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Blame SOURCES/0084-journal-remote-verify-entry-length-from-header.patch

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From ad18012c46724aa097f37015a8036a4343206efe Mon Sep 17 00:00:00 2001
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From: =?UTF-8?q?Zbigniew=20J=C4=99drzejewski-Szmek?= <zbyszek@in.waw.pl>
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Date: Fri, 7 Dec 2018 12:47:14 +0100
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Subject: [PATCH] journal-remote: verify entry length from header
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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Calling mhd_respond(), which ulimately calls MHD_queue_response() is
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ineffective at point, becuase MHD_queue_response() immediately returns
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MHD_NO signifying an error, because the connection is in state
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MHD_CONNECTION_CONTINUE_SENT.
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As Christian Grothoff kindly explained:
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> You are likely calling MHD_queue_repsonse() too late: once you are
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> receiving upload_data, HTTP forces you to process it all. At this time,
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> MHD has already sent "100 continue" and cannot take it back (hence you
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> get MHD_NO!).
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>
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> In your request handler, the first time when you are called for a
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> connection (and when hence *upload_data_size == 0 and upload_data ==
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> NULL) you must check the content-length header and react (with
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> MHD_queue_response) based on this (to prevent MHD from automatically
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> generating 100 continue).
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If we ever encounter this kind of error, print a warning and immediately
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abort the connection. (The alternative would be to keep reading the data,
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but ignore it, and return an error after we get to the end of data.
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That is possible, but of course puts additional load on both the
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sender and reciever, and doesn't seem important enough just to return
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a good error message.)
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Note that sending of the error does not work (the connection is always aborted
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when MHD_queue_response is used with MHD_RESPMEM_MUST_FREE, as in this case)
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with libµhttpd 0.59, but works with 0.61:
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https://src.fedoraproject.org/rpms/libmicrohttpd/pull-request/1
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(cherry-picked from commit 7fdb237f5473cb8fc2129e57e8a0039526dcb4fd)
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Related: #1664977
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---
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 src/journal-remote/journal-remote-main.c | 34 +++++++++++++++++-------
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 1 file changed, 24 insertions(+), 10 deletions(-)
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diff --git a/src/journal-remote/journal-remote-main.c b/src/journal-remote/journal-remote-main.c
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index 8fda9d1499..e9b3702e8a 100644
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--- a/src/journal-remote/journal-remote-main.c
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+++ b/src/journal-remote/journal-remote-main.c
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@@ -210,16 +210,14 @@ static int process_http_upload(
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                                    journal_remote_server_global->seal);
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                 if (r == -EAGAIN)
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                         break;
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-                else if (r < 0) {
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-                        log_warning("Failed to process data for connection %p", connection);
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+                if (r < 0) {
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                         if (r == -E2BIG)
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-                                return mhd_respondf(connection,
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-                                                    r, MHD_HTTP_PAYLOAD_TOO_LARGE,
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-                                                    "Entry is too large, maximum is " STRINGIFY(DATA_SIZE_MAX) " bytes.");
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+                                log_warning_errno(r, "Entry is too above maximum of %u, aborting connection %p.",
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+                                                  DATA_SIZE_MAX, connection);
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                         else
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-                                return mhd_respondf(connection,
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-                                                    r, MHD_HTTP_UNPROCESSABLE_ENTITY,
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-                                                    "Processing failed: %m.");
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+                                log_warning_errno(r, "Failed to process data, aborting connection %p: %m",
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+                                                  connection);
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+                        return MHD_NO;
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                 }
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         }
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@@ -253,6 +251,7 @@ static int request_handler(
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         const char *header;
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         int r, code, fd;
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         _cleanup_free_ char *hostname = NULL;
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+        size_t len;
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         assert(connection);
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         assert(connection_cls);
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@@ -272,12 +271,27 @@ static int request_handler(
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         if (!streq(url, "/upload"))
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                 return mhd_respond(connection, MHD_HTTP_NOT_FOUND, "Not found.");
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-        header = MHD_lookup_connection_value(connection,
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-                                             MHD_HEADER_KIND, "Content-Type");
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+        header = MHD_lookup_connection_value(connection, MHD_HEADER_KIND, "Content-Type");
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         if (!header || !streq(header, "application/vnd.fdo.journal"))
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                 return mhd_respond(connection, MHD_HTTP_UNSUPPORTED_MEDIA_TYPE,
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                                    "Content-Type: application/vnd.fdo.journal is required.");
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+        header = MHD_lookup_connection_value(connection, MHD_HEADER_KIND, "Content-Length");
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+        if (!header)
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+                return mhd_respond(connection, MHD_HTTP_LENGTH_REQUIRED,
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+                                   "Content-Length header is required.");
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+        r = safe_atozu(header, &len;;
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+        if (r < 0)
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+                return mhd_respondf(connection, r, MHD_HTTP_LENGTH_REQUIRED,
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+                                    "Content-Length: %s cannot be parsed: %m", header);
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+
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+        if (len > ENTRY_SIZE_MAX)
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+                /* When serialized, an entry of maximum size might be slightly larger,
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+                 * so this does not correspond exactly to the limit in journald. Oh well.
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+                 */
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+                return mhd_respondf(connection, 0, MHD_HTTP_PAYLOAD_TOO_LARGE,
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+                                    "Payload larger than maximum size of %u bytes", ENTRY_SIZE_MAX);
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+
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         {
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                 const union MHD_ConnectionInfo *ci;
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