CVE-2026-23364: Linux内核ksmbd时序攻击漏洞

// Conceptual PoC demonstrating the timing difference vulnerability // This C code illustrates why memcmp is unsafe for MACs #include <stdio.h> #include <string.h> #include <stdint.h> // Vulnerable implementation using memcmp (variable time) int vulnerable_mac_check(const uint8_t *a, const uint8_t *b, size_t len) { // memcmp returns 0 on match, non-zero on mismatch // It exits early on the first differing byte, leaking timing info return memcmp(a, b, len) == 0; } // Secure implementation (conceptual constant time) int secure_mac_check(const uint8_t *a, const uint8_t *b, size_t len) { volatile uint8_t result = 0; for (size_t i = 0; i < len; i++) { result |= (a[i] ^ b[i]); // Always iterates through the whole buffer } return result == 0; } // In a real attack scenario against ksmbd: // 1. Attacker sends packets with varying MAC bytes. // 2. Measures response time (microseconds). // 3. If time is shorter, the mismatch occurred early in the string. // 4. If time is longer, the mismatch occurred later or no mismatch. // 5. Reconstruct the valid MAC byte by byte.