CT_POLICY_EVAL_CTX_NEW(3ossl)

💅 CT_POLICY_EVAL_CTX_NEW(3ossl) — bestie edition

okay so this is CT_POLICY_EVAL_CTX_NEW from the 3ossl manual set, and it's giving "the little container that holds all the receipts for Certificate Transparency checks." stay with me, it's actually so good.

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✨ NAME ✨

CT_POLICY_EVAL_CTX_new_ex, CT_POLICY_EVAL_CTX_new, CT_POLICY_EVAL_CTX_free, CT_POLICY_EVAL_CTX_get0_cert, CT_POLICY_EVAL_CTX_set1_cert, CT_POLICY_EVAL_CTX_get0_issuer, CT_POLICY_EVAL_CTX_set1_issuer, CT_POLICY_EVAL_CTX_get0_log_store, CT_POLICY_EVAL_CTX_set_shared_CTLOG_STORE, CT_POLICY_EVAL_CTX_get_time, CT_POLICY_EVAL_CTX_set_time — this whole squad of functions encapsulates the data required to evaluate whether SCTs meet a Certificate Transparency policy. 🫶

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🌈 SYNOPSIS 🌈

#include <openssl/ct.h>

CT_POLICY_EVAL_CTX *CT_POLICY_EVAL_CTX_new_ex(OSSL_LIB_CTX *libctx,
                                              const char *propq);
CT_POLICY_EVAL_CTX *CT_POLICY_EVAL_CTX_new(void);
void CT_POLICY_EVAL_CTX_free(CT_POLICY_EVAL_CTX *ctx);
X509* CT_POLICY_EVAL_CTX_get0_cert(const CT_POLICY_EVAL_CTX *ctx);
int CT_POLICY_EVAL_CTX_set1_cert(CT_POLICY_EVAL_CTX *ctx, X509 *cert);
X509* CT_POLICY_EVAL_CTX_get0_issuer(const CT_POLICY_EVAL_CTX *ctx);
int CT_POLICY_EVAL_CTX_set1_issuer(CT_POLICY_EVAL_CTX *ctx, X509 *issuer);
const CTLOG_STORE *CT_POLICY_EVAL_CTX_get0_log_store(const CT_POLICY_EVAL_CTX *ctx);
void CT_POLICY_EVAL_CTX_set_shared_CTLOG_STORE(CT_POLICY_EVAL_CTX *ctx,
                                               CTLOG_STORE *log_store);
uint64_t CT_POLICY_EVAL_CTX_get_time(const CT_POLICY_EVAL_CTX *ctx);
void CT_POLICY_EVAL_CTX_set_time(CT_POLICY_EVAL_CTX *ctx, uint64_t time_in_ms);

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🌸 DESCRIPTION 🌸

so a CT_POLICY_EVAL_CTX is this little vibe-holder that gets used by functions checking whether Signed Certificate Timestamps (SCTs) fulfil a Certificate Transparency (CT) policy. and like, the policy could be anything — for example, that at least one valid SCT is available. to actually figure that out, you gotta verify an SCT's timestamp and its signature. and for that you need, bestie:

• the public key of the log that issued the SCT
• the certificate that the SCT was issued for
• the issuer certificate (only if the SCT was issued for a pre-certificate)
• the current time

all four of those requirements get met using the setters down below. no cap. 💅

CT_POLICY_EVAL_CTX_new_ex() creates an empty policy evaluation context and associates it with the given library context libctx and property query string propq. iconic behaviour honestly.

CT_POLICY_EVAL_CTX_new() does the same thing as CT_POLICY_EVAL_CTX_new_ex() except that it uses the default library context and property query string. the low-effort-but-still-slaying version, we love her. ✨

the CT_POLICY_EVAL_CTX should then be populated using:

• CT_POLICY_EVAL_CTX_set1_cert() to provide the certificate the SCTs were issued for
  • increments the reference count of the certificate.
• CT_POLICY_EVAL_CTX_set1_issuer() to provide the issuer certificate
  • increments the reference count of the certificate.
• CT_POLICY_EVAL_CTX_set_shared_CTLOG_STORE() to provide a list of logs that are trusted as sources of SCTs
  • holds a pointer to the CTLOG_STORE, so the CTLOG_STORE must outlive the CT_POLICY_EVAL_CTX. ⚠️ like, do not let it get freed first, that's a whole mess.
• CT_POLICY_EVAL_CTX_set_time() to set the time SCTs should be compared with to determine if they are valid
  • the SCT timestamp will be compared to this time to check whether the SCT was issued in the future. RFC6962 states that "TLS clients MUST reject SCTs whose timestamp is in the future". by default, this will be set to 5 minutes in the future (e.g. (time() + 300) * 1000), to allow for clock drift. ⏰
  • the time should be in milliseconds since the Unix Epoch.

each setter has a matching getter for accessing the current value. matched set, we love a coordinated moment. 🎀

when no longer required, the CT_POLICY_EVAL_CTX should be passed to CT_POLICY_EVAL_CTX_free() to delete it. and if the argument to CT_POLICY_EVAL_CTX_free() is NULL, nothing is done — totally safe, no drama. 💜

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🦋 NOTES 🦋

the issuer certificate only needs to be provided if at least one of the SCTs was issued for a pre-certificate. this will be the case for SCTs embedded in a certificate (i.e. those in an X.509 extension), but may not be the case for SCTs found in the TLS SCT extension or OCSP response. iykyk. 🙈

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⭐ RETURN VALUES ⭐

CT_POLICY_EVAL_CTX_new_ex() and CT_POLICY_EVAL_CTX_new() will return NULL if malloc fails. 😭 that's it, that's the whole list — allocation goes wrong, you get nothing back.

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👑 SEE ALSO 👑

ct(7) — go read it, it's the parent lore.

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🧚 HISTORY 🧚

CT_POLICY_EVAL_CTX_new_ex was added in OpenSSL 3.0. all other functions were added in OpenSSL 1.1.0. glow-up timeline fr fr. 🔥

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💖 COPYRIGHT 💖

Copyright 2016-2024 The OpenSSL Project Authors. All Rights Reserved.

Licensed under the Apache License 2.0 (the "License"). You may not use this file except in compliance with the License. You can obtain a copy in the file LICENSE in the source distribution or at <https://www.openssl.org/source/license.html>.

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and that's the whole page, bestie 🍓 — brought to you by 3.5.0, dated 2026-09-25, filed under CT_POLICY_EVAL_CTX_NEW(3ossl). mwah 💋