/* Provenance: openssl/openssl tls_parse_stoc_alpn (fixed).
 * repo: openssl/openssl
 * commit: 4b375b998798dd516d367036773073e1b88e6433
 * parent: 189a7ed3e380e34ea38fe4190a7c9396bace0fb7
 * commit_url: https://github.com/openssl/openssl/commit/4b375b998798dd516d367036773073e1b88e6433
 * cve: CVE-2024-5535
 * license: Apache-2.0
 * function: tls_parse_stoc_alpn
 * relpath: ssl/statem/extensions_clnt.c
 */

int tls_parse_stoc_alpn(SSL *s, PACKET *pkt, unsigned int context, X509 *x,
                        size_t chainidx)
{
    size_t len;
    PACKET confpkt, protpkt;
    int valid = 0;

    /* We must have requested it. */
    if (!s->s3.alpn_sent) {
        SSLfatal(s, SSL_AD_UNSUPPORTED_EXTENSION, SSL_R_BAD_EXTENSION);
        return 0;
    }
    /*-
     * The extension data consists of:
     *   uint16 list_length
     *   uint8 proto_length;
     *   uint8 proto[proto_length];
     */
    if (!PACKET_get_net_2_len(pkt, &len)
        || PACKET_remaining(pkt) != len || !PACKET_get_1_len(pkt, &len)
        || PACKET_remaining(pkt) != len) {
        SSLfatal(s, SSL_AD_DECODE_ERROR, SSL_R_BAD_EXTENSION);
        return 0;
    }

    /* It must be a protocol that we sent */
    if (!PACKET_buf_init(&confpkt, s->ext.alpn, s->ext.alpn_len)) {
        SSLfatal(s, SSL_AD_INTERNAL_ERROR, ERR_R_INTERNAL_ERROR);
        return 0;
    }
    while (PACKET_get_length_prefixed_1(&confpkt, &protpkt)) {
        if (PACKET_remaining(&protpkt) != len)
            continue;
        if (memcmp(PACKET_data(pkt), PACKET_data(&protpkt), len) == 0) {
            /* Valid protocol found */
            valid = 1;
            break;
        }
    }

    if (!valid) {
        /* The protocol sent from the server does not match one we advertised */
        SSLfatal(s, SSL_AD_DECODE_ERROR, SSL_R_BAD_EXTENSION);
        return 0;
    }

    OPENSSL_free(s->s3.alpn_selected);
    s->s3.alpn_selected = OPENSSL_malloc(len);
    if (s->s3.alpn_selected == NULL) {
        s->s3.alpn_selected_len = 0;
        SSLfatal(s, SSL_AD_INTERNAL_ERROR, ERR_R_INTERNAL_ERROR);
        return 0;
    }
    if (!PACKET_copy_bytes(pkt, s->s3.alpn_selected, len)) {
        SSLfatal(s, SSL_AD_DECODE_ERROR, SSL_R_BAD_EXTENSION);
        return 0;
    }
    s->s3.alpn_selected_len = len;

    if (s->session->ext.alpn_selected == NULL
            || s->session->ext.alpn_selected_len != len
            || memcmp(s->session->ext.alpn_selected, s->s3.alpn_selected, len)
               != 0) {
        /* ALPN not consistent with the old session so cannot use early_data */
        s->ext.early_data_ok = 0;
    }
    if (!s->hit) {
        /*
         * This is a new session and so alpn_selected should have been
         * initialised to NULL. We should update it with the selected ALPN.
         */
        if (!ossl_assert(s->session->ext.alpn_selected == NULL)) {
            SSLfatal(s, SSL_AD_INTERNAL_ERROR, ERR_R_INTERNAL_ERROR);
            return 0;
        }
        s->session->ext.alpn_selected =
            OPENSSL_memdup(s->s3.alpn_selected, s->s3.alpn_selected_len);
        if (s->session->ext.alpn_selected == NULL) {
            s->session->ext.alpn_selected_len = 0;
            SSLfatal(s, SSL_AD_INTERNAL_ERROR, ERR_R_INTERNAL_ERROR);
            return 0;
        }
        s->session->ext.alpn_selected_len = s->s3.alpn_selected_len;
    }

    return 1;
}