ['total',sorted(cells.items())]
    if r['total']>x['quota']: return ['quota',sorted(cells.items())]
    if r['start']<0 or r['stop']<r['start'] or r['stop']>r['total']: return ['bounds',sorted(cells.items())]
    if len(r['body'])!=r['stop']-r['start']: return ['length',sorted(cells.items())]
    if any(i in cells and cells[i]!=c for i,c in enumerate(r['body'],r['start'])): return ['conflict',sorted(cells.items())]
    for i,c in enumerate(r['body'],r['start']): cells[i]=c
    complete=set(cells)==set(range(x['total']))
    return ['complete' if complete else 'partial',sorted(cells.items())]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('method-gate fixture 0', json.loads(json.dumps(solve({'session':'s','generation':2,'total':3,'quota':5,'cells':[[0,'a']],'request':{'method':'PUT','session':'s','generation':2,'total':3,'start':1,'stop':3,'body':'bc'}}))), json.loads(json.dumps(['complete',[[0,'a'],[1,'b'],[2,'c']]])))
check('method-gate fixture 1', json.loads(json.dumps(solve({'session':'s','generation':2,'total':3,'quota':5,'cells':[[0,'a']],'request':{'method':'POST','session':'s','generation':2,'total':3,'start':1,'stop':2,'body':'b'}}))), json.loads(json.dumps(['method',[[0,'a']]])))
check('method-gate fixture 2', json.loads(json.dumps(solve({'session':'s','generation':2,'total':3,'quota':5,'cells':[],'request':{'method':'PUT','session':'other','generation':2,'total':3,'start':0,'stop':1,'body':'a'}}))), json.loads(json.dumps(['session',[]])))
check('method-gate fixture 3', json.loads(json.dumps(solve({'session':'s','generation':2,'total':3,'quota':5,'cells':[],'request':{'method':'PUT','session':'s','generation':3,'total':3,'start':0,'stop':1,'body':'a'}}))), json.loads(json.dumps(['generation',[]])))
check('method-gate fixture 4', json.loads(json.dumps(solve({'session':'s','generation':2,'total':3,'quota':5,'cells':[],'request':{'method':'PUT','session':'s','generation':2,'total':4,'start':0,'stop':1,'body':'a'}}))), json.loads(json.dumps(['total',[]])))
check('method-gate fixture 5', json.loads(json.dumps(solve({'session':'s','generation':2,'total':3,'quota':2,'cells':[],'request':{'method':'PUT','session':'s','generation':2,'total':3,'start':0,'stop':1,'body':'a'}}))), json.loads(json.dumps(['quota',[]])))
check('method-gate fixture 6', json.loads(json.dumps(solve({'session':'s','generation':2,'total':3,'quota':5,'cells':[],'request':{'method':'PUT','session':'s','generation':2,'total':3,'start':-1,'stop':0,'body':'a'}}))), json.loads(json.dumps(['bounds',[]])))
check('method-gate fixture 7', json.loads(json.dumps(solve({'session':'s','generation':2,'total':3,'quota':5,'cells':[],'request':{'method':'PUT','session':'s','generation':2,'total':3,'start':1,'stop':3,'body':'b'}}))), json.loads(json.dumps(['length',[]])))
check('method-gate fixture 8', json.loads(json.dumps(solve({'session':'s','generation':2,'total':3,'quota':5,'cells':[[0,'a']],'request':{'method':'PUT','session':'s','generation':2,'total':3,'start':0,'stop':1,'body':'x'}}))), json.loads(json.dumps(['conflict',[[0,'a']]])))
check('method-gate fixture 9', json.loads(json.dumps(solve({'session':'s','generation':2,'total':3,'quota':5,'cells':[[0,'a']],'request':{'method':'PUT','session':'s','generation':2,'total':3,'start':0,'stop':1,'body':'a'}}))), json.loads(json.dumps(['partial',[[0,'a']]])))
check('method-gate fixture 10', json.loads(json.dumps(solve({'session':'s','generation':2,'total':N,'quota':10,'cells':[],'request':{'method':'PUT','session':'s','generation':2,'total':N,'start':0,'stop':N,'body':"p"*N}}))), json.loads(json.dumps(['complete',[[i,"p"] for i in range(N)]])))
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 fixtureActualExpectedOutcome
method-gate fixture 0['complete', [[0, 'a'], [1, 'b'], [2, 'c']]]['complete', [[0, 'a'], [1, 'b'], [2, 'c']]]Passed
method-gate fixture 1['partial', [[0, 'a'], [1, 'b']]]['method', [[0, 'a']]]Failed
method-gate fixture 2['session', []]['session', []]Passed
method-gate fixture 3['generation', []]['generation', []]Passed
method-gate fixture 4['total', []]['total', []]Passed
method-gate fixture 5['quota', []]['quota', []]Passed
method-gate fixture 6['bounds', []]['bounds', []]Passed
method-gate fixture 7['length', []]['length', []]Passed
method-gate fixture 8['conflict', [[0, 'a']]]['conflict', [[0, 'a']]]Passed
method-gate fixture 9['partial', [[0, 'a']]]['partial', [[0, 'a']]]Passed
method-gate fixture 10['complete', [[0, 'p']]]['complete', [[0, 'p']]]Passed

SHA-256 / 2b844893cdcd28592807fcd4134990de7072bae01867a7d31d4b555bd55ceeef

2 / The unsuccessful fix

Exit 1
"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(x):
    cells=dict(x['cells'])
    r=x['request']
    if r['method'] not in ('PUT','POST'): return ['method',sorted(cells.items())]
    if r['session']!=x['session']: return ['session',sorted(cells.items())]
    if r['generation']!=x['generation']: return ['generation',sorted(cells.items())]
    if r['total']!=x['total']: return ['total',sorted(cells.items())]
    if r['total']>x['quota']: return ['quota',sorted(cells.items())]
    if r['start']<0 or r['stop']<r['start'] or r['stop']>r['total']: return ['bounds',sorted(cells.items())]
    if len(r['body'])!=r['stop']-r['start']: return ['length',sorted(cells.items())]
    if any(i in cells and cells[i]!=c for i,c in enumerate(r['body'],r['start'])): return ['conflict',sorted(cells.items())]
    for i,c in enumerate(r['body'],r['start']): cells[i]=c
    complete=set(cells)==set(range(x['total']))
    return ['complete' if complete else 'partial',sorted(cells.items())]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('method-gate fixture 0', json.loads(json.dumps(solve({'session':'s','generation':2,'total':3,'quota':5,'cells':[[0,'a']],'request':{'method':'PUT','session':'s','generation':2,'total':3,'start':1,'stop':3,'body':'bc'}}))), json.loads(json.dumps(['complete',[[0,'a'],[1,'b'],[2,'c']]])))
check('method-gate fixture 1', json.loads(json.dumps(solve({'session':'s','generation':2,'total':3,'quota':5,'cells':[[0,'a']],'request':{'method':'POST','session':'s','generation':2,'total':3,'start':1,'stop':2,'body':'b'}}))), json.loads(json.dumps(['method',[[0,'a']]])))
check('method-gate fixture 2', json.loads(json.dumps(solve({'session':'s','generation':2,'total':3,'quota':5,'cells':[],'request':{'method':'PUT','session':'other','generation':2,'total':3,'start':0,'stop':1,'body':'a'}}))), json.loads(json.dumps(['session',[]])))
check('method-gate fixture 3', json.loads(json.dumps(solve({'session':'s','generation':2,'total':3,'quota':5,'cells':[],'request':{'method':'PUT','session':'s','generation':3,'total':3,'start':0,'stop':1,'body':'a'}}))), json.loads(json.dumps(['generation',[]])))
check('method-gate fixture 4', json.loads(json.dumps(solve({'session':'s','generation':2,'total':3,'quota':5,'cells':[],'request':{'method':'PUT','session':'s','generation':2,'total':4,'start':0,'stop':1,'body':'a'}}))), json.loads(json.dumps(['total',[]])))
check('method-gate fixture 5', json.loads(json.dumps(solve({'session':'s','generation':2,'total':3,'quota':2,'cells':[],'request':{'method':'PUT','session':'s','generation':2,'total':3,'start':0,'stop':1,'body':'a'}}))), json.loads(json.dumps(['quota',[]])))
check('method-gate fixture 6', json.loads(json.dumps(solve({'session':'s','generation':2,'total':3,'quota':5,'cells':[],'request':{'method':'PUT','session':'s','generation':2,'total':3,'start':-1,'stop':0,'body':'a'}}))), json.loads(json.dumps(['bounds',[]])))
check('method-gate fixture 7', json.loads(json.dumps(solve({'session':'s','generation':2,'total':3,'quota':5,'cells':[],'request':{'method':'PUT','session':'s','generation':2,'total':3,'start':1,'stop':3,'body':'b'}}))), json.loads(json.dumps(['length',[]])))
check('method-gate fixture 8', json.loads(json.dumps(solve({'session':'s','generation':2,'total':3,'quota':5,'cells':[[0,'a']],'request':{'method':'PUT','session':'s','generation':2,'total':3,'start':0,'stop':1,'body':'x'}}))), json.loads(json.dumps(['conflict',[[0,'a']]])))
check('method-gate fixture 9', json.loads(json.dumps(solve({'session':'s','generation':2,'total':3,'quota':5,'cells':[[0,'a']],'request':{'method':'PUT','session':'s','generation':2,'total':3,'start':0,'stop':1,'body':'a'}}))), json.loads(json.dumps(['partial',[[0,'a']]])))
check('method-gate fixture 10', json.loads(json.dumps(solve({'session':'s','generation':2,'total':N,'quota':10,'cells':[],'request':{'method':'PUT','session':'s','generation':2,'total':N,'start':0,'stop':N,'body':"p"*N}}))), json.loads(json.dumps(['complete',[[i,"p"] for i in range(N)]])))
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 fixtureActualExpectedOutcome
method-gate fixture 0['complete', [[0, 'a'], [1, 'b'], [2, 'c']]]['complete', [[0, 'a'], [1, 'b'], [2, 'c']]]Passed
method-gate fixture 1['partial', [[0, 'a'], [1, 'b']]]['method', [[0, 'a']]]Failed
method-gate fixture 2['session', []]['session', []]Passed
method-gate fixture 3['generation', []]['generation', []]Passed
method-gate fixture 4['total', []]['total', []]Passed
method-gate fixture 5['quota', []]['quota', []]Passed
method-gate fixture 6['bounds', []]['bounds', []]Passed
method-gate fixture 7['length', []]['length', []]Passed
method-gate fixture 8['conflict', [[0, 'a']]]['conflict', [[0, 'a']]]Passed
method-gate fixture 9['partial', [[0, 'a']]]['partial', [[0, 'a']]]Passed
method-gate fixture 10['complete', [[0, 'p']]]['complete', [[0, 'p']]]Passed

SHA-256 / c7b4c5c6164259e49cc865519778bbd367074f57291b92144393fa782153805f

3 / The verified repair

Exit 0
"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(x):
    cells=dict(x['cells'])
    r=x['request']
    if r['method']!='PUT': return ['method',sorted(cells.items())]
    if r['session']!=x['session']: return ['session',sorted(cells.items())]
    if r['generation']!=x['generation']: return ['generation',sorted(cells.items())]
    if r['total']!=x['total']: return ['total',sorted(cells.items())]
    if r['total']>x['quota']: return ['quota',sorted(cells.items())]
    if r['start']<0 or r['stop']<r['start'] or r['stop']>r['total']: return ['bounds',sorted(cells.items())]
    if len(r['body'])!=r['stop']-r['start']: return ['length',sorted(cells.items())]
    if any(i in cells and cells[i]!=c for i,c in enumerate(r['body'],r['start'])): return ['conflict',sorted(cells.items())]
    for i,c in enumerate(r['body'],r['start']): cells[i]=c
    complete=set(cells)==set(range(x['total']))
    return ['complete' if complete else 'partial',sorted(cells.items())]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('method-gate fixture 0', json.loads(json.dumps(solve({'session':'s','generation':2,'total':3,'quota':5,'cells':[[0,'a']],'request':{'method':'PUT','session':'s','generation':2,'total':3,'start':1,'stop':3,'body':'bc'}}))), json.loads(json.dumps(['complete',[[0,'a'],[1,'b'],[2,'c']]])))
check('method-gate fixture 1', json.loads(json.dumps(solve({'session':'s','generation':2,'total':3,'quota':5,'cells':[[0,'a']],'request':{'method':'POST','session':'s','generation':2,'total':3,'start':1,'stop':2,'body':'b'}}))), json.loads(json.dumps(['method',[[0,'a']]])))
check('method-gate fixture 2', json.loads(json.dumps(solve({'session':'s','generation':2,'total':3,'quota':5,'cells':[],'request':{'method':'PUT','session':'other','generation':2,'total':3,'start':0,'stop':1,'body':'a'}}))), json.loads(json.dumps(['session',[]])))
check('method-gate fixture 3', json.loads(json.dumps(solve({'session':'s','generation':2,'total':3,'quota':5,'cells':[],'request':{'method':'PUT','session':'s','generation':3,'total':3,'start':0,'stop':1,'body':'a'}}))), json.loads(json.dumps(['generation',[]])))
check('method-gate fixture 4', json.loads(json.dumps(solve({'session':'s','generation':2,'total':3,'quota':5,'cells':[],'request':{'method':'PUT','session':'s','generation':2,'total':4,'start':0,'stop':1,'body':'a'}}))), json.loads(json.dumps(['total',[]])))
check('method-gate fixture 5', json.loads(json.dumps(solve({'session':'s','generation':2,'total':3,'quota':2,'cells':[],'request':{'method':'PUT','session':'s','generation':2,'total':3,'start':0,'stop':1,'body':'a'}}))), json.loads(json.dumps(['quota',[]])))
check('method-gate fixture 6', json.loads(json.dumps(solve({'session':'s','generation':2,'total':3,'quota':5,'cells':[],'request':{'method':'PUT','session':'s','generation':2,'total':3,'start':-1,'stop':0,'body':'a'}}))), json.loads(json.dumps(['bounds',[]])))
check('method-gate fixture 7', json.loads(json.dumps(solve({'session':'s','generation':2,'total':3,'quota':5,'cells':[],'request':{'method':'PUT','session':'s','generation':2,'total':3,'start':1,'stop':3,'body':'b'}}))), json.loads(json.dumps(['length',[]])))
check('method-gate fixture 8', json.loads(json.dumps(solve({'session':'s','generation':2,'total':3,'quota':5,'cells':[[0,'a']],'request':{'method':'PUT','session':'s','generation':2,'total':3,'start':0,'stop':1,'body':'x'}}))), json.loads(json.dumps(['conflict',[[0,'a']]])))
check('method-gate fixture 9', json.loads(json.dumps(solve({'session':'s','generation':2,'total':3,'quota':5,'cells':[[0,'a']],'request':{'method':'PUT','session':'s','generation':2,'total':3,'start':0,'stop':1,'body':'a'}}))), json.loads(json.dumps(['partial',[[0,'a']]])))
check('method-gate fixture 10', json.loads(json.dumps(solve({'session':'s','generation':2,'total':N,'quota':10,'cells':[],'request':{'method':'PUT','session':'s','generation':2,'total':N,'start':0,'stop':N,'body':"p"*N}}))), json.loads(json.dumps(['complete',[[i,"p"] for i in range(N)]])))
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 fixtureActualExpectedOutcome
method-gate fixture 0['complete', [[0, 'a'], [1, 'b'], [2, 'c']]]['complete', [[0, 'a'], [1, 'b'], [2, 'c']]]Passed
method-gate fixture 1['method', [[0, 'a']]]['method', [[0, 'a']]]Passed
method-gate fixture 2['session', []]['session', []]Passed
method-gate fixture 3['generation', []]['generation', []]Passed
method-gate fixture 4['total', []]['total', []]Passed
method-gate fixture 5['quota', []]['quota', []]Passed
method-gate fixture 6['bounds', []]['bounds', []]Passed
method-gate fixture 7['length', []]['length', []]Passed
method-gate fixture 8['conflict', [[0, 'a']]]['conflict', [[0, 'a']]]Passed
method-gate fixture 9['partial', [[0, 'a']]]['partial', [[0, 'a']]]Passed
method-gate fixture 10['complete', [[0, 'p']]]['complete', [[0, 'p']]]Passed

SHA-256 / 6248e57917c0bd442ce97978860ec60fca644b9c2acda90e4810f7e7df4d611a

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 2026-09-29T14:41:22.055640+00:00.

Case digest / 3fd86cbc3a3e7848f77040f63b9ced604a1f4209dbe719de65d454ccda2c501b