103 lines
4.5 KiB
Groff
103 lines
4.5 KiB
Groff
.\" generated by cd2nroff 0.1 from CURLOPT_SSL_OPTIONS.md
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.TH CURLOPT_SSL_OPTIONS 3 "2025-07-07" libcurl
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.SH NAME
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CURLOPT_SSL_OPTIONS \- SSL behavior options
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.SH SYNOPSIS
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.nf
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#include <curl/curl.h>
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CURLcode curl_easy_setopt(CURL *handle, CURLOPT_SSL_OPTIONS, long bitmask);
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.fi
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.SH DESCRIPTION
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Pass a long with a bitmask to tell libcurl about specific SSL
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behaviors. Available bits:
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.IP CURLSSLOPT_ALLOW_BEAST
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Tells libcurl to not attempt to use any workarounds for a security flaw in the
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SSL3 and TLS1.0 protocols. If this option is not used or this bit is set to 0,
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the SSL layer libcurl uses may use a work\-around for this flaw although it
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might cause interoperability problems with some (older) SSL implementations.
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WARNING: avoiding this work\-around lessens the security, and by setting this
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option to 1 you ask for exactly that. This option is only supported for Secure
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Transport and OpenSSL.
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.IP CURLSSLOPT_NO_REVOKE
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Tells libcurl to disable certificate revocation checks for those SSL backends
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where such behavior is present. This option is only supported for Schannel
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(the native Windows SSL library), with an exception in the case of Windows\(aq
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Untrusted Publishers block list which it seems cannot be bypassed. (Added in
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7.44.0)
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.IP CURLSSLOPT_NO_PARTIALCHAIN
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Tells libcurl to not accept "partial" certificate chains, which it otherwise
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does by default. This option is only supported for OpenSSL and fails the
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certificate verification if the chain ends with an intermediate certificate
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and not with a root cert. (Added in 7.68.0)
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.IP CURLSSLOPT_REVOKE_BEST_EFFORT
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Tells libcurl to ignore certificate revocation checks in case of missing or
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offline distribution points for those SSL backends where such behavior is
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present. This option is only supported for Schannel (the native Windows SSL
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library). If combined with \fICURLSSLOPT_NO_REVOKE\fP, the latter takes
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precedence. (Added in 7.70.0)
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.IP CURLSSLOPT_NATIVE_CA
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Tell libcurl to use the operating system\(aqs native CA store for certificate
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verification. This option is independent of other CA certificate locations set
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at run time or build time. Those locations are searched in addition to the
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native CA store.
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Works with wolfSSL on Windows, Linux (Debian, Ubuntu, Gentoo, Fedora, RHEL),
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macOS, Android and iOS (added in 8.3.0); with GnuTLS (added in 8.5.0) and with
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OpenSSL and its forks (LibreSSL, BoringSSL, etc) on Windows (Added in 7.71.0).
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This works with rustls on Windows, macOS, Android and iOS. On Linux it is
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equivalent to using the Mozilla CA certificate bundle. When used with rustls
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_only_ the native CA store is consulted, not other locations set at run time or
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build time. (Added in 8.13.0)
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.IP CURLSSLOPT_AUTO_CLIENT_CERT
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Tell libcurl to automatically locate and use a client certificate for
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authentication, when requested by the server. This option is only supported
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for Schannel (the native Windows SSL library). Prior to 7.77.0 this was the
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default behavior in libcurl with Schannel. Since the server can request any
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certificate that supports client authentication in the OS certificate store it
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could be a privacy violation and unexpected.
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(Added in 7.77.0)
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.IP CURLSSLOPT_EARLYDATA
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Tell libcurl to try sending application data as TLS1.3 early data. This option
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is supported for GnuTLS, wolfSSL, quictls and OpenSSL (but not BoringSSL
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or AWS\-LC). It works on TCP and QUIC connections using ngtcp2.
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This option works on a best effort basis,
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in cases when it wasn\(aqt possible to send early data the request is resent
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normally post\-handshake.
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This option does not work when using QUIC.
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(Added in 8.11.0 for GnuTLS and 8.13.0 for wolfSSL, quictls and OpenSSL)
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.SH DEFAULT
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0
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.SH PROTOCOLS
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This functionality affects all TLS based protocols: HTTPS, FTPS, IMAPS, POP3S, SMTPS etc.
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All TLS backends support this option.
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.SH EXAMPLE
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.nf
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int main(void)
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{
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CURL *curl = curl_easy_init();
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if(curl) {
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CURLcode res;
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curl_easy_setopt(curl, CURLOPT_URL, "https://example.com/");
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/* weaken TLS only for use with silly servers */
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curl_easy_setopt(curl, CURLOPT_SSL_OPTIONS, (long)CURLSSLOPT_ALLOW_BEAST |
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CURLSSLOPT_NO_REVOKE);
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res = curl_easy_perform(curl);
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curl_easy_cleanup(curl);
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}
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}
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.fi
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.SH AVAILABILITY
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Added in curl 7.25.0
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.SH RETURN VALUE
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\fIcurl_easy_setopt(3)\fP returns a CURLcode indicating success or error.
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CURLE_OK (0) means everything was OK, non\-zero means an error occurred, see
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\fIlibcurl\-errors(3)\fP.
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.SH SEE ALSO
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.BR CURLOPT_PROXY_SSL_OPTIONS (3),
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.BR CURLOPT_SSLVERSION (3),
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.BR CURLOPT_SSL_CIPHER_LIST (3)
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