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 [email protected].

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 5.6.0 (Mar 24, 2023)

Release 5.6.0 has been developed according to wolfSSL's development and QA process (see link below) and successfully passed the quality criteria. https://www.wolfssl.com/about/wolfssl-software-development-process-quality-assurance

NOTE: * --enable-heapmath is being deprecated and will be removed by 2024 * This release makes ASN Template the default with ./configure, the previous ASN parsing can be built with --enable-asn=original

Release 5.6.0 of wolfSSL embedded TLS has bug fixes and new features including:

New Feature Additions

ASN template is now the default ASN parsing implementation when compiling with configure
Added in support for TLS v1.3 Encrypted Client Hello (ECH) and HPKE (Hybrid Public Key Encryption)
DTLS 1.3 stateless server ClientHello parsing support added

Ports

Add RX64/RX71 SHA hardware support
Port to RT1170 and expand NXP CAAM driver support
Add NuttX integration files for ease of use
Updated Stunnel support for version 5.67 Compatibility Layer
Add in support for AES-CCM with EVP
BN compatibility API refactoring and separate API created
Expanding public key type cipher suite list strings support

Misc.

Support pthread_rwlock and add enable option
Add wolfSSL_CertManagerLoadCABuffer_ex() that takes a user certificate chain flag and additional verify flag options
Docker build additions for wolfSSL library and wolfCLU application
Add favorite drink pilot attribute type to get it from the encoding
Added in support for indefinite length BER parsing with PKCS12
Add dynamic session cache which allocates sessions from the heap with macro SESSION_CACHE_DYNAMIC_MEM

Improvements / Optimizations

Tests

Additional CI (continuous integration) testing and leveraging of GitHub workflows
Add CI testing for wpa_supplicant, OpenWrt and OpenVPN using GitHub workflows
Add compilation of Espressif to GitHub workflows tests
Refactoring and improving error results with wolfCrypt unit test application
Minor warning fixes from Coverity static analysis scan
Add new SHA-512/224 and SHA-512/256 tests
Used codespell and fixed some minor typos

Ports

Improve TLS1.2 client authentication to use TSIP
Updated Kyber macro to be WOLFSSL_HAVE_KYBER and made changes that make Kyber work on STM32
AES-GCM Windows assembly additions
CRLF line endings, trailing spaces for C# Wrapper Projects Compatibility Layer
Update PubKey and Key PEM-to-DER APIs to support return of needed DER size
Allow reading ENC EC PRIVATE KEY as well via wolfSSL_PEM_read_bio_ECPrivateKey
Improve wolfSSL_EC_POINT_cmp to handle Jacobian ordinates
Fix issue with BIO_reset() and add BIO_FLAGS_MEM_RDONLY flag support for read only BIOs

SP

In SP math library rework mod 3 and use count leading zero instruction
Fix with SP ECC sign to reject the random k generated when r is 0
With SP math add better detection of when add won't work and double is needed with point_add_qz1 internal function
With SP int fail when buffer writing to is too small for number rather than discarding the extra values

Builds

Define WOLFSSL_SP_SMALL_STACK if wolfSSL is build with --enable-smallstack
Fix CMake to exclude libm when DH is not enabled
Allow building of SAKKE as external non-FIPS algorithm with wolfmikey product
Add option to add library suffix, --with-libsuffix
ASN template compile option WOLFSSL_ASN_INT_LEAD_0_ANY to allow leading zeros
Add user_settings.h template for wolfTPM to examples/configs/user_settings_wolftpm.h
Purge the AES variant of Dilithium
Expand WOLFSSL_NO_ASN_STRICT to allow parsing of explicit ECC public key
Remove relocatable text in ARMv7a AES assembly for use with FIPS builds
Expand checking for hardware that supports ARMv7a neon with autotools configure
Sanity check on allocation fails with DSA and FP_ECC build when zeroizing internal buffer
Additional TLS alerts sent when compiling with WOLFSSL_EXTRA_ALERTS macro defined

Benchmarking

Update wolfCrypt benchmark Windows build files to support x64 Platform
Add SHA512/224 and SHA512/256 benchmarks, fixed CVS macro and display sizes
Separate AES-GCM streaming runs when benchmarked
No longer call external implementation of Kyber from benchmark
Fix for benchmarking shake with custom block size
Fixes for benchmark help -alg list and block format Documentation/Examples
Document use of wc_AesFree() and update documentation of Ed25519 with Doxygen
Move the wolfSSL Configuration section higher in QUIC.md
Add Japanese Doxygen documentation for cmac.h, quic.h and remove incomplete Japanese doxygen in asn_public.h
Espressif examples run with local wolfSSL now with no additional setup needed
Added a fix for StartTLS use In the example client
Add a base-line user_settings.h for use with FIPS 140-3 in XCode example app

Optimizations

AES-NI usage added for AES modes ECB/CTR/XTS

Misc

Update AES-GCM stream decryption to allow long IVs
Internal refactor to use wolfSSL_Ref functions when incrementing or decrementing the structures reference count and fixes for static analysis reports
Cleanup function logging making adjustments to the debug log print outs
Remove realloc dependency in DtlsMsgCombineFragBuckets function
Refactor to use WOLFSSL_CTX’s cipher suite list when possible
Update internal padding of 0’s with DSA sign and additional tests with mp_to_unsigned_bin_len function
With DTLS SRTP use wolfSSL_export_keying_material instead of wc_PRF_TLS
Updated macro naming from HAVE_KYBER to be WOLFSSL_HAVE_KYBER
Update AES XTS encrypt to handle in-place encryption properly
With TLS 1.3 add option to require only PSK with DHE

Fixes

Ports

Fix for AES use with CAAM on imx8qxp with SECO builds
Fix for PIC32 crypto HW and unused TLSX_SetResponse
Fix warning if ltime is unsigned seen with QNX build
Updates and fix for Zephyr project support
Include sys/time.h for WOLFSSL_RIOT_OS
Move X509_V errors from enums to defines for use with HAProxy CLI
Fix IAR compiler warnings resolved
Fix for STM32 Hash peripherals (like on F437) with FIFO depth = 1
ESP32 fix for SHA384 init with hardware acceleration

Builds

Add WOLFSSL_IP_ALT_NAME macro define to --enable-curl
Fixes for building with C++17 and avoiding clashing with byte naming
Fixes SP math all build issue with small-stack and no hardening
Fix for building with ASN template with NO_ASN_TIME defined
Fix building FIPSv2 with WOLFSSL_ECDSA_SET_K defined
Don't allow aesgcm-stream option with kcapi
Fix DTLS test case for when able to read peers close notify alert on FreeBSD systems
Fix for "expression must have a constant value" in tls13.c with Green Hills compiler
Fixes for building KCAPI with opensslextra enabled
Fix warnings of shadows min and subscript with i486-netbsd-gcc compiler
Fix issue with async and WOLFSSL_CHECK_ALERT_ON_ERR
Fix for PKCS7 with asynchronous crypto enabled

Math Library

SP Aarch64 fix for conditional changed in asm needing "cc" and fix for ECC P256 mont reduce
In SP builds add sanity check with DH exp. to check the output length for minimum size
In SP math fix scalar length check with EC scalar multiply
With SP int fix handling negative character properly with read radix
Add error checks before setting variable err in SP int with the function sp_invmod_mont_ct
Fix to add sanity check for malloc of zero size in fastmath builds
In fastmath fix a possible overflow in fp_to_unsigned_bin_len length check
Heapmath fast mod. reduce fix

Compatibility Layer

Fixes for encoding/decoding ecc public keys and ensure i2d public key functions do not include any private key information
Fix for EVP_EncryptUpdate to update outl on empty input
Fix SE050 RSA public key loading and RSA/ECC SE050 TLS Compatibility
Rework EC API and validate point after setting it
Fix for X509 RSA PSS with compatibility layer functions
Fix size of structures used with SHA operations when built with opensslextra for Espressif hardware accelerated hashing
Added sanity check on key length with wolfSSL_CMAC_Init function
Fix for return value type conversion of bad mutex error in logging function
Fix NID conflict NID_givenName and NID_md5WithRSAEncryption
Fix unguarded XFPRINTF calls with opensslextra build
Fix wolfSSL_ASN1_INTEGER_to_BN for negative values
Fix for potential ASN1_STRING leak in wolfSSL_X509_NAME_ENTRY_create_by_txt and wolfSSL_X509_NAME_ENTRY_create_by_NID when memory allocation fails

Misc.

Add sanity check to prevent an out of bounds read with OCSP response decoding
Sanity check to not allow 0 length with bit string and integer when parsing ASN1 syntax
Adjust RNG sanity checks and remove error prone first byte comparison
With PKCS7 add a fix for GetAsnTimeString() to correctly increment internal data pointer
PKCS7 addition of sequence around algo parameters with authenvelop
DSA fixes for clearing mp_int before re-reading data and avoid mp_clear without first calling mp_init
Fix for SRTP setting bitfield when it is encoded for the TLS extension
Fix for handling small http headers when doing CRL verification
Fix for ECCSI hash function to validate the output size and curve size
Fix for value of givenName and name being reversed with CSR generation
Fix for error type returned (OCSP_CERT_UNKNOWN) with OCSP verification
Fix for a potential memory leak with ProcessCSR when handling OCSP responses
Fix for VERIFY_SKIP_DATE flag not ignoring date errors when set
Fix for zlib decompression buffer issue with PKCS7
Fix for DTLS message pool send size used and DTLS server saving of the handshake sequence
Fix to propagate WOLFSSL_TICKET_RET_CREATE error return value from DoDecryptTicket()
Fix for handling long session IDs with TLS 1.3 session tickets
Fix for AES-GCM streaming when caching an IV
Fix for test case with older selftest that returns bad padding instead of salt len error
Add fix for siphash cache and added in additional tests
Fix potential out of bounds memset to 0 in error case with session export function used with --enable-sessionexport builds
Fix possible NULL dereference in TLSX_CSR_Parse with TLS 1.3
Fix for sanity check on RSA pad length with no padding using the build macro WC_RSA_NO_PADDING