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author | Petr Písař <ppisar@redhat.com> | 2018-02-26 13:48:00 +0100 |
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committer | Slávek Banko <slavek.banko@axis.cz> | 2019-03-03 16:04:38 +0100 |
commit | 20e7000d0cd56ab6e10d8f22b9caf922e655402c (patch) | |
tree | 6c4e3bf1c50c29d6e56c8b78a6b4bfbbb65dbf77 /krfb | |
parent | 6221931c63e88eda17f9bd3128470bffb3b2cee3 (diff) | |
download | tdenetwork-20e7000d0cd56ab6e10d8f22b9caf922e655402c.tar.gz tdenetwork-20e7000d0cd56ab6e10d8f22b9caf922e655402c.zip |
Limit client cut text length to 1 MB
This patch constrains a client cut text length to 1 MB. Otherwise
a client could make server allocate 2 GB of memory and that seems to
be to much to classify it as a denial of service.
The limit also prevents from an integer overflow followed by copying
an uninitilized memory when processing msg.cct.length value larger
than SIZE_MAX or INT_MAX - sz_rfbClientCutTextMsg.
This patch also corrects accepting length value of zero (malloc(0) is
interpreted on differnet systems differently).
CVE-2018-7225
<https://github.com/LibVNC/libvncserver/issues/218>
(cherry picked from commit 28afb6c537dc82ba04d5f245b15ca7205c6dbb9c)
Diffstat (limited to 'krfb')
-rw-r--r-- | krfb/libvncserver/rfbserver.c | 21 |
1 files changed, 20 insertions, 1 deletions
diff --git a/krfb/libvncserver/rfbserver.c b/krfb/libvncserver/rfbserver.c index 66cc4ee3..5725d068 100644 --- a/krfb/libvncserver/rfbserver.c +++ b/krfb/libvncserver/rfbserver.c @@ -52,6 +52,9 @@ typedef int socklen_t; #define DEBUGPROTO(x) #endif +/* PRIu32 */ +#include <inttypes.h> + rfbClientPtr pointerClient = NULL; /* Mutex for pointer events */ static void rfbProcessClientProtocolVersion(rfbClientPtr cl); @@ -898,7 +901,23 @@ rfbProcessClientNormalMessage(cl) msg.cct.length = Swap32IfLE(msg.cct.length); - str = (char *)malloc(msg.cct.length); + /* uint32_t input is passed to malloc()'s size_t argument, + * to rfbReadExact()'s int argument, to rfbStatRecordMessageRcvd()'s int + * argument increased of sz_rfbClientCutTextMsg, and to setXCutText()'s int + * argument. Here we impose a limit of 1 MB so that the value fits + * into all of the types to prevent from misinterpretation and thus + * from accessing uninitialized memory (CVE-2018-7225) and also to + * prevent from a denial-of-service by allocating to much memory in + * the server. */ + if (msg.cct.length > 1<<20) { + rfbLog("rfbClientCutText: too big cut text length requested: %" PRIu32 "\n", + msg.cct.length); + rfbCloseClient(cl); + return; + } + + /* Allow zero-length client cut text. */ + str = (char *)calloc(msg.cct.length ? msg.cct.length : 1, 1); if ((n = ReadExact(cl, str, msg.cct.length)) <= 0) { if (n != 0) |