---
name: "libressl-SSL_CTX_set_max_cert_list"
section: "3"
platform: "linux"
package: "libressl"
version: "4.4.0-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/libressl-SSL_CTX_set_max_cert_list"
---

# libressl-SSL\_CTX\_set\_max\_cert\_list(3)

manipulate allowed size for the peer's certificate chain

## NAME

**SSL\_CTX\_set\_max\_cert\_list**, **SSL\_CTX\_get\_max\_cert\_list**, **SSL\_set\_max\_cert\_list**, **SSL\_get\_max\_cert\_list** – manipulate allowed size for the peer's certificate chain

## SYNOPSIS

SSL Library (libssl, -lssl) libcrypto

**#include \<openssl/ssl.h\>**

*long*\

**SSL\_CTX\_set\_max\_cert\_list**(*SSL\_CTX \*ctx*, *long size*);

*long*\

**SSL\_CTX\_get\_max\_cert\_list**(*SSL\_CTX \*ctx*);

*long*\

**SSL\_set\_max\_cert\_list**(*SSL \*ssl*, *long size*);

*long*\

**SSL\_get\_max\_cert\_list**(*SSL \*ctx*);

## DESCRIPTION

**SSL\_CTX\_set\_max\_cert\_list**() sets the maximum size allowed for the peer's certificate chain for all *SSL* objects created from *ctx* to be *size* bytes. The *SSL* objects inherit the setting valid for *ctx* at the time SSL\_new(3) is being called.

**SSL\_CTX\_get\_max\_cert\_list**() returns the currently set maximum size for *ctx*.

**SSL\_set\_max\_cert\_list**() sets the maximum size allowed for the peer's certificate chain for *ssl* to be *size* bytes. This setting stays valid until a new value is set.

**SSL\_get\_max\_cert\_list**() returns the currently set maximum size for *ssl*.

During the handshake process, the peer may send a certificate chain. The TLS/SSL standard does not give any maximum size of the certificate chain. The OpenSSL library handles incoming data by a dynamically allocated buffer. In order to prevent this buffer from growing without bound due to data received from a faulty or malicious peer, a maximum size for the certificate chain is set.

The default value for the maximum certificate chain size is 100kB (30kB on the 16bit DOS platform). This should be sufficient for usual certificate chains (OpenSSL's default maximum chain length is 10, see SSL\_CTX\_set\_verify(3), and certificates without special extensions have a typical size of 1-2kB).

For special applications it can be necessary to extend the maximum certificate chain size allowed to be sent by the peer. See for example the work on and at **https://www.ietf.org/** and **http://www.globus.org/**.

Under normal conditions it should never be necessary to set a value smaller than the default, as the buffer is handled dynamically and only uses the memory actually required by the data sent by the peer.

If the maximum certificate chain size allowed is exceeded, the handshake will fail with a SSL\_R\_EXCESSIVE\_MESSAGE\_SIZE error.

## RETURN VALUES

**SSL\_CTX\_set\_max\_cert\_list**() and **SSL\_set\_max\_cert\_list**() return the previously set value.

**SSL\_CTX\_get\_max\_cert\_list**() and **SSL\_get\_max\_cert\_list**() return the currently set value.

## SEE ALSO

[ssl(3)](/ssl/3.md), SSL\_CTX\_ctrl(3), SSL\_CTX\_set\_verify(3), SSL\_new(3)

## HISTORY

These functions first appeared in OpenSSL 0.9.7 and have been available since OpenBSD 3.2.