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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 5.3.0 (May 3rd, 2022)

Release 5.3.0 of wolfSSL embedded TLS has bug fixes and new features including:

New Feature Additions

Ports

Updated support for Stunnel to version 5.61
Add i.MX8 NXP SECO use for secure private ECC keys and expand cryptodev-linux for use with the RSA/Curve25519 with the Linux CAAM driver
Allow encrypt then mac with Apache port
Update Renesas TSIP version to 1.15 on GR-ROSE and certificate signature data for TSIP / SCE example
Add IAR MSP430 example, located in IDE/IAR-MSP430 directory
Add support for FFMPEG with the enable option --enable-ffmpeg, FFMPEG is used for recording and converting video and audio (https://ffmpeg.org/)
Update the bind port to version 9.18.0

Post Quantum

Add Post-quantum KEM benchmark for STM32
Enable support for using post quantum algorithms with embedded STM32 boards and port to STM32U585

Compatibility Layer Additions

Add port to support libspdm (https://github.com/DMTF/libspdm/blob/main/README.md), compatibility functions added for the port were:
- ASN1_TIME_compare
- DH_new_by_nid
- OBJ_length, OBJ_get0_data,
- EVP layer ChaCha20-Poly1305, HKDF
- EC_POINT_get_affine_coordinates
- EC_POINT_set_affine_coordinates
Additional functions added were:
- EC_KEY_print_fp
- EVP_PKEY_paramgen
- EVP_PKEY_sign/verify functionality
- PEM_write_RSAPublicKey
- PEM_write_EC_PUBKEY
- PKCS7_sign
- PKCS7_final
- SMIME_write_PKCS7
- EC_KEY/DH_up_ref
- EVP_DecodeBlock
- EVP_EncodeBlock
- EC_KEY_get_conv_form
- BIO_eof
- Add support for BIO_CTRL_SET and BIO_CTRL_GET
Add compile time support for the type SSL_R_NULL_SSL_METHOD_PASSED
Enhanced X509_NAME_print_ex() to support RFC5523 basic escape
More checks on OPENSSL_VERSION_NUMBER for API prototype differences
Add extended key usage support to wolfSSL_X509_set_ext
SSL_VERIFY_FAIL_IF_NO_PEER_CERT now can also connect with compatibility layer enabled and a TLS 1.3 PSK connection is used
Improve wolfSSL_BN_rand to handle non byte boundaries and top/bottom parameters
Changed X509_V_ERR codes to better match OpenSSL values used
Improve wolfSSL_i2d_X509_name to allow for a NULL input in order to get the expected resulting size
Enhance the smallstack build to reduce stack size farther when built with compatibility layer enabled

Misc.

Sniffer asynchronous support addition, handling of DH shared secret and tested with Intel QuickAssist
Added in support for OCSP with IPv6
Enhance SP (single precision) optimizations for use with the ECC P521
Add new public API wc_CheckCertSigPubKey() for use to easily check the signature of a certificate given a public key buffer
Add CSR (Certificate Signing Request) userId support in subject name
Injection and parsing of custom extensions in X.509 certificates
Add WOLF_CRYPTO_CB_ONLY_RSA and WOLF_CRYPTO_CB_ONLY_ECC to reduce code size if using only crypto callback functions with RSA and ECC
Created new --enable-engine configure flag used to build wolfSSL for use with wolfEngine
With TLS 1.3 PSK, when WOLFSSL_PSK_MULTI_ID_PER_CS is defined multiple IDs for a cipher suite can be handled
Added private key id/label support with improving the PK (Public Key) callbacks
Support for Intel QuickAssist ECC KeyGen acceleration
Add the function wolfSSL_CTX_SetCertCbCtx to set user context for certificate call back
Add the functions wolfSSL_CTX_SetEccSignCtx(WOLFSSL_CTX* ctx, void userCtx) and wolfSSL_CTX_GetEccSignCtx(WOLFSSL_CTX ctx) for setting and getting a user context
wolfRand for AMD --enable-amdrand

Fixes

PORT Fixes

KCAPI memory optimizations and page alignment fixes for ECC, AES mode fixes and reduction to memory usage
Add the new kdf.c file to the TI-RTOS build
Fix wait-until-done in RSA hardware primitive acceleration of ESP-IDF port
IOTSafe workarounds when reading files with ending 0’s and for ECC signatures

Math Library Fixes

Sanity check with SP math that ECC points ordinates are not greater than modulus length
Additional sanity checks that _sp_add_d does not error due to overflow
Wycheproof fixes, testing integration, and fixes for AVX / AArch64 ASM edge case tests
TFM fp_div_2_ct rework to avoid potential overflow

Misc.

Fix for PKCS#7 with Crypto Callbacks
Fix for larger curve sizes with deterministic ECC sign
Fixes for building wolfSSL alongside openssl using --enable-opensslcoexist
Fix for compatibility layer handling of certificates with SHA256 SKID (Subject Key ID)
Fix for wolfSSL_ASN1_TIME_diff erroring out on a return value of 0 from mktime
Remove extra padding when AES-CBC encrypted with PemToDer
Fixes for TLS v1.3 early data with async.
Fixes for async disables around the DevCopy calls
Fixes for Windows AES-NI with clang compiler
Fix for handling the detection of processing a plaintext TLS alert packet
Fix for potential memory leak in an error case with TLSX supported groups
Sanity check on input size in DecodeNsCertType
AES-GCM stack alignment fixes with assembly code written for AVX/AVX2
Fix for PK callbacks with server side and setting a public key

Improvements/Optimizations

Build Options and Warnings

Added example user settings template for FIPS v5 ready
Automake file touch cleanup for use with Yocto devtool
Allow disabling forced 'make clean' at the end of ./configure by using --disable-makeclean
Enable TLS 1.3 early data when specifying --enable-all option
Disable PK Callbacks with JNI FIPS builds
Add a FIPS cert 3389 ready option, this is the fips-ready build
Support (no)inline with Wind River Diab compiler
ECDH_compute_key allow setting of globalRNG with FIPS 140-3
Add logic equivalent to configure.ac in settings.h for Poly1305
Fixes to support building opensslextra with SP math
CPP protection for extern references to x86_64 asm code
Updates and enhancements for Espressif ESP-IDF wolfSSL setup_win.bat
Documentation improvements with auto generation
Fix reproducible-build for working an updated version of libtool, version 2.4.7
Fixes for Diab C89 and armclang
Fix mcapi_test.c to include the settings.h before crypto.h
Update and handle builds with NO_WOLFSSL_SERVER and NO_WOLFSSL_CLIENT
Fix for some macro defines with FIPS 140-3 build so that RSA_PKCS1_PSS_PADDING can be used with RSA sign/verify functions

Math Libraries

Add RSA/DH check for even modulus
Enhance TFM math to handle more alloc failure cases gracefully
SP ASM performance improvements mostly around AArch64
SP ASM improvements for additional cache attack resistance
Add RSA check for small difference between p and q
6-8% performance increase with ECC operations using SP int by improving the Montgomery Reduction

Testing and Validation

All shell scripts in source tree now tested for correctness using shellcheck and bash -n
Added build testing under gcc-12 and -std=c++17 and fixed warnings
TLS 1.3 script test improvement to wait for server to write file
Unit tests for ECC r/s zeroness handling
CI server was expanded with a very “quiet” machine that can support multiple ContantTime tests ensuring ongoing mitigation against side-channel timing based attacks. Algorithms being assessed on this machine are: AES-CBC, AES-GCM, CHACHA20, ECC, POLY1305, RSA, SHA256, SHA512, CURVE25519.
Added new multi configuration windows builds to CI testing for greater testing coverage of windows use-cases

Misc.

Support for ECC import to check validity of key on import even if one of the coordinates (x or y) is 0
Modify example app to work with FreeRTOS+IoT
Ease of access for cert used for verifying a PKCS#7 bundle
Clean up Visual Studio output and intermediate directories
With TLS 1.3 fail immediately if a server sends empty certificate message
Enhance the benchmark application to support multi-threaded testing
Improvement for wc_EccPublicKeyToDer to not overestimate the buffer size required
Fix to check if wc_EccPublicKeyToDer has enough output buffer space
Fix year 2038 problem in wolfSSL_ASN1_TIME_diff
Various portability improvements (Time, DTLS epoch size, IV alloc)
Prefer status_request_v2 over status_request when both are present
Add separate "struct stat" definition XSTATSTRUCT to make overriding XSTAT easier for portability
With SipHash replace gcc specific ASM instruction with generic
Don't force a ECC CA when a custom CA is passed with -A
Add peer authentication failsafe for TLS 1.2 and below
Improve parsing of UID from subject and issuer name with the compatibility layer by
Fallback to full TLS handshake if session ticket fails
Internal refactoring of code to reduce ssl.c file size