Point the scanner merge at /scanner/dast and skip non-JSON responses (#122) - #123
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…/scanner (SasanLabs#122) The other two apps already pointed at /scanner/dast. The Java one could not, because that endpoint did not exist until SasanLabs/VulnerableApp#725 landed as PR #733. It exists now, so facade no longer has to call the path that answers with a Deprecation header. With only this commit applied the merged payload is unchanged: 153 entries under VulnerableApp before and after, and the whole response byte for byte identical. The next commit in this branch does change it, by 69 bytes, deliberately.
VulnerableApp-php answers both scanner endpoints with HTTP 200, Content-Type text/html, and a body naming the path it was asked for, so the dast one reads "/VulnerableApp-php/scanner/dast is not available" and the sast one the same with sast. The merge only looked at the status, so that sentence was spliced into the aggregate as if it were a JSON value and the whole response stopped being JSON. Measured on the docker-compose.without_llm.yml stack: before the change /scanner/dast and /scanner/sast both failed to parse, after it they parse and carry 153 and 154 entries. /VulnerabilityDefinitions is byte for byte unchanged, since all three apps return JSON there.
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Included review availability: Your plan provides up to 1 included review per hour; 0 remain after this review. 📝 WalkthroughWalkthroughThe facade now validates aggregated response bodies as complete JSON objects or arrays. The DAST aggregation route now requests the base application's ChangesDAST aggregation
Estimated code review effort: 2 (Simple) | ~10 minutes Merge Risk: ⚪ Minimal · up to This localized change updates the scanner endpoint and ignores successful responses that are not valid JSON; no actionable merge-blocking risk remains after normal checks and review. 🚥 Pre-merge checks | ✅ 4 | ❌ 1❌ Failed checks (1 warning)
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In `@lua-modules/vulnerableapp_utility.lua`:
- Around line 3-13: Update carries_json to reject responses marked truncated,
decode response.body using OpenResty’s cjson.safe module, and return true only
when decoding succeeds with an object or array result; remove the
first-character heuristic while preserving the existing status, body, and
missing-response checks.
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lua-modules/vulnerableapp_utility.luanginx.conf
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The previous commit accepted a body whose first non-space character was
a brace or a bracket. That is enough to keep the php sentence out, but
not enough in general: a body of {error} passes it, and so does one that
starts as JSON and is cut off part way. Either would put the aggregate
back in the state this PR set out to fix.
carries_json now refuses a response the subrequest reported as
truncated, and decodes the body with OpenResty's bundled cjson.safe,
accepting it only when the result is an object or an array. The
automated review on this PR raised both points.
Two decisions worth stating. The decoded value is thrown away and the
merge still splices the raw bytes, so each app's own key order and
formatting reach the caller exactly as before. And a bare number or
string is refused even though it is valid JSON, because the aggregate
maps an app name to its findings; that also keeps the behaviour the
first-character check already had.
On the docker-compose.without_llm.yml stack the output does not move:
/scanner/dast, /scanner/sast and /VulnerabilityDefinitions are byte for
byte identical to the previous commit, and /VulnerabilityDefinitions is
still byte for byte identical to main. Nine cases were then driven
through merge_vulnerability_information directly, twice: a truncated
flag, a truncated body, {error}, a plain sentence, a bare number, a 404
and an empty object all behave as described, and the merged document
parses in every one of them, including the case where every app is
refused and the result is {}.
cjson.safe was checked in openresty/openresty:alpine, the image this
Dockerfile builds on, and decoding the 26 KB, 153-entry scanner response
there stays under 0.1 ms, measured at 0.06 to 0.08 ms across runs.
luacheck reports 0 warnings and 0 errors.
preetkaran20
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preetkaran20
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Lgtm, thanks a lot for the great PR @vianbas as always
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2 participants
Closes #122.
Two changes. The first is the one line this issue had left. The second is a defect I hit while checking the first, in the same two endpoints, and it corrects something I got wrong on the issue thread.
/scanner/dastnow captures the Java app at/scanner/dastThe other two apps already pointed there. The Java one could not, because that endpoint did not exist yet. It landed as SasanLabs/VulnerableApp#733, so facade no longer has to call the bare path that answers with a
Deprecationheader.The 153 entries under
VulnerableAppare the same objects before and after, and with only this commit applied the whole merged response is byte for byte identical tomain.The full response does change once the second commit is in, by 69 bytes, because the malformed fragment described below stops being appended. That is the point of the second commit rather than a side effect of this one.
The merge now skips a 200 response whose body is not JSON
VulnerableApp-phpanswers both scanner paths with HTTP 200,Content-Type: text/html, and a body naming the path it was asked for, so/VulnerableApp-php/scanner/dast is not availablefor one and thesastwording for the other. I read that as the endpoint not being implemented there, but the observation is the status, the type and the body.merge_vulnerability_informationonly looked at the status, so that sentence was concatenated in where a JSON array was expected:Both
/scanner/dastand/scanner/sasttherefore return something no JSON parser accepts, which would matter for the comparator proposed in SasanLabs/VulnerableApp#726, since that issue has facade as the thing it calls. That issue is still open and unimplemented, so nothing is broken by it today./VulnerabilityDefinitionsis not affected today, because all three apps implement it and return JSON, and its response parses before and after this change. The guard is in the shared function rather than in the scanner blocks so that the next app to answer 200 with a message does not reopen this.Correcting my earlier comment
In my comment above the scope table says, for degrading gracefully when an app is down, "present, responses whose status is not 200 are skipped". The reasoning in that second half is the incomplete part: skipping on status alone is not enough when an app answers 200 with something that is not JSON. The row holds for
/VulnerabilityDefinitionsand not for the scanner blocks. I had read the code rather than run it, which that comment did say, and running it is what showed the difference.How I checked it
Against
docker-compose.without_llm.yml, soENABLE_VULNERABLEAPP_JSP=true,ENABLE_VULNERABLEAPP_PHP=true,ENABLE_LLMFORGE=false.The published facade image bakes in its own
nginx.confand Lua module, and I checked that the bakednginx.confis identical tomain. Running the stack as is therefore measuresmain, which is the first column below. To measure this branch without rebuilding the image, mount the two changed files over it:Drop the
-f override.ymlto get the first column instead, where the twocurlcalls fail to parse rather than printing counts. Themkdiris there becausedocker-compose.without_llm.ymlmounts./templates, which is not in the repository, and theuntilloop is becauseup -dreturns before the Java application is serving.main/scanner/dast/scanner/sast/VulnerabilityDefinitionsmainOne consequence worth stating rather than leaving to be discovered:
VulnerableApp-phphad a key in the merged scanner responses before this change, holding that sentence, and it has no key after. The merged object is{"VulnerableApp": [...]}alone on this stack, since jsp answers 404 and php answers a non-JSON body. That is the same shape/VulnerabilityDefinitionswould take if those apps stopped returning JSON there.The four scanner responses were each fetched twice and the two fetches were byte identical every time. The
/VulnerabilityDefinitionsrow is one fetch per column, compared withcmp, not two.VulnerableApp-jspreturns 404 for both scanner paths, so it is left out of the merge onmainand on this branch alike, which is the existing behaviour and not something this changes.To confirm that config line is what selects the path rather than something else, I pointed it at a path that does not exist and the
VulnerableAppkey disappeared from the response, leaving 71 bytes.luacheck .inlua-modules/reports 0 warnings and 0 errors over 1 file. That is the command the Compile workflow runs, though I ran it in an Alpine container rather than on the workflow's Ubuntu runner.Two things worth saying plainly
carries_jsondecodes the body with OpenResty's bundledcjson.safeand accepts it only when the result is an object or an array. It also refuses a response the subrequest reported as truncated. The decoded value is thrown away and the merge still splices the raw bytes, so each app's own key order and formatting reach the caller unchanged.It started as a check on the first non-space character, which was enough to keep the php sentence out but let
{error}and a body cut off part way through slip past. The automated review on this PR raised both, and the third commit fixes them. Output on this stack does not move: all three endpoints are byte for byte identical to the second commit.The
llmforgepath is unchanged but I did not exercise it, since the stack I ran setsENABLE_LLMFORGE=false. You said on the issue that DAST and SAST for LLMForge are worth skipping for now, so the scanner blocks still capture three apps.Summary by CodeRabbit