// CVE-2026-21444 Proof of Concept
// This PoC demonstrates the IV handling issue in libtpms
// Compile: gcc -o poc poc.c -ltpms -lssl -lcrypto
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <tpms/tpm_library.h>
#include <openssl/evp.h>
#define TEST_DATA_SIZE 64
void demonstrate_iv_mismatch() {
printf("[*] CVE-2026-21444 PoC - libtpms IV Handling Issue\n");
printf("[*] Affected versions: libtpms 0.10.0, 0.10.1\n\n");
// Simulate the vulnerable behavior
unsigned char initial_iv[16] = {0};
unsigned char incorrect_iv[16] = {0};
unsigned char correct_iv[16] = {0};
unsigned char plaintext[TEST_DATA_SIZE] = "Sensitive data requiring encryption";
unsigned char ciphertext[TEST_DATA_SIZE];
// Initialize OpenSSL context
EVP_CIPHER_CTX *ctx = EVP_CIPHER_CTX_new();
if (!ctx) {
printf("[-] Failed to create cipher context\n");
return;
}
// Set initial IV
memcpy(initial_iv, (unsigned char[]){0x12, 0x34, 0x56, 0x78, 0x9A, 0xBC, 0xDE, 0xF0}, 8);
// Initialize encryption with initial IV
EVP_EncryptInit_ex(ctx, EVP_aes_128_cbc(), NULL,
(unsigned char*)"0123456789ABCDEF", initial_iv);
int len = 0;
int ciphertext_len = 0;
// Encrypt data
EVP_EncryptUpdate(ctx, ciphertext, &len, plaintext, TEST_DATA_SIZE);
ciphertext_len = len;
EVP_EncryptFinal_ex(ctx, ciphertext + len, &len);
ciphertext_len += len;
// Get IV after encryption
EVP_CIPHER_CTX_get_iv(ctx, correct_iv, 16);
// Simulate vulnerable behavior - libtpms returns initial IV instead
memcpy(incorrect_iv, initial_iv, 16);
printf("[+] Initial IV: ");
for(int i = 0; i < 16; i++) printf("%02X ", initial_iv[i]);
printf("\n");
printf("[+] Correct IV (post): ");
for(int i = 0; i < 16; i++) printf("%02X ", correct_iv[i]);
printf("\n");
printf("[!] Vulnerable returns: ");
for(int i = 0; i < 16; i++) printf("%02X ", incorrect_iv[i]);
printf("\n\n");
printf("[-] VULNERABLE: libtpms returns initial IV instead of final IV\n");
printf("[-] Impact: Subsequent encryption/decryption uses incorrect IV\n");
printf("[-] This weakens CBC mode encryption chain and data confidentiality\n");
EVP_CIPHER_CTX_free(ctx);
printf("\n[*] Recommendation: Upgrade to libtpms >= 0.10.2\n");
}
int main(int argc, char *argv[]) {
demonstrate_iv_mismatch();
return 0;
}