diff mbox series

[PATCHv2] debuginfod: Check result of calling MHD_add_response_header.

Message ID 20211201145112.16263-1-mark@klomp.org
State Superseded
Headers show
Series [PATCHv2] debuginfod: Check result of calling MHD_add_response_header. | expand

Commit Message

Mark Wielaard Dec. 1, 2021, 2:51 p.m. UTC
Although unlikely the MHD_add_response_header can fail for
various reasons.  If it fails something odd is going on.
So check we can actually add a response header and log an
error if we cannot.

Signed-off-by: Mark Wielaard <mark@klomp.org>
---

 This version only check and logs the error, but still uses the
 response object.

 debuginfod/ChangeLog      | 10 +++++
 debuginfod/debuginfod.cxx | 87 +++++++++++++++++++++++++++++----------
 2 files changed, 75 insertions(+), 22 deletions(-)

Comments

Frank Ch. Eigler Dec. 1, 2021, 3:23 p.m. UTC | #1
Hi -

> Although unlikely the MHD_add_response_header can fail for
> various reasons.  If it fails something odd is going on.
> So check we can actually add a response header and log an
> error if we cannot.

TBH I wouldn't bother even this much checking.  It just uglifies the
code.  If it would make covscan happier, I'd stick a (void) in front
of the add-header calls.



> -    MHD_add_response_header (r, "Content-Type", "text/plain");
> -    MHD_RESULT rc = MHD_queue_response (c, code, r);
> +    MHD_RESULT rc1, rc2;
> +    rc1 = MHD_add_response_header (r, "Content-Type", "text/plain");
> +    rc2 = MHD_queue_response (c, code, r);
>      MHD_destroy_response (r);
> -    return rc;
> +    return (rc1 == MHD_NO || rc2 == MHD_NO) ? MHD_NO : MHD_YES;


e.g. this part won't work: returning MHD_NO causes libmicrohttpd to
send a 503 error back to the caller, regardless of our intended one.

> +        if (MHD_add_response_header (resp, "Last-Modified", datebuf) == MHD_NO)
> +          if (verbose)
> +            obatched(clog) << "Error: couldn't add Last-Modified header"
> +                           << endl;
>      }

e.g., we normally report errors to the logs, regardless of verbosity
settings.


> +      if (MHD_add_response_header (r, "Content-Type",
> +                                   "application/octet-stream") == MHD_NO
> +          || MHD_add_response_header (r, "X-DEBUGINFOD-SIZE",
> +                                      to_string(s.st_size).c_str()) == MHD_NO
> +          || MHD_add_response_header (r, "X-DEBUGINFOD-FILE",
> +                                      file.c_str()) == MHD_NO)

e.g., this formulation makes it impossible to add some headers if a
previous one failed.


- FChE
Mark Wielaard Dec. 8, 2021, 3:10 p.m. UTC | #2
Hi Frank,

On Wed, 2021-12-01 at 10:23 -0500, Frank Ch. Eigler wrote:
> > Although unlikely the MHD_add_response_header can fail for
> > various reasons.  If it fails something odd is going on.
> > So check we can actually add a response header and log an
> > error if we cannot.
> 
> TBH I wouldn't bother even this much checking.  It just uglifies the
> code.  If it would make covscan happier, I'd stick a (void) in front
> of the add-header calls.

That is really just like ignoring the issue imho. But you are right
that it uglifies the code, I'll wrap the calls in an helper function.

> > -    MHD_add_response_header (r, "Content-Type", "text/plain");
> > -    MHD_RESULT rc = MHD_queue_response (c, code, r);
> > +    MHD_RESULT rc1, rc2;
> > +    rc1 = MHD_add_response_header (r, "Content-Type",
> > "text/plain");
> > +    rc2 = MHD_queue_response (c, code, r);
> >      MHD_destroy_response (r);
> > -    return rc;
> > +    return (rc1 == MHD_NO || rc2 == MHD_NO) ? MHD_NO : MHD_YES;
> 
> e.g. this part won't work: returning MHD_NO causes libmicrohttpd to
> send a 503 error back to the caller, regardless of our intended one.

OK, so we only want to report MHD_NO here when MHD_queue_response
fails.

> > +        if (MHD_add_response_header (resp, "Last-Modified",
> > datebuf) == MHD_NO)
> > +          if (verbose)
> > +            obatched(clog) << "Error: couldn't add Last-Modified
> > header"
> > +                           << endl;
> >      }
> 
> e.g., we normally report errors to the logs, regardless of verbosity
> settings.

OK, I'll remove the if (verbose).

> > +      if (MHD_add_response_header (r, "Content-Type",
> > +                                   "application/octet-stream") ==
> > MHD_NO
> > +          || MHD_add_response_header (r, "X-DEBUGINFOD-SIZE",
> > +                                      to_string(s.st_size).c_str()
> > ) == MHD_NO
> > +          || MHD_add_response_header (r, "X-DEBUGINFOD-FILE",
> > +                                      file.c_str()) == MHD_NO)
> 
> e.g., this formulation makes it impossible to add some headers if a
> previous one failed.

It is likely that if one fails, then all others fail similarly, but I
see your point. Any header is better than no headers at all.

Thanks,

Mark
diff mbox series

Patch

diff --git a/debuginfod/ChangeLog b/debuginfod/ChangeLog
index 822bd637..3866e7fa 100644
--- a/debuginfod/ChangeLog
+++ b/debuginfod/ChangeLog
@@ -1,3 +1,13 @@ 
+2021-12-01  Mark Wielaard  <mark@klomp.org>
+
+	* debuginfod.cxx (reportable_exception::mhd_send_response): Check
+	MHD_add_response_header result.
+	(add_mhd_last_modified): Likewise.
+	(handle_buildid_f_match): Likewise.
+	(handle_buildid_r_match): Likewise.
+	(handle_metrics): Likewise.
+	(handle_root): Likewise.
+
 2021-11-10  √Črico N. Rolim  <erico.erc@gmail.com>
 
 	* debuginfod.cxx: include "system.h" under 'extern "C"' block.
diff --git a/debuginfod/debuginfod.cxx b/debuginfod/debuginfod.cxx
index 764e7b94..b3416134 100644
--- a/debuginfod/debuginfod.cxx
+++ b/debuginfod/debuginfod.cxx
@@ -1,5 +1,6 @@ 
 /* Debuginfo-over-http server.
    Copyright (C) 2019-2021 Red Hat, Inc.
+   Copyright (C) 2021 Mark J. Wielaard <mark@klomp.org>
    This file is part of elfutils.
 
    This file is free software; you can redistribute it and/or modify
@@ -646,10 +647,11 @@  struct reportable_exception
     MHD_Response* r = MHD_create_response_from_buffer (message.size(),
                                                        (void*) message.c_str(),
                                                        MHD_RESPMEM_MUST_COPY);
-    MHD_add_response_header (r, "Content-Type", "text/plain");
-    MHD_RESULT rc = MHD_queue_response (c, code, r);
+    MHD_RESULT rc1, rc2;
+    rc1 = MHD_add_response_header (r, "Content-Type", "text/plain");
+    rc2 = MHD_queue_response (c, code, r);
     MHD_destroy_response (r);
-    return rc;
+    return (rc1 == MHD_NO || rc2 == MHD_NO) ? MHD_NO : MHD_YES;
   }
 };
 
@@ -1076,10 +1078,15 @@  add_mhd_last_modified (struct MHD_Response *resp, time_t mtime)
       char datebuf[80];
       size_t rc = strftime (datebuf, sizeof (datebuf), "%a, %d %b %Y %T GMT", now);
       if (rc > 0 && rc < sizeof (datebuf))
-        (void) MHD_add_response_header (resp, "Last-Modified", datebuf);
+        if (MHD_add_response_header (resp, "Last-Modified", datebuf) == MHD_NO)
+          if (verbose)
+            obatched(clog) << "Error: couldn't add Last-Modified header"
+                           << endl;
     }
 
-  (void) MHD_add_response_header (resp, "Cache-Control", "public");
+  if (MHD_add_response_header (resp, "Cache-Control", "public") == MHD_NO)
+    if (verbose)
+      obatched(clog) << "Error: couldn't add Cache-Control header" << endl;
 }
 
 
@@ -1125,10 +1132,16 @@  handle_buildid_f_match (bool internal_req_t,
     }
   else
     {
-      MHD_add_response_header (r, "Content-Type", "application/octet-stream");
       std::string file = b_source0.substr(b_source0.find_last_of("/")+1, b_source0.length());
-      MHD_add_response_header (r, "X-DEBUGINFOD-SIZE", to_string(s.st_size).c_str() );
-      MHD_add_response_header (r, "X-DEBUGINFOD-FILE", file.c_str() );
+      if (MHD_add_response_header (r, "Content-Type",
+                                   "application/octet-stream") == MHD_NO
+          || MHD_add_response_header (r, "X-DEBUGINFOD-SIZE",
+                                      to_string(s.st_size).c_str()) == MHD_NO
+          || MHD_add_response_header (r, "X-DEBUGINFOD-FILE",
+                                      file.c_str()) == MHD_NO)
+        if (verbose)
+          obatched(clog) << "Error: cannot add response headers for "
+                         << b_source0 << endl;
       add_mhd_last_modified (r, s.st_mtime);
       if (verbose > 1)
         obatched(clog) << "serving file " << b_source0 << endl;
@@ -1597,10 +1610,17 @@  handle_buildid_r_match (bool internal_req_p,
 
       inc_metric ("http_responses_total","result","archive fdcache");
 
-      MHD_add_response_header (r, "Content-Type", "application/octet-stream");
-      MHD_add_response_header (r, "X-DEBUGINFOD-SIZE", to_string(fs.st_size).c_str());
-      MHD_add_response_header (r, "X-DEBUGINFOD-ARCHIVE", b_source0.c_str());
-      MHD_add_response_header (r, "X-DEBUGINFOD-FILE", b_source1.c_str());
+      if (MHD_add_response_header (r, "Content-Type",
+                                   "application/octet-stream") == MHD_NO
+          || MHD_add_response_header (r, "X-DEBUGINFOD-SIZE",
+                                      to_string(fs.st_size).c_str()) == MHD_NO
+          || MHD_add_response_header (r, "X-DEBUGINFOD-ARCHIVE",
+                                      b_source0.c_str()) == MHD_NO
+          || MHD_add_response_header (r, "X-DEBUGINFOD-FILE",
+                                      b_source1.c_str()) == MHD_NO)
+        if (verbose)
+          obatched(clog) << "Error: cannot add response header for "
+                         << b_source0 << endl;
       add_mhd_last_modified (r, fs.st_mtime);
       if (verbose > 1)
         obatched(clog) << "serving fdcache archive " << b_source0 << " file " << b_source1 << endl;
@@ -1741,12 +1761,20 @@  handle_buildid_r_match (bool internal_req_p,
         }
       else
         {
-          MHD_add_response_header (r, "Content-Type", "application/octet-stream");
           std::string file = b_source1.substr(b_source1.find_last_of("/")+1, b_source1.length());
-          MHD_add_response_header (r, "X-DEBUGINFOD-SIZE", to_string(fs.st_size).c_str());
-          MHD_add_response_header (r, "X-DEBUGINFOD-ARCHIVE", b_source0.c_str());
-          MHD_add_response_header (r, "X-DEBUGINFOD-FILE", file.c_str());
-
+          if (MHD_add_response_header (r, "Content-Type",
+				       "application/octet-stream") == MHD_NO
+	      || MHD_add_response_header (r, "X-DEBUGINFOD-SIZE",
+					  to_string(fs.st_size).c_str()) == MHD_NO
+	      || MHD_add_response_header (r, "X-DEBUGINFOD-ARCHIVE",
+					  b_source0.c_str()) == MHD_NO
+	      || MHD_add_response_header (r, "X-DEBUGINFOD-FILE",
+					  file.c_str()) == MHD_NO)
+	    {
+	      if (verbose)
+		obatched(clog) << "Error: cannot create response header for "
+			       << b_source0 << endl;
+	    }
           add_mhd_last_modified (r, archive_entry_mtime(e));
           if (verbose > 1)
             obatched(clog) << "serving archive " << b_source0 << " file " << b_source1 << endl;
@@ -2012,7 +2040,12 @@  and will not query the upstream servers");
           auto r = MHD_create_response_from_fd ((uint64_t) s.st_size, fd);
           if (r)
             {
-              MHD_add_response_header (r, "Content-Type", "application/octet-stream");
+              if (MHD_add_response_header (r, "Content-Type",
+                                           "application/octet-stream") == MHD_NO)
+                if (verbose)
+                  obatched(clog) << "Error: couldn't add Content-Type header"
+                                 << endl;
+
               add_mhd_last_modified (r, s.st_mtime);
               if (verbose > 1)
                 obatched(clog) << "serving file from upstream debuginfod/cache" << endl;
@@ -2163,8 +2196,13 @@  handle_metrics (off_t* size)
   MHD_Response* r = MHD_create_response_from_buffer (os.size(),
                                                      (void*) os.c_str(),
                                                      MHD_RESPMEM_MUST_COPY);
-  *size = os.size();
-  MHD_add_response_header (r, "Content-Type", "text/plain");
+  if (r != NULL)
+    {
+      *size = os.size();
+      if (MHD_add_response_header (r, "Content-Type", "text/plain") == MHD_NO)
+        if (verbose)
+          obatched(clog) << "Error: couldn't add Content-Type header" << endl;
+    }
   return r;
 }
 
@@ -2176,8 +2214,13 @@  handle_root (off_t* size)
   MHD_Response* r = MHD_create_response_from_buffer (version.size (),
 						     (void *) version.c_str (),
 						     MHD_RESPMEM_PERSISTENT);
-  *size = version.size ();
-  MHD_add_response_header (r, "Content-Type", "text/plain");
+  if (r != NULL)
+    {
+      *size = version.size ();
+      if (MHD_add_response_header (r, "Content-Type", "text/plain") == MHD_NO)
+        if (verbose)
+          obatched(clog) << "Error: couldn't add Content-Type header" << endl;
+    }
   return r;
 }