Fix missing tag_size entry for sm4-128-gcm causing zero tag for chacha20/xchacha20 AEAD ciphers

[Copilot]

When sm4-128-gcm was inserted at index 3 in the AEAD cipher tables and AEAD_CIPHER_NUM was bumped, supported_aead_ciphers_tag_size was left with only 4 entries. With 5 ciphers but 4 tag-size entries, chacha20-ietf-poly1305 (now index 4) and xchacha20-ietf-poly1305 (index 5) silently got a zero tag size — breaking authentication tag append/verify for those ciphers entirely.

Changes

• src/aead.h — AEAD_CIPHER_NUM 4→5 (5→6 with xchacha)
• src/aead.c
  • Add #define SM4128GCM 3; renumber CHACHA20POLY1305IETF to 4, XCHACHA20POLY1305IETF to 5
  • Add "sm4-128-gcm" / "SM4-128-GCM" to name tables
  • Fix supported_aead_ciphers_tag_size — add missing entry so all 5 slots are populated:

    // Before (4 entries, AEAD_CIPHER_NUM=5 → chacha20 tag_size=0):
    static const int supported_aead_ciphers_tag_size[AEAD_CIPHER_NUM] = {
        16, 16, 16, 16,
    };
    // After:
    static const int supported_aead_ciphers_tag_size[AEAD_CIPHER_NUM] = {
        16, 16, 16, 16, 16,  // aes-128, aes-192, aes-256, sm4-128, chacha20
    };

  • Update nonce/key size tables; add SM4128GCM case to encrypt/decrypt switches
• src/stream.h — STREAM_CIPHER_NUM 21→23
• src/stream.c — Add SM4_128_CBC (index 13) and SM4_128_CTR (index 14); shift existing defines; populate mbedTLS name, nonce, and key size arrays
• src/utils.c — Add SM4 ciphers to usage() output