/* Provenance: openssl/openssl alpn_select_cb (fixed).
 * repo: openssl/openssl
 * commit: 6cc511826f09e513b4ec066d9b95acaf4f86d991
 * parent: 015255851371757d54c2560643eb3b3a88123cf1
 * commit_url: https://github.com/openssl/openssl/commit/6cc511826f09e513b4ec066d9b95acaf4f86d991
 * cve: CVE-2024-5535
 * license: Apache-2.0
 * function: alpn_select_cb
 * relpath: ssl/quic/quic_tserver.c
 */

static int alpn_select_cb(SSL *ssl, const unsigned char **out,
                          unsigned char *outlen, const unsigned char *in,
                          unsigned int inlen, void *arg)
{
    QUIC_TSERVER *srv = arg;
    static const unsigned char alpndeflt[] = {
        8, 'o', 's', 's', 'l', 't', 'e', 's', 't'
    };
    static const unsigned char *alpn;
    size_t alpnlen;

    if (srv->args.alpn == NULL) {
        alpn = alpndeflt;
        alpnlen = sizeof(alpndeflt);
    } else {
        alpn = srv->args.alpn;
        alpnlen = srv->args.alpnlen;
    }

    if (SSL_select_next_proto((unsigned char **)out, outlen, alpn, alpnlen,
                              in, inlen) != OPENSSL_NPN_NEGOTIATED)
        return SSL_TLSEXT_ERR_ALERT_FATAL;

    return SSL_TLSEXT_ERR_OK;
}