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FA-27116 / HTTP ranges / Open access

A bounded Content-Range upload endpoint validates chunk admission: negative upload coordinates cannot address the end of storage · case 01

A bounded Content-Range upload endpoint validates chunk admission: negative upload coordinates cannot address the end of storage.

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

ROOT CAUSE

The ranged-upload-admission-negative-range decision uses 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['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']!='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']<-1 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 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['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('negative-range 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('negative-range 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('negative-range 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('negative-range 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('negative-range 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('negative-range 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('negative-range 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('negative-range 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('negative-range 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('negative-range 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('negative-range 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
negative-range fixture 0['complete', [[0, 'a'], [1, 'b'], [2, 'c']]]['complete', [[0, 'a'], [1, 'b'], [2, 'c']]]Passed
negative-range fixture 1['method', [[0, 'a']]]['method', [[0, 'a']]]Passed
negative-range fixture 2['session', []]['session', []]Passed
negative-range fixture 3['generation', []]['generation', []]Passed
negative-range fixture 4['total', []]['total', []]Passed
negative-range fixture 5['quota', []]['quota', []]Passed
negative-range fixture 6['partial', [[-1, 'a']]]['bounds', []]Failed
negative-range fixture 7['length', []]['length', []]Passed
negative-range fixture 8['conflict', [[0, 'a']]]['conflict', [[0, 'a']]]Passed
negative-range fixture 9['partial', [[0, 'a']]]['partial', [[0, 'a']]]Passed
negative-range fixture 10['complete', [[0, 'p']]]['complete', [[0, 'p']]]Passed

SHA-256 / 318237847cb959c6496b44f83e5f654e721d5f13bb6ffaf515b494d35b2811f4

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']!='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']<-1 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('negative-range 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('negative-range 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('negative-range 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('negative-range 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('negative-range 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('negative-range 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('negative-range 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('negative-range 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('negative-range 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('negative-range 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('negative-range 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
negative-range fixture 0['complete', [[0, 'a'], [1, 'b'], [2, 'c']]]['complete', [[0, 'a'], [1, 'b'], [2, 'c']]]Passed
negative-range fixture 1['method', [[0, 'a']]]['method', [[0, 'a']]]Passed
negative-range fixture 2['session', []]['session', []]Passed
negative-range fixture 3['generation', []]['generation', []]Passed
negative-range fixture 4['total', []]['total', []]Passed
negative-range fixture 5['quota', []]['quota', []]Passed
negative-range fixture 6['partial', [[-1, 'a']]]['bounds', []]Failed
negative-range fixture 7['length', []]['length', []]Passed
negative-range fixture 8['conflict', [[0, 'a']]]['conflict', [[0, 'a']]]Passed
negative-range fixture 9['partial', [[0, 'a']]]['partial', [[0, 'a']]]Passed
negative-range fixture 10['complete', [[0, 'p']]]['complete', [[0, 'p']]]Passed

SHA-256 / 4fba6abb99fd7818e796836c4bdc9f40e6b3d03d6c408698d8636b66b3ec8f75

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('negative-range 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('negative-range 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('negative-range 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('negative-range 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('negative-range 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('negative-range 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('negative-range 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('negative-range 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('negative-range 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('negative-range 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('negative-range 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
negative-range fixture 0['complete', [[0, 'a'], [1, 'b'], [2, 'c']]]['complete', [[0, 'a'], [1, 'b'], [2, 'c']]]Passed
negative-range fixture 1['method', [[0, 'a']]]['method', [[0, 'a']]]Passed
negative-range fixture 2['session', []]['session', []]Passed
negative-range fixture 3['generation', []]['generation', []]Passed
negative-range fixture 4['total', []]['total', []]Passed
negative-range fixture 5['quota', []]['quota', []]Passed
negative-range fixture 6['bounds', []]['bounds', []]Passed
negative-range fixture 7['length', []]['length', []]Passed
negative-range fixture 8['conflict', [[0, 'a']]]['conflict', [[0, 'a']]]Passed
negative-range fixture 9['partial', [[0, 'a']]]['partial', [[0, 'a']]]Passed
negative-range fixture 10['complete', [[0, 'p']]]['complete', [[0, 'p']]]Passed

SHA-256 / e1e1ab5814e009bb1ba1ccd001d894f01e42e08064e6916e3b2f2c7d50363b08

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 2026-09-29T14:41:22.157880+00:00.

Case digest / ec9fb224e732c30499d68b00415ed51bee19eef5bd012bb55190722206d056fc