size_t CRYPTO_ccm128_tag(CCM128_CONTEXT *ctx, unsigned char *tag, size_t len)
{
    unsigned int M = (ctx->nonce.c[0] >> 3) & 7;
    M *= 2;
    M += 2;
    if (len < M)
        return 0;
    memcpy(tag, ctx->cmac.c, M);
    return M;
}
['static int aes_ccm_tls_cipher(EVP_CIPHER_CTX *ctx, unsigned char *out,\n                              const unsigned char *in, size_t len)\n{\n    EVP_AES_CCM_CTX *cctx = EVP_C_DATA(EVP_AES_CCM_CTX,ctx);\n    CCM128_CONTEXT *ccm = &cctx->ccm;\n    if (out != in || len < (EVP_CCM_TLS_EXPLICIT_IV_LEN + (size_t)cctx->M))\n        return -1;\n    if (EVP_CIPHER_CTX_encrypting(ctx))\n        memcpy(out, EVP_CIPHER_CTX_buf_noconst(ctx),\n               EVP_CCM_TLS_EXPLICIT_IV_LEN);\n    memcpy(EVP_CIPHER_CTX_iv_noconst(ctx) + EVP_CCM_TLS_FIXED_IV_LEN, in,\n           EVP_CCM_TLS_EXPLICIT_IV_LEN);\n    len -= EVP_CCM_TLS_EXPLICIT_IV_LEN + cctx->M;\n    if (CRYPTO_ccm128_setiv(ccm, EVP_CIPHER_CTX_iv_noconst(ctx), 15 - cctx->L,\n                            len))\n            return -1;\n    CRYPTO_ccm128_aad(ccm, EVP_CIPHER_CTX_buf_noconst(ctx), cctx->tls_aad_len);\n    in += EVP_CCM_TLS_EXPLICIT_IV_LEN;\n    out += EVP_CCM_TLS_EXPLICIT_IV_LEN;\n    if (EVP_CIPHER_CTX_encrypting(ctx)) {\n        if (cctx->str ? CRYPTO_ccm128_encrypt_ccm64(ccm, in, out, len,\n                                                    cctx->str) :\n            CRYPTO_ccm128_encrypt(ccm, in, out, len))\n            return -1;\n        if (!CRYPTO_ccm128_tag(ccm, out + len, cctx->M))\n            return -1;\n        return len + EVP_CCM_TLS_EXPLICIT_IV_LEN + cctx->M;\n    } else {\n        if (cctx->str ? !CRYPTO_ccm128_decrypt_ccm64(ccm, in, out, len,\n                                                     cctx->str) :\n            !CRYPTO_ccm128_decrypt(ccm, in, out, len)) {\n            unsigned char tag[16];\n            if (CRYPTO_ccm128_tag(ccm, tag, cctx->M)) {\n                if (!CRYPTO_memcmp(tag, in + len, cctx->M))\n                    return len;\n            }\n        }\n        OPENSSL_cleanse(out, len);\n        return -1;\n    }\n}', 'size_t CRYPTO_ccm128_tag(CCM128_CONTEXT *ctx, unsigned char *tag, size_t len)\n{\n    unsigned int M = (ctx->nonce.c[0] >> 3) & 7;\n    M *= 2;\n    M += 2;\n    if (len < M)\n        return 0;\n    memcpy(tag, ctx->cmac.c, M);\n    return M;\n}']