提出 #808445: Open5gs PCF v2.7.7 Denial of Service

### Open5GS Release, Revision, or Tag

v2.7.7

### Steps to reproduce

### Description

This merged report covers the two confirmed `Npcf_PolicyAuthorization`
reachability variants that hit the same crash site:

```c
from_str = strstr(&rx_flow->description[strlen("permit in")], "from");
ogs_assert(from_str);
```

at `../lib/proto/types.c:938`.

The shared payload shape is the same in both cases:

```text
fDescs = ["permit in"]
```

Confirmed reachability variants:

1. `POST /npcf-policyauthorization/v1/app-sessions`
2. `PATCH /npcf-policyauthorization/v1/app-sessions/{appSessionId}`

The immediate callers differ, but the crash site and malformed flow-description
root cause are identical.

### Root cause

- Shared crash site:
`../lib/proto/types.c:938`
- Root cause family:
parser/business-logic mismatch
- Create-path caller:
`ogs_pcc_rule_install_flow_from_media()`
- Update-path caller:
`ogs_pcc_rule_num_of_flow_equal_to_media()`
- Controlling field:
`ascReqData.medComponents[*].medSubComps[*].fDescs[*]`

### Logs

```shell
### Create Reproduction

Create an app session with:

{"ascReqData":{"medComponents":{"1":{"medSubComps":{"1":{"fDescs":["permit in"]}}}}}}

Observed in the confirmed run:

04/11 17:57:24.739: [core] FATAL: flow_rx_to_gx: Assertion `from_str' failed. (../lib/proto/types.c:938)

### Update Reproduction

Patch an existing app session with the same malformed flow description:

{"ascReqData":{"medComponents":{"1":{"medSubComps":{"1":{"fDescs":["permit in"]}}}}}}

Observed in the confirmed run:

04/11 17:58:54.874: [core] FATAL: flow_rx_to_gx: Assertion `from_str' failed. (../lib/proto/types.c:938)
```

### Expected behaviour

PCF should reject malformed `permit in` AF flow descriptions with a normal client error on both create and update routes.

### Observed Behaviour

Both create and update reachability variants hit the same `flow_rx_to_gx()` assertion and restart the PCF process.

### eNodeB/gNodeB

Not required.

### UE Models and versions

Not required.

• ソース: ⚠️ https://github.com/open5gs/open5gs/issues/4441
• ユーザー: LinZiyu (UID 94035)
• 送信: 2026年04月20日 20:38 (2 月 ago)
• モデレーション: 2026年05月09日 09:35 (19 days later)
• ステータス: 承諾済み
• VulDBエントリ: 362443 [Open5GS 迄 2.7.7 /lib/proto/types.c ogs_pcc_rule_install_flow_from_media サービス拒否]
• ポイント: 20