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GHSA-9c5w-9q3f-3hv7
No affected components available
Minder's HandleGithubWebhook is susceptible to a denial of service attack from an untrusted HTTP request. The vulnerability exists before the request has been validated, and as such the request is still untrusted at the point of failure. This allows an attacker with the ability to send requests to HandleGithubWebhook to crash the Minder controlplane and deny other users from using it.
One of the first things that HandleGithubWebhook does is to validate the payload signature. This is done by way of the internal helper validatePayloadSignature:
https://github.com/stacklok/minder/blob/ee66f6c0763212503c898cfefb65ce1450c7f5ac/internal/controlplane/handlers_githubwebhooks.go#L213-L218
validatePayloadSignature generates a reader from the incoming request by way of the internal helper readerFromRequest:
https://github.com/stacklok/minder/blob/ee66f6c0763212503c898cfefb65ce1450c7f5ac/internal/controlplane/handlers_githubwebhooks.go#L337-L342
To create a reader from the incoming request, readerFromRequest first reads the request body entirely into memory on line 368:
https://github.com/stacklok/minder/blob/ee66f6c0763212503c898cfefb65ce1450c7f5ac/internal/controlplane/handlers_githubwebhooks.go#L367-L377
This is a vulnerability, since an HTTP request with a large body can exhaust the memory of the machine running Minder and cause the Go runtime to crash Minder.
Note that this occurs before Minder has validated the request, and as such, the request is still untrusted.
To test this out, we can use the existing TestHandleWebHookRepository unit test and modify the HTTP request body to be large.
To do that, change these lines:
https://github.com/stacklok/minder/blob/ee66f6c0763212503c898cfefb65ce1450c7f5ac/internal/controlplane/handlers_githubwebhooks_test.go#L278-L283
... to these lines:
packageJson, err := json.Marshal(event)
require.NoError(t, err, "failed to marshal package event")
maliciousBody := strings.NewReader(strings.Repeat("1337", 1000000000))
maliciousBodyReader := io.MultiReader(maliciousBody, maliciousBody, maliciousBody, maliciousBody, maliciousBody)
_ = packageJson
client := &http.Client{}
req, err := http.NewRequest("POST", fmt.Sprintf("http://%s", addr), maliciousBodyReader)
require.NoError(t, err, "failed to create request")
Then run the unit test again. WARNING, SAVE ALL WORK BEFORE DOING THIS.
On my local machine, this causes the machine to freeze, and Go finally performs a sigkill:
signal: killed
FAIL github.com/stacklok/minder/internal/controlplane 30.759s
FAIL
The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker does not need any special privileges or access rights. No user interaction is needed for the attacker to exploit this vulnerability. The impact is confined to the system where the vulnerability exists. There is a high impact on the availability of the system.
Exploitation attempts have been detected. Elevated vigilance and prompt remediation are advised.
The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.
We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.
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