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wolfSSL Embedded SSL/TLS Library

The wolfSSL embedded SSL library (formerly CyaSSL) is a lightweight SSL/TLS library written in ANSI C and targeted for embedded, RTOS, and resource-constrained environments - primarily because of its small size, speed, and feature set. It is commonly used in standard operating environments as well because of its royalty-free pricing and excellent cross platform support. wolfSSL supports industry standards up to the current TLS 1.3 and DTLS 1.2, is up to 20 times smaller than OpenSSL, and offers progressive ciphers such as ChaCha20, Curve25519, Blake2b and Post-Quantum TLS 1.3 groups. User benchmarking and feedback reports dramatically better performance when using wolfSSL over OpenSSL.

wolfSSL is powered by the wolfCrypt cryptography library. Two versions of wolfCrypt have been FIPS 140-2 validated (Certificate #2425 and certificate #3389). FIPS 140-3 validation is in progress. For additional information, visit the wolfCrypt FIPS FAQ or contact fips@wolfssl.com.

Why Choose wolfSSL?

There are many reasons to choose wolfSSL as your embedded, desktop, mobile, or enterprise SSL/TLS solution. Some of the top reasons include size (typical footprint sizes range from 20-100 kB), support for the newest standards (SSL 3.0, TLS 1.0, TLS 1.1, TLS 1.2, TLS 1.3, DTLS 1.0, and DTLS 1.2), current and progressive cipher support (including stream ciphers), multi-platform, royalty free, and an OpenSSL compatibility API to ease porting into existing applications which have previously used the OpenSSL package. For a complete feature list, see Chapter 4 of the wolfSSL manual.

Notes, Please Read

Note 1

wolfSSL as of 3.6.6 no longer enables SSLv3 by default. wolfSSL also no longer supports static key cipher suites with PSK, RSA, or ECDH. This means if you plan to use TLS cipher suites you must enable DH (DH is on by default), or enable ECC (ECC is on by default), or you must enable static key cipher suites with one or more of the following defines:

WOLFSSL_STATIC_DH
WOLFSSL_STATIC_RSA
WOLFSSL_STATIC_PSK

Though static key cipher suites are deprecated and will be removed from future versions of TLS. They also lower your security by removing PFS.

When compiling ssl.c, wolfSSL will now issue a compiler error if no cipher suites are available. You can remove this error by defining WOLFSSL_ALLOW_NO_SUITES in the event that you desire that, i.e., you're not using TLS cipher suites.

Note 2

wolfSSL takes a different approach to certificate verification than OpenSSL does. The default policy for the client is to verify the server, this means that if you don't load CAs to verify the server you'll get a connect error, no signer error to confirm failure (-188).

If you want to mimic OpenSSL behavior of having SSL_connect succeed even if verifying the server fails and reducing security you can do this by calling:

wolfSSL_CTX_set_verify(ctx, WOLFSSL_VERIFY_NONE, NULL);

before calling wolfSSL_new();. Though it's not recommended.

Note 3

The enum values SHA, SHA256, SHA384, SHA512 are no longer available when wolfSSL is built with --enable-opensslextra (OPENSSL_EXTRA) or with the macro NO_OLD_SHA_NAMES. These names get mapped to the OpenSSL API for a single call hash function. Instead the name WC_SHA, WC_SHA256, WC_SHA384 and WC_SHA512 should be used for the enum name.

wolfSSL Release 5.5.2 (Oct 28, 2022)

Release 5.5.2 of wolfSSL embedded TLS has bug fixes and new features including:

Vulnerabilities

[Med] In the case that the WOLFSSL_CALLBACKS macro is set when building wolfSSL, there is a potential heap over read of 5 bytes when handling TLS 1.3 client connections. This heap over read is limited to wolfSSL builds explicitly setting the macro WOLFSSL_CALLBACKS, the feature does not get turned on by any other build options. The macro WOLFSSL_CALLBACKS is intended for debug use only, but if having it enabled in production, users are recommended to disable WOLFSSL_CALLBACKS. Users enabling WOLFSSL_CALLBACKS are recommended to update their version of wolfSSL. Thanks to Lucca Hirschi and Steve Kremer from LORIA, Inria and Max Ammann from Trail of Bits for finding and reporting the bug with the tlspuffin tool developed partly at LORIA and Trail of Bits. CVE 2022-42905

Release 5.5.2 of wolfSSL embedded TLS has bug fixes and new features including:

New Feature Additions

Add function wolfSSL_CTX_load_system_CA_certs to load system CA certs into a WOLFSSL_CTX and --sys-ca-certs option to example client
Add wolfSSL_set1_host to OpenSSL compatible API
Added the function sk_X509_shift
AES x86 ASM for AES-CBC and GCM performance enhancements
Add assembly for AES for ARM32 without using crypto hardware instructions
Xilinx Versal port and hardware acceleration tie in
SP Cortex-M support for ICCARM

Enhancements

Add snifftest vcxproj file and documentation
Nucleus Thread Types supported
Handle certificates with RSA-PSS signature that have RSAk public keys
Small stack build improvements
DTLS 1.3 improvements for Alerts and unit tests
Add a binary search for CRL
Improvement of SSL/CTX_set_max_early_data() for client side
Remove unused ASN1_GENERALIZEDTIME enum value from wolfssl/ssl.h
Add user_settings.h for Intel/M1 FIPSv2 macOS C++ projects
Add dtlscid.test to ‘make check’ unit testing
Generate an assembler-safe user_settings.h in configure.ac and CMakeLists.txt
ForceZero enabled with USE_FAST_MATH
Add TLS 1.3 support of ticketNonce sizes bigger than MAX_TICKET_NONCE_SZ
FIPSv2 builds on win10 adjust for new fastmath default in settings.h
Add IRQ install for Aruix example

Fixes

When looking up the session by ID on the server, check that the protocol version of the SSL and session match on TLS 1.3 or not
Fix for potential EVP_PKEY_DH memory leak with OPENSSL_EXTRA
Curve448 32-bit C code: handle corner case
Fixup builds using WOLFSSL_LOG_PRINTF
Correct DIST_POINT_NAME type value
Do not perform IV Wrap test when using cert3389 inlined armasm
Fix for Linux kernel module and stdio.h
(D)TLS: send alert on version mismatch
Fix PKCS#7 SignedData verification when signer cert is not first in SET
Fix bug with wolfIO_TcpConnect not working with timeout on Windows
Fix output length bug in SP non-blocking ECC shared secret gen
Fix build with enable-fastmath and disable-rsa
Correct wolfSSL_sk_X509_new in OpenSSL compatible API
Fixes for SP and x86_64 with MSVC
Fix wrong size using DTLSv1.3 in RestartHandshakeHashWithCookie
Fix redundant file include with TI RTOS build
Fix wolfCrypt only build with wincrypt.h
DTLS 1.2: Reset state when sending HelloVerifyRequest