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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 5.5.1 (Sep 28, 2022)

Release 5.5.1 of wolfSSL embedded TLS has bug fixes and new features including:

Vulnerabilities

[Med] Denial of service attack and buffer overflow against TLS 1.3 servers using session ticket resumption. When built with --enable-session-ticket and making use of TLS 1.3 server code in wolfSSL, there is the possibility of a malicious client to craft a malformed second ClientHello packet that causes the server to crash. This issue is limited to when using both --enable-session-ticket and TLS 1.3 on the server side. Users with TLS 1.3 servers, and having --enable-session-ticket, should update to the latest version of wolfSSL. Thanks to Max at Trail of Bits for the report and "LORIA, INRIA, France" for research on tlspuffin.

New Feature Additions

Add support for non-blocking ECC key gen and shared secret gen for P-256/384/521
Add support for non-blocking ECDHE/ECDSA in TLS/DTLS layer.
Port to NXP RT685 with FreeRTOS
Add option to build post quantum Kyber API (--enable-kyber)
Add post quantum algorithm sphincs to wolfCrypt
Config. option to force no asm with SP build (--enable-sp=noasm)
Allow post quantum keyshare for DTLS 1.3

Enhancements

DTLSv1.3: Do HRR Cookie exchange by default
Add wolfSSL_EVP_PKEY_new_CMAC_key to OpenSSL compatible API
Update ide win10 build files to add missing sp source files
Improve Workbench docs
Improve EVP support for CHACHA20_POLY1305
Improve wc_SetCustomExtension documentation
RSA-PSS with OCSP and add simple OCSP response DER verify test case
Clean up some FIPS versioning logic in configure.ac and WIN10 user_settings.h
Don't over-allocate memory for DTLS fragments
Add WOLFSSL_ATECC_TFLXTLS for Atmel port
SHA-3 performance improvements with x86_64 assembly
Add code to fallback to S/W if TSIP cannot handle
Improves entropy with VxWorks
Make time in milliseconds 64-bits for longer session ticket lives
Support for setting cipher list with bytes
wolfSSL_set1_curves_list(), wolfSSL_CTX_set1_curves_list() improvements
Add to RSAES-OAEP key parsing for pkcs7
Add missing DN nid to work with PrintName()
SP int: default to 16 bit word size when NO_64BIT defined
Limit the amount of fragments we store per a DTLS connection and error out when max limit is reached
Detect when certificate's RSA public key size is too big and fail on loading of certificate

Fixes

Fix for async with OCSP non-blocking in ProcessPeerCerts
Fixes for building with 32-bit and socket size sign/unsigned mismatch
Fix Windows CMakeList compiler options
TLS 1.3 Middle-Box compat: fix missing brace
Configuration consistency fixes for RSA keys and way to force disable of private keys
Fix for Aarch64 Mac M1 SP use
Fix build errors and warnings for MSVC with DTLS 1.3
Fix HMAC compat layer function for SHA-1
Fix DTLS 1.3 do not negotiate ConnectionID in HelloRetryRequest
Check return from call to wc_Time
SP math: fix build configuration with opensslall
Fix for async session tickets
SP int mp_init_size fixes when SP_WORD_SIZE == 8
Ed. function to make public key now checks for if the private key flag is set
Fix HashRaw WC_SHA256_DIGEST_SIZE for wc_Sha256GetHash
Fix for building with PSK only
Set correct types in wolfSSLsk*_new functions
Sanity check that size passed to mp_init_size() is no more than SP_INT_DIGITS