rfc/patch: user-agent distro-description for debuginfod http traffic

[Frank Ch. Eigler]

Hi -

commit 53aac40e9577168b886dfeecb77e5a72d2666fc9 (HEAD -> fche/debuginfod-useragent, origin/fche/debuginfod-useragent)
Author: Frank Ch. Eigler <fche@redhat.com>
Date:   Mon Jan 6 04:29:21 2020 -0500

    debuginfod: pass a distro-summary User-Agent request header
    
    It may be useful for a debuginfod server operator to know what kinds
    of clients make webapi requests.  This is mainly as a
    telemetry/diagnostic (though the data cannot be really trusted).  It
    may also be useful to automate downloading of distro packages to a
    debuginfod server in the case of an unknown hex buildid.  doc/testing
    not affected as these are diagnostics.

diff --git a/debuginfod/ChangeLog b/debuginfod/ChangeLog
index 1582eba5bc0e..bed3ad7814ff 100644
--- a/debuginfod/ChangeLog
+++ b/debuginfod/ChangeLog
@@ -1,3 +1,10 @@
+2020-01-06  Frank Ch. Eigler  <fche@redhat.com>
+
+	* Makefile.am: Create a build-time header with lsb/uname info.
+	* debuginfod-client.c: Pass above as additional User-Agent request header.
+	* debuginfod.cxx (conninfo): Print this and X-Forwarded-For, as per
+	apache httpd reverse-proxy chain.
+
 2019-12-22  Frank Ch. Eigler  <fche@redhat.com>
 
 	* debuginfod.cxx (*_rpm_*): Rename to *_archive_* throughout.
diff --git a/debuginfod/Makefile.am b/debuginfod/Makefile.am
index 52ead30aebf8..20a70545755a 100644
--- a/debuginfod/Makefile.am
+++ b/debuginfod/Makefile.am
@@ -67,6 +67,20 @@ debuginfod_find_LDADD = $(libeu) $(libdebuginfod)
 noinst_LIBRARIES = libdebuginfod.a
 noinst_LIBRARIES += libdebuginfod_pic.a
 
+debuginfod-client-useragent.h:
+	if type uname 2>/dev/null; then \
+		echo '#define DEBUGINFOD_CLIENT_USERAGENT_1 "'`uname -sm | sed -e 's, ,/,g'`'"' > $@; \
+	else \
+		echo '#define DEBUGINFOD_CLIENT_USERAGENT_1 ""' > $@; \
+	fi
+	if type lsb_release 2>/dev/null; then \
+		echo '#define DEBUGINFOD_CLIENT_USERAGENT_2 "'`lsb_release -sir | sed -e 's, ,/,g'`'"' >> $@; \
+	else \
+		echo '#define DEBUGINFOD_CLIENT_USERAGENT_2 ""' > $@; \
+	fi
+	echo '#define DEBUGINFOD_CLIENT_USERAGENT DEBUGINFOD_CLIENT_USERAGENT_1 "," DEBUGINFOD_CLIENT_USERAGENT_2' >> $@
+
+libdebuginfod: debuginfod-client-useragent.h
 libdebuginfod_a_SOURCES = debuginfod-client.c
 libdebuginfod_pic_a_SOURCES = debuginfod-client.c
 am_libdebuginfod_pic_a_OBJECTS = $(libdebuginfod_a_SOURCES:.c=.os)
@@ -98,7 +112,7 @@ uninstall: uninstall-am
 
 EXTRA_DIST = libdebuginfod.map
 MOSTLYCLEANFILES = $(am_libdebuginfod_pic_a_OBJECTS) libdebuginfod.so.$(VERSION)
-CLEANFILES += $(am_libdebuginfod_pic_a_OBJECTS) libdebuginfod.so
+CLEANFILES += $(am_libdebuginfod_pic_a_OBJECTS) libdebuginfod.so debuginfod-client-useragent.h
 
 # automake std-options override: arrange to pass LD_LIBRARY_PATH
 installcheck-binPROGRAMS: $(bin_PROGRAMS)
diff --git a/debuginfod/debuginfod-client.c b/debuginfod/debuginfod-client.c
index 9a4a0e0fc421..3c3610023e46 100644
--- a/debuginfod/debuginfod-client.c
+++ b/debuginfod/debuginfod-client.c
@@ -40,6 +40,7 @@
 
 #include "config.h"
 #include "debuginfod.h"
+#include "debuginfod-client-useragent.h"
 #include "system.h"
 #include <assert.h>
 #include <dirent.h>
@@ -514,7 +515,7 @@ debuginfod_query_server (debuginfod_client *c,
       curl_easy_setopt(data[i].handle, CURLOPT_NOSIGNAL, (long) 1);
       curl_easy_setopt(data[i].handle, CURLOPT_AUTOREFERER, (long) 1);
       curl_easy_setopt(data[i].handle, CURLOPT_ACCEPT_ENCODING, "");
-      curl_easy_setopt(data[i].handle, CURLOPT_USERAGENT, (void*) PACKAGE_STRING);
+      curl_easy_setopt(data[i].handle, CURLOPT_USERAGENT, (void*) PACKAGE_NAME "/" PACKAGE_VERSION "," DEBUGINFOD_CLIENT_USERAGENT);
 
       curl_multi_add_handle(curlm, data[i].handle);
       server_url = strtok_r(NULL, url_delim, &strtok_saveptr);
diff --git a/debuginfod/debuginfod-find.c b/debuginfod/debuginfod-find.c
index 8bd3a3dba7a0..fc7c373c93d1 100644
--- a/debuginfod/debuginfod-find.c
+++ b/debuginfod/debuginfod-find.c
@@ -1,6 +1,6 @@
 /* Command-line frontend for retrieving ELF / DWARF / source files
    from the debuginfod.
-   Copyright (C) 2019 Red Hat, Inc.
+   Copyright (C) 2019-2020 Red Hat, Inc.
    This file is part of elfutils.
 
    This file is free software; you can redistribute it and/or modify
diff --git a/debuginfod/debuginfod.cxx b/debuginfod/debuginfod.cxx
index 70cb95fecd65..2c1a77876677 100644
--- a/debuginfod/debuginfod.cxx
+++ b/debuginfod/debuginfod.cxx
@@ -1,5 +1,5 @@
 /* Debuginfo-over-http server.
-   Copyright (C) 2019 Red Hat, Inc.
+   Copyright (C) 2019-2020 Red Hat, Inc.
    This file is part of elfutils.
 
    This file is free software; you can redistribute it and/or modify
@@ -751,7 +751,12 @@ conninfo (struct MHD_Connection * conn)
     hostname[0] = servname[0] = '\0';
   }
 
-  return string(hostname) + string(":") + string(servname);
+  // extract headers relevant to administration
+  const char* user_agent = MHD_lookup_connection_value (conn, MHD_HEADER_KIND, "User-Agent") ?: "";
+  const char* x_forwarded_for = MHD_lookup_connection_value (conn, MHD_HEADER_KIND, "X-Forwarded-For") ?: "";
+  // NB: these are untrustworthy, beware if machine-processing log files
+
+  return string(hostname) + string(":") + string(servname) + string(" UA:") + string(user_agent) + string(" XFF:") + string(x_forwarded_for);
 }