CVE-2026-31719: Linux内核Kerberos解密完整性验证绕过

/* * Conceptual PoC for CVE-2026-31719 * Demonstrating the missing callback chain in the vulnerable decrypt path. * This code is illustrative of the kernel logic flaw. */ #include <linux/crypto.h> #include <linux/kernel.h> // Simulated structure of the request struct krb5enc_request { struct crypto_async_request base; struct skcipher_request *skreq; // ... other fields }; // The function that performs the hash verification void krb5enc_dispatch_decrypt_hash(struct krb5enc_request *req) { // Integrity check logic (HMAC verification) happens here printk(KERN_DEBUG "Verifying hash..."); } // VULNERABLE FUNCTION LOGIC static int vulnerable_krb5enc_dispatch_decrypt(struct krb5enc_request *req) { int ret; // ... // Prepare the skcipher request // BUG: The completion callback is set directly to the caller's handler. // When skcipher completes asynchronously, it calls 'req->base.complete', // skipping 'krb5enc_dispatch_decrypt_hash' entirely. req->base.complete = caller_completion_handler; ret = crypto_skcipher_decrypt(req->skreq); // If the operation is in progress (async), the function returns here. // The hash verification is NEVER called for async completions. if (ret == -EINPROGRESS || ret == -EBUSY) return ret; // Only reached if operation was synchronous krb5enc_dispatch_decrypt_hash(req); return ret; } // EXPLOIT SCENARIO: // An attacker sends a packet that triggers the async path (e.g., large data). // The kernel returns -EINPROGRESS, completes decryption in hardware/softirq, // calls 'caller_completion_handler', and the application uses the data // without 'krb5enc_dispatch_decrypt_hash' ever verifying the integrity.