With curl's options
CURLOPT_SSL_CIPHER_LIST
and
--ciphers
users can control which ciphers to consider when negotiating TLS connections.
TLS 1.3 ciphers are supported since curl 7.61 for OpenSSL 1.1.1+, and since
curl 7.85 for Schannel with options
CURLOPT_TLS13_CIPHERS
and
--tls13-ciphers
. If you are using a different SSL backend you can try setting TLS 1.3 cipher
suites by using the respective regular cipher option.
The names of the known ciphers differ depending on which TLS backend that libcurl was built to use. This is an attempt to list known cipher names.
(based on OpenSSL docs)
When specifying multiple cipher names, separate them with colon (:
).
NULL-MD5
NULL-SHA
RC4-MD5
RC4-SHA
IDEA-CBC-SHA
DES-CBC3-SHA
DH-DSS-DES-CBC3-SHA
DH-RSA-DES-CBC3-SHA
DHE-DSS-DES-CBC3-SHA
DHE-RSA-DES-CBC3-SHA
ADH-RC4-MD5
ADH-DES-CBC3-SHA
NULL-MD5
NULL-SHA
RC4-MD5
RC4-SHA
IDEA-CBC-SHA
DES-CBC3-SHA
DHE-DSS-DES-CBC3-SHA
DHE-RSA-DES-CBC3-SHA
ADH-RC4-MD5
ADH-DES-CBC3-SHA
AES128-SHA
AES256-SHA
DH-DSS-AES128-SHA
DH-DSS-AES256-SHA
DH-RSA-AES128-SHA
DH-RSA-AES256-SHA
DHE-DSS-AES128-SHA
DHE-DSS-AES256-SHA
DHE-RSA-AES128-SHA
DHE-RSA-AES256-SHA
ADH-AES128-SHA
ADH-AES256-SHA
SEED-SHA
DH-DSS-SEED-SHA
DH-RSA-SEED-SHA
DHE-DSS-SEED-SHA
DHE-RSA-SEED-SHA
ADH-SEED-SHA
GOST94-GOST89-GOST89
GOST2001-GOST89-GOST89
GOST94-NULL-GOST94
GOST2001-NULL-GOST94
ECDHE-RSA-NULL-SHA
ECDHE-RSA-RC4-SHA
ECDHE-RSA-DES-CBC3-SHA
ECDHE-RSA-AES128-SHA
ECDHE-RSA-AES256-SHA
ECDHE-ECDSA-NULL-SHA
ECDHE-ECDSA-RC4-SHA
ECDHE-ECDSA-DES-CBC3-SHA
ECDHE-ECDSA-AES128-SHA
ECDHE-ECDSA-AES256-SHA
AECDH-NULL-SHA
AECDH-RC4-SHA
AECDH-DES-CBC3-SHA
AECDH-AES128-SHA
AECDH-AES256-SHA
NULL-SHA256
AES128-SHA256
AES256-SHA256
AES128-GCM-SHA256
AES256-GCM-SHA384
DH-RSA-AES128-SHA256
DH-RSA-AES256-SHA256
DH-RSA-AES128-GCM-SHA256
DH-RSA-AES256-GCM-SHA384
DH-DSS-AES128-SHA256
DH-DSS-AES256-SHA256
DH-DSS-AES128-GCM-SHA256
DH-DSS-AES256-GCM-SHA384
DHE-RSA-AES128-SHA256
DHE-RSA-AES256-SHA256
DHE-RSA-AES128-GCM-SHA256
DHE-RSA-AES256-GCM-SHA384
DHE-DSS-AES128-SHA256
DHE-DSS-AES256-SHA256
DHE-DSS-AES128-GCM-SHA256
DHE-DSS-AES256-GCM-SHA384
ECDHE-RSA-AES128-SHA256
ECDHE-RSA-AES256-SHA384
ECDHE-RSA-AES128-GCM-SHA256
ECDHE-RSA-AES256-GCM-SHA384
ECDHE-ECDSA-AES128-SHA256
ECDHE-ECDSA-AES256-SHA384
ECDHE-ECDSA-AES128-GCM-SHA256
ECDHE-ECDSA-AES256-GCM-SHA384
ADH-AES128-SHA256
ADH-AES256-SHA256
ADH-AES128-GCM-SHA256
ADH-AES256-GCM-SHA384
AES128-CCM
AES256-CCM
DHE-RSA-AES128-CCM
DHE-RSA-AES256-CCM
AES128-CCM8
AES256-CCM8
DHE-RSA-AES128-CCM8
DHE-RSA-AES256-CCM8
ECDHE-ECDSA-AES128-CCM
ECDHE-ECDSA-AES256-CCM
ECDHE-ECDSA-AES128-CCM8
ECDHE-ECDSA-AES256-CCM8
ECDHE-ECDSA-CAMELLIA128-SHA256
ECDHE-ECDSA-CAMELLIA256-SHA384
ECDHE-RSA-CAMELLIA128-SHA256
ECDHE-RSA-CAMELLIA256-SHA384
(Note these ciphers are set with CURLOPT_TLS13_CIPHERS
and --tls13-ciphers
)
TLS_AES_256_GCM_SHA384
TLS_CHACHA20_POLY1305_SHA256
TLS_AES_128_GCM_SHA256
TLS_AES_128_CCM_8_SHA256
TLS_AES_128_CCM_SHA256
RC4-SHA
,
RC4-MD5
,
DES-CBC3-SHA
,
AES128-SHA
,
AES256-SHA
,
NULL-SHA
,
NULL-SHA256
,
DHE-RSA-AES128-SHA
,
DHE-RSA-AES256-SHA
,
DHE-PSK-AES256-GCM-SHA384
,
DHE-PSK-AES128-GCM-SHA256
,
PSK-AES256-GCM-SHA384
,
PSK-AES128-GCM-SHA256
,
DHE-PSK-AES256-CBC-SHA384
,
DHE-PSK-AES128-CBC-SHA256
,
PSK-AES256-CBC-SHA384
,
PSK-AES128-CBC-SHA256
,
PSK-AES128-CBC-SHA
,
PSK-AES256-CBC-SHA
,
DHE-PSK-AES128-CCM
,
DHE-PSK-AES256-CCM
,
PSK-AES128-CCM
,
PSK-AES256-CCM
,
PSK-AES128-CCM-8
,
PSK-AES256-CCM-8
,
DHE-PSK-NULL-SHA384
,
DHE-PSK-NULL-SHA256
,
PSK-NULL-SHA384
,
PSK-NULL-SHA256
,
PSK-NULL-SHA
,
HC128-MD5
,
HC128-SHA
,
HC128-B2B256
,
AES128-B2B256
,
AES256-B2B256
,
RABBIT-SHA
,
NTRU-RC4-SHA
,
NTRU-DES-CBC3-SHA
,
NTRU-AES128-SHA
,
NTRU-AES256-SHA
,
AES128-CCM-8
,
AES256-CCM-8
,
ECDHE-ECDSA-AES128-CCM
,
ECDHE-ECDSA-AES128-CCM-8
,
ECDHE-ECDSA-AES256-CCM-8
,
ECDHE-RSA-AES128-SHA
,
ECDHE-RSA-AES256-SHA
,
ECDHE-ECDSA-AES128-SHA
,
ECDHE-ECDSA-AES256-SHA
,
ECDHE-RSA-RC4-SHA
,
ECDHE-RSA-DES-CBC3-SHA
,
ECDHE-ECDSA-RC4-SHA
,
ECDHE-ECDSA-DES-CBC3-SHA
,
AES128-SHA256
,
AES256-SHA256
,
DHE-RSA-AES128-SHA256
,
DHE-RSA-AES256-SHA256
,
ECDH-RSA-AES128-SHA
,
ECDH-RSA-AES256-SHA
,
ECDH-ECDSA-AES128-SHA
,
ECDH-ECDSA-AES256-SHA
,
ECDH-RSA-RC4-SHA
,
ECDH-RSA-DES-CBC3-SHA
,
ECDH-ECDSA-RC4-SHA
,
ECDH-ECDSA-DES-CBC3-SHA
,
AES128-GCM-SHA256
,
AES256-GCM-SHA384
,
DHE-RSA-AES128-GCM-SHA256
,
DHE-RSA-AES256-GCM-SHA384
,
ECDHE-RSA-AES128-GCM-SHA256
,
ECDHE-RSA-AES256-GCM-SHA384
,
ECDHE-ECDSA-AES128-GCM-SHA256
,
ECDHE-ECDSA-AES256-GCM-SHA384
,
ECDH-RSA-AES128-GCM-SHA256
,
ECDH-RSA-AES256-GCM-SHA384
,
ECDH-ECDSA-AES128-GCM-SHA256
,
ECDH-ECDSA-AES256-GCM-SHA384
,
CAMELLIA128-SHA
,
DHE-RSA-CAMELLIA128-SHA
,
CAMELLIA256-SHA
,
DHE-RSA-CAMELLIA256-SHA
,
CAMELLIA128-SHA256
,
DHE-RSA-CAMELLIA128-SHA256
,
CAMELLIA256-SHA256
,
DHE-RSA-CAMELLIA256-SHA256
,
ECDHE-RSA-AES128-SHA256
,
ECDHE-ECDSA-AES128-SHA256
,
ECDH-RSA-AES128-SHA256
,
ECDH-ECDSA-AES128-SHA256
,
ECDHE-RSA-AES256-SHA384
,
ECDHE-ECDSA-AES256-SHA384
,
ECDH-RSA-AES256-SHA384
,
ECDH-ECDSA-AES256-SHA384
,
ECDHE-RSA-CHACHA20-POLY1305
,
ECDHE-ECDSA-CHACHA20-POLY1305
,
DHE-RSA-CHACHA20-POLY1305
,
ECDHE-RSA-CHACHA20-POLY1305-OLD
,
ECDHE-ECDSA-CHACHA20-POLY1305-OLD
,
DHE-RSA-CHACHA20-POLY1305-OLD
,
ADH-AES128-SHA
,
QSH
,
RENEGOTIATION-INFO
,
IDEA-CBC-SHA
,
ECDHE-ECDSA-NULL-SHA
,
ECDHE-PSK-NULL-SHA256
,
ECDHE-PSK-AES128-CBC-SHA256
,
PSK-CHACHA20-POLY1305
,
ECDHE-PSK-CHACHA20-POLY1305
,
DHE-PSK-CHACHA20-POLY1305
,
EDH-RSA-DES-CBC3-SHA
,
Schannel allows the enabling and disabling of encryption algorithms, but not specific cipher suites, prior to TLS 1.3. The algorithms are defined by Microsoft.
The algorithms below are for TLS 1.2 and earlier. TLS 1.3 is covered in the next section.
There is also the case that the selected algorithm is not supported by the
protocol or does not match the ciphers offered by the server during the SSL
negotiation. In this case curl returns error
CURLE_SSL_CONNECT_ERROR (35) SEC_E_ALGORITHM_MISMATCH
and the request fails.
CALG_MD2
,
CALG_MD4
,
CALG_MD5
,
CALG_SHA
,
CALG_SHA1
,
CALG_MAC
,
CALG_RSA_SIGN
,
CALG_DSS_SIGN
,
CALG_NO_SIGN
,
CALG_RSA_KEYX
,
CALG_DES
,
CALG_3DES_112
,
CALG_3DES
,
CALG_DESX
,
CALG_RC2
,
CALG_RC4
,
CALG_SEAL
,
CALG_DH_SF
,
CALG_DH_EPHEM
,
CALG_AGREEDKEY_ANY
,
CALG_HUGHES_MD5
,
CALG_SKIPJACK
,
CALG_TEK
,
CALG_CYLINK_MEK
,
CALG_SSL3_SHAMD5
,
CALG_SSL3_MASTER
,
CALG_SCHANNEL_MASTER_HASH
,
CALG_SCHANNEL_MAC_KEY
,
CALG_SCHANNEL_ENC_KEY
,
CALG_PCT1_MASTER
,
CALG_SSL2_MASTER
,
CALG_TLS1_MASTER
,
CALG_RC5
,
CALG_HMAC
,
CALG_TLS1PRF
,
CALG_HASH_REPLACE_OWF
,
CALG_AES_128
,
CALG_AES_192
,
CALG_AES_256
,
CALG_AES
,
CALG_SHA_256
,
CALG_SHA_384
,
CALG_SHA_512
,
CALG_ECDH
,
CALG_ECMQV
,
CALG_ECDSA
,
CALG_ECDH_EPHEM
,
As of curl 7.77.0, you can also pass SCH_USE_STRONG_CRYPTO
as a cipher name
to constrain the set of available ciphers as specified in the Schannel
documentation.
Note that the supported ciphers in this case follow the OS version, so if you
are running an outdated OS you might still be supporting weak ciphers.
You can set TLS 1.3 ciphers for Schannel by using CURLOPT_TLS13_CIPHERS
or
--tls13-ciphers
with the names below.
If TLS 1.3 cipher suites are set then libcurl adds or restricts Schannel TLS 1.3 algorithms automatically. Essentially, libcurl is emulating support for individual TLS 1.3 cipher suites since Schannel does not support it directly.
TLS_AES_256_GCM_SHA384
TLS_AES_128_GCM_SHA256
TLS_CHACHA20_POLY1305_SHA256
TLS_AES_128_CCM_8_SHA256
TLS_AES_128_CCM_SHA256
Note if you set TLS 1.3 ciphers without also setting the minimum TLS version
to 1.3 then it is possible Schannel may negotiate an earlier TLS version and
cipher suite if your libcurl and OS settings allow it. You can set the minimum
TLS version by using CURLOPT_SSLVERSION
or --tlsv1.3
.
BearSSL ciphers can be specified by either the OpenSSL name (ECDHE-RSA-AES128-GCM-SHA256
) or the IANA name (TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256
).
Since BearSSL 0.1:
DES-CBC3-SHA
AES128-SHA
AES256-SHA
AES128-SHA256
AES256-SHA256
AES128-GCM-SHA256
AES256-GCM-SHA384
ECDH-ECDSA-DES-CBC3-SHA
ECDH-ECDSA-AES128-SHA
ECDH-ECDSA-AES256-SHA
ECDHE-ECDSA-DES-CBC3-SHA
ECDHE-ECDSA-AES128-SHA
ECDHE-ECDSA-AES256-SHA
ECDH-RSA-DES-CBC3-SHA
ECDH-RSA-AES128-SHA
ECDH-RSA-AES256-SHA
ECDHE-RSA-DES-CBC3-SHA
ECDHE-RSA-AES128-SHA
ECDHE-RSA-AES256-SHA
ECDHE-ECDSA-AES128-SHA256
ECDHE-ECDSA-AES256-SHA384
ECDH-ECDSA-AES128-SHA256
ECDH-ECDSA-AES256-SHA384
ECDHE-RSA-AES128-SHA256
ECDHE-RSA-AES256-SHA384
ECDH-RSA-AES128-SHA256
ECDH-RSA-AES256-SHA384
ECDHE-ECDSA-AES128-GCM-SHA256
ECDHE-ECDSA-AES256-GCM-SHA384
ECDH-ECDSA-AES128-GCM-SHA256
ECDH-ECDSA-AES256-GCM-SHA384
ECDHE-RSA-AES128-GCM-SHA256
ECDHE-RSA-AES256-GCM-SHA384
ECDH-RSA-AES128-GCM-SHA256
ECDH-RSA-AES256-GCM-SHA384
Since BearSSL 0.2:
ECDHE-RSA-CHACHA20-POLY1305
ECDHE-ECDSA-CHACHA20-POLY1305
Since BearSSL 0.6:
AES128-CCM
AES256-CCM
AES128-CCM8
AES256-CCM8
ECDHE-ECDSA-AES128-CCM
ECDHE-ECDSA-AES256-CCM
ECDHE-ECDSA-AES128-CCM8
ECDHE-ECDSA-AES256-CCM8