[PATCH log-tracker] handle smtp filter message: prevent panicking with non-standard output

[PATCH log-tracker] handle smtp filter message: prevent panicking with non-standard output

[Dominik Csapak]

Currently a custom checkscript can print it's output into the syslog
under the guise of the pmg-smtp-filter unit, so it will picked up
by the log tracker. In case there is a line with a delimiter and nothing
after it, every thing before is detected as a qid but the remaining
message only contains the delimiter.

Prevent the panicking here by checking its length beforehand.

While the real fix is either to prevent custom check scripts to output
to syslog, or to prefix it with something we can filter away here,
protecting against malformed output still makes sense.

Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>
---
 src/main.rs | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/src/main.rs b/src/main.rs
index efdfd30..4787a36 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -115,6 +115,11 @@ fn handle_pmg_smtp_filter_message(msg: &[u8], parser: &mut Parser, complete_line
         Some((q, m)) => (q, m),
         None => return,
     };
+    if data.len() < 2 {
+        // after the QID there is no separator and space, so it can't be a proper smtp-filter
+        // message. It's possibly output from a custom check script or a malformed log line.
+        return;
+    }
     // skip ': ' following the QID
     let data = &data[2..];
 
-- 
2.47.3

Re: [PATCH log-tracker] handle smtp filter message: prevent panicking with non-standard output

[Thomas Lamprecht]

On 10/06/2026 15:15, Dominik Csapak wrote:
> Currently a custom checkscript can print it's output into the syslog
> under the guise of the pmg-smtp-filter unit, so it will picked up
> by the log tracker. In case there is a line with a delimiter and nothing
> after it, every thing before is detected as a qid but the remaining
> message only contains the delimiter.
> 
> Prevent the panicking here by checking its length beforehand.
> 
> While the real fix is either to prevent custom check scripts to output
> to syslog, or to prefix it with something we can filter away here,
> protecting against malformed output still makes sense.
> 
> Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>
> ---
>  src/main.rs | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/src/main.rs b/src/main.rs
> index efdfd30..4787a36 100644
> --- a/src/main.rs
> +++ b/src/main.rs
> @@ -115,6 +115,11 @@ fn handle_pmg_smtp_filter_message(msg: &[u8], parser: &mut Parser, complete_line
>          Some((q, m)) => (q, m),
>          None => return,
>      };
> +    if data.len() < 2 {
> +        // after the QID there is no separator and space, so it can't be a proper smtp-filter
> +        // message. It's possibly output from a custom check script or a malformed log line.

this comment confuses me, reads like a separator and space after a QID
being wrong, but it's what's expected, with the &data[2..]; IMO no comment
would be required, but short one can be fine - will squash that in on applying.

> +        return;
> +    }
>      // skip ': ' following the QID
>      let data = &data[2..];
>  

Re: [PATCH log-tracker] handle smtp filter message: prevent panicking with non-standard output

[Dominik Csapak]

On 6/10/26 3:51 PM, Thomas Lamprecht wrote:
> On 10/06/2026 15:15, Dominik Csapak wrote:
>> Currently a custom checkscript can print it's output into the syslog
>> under the guise of the pmg-smtp-filter unit, so it will picked up
>> by the log tracker. In case there is a line with a delimiter and nothing
>> after it, every thing before is detected as a qid but the remaining
>> message only contains the delimiter.
>>
>> Prevent the panicking here by checking its length beforehand.
>>
>> While the real fix is either to prevent custom check scripts to output
>> to syslog, or to prefix it with something we can filter away here,
>> protecting against malformed output still makes sense.
>>
>> Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>
>> ---
>>   src/main.rs | 5 +++++
>>   1 file changed, 5 insertions(+)
>>
>> diff --git a/src/main.rs b/src/main.rs
>> index efdfd30..4787a36 100644
>> --- a/src/main.rs
>> +++ b/src/main.rs
>> @@ -115,6 +115,11 @@ fn handle_pmg_smtp_filter_message(msg: &[u8], parser: &mut Parser, complete_line
>>           Some((q, m)) => (q, m),
>>           None => return,
>>       };
>> +    if data.len() < 2 {
>> +        // after the QID there is no separator and space, so it can't be a proper smtp-filter
>> +        // message. It's possibly output from a custom check script or a malformed log line.
> 
> this comment confuses me, reads like a separator and space after a QID
> being wrong, but it's what's expected, with the &data[2..]; IMO no comment
> would be required, but short one can be fine - will squash that in on applying.

ah ok sorry, i wanted to express that this is missing in this branch,
so after the length check shows it's shorter

> 
>> +        return;
>> +    }
>>       // skip ': ' following the QID
>>       let data = &data[2..];
>>   
> 

applied: [PATCH log-tracker] handle smtp filter message: prevent panicking with non-standard output

[Thomas Lamprecht]

On 10/06/2026 15:15, Dominik Csapak wrote:
> Currently a custom checkscript can print it's output into the syslog
> under the guise of the pmg-smtp-filter unit, so it will picked up
> by the log tracker. In case there is a line with a delimiter and nothing
> after it, every thing before is detected as a qid but the remaining
> message only contains the delimiter.
> 
> Prevent the panicking here by checking its length beforehand.
> 
> While the real fix is either to prevent custom check scripts to output
> to syslog, or to prefix it with something we can filter away here,
> protecting against malformed output still makes sense.

ack, and in fact it shouldn't be to hard to address that there too,
but yeah the log-tracker panicking is not great in any case.

> 
> Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>
> ---
>  src/main.rs | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/src/main.rs b/src/main.rs
> index efdfd30..4787a36 100644
> --- a/src/main.rs
> +++ b/src/main.rs
> @@ -115,6 +115,11 @@ fn handle_pmg_smtp_filter_message(msg: &[u8], parser: &mut Parser, complete_line
>          Some((q, m)) => (q, m),
>          None => return,
>      };
> +    if data.len() < 2 {
> +        // after the QID there is no separator and space, so it can't be a proper smtp-filter
> +        // message. It's possibly output from a custom check script or a malformed log line.
> +        return;
> +    }
>      // skip ': ' following the QID
>      let data = &data[2..];
>  


For the record: Stoiko already applied this [0], I did a follow-up commit to catch the other
sites by refactoring this into a helper [1].

[0]: https://git.proxmox.com/?p=pmg-log-tracker.git;a=commitdiff;h=93bdf686a90d834b23704edd05f308a4d812e81c
[1]: https://git.proxmox.com/?p=pmg-log-tracker.git;a=commitdiff;h=d1231c2c9533fc42b39d98eca48994f0d4426552