[PATCH] python: Hide error message when modifying non-local fcontext

[PATCH] python: Hide error message when modifying non-local fcontext

[Vit Mojzis]

Fixes:
  # semanage fcontext -f f -m -t passwd_file_t /etc/security/opasswd
  libsemanage.dbase_llist_query: could not query record value (No such file or directory).

Signed-off-by: Vit Mojzis <vmojzis@redhat.com>
---
 python/semanage/seobject.py | 19 ++++++++++++++++++-
 1 file changed, 18 insertions(+), 1 deletion(-)

diff --git a/python/semanage/seobject.py b/python/semanage/seobject.py
index 0782c082..2d52f53c 100644
--- a/python/semanage/seobject.py
+++ b/python/semanage/seobject.py
@@ -177,6 +177,22 @@ except (OSError, ImportError):
             for l in self.log_list:
                 syslog.syslog(syslog.LOG_INFO, message + l)
 
+# Define a context manager to suppress stderr.
+class suppress_stderr(object):
+    def __init__(self):
+        # Open a /dev/null file to be used as stderr
+        self.null =  os.open(os.devnull,os.O_RDWR)
+        self.save_fd = os.dup(2)
+
+    def __enter__(self):
+        # Set stderr to the null file
+        os.dup2(self.null,2)
+
+    def __exit__(self, *_):
+        # Restore stderr
+        os.dup2(self.save_fd,2)
+        os.close(self.null)
+
 
 class nulllogger:
 
@@ -2510,7 +2526,8 @@ class fcontextRecords(semanageRecords):
                 raise ValueError(_("File context for %s is not defined") % target)
 
         try:
-            (rc, fcontext) = semanage_fcontext_query_local(self.sh, k)
+            with suppress_stderr():
+                (rc, fcontext) = semanage_fcontext_query_local(self.sh, k)
         except OSError:
             try:
                 (rc, fcontext) = semanage_fcontext_query(self.sh, k)
-- 
2.35.3

Re: [PATCH] python: Hide error message when modifying non-local fcontext

[James Carter]

On Wed, Sep 14, 2022 at 6:08 PM Vit Mojzis <vmojzis@redhat.com> wrote:
>
> Fixes:
>   # semanage fcontext -f f -m -t passwd_file_t /etc/security/opasswd
>   libsemanage.dbase_llist_query: could not query record value (No such file or directory).
>
> Signed-off-by: Vit Mojzis <vmojzis@redhat.com>
> ---
>  python/semanage/seobject.py | 19 ++++++++++++++++++-
>  1 file changed, 18 insertions(+), 1 deletion(-)
>
> diff --git a/python/semanage/seobject.py b/python/semanage/seobject.py
> index 0782c082..2d52f53c 100644
> --- a/python/semanage/seobject.py
> +++ b/python/semanage/seobject.py
> @@ -177,6 +177,22 @@ except (OSError, ImportError):
>              for l in self.log_list:
>                  syslog.syslog(syslog.LOG_INFO, message + l)
>
> +# Define a context manager to suppress stderr.
> +class suppress_stderr(object):
> +    def __init__(self):
> +        # Open a /dev/null file to be used as stderr
> +        self.null =  os.open(os.devnull,os.O_RDWR)
> +        self.save_fd = os.dup(2)
> +
> +    def __enter__(self):
> +        # Set stderr to the null file
> +        os.dup2(self.null,2)
> +
> +    def __exit__(self, *_):
> +        # Restore stderr
> +        os.dup2(self.save_fd,2)
> +        os.close(self.null)
> +
>
>  class nulllogger:
>
> @@ -2510,7 +2526,8 @@ class fcontextRecords(semanageRecords):
>                  raise ValueError(_("File context for %s is not defined") % target)
>
>          try:
> -            (rc, fcontext) = semanage_fcontext_query_local(self.sh, k)
> +            with suppress_stderr():
> +                (rc, fcontext) = semanage_fcontext_query_local(self.sh, k)
>          except OSError:
>              try:
>                  (rc, fcontext) = semanage_fcontext_query(self.sh, k)
> --
> 2.35.3
>

I think it is better to rework semanage/seobject.py so that there is
no error. I sent a patch to the list that should fix this.
Thanks for the report. Sorry that it took so long to get to.
Jim

Re: [PATCH] python: Hide error message when modifying non-local fcontext

[Vit Mojzis]

On 10/19/22 21:06, James Carter wrote:
> On Wed, Sep 14, 2022 at 6:08 PM Vit Mojzis <vmojzis@redhat.com> wrote:
>>
>> Fixes:
>>    # semanage fcontext -f f -m -t passwd_file_t /etc/security/opasswd
>>    libsemanage.dbase_llist_query: could not query record value (No such file or directory).
>>
>> Signed-off-by: Vit Mojzis <vmojzis@redhat.com>
>> ---
>>   python/semanage/seobject.py | 19 ++++++++++++++++++-
>>   1 file changed, 18 insertions(+), 1 deletion(-)
>>
>> diff --git a/python/semanage/seobject.py b/python/semanage/seobject.py
>> index 0782c082..2d52f53c 100644
>> --- a/python/semanage/seobject.py
>> +++ b/python/semanage/seobject.py
>> @@ -177,6 +177,22 @@ except (OSError, ImportError):
>>               for l in self.log_list:
>>                   syslog.syslog(syslog.LOG_INFO, message + l)
>>
>> +# Define a context manager to suppress stderr.
>> +class suppress_stderr(object):
>> +    def __init__(self):
>> +        # Open a /dev/null file to be used as stderr
>> +        self.null =  os.open(os.devnull,os.O_RDWR)
>> +        self.save_fd = os.dup(2)
>> +
>> +    def __enter__(self):
>> +        # Set stderr to the null file
>> +        os.dup2(self.null,2)
>> +
>> +    def __exit__(self, *_):
>> +        # Restore stderr
>> +        os.dup2(self.save_fd,2)
>> +        os.close(self.null)
>> +
>>
>>   class nulllogger:
>>
>> @@ -2510,7 +2526,8 @@ class fcontextRecords(semanageRecords):
>>                   raise ValueError(_("File context for %s is not defined") % target)
>>
>>           try:
>> -            (rc, fcontext) = semanage_fcontext_query_local(self.sh, k)
>> +            with suppress_stderr():
>> +                (rc, fcontext) = semanage_fcontext_query_local(self.sh, k)
>>           except OSError:
>>               try:
>>                   (rc, fcontext) = semanage_fcontext_query(self.sh, k)
>> --
>> 2.35.3
>>
> 
> I think it is better to rework semanage/seobject.py so that there is
> no error. I sent a patch to the list that should fix this.
> Thanks for the report. Sorry that it took so long to get to.
> Jim

Hi Jim,
thank you for looking into this. I agree that your solution is much more 
elegant and should be used instead.

Vit