Android/frameworks_base
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

Captive portal: better detect empty responses

Browse Source 
The captive portal detection logic treats empty http responses with a
Content-Length of 0 as not coming from a portal.

However when the Content-Length is missing from the response header, the
empty response is not detected as such and is classified as a captive
portal answer.

When this happens for the http probe, the portal detection logic will
short circuit the detection and wrongly report a portal. The system
validates the network in such conditions only if the https probe
returns a successful connection faster than the http probe.

This patch attempts to better detect empty responses by trying to read
the first byte from the response body when the Content-Length is missing
for 200 responses.

Test: build, flashed + manual tests.
Bug: 33498325
Change-Id: Ie2e5c6a9dc3740e4a2304034879b5ed60f277ade
This commit is contained in:
Hugo Benichi
2017-01-11 16:23:26 +09:00
parent a00c235600
commit cb4aa4d412
1 changed files with 20 additions and 13 deletions
Download Patch File Download Diff File Expand all files Collapse all files

33
services/core/java/com/android/server/connectivity/NetworkMonitor.java
View File

@@ -809,19 +809,26 @@ public class NetworkMonitor extends StateMachine {
// portal. If it is considered a captive portal, a different sign-in URL
// is needed (i.e. can't browse a 204). This could be the result of an HTTP
// proxy server.
// Consider 200 response with "Content-length=0" to not be a captive portal.
// There's no point in considering this a captive portal as the user cannot
// sign-in to an empty page. Probably the result of a broken transparent proxy.
// See http://b/9972012.
if (httpResponseCode == 200 && urlConnection.getContentLength() == 0) {
validationLog("Empty 200 response interpreted as 204 response.");
httpResponseCode = 204;
}
if (httpResponseCode == 200 && probeType == ValidationProbeEvent.PROBE_PAC) {
validationLog("PAC fetch 200 response interpreted as 204 response.");
httpResponseCode = 204;
if (httpResponseCode == 200) {
if (probeType == ValidationProbeEvent.PROBE_PAC) {
validationLog("PAC fetch 200 response interpreted as 204 response.");
httpResponseCode = 204;
} else if (urlConnection.getContentLengthLong() == 0) {
// Consider 200 response with "Content-length=0" to not be a captive portal.
// There's no point in considering this a captive portal as the user cannot
// sign-in to an empty page. Probably the result of a broken transparent proxy.
// See http://b/9972012.
validationLog(
"200 response with Content-length=0 interpreted as 204 response.");
httpResponseCode = 204;
} else if (urlConnection.getContentLengthLong() == -1) {
// When no Content-length (default value == -1), attempt to read a byte from the
// response. Do not use available() as it is unreliable. See http://b/33498325.
if (urlConnection.getInputStream().read() == -1) {
validationLog("Empty 200 response interpreted as 204 response.");
httpResponseCode = 204;
}
}
}
} catch (IOException e) {
validationLog("Probably not a portal: exception " + e);