X509_LOOKUP_HASH_DIR(3ossl)

📦
version 3.5.9 · 8 versions
, in fedora 43, fedora 44

💖 NAME 💖

X509_LOOKUP_hash_dir, X509_LOOKUP_file, X509_LOOKUP_store, X509_load_cert_file_ex, X509_load_cert_file, X509_load_crl_file, X509_load_cert_crl_file_ex, X509_load_cert_crl_file — bestie, these are the default OpenSSL certificate lookup methods 👑

(also this whole page is X509_LOOKUP_HASH_DIR(3ossl) from the OpenSSL manual, so like, that's the vibe check we're doing today 🦋)

✨ SYNOPSIS ✨

#include <openssl/x509_vfy.h>

X509_LOOKUP_METHOD *X509_LOOKUP_hash_dir(void);
X509_LOOKUP_METHOD *X509_LOOKUP_file(void);
X509_LOOKUP_METHOD *X509_LOOKUP_store(void);

int X509_load_cert_file_ex(X509_LOOKUP *ctx, const char *file, int type,
                           OSSL_LIB_CTX *libctx, const char *propq);
int X509_load_cert_file(X509_LOOKUP *ctx, const char *file, int type);
int X509_load_crl_file(X509_LOOKUP *ctx, const char *file, int type);
int X509_load_cert_crl_file_ex(X509_LOOKUP *ctx, const char *file, int type,
                               OSSL_LIB_CTX *libctx, const char *propq);
int X509_load_cert_crl_file(X509_LOOKUP *ctx, const char *file, int type);

🌸 DESCRIPTION 🌸

So X509_LOOKUP_hash_dir and X509_LOOKUP_file are two certificate lookup methods you use with X509_STORE, and they're provided by the OpenSSL library. 💅

Okay but here's the tea: if you're just a normal user of the library, you typically do not need to create instances of these methods manually — they get created automatically for you by X509_STORE_load_locations(3) or SSL_CTX_load_verify_locations(3). Iconic behaviour, honestly, it just handles it. 🫶

Internally, the loading of certificates and CRLs is implemented via the functions X509_load_cert_crl_file, X509_load_cert_file and X509_load_crl_file. These functions support a parameter called type, which can be one of the constants FILETYPE_PEM, FILETYPE_ASN1 and FILETYPE_DEFAULT. And what do they do with it? They load certificates and/or CRLs from the specified file into the memory cache of the X509_STORE objects that the given ctx parameter is associated with. ✨

Now, X509_load_cert_file and X509_load_crl_file can load both PEM and DER formats depending on the type value. But lowkey important detail: DER format can't contain more than one certificate or CRL object, whereas PEM can contain several concatenated PEM objects. So because of that, X509_load_cert_crl_file with FILETYPE_ASN1 is equivalent to X509_load_cert_file. 🎀

The constant FILETYPE_DEFAULT with a NULL filename causes these functions to load the default certificate store file (see X509_STORE_set_default_paths(3).

These functions return the number of objects loaded from file, or 0 in case of error. 💀

Both methods support adding several certificate locations into one X509_STORE. Periodt.

This page documents the certificate store formats used by these methods and the caching policy. Let's gooo 👇

📁 File Method 📁

The X509_LOOKUP_file method loads all the certificates or CRLs present in a file into memory at the time the file is added as a lookup source.

File format is ASCII text which contains concatenated PEM certificates and CRLs. Simple as that bestie. 🍓

This method should be used by applications which work with a small set of CAs.

🗂️ Hashed Directory Method 🗂️

X509_LOOKUP_hash_dir is the more advanced one, okay, it's giving main character energy 👑 — it loads certificates and CRLs on demand, and caches them in memory once they're loaded. And as of OpenSSL 1.0.0, it also checks for newer CRLs upon each lookup, so that newer CRLs show up as soon as they appear in the directory. We love a fresh CRL. ✨

The directory should contain one certificate or CRL per file in PEM format, with a filename of the form hash.N for a certificate, or hash.rN for a CRL. The hash is the value returned by the X509_NAME_hash_ex(3) function applied to the subject name for certificates, or the issuer name for CRLs. You can also get that hash via the -hash option of the openssl-x509(1) or openssl-crl(1) commands. 💅

The .N or .rN suffix is a sequence number that starts at zero, and gets incremented consecutively for each certificate or CRL with the same hash value. And ngl, gaps in the sequence numbers are not supported — it's assumed that there are no more objects with the same hash beyond the first missing number in the sequence. 🙈

Sequence numbers make it possible for the directory to contain multiple certificates with the same subject name hash value. For example, it's possible to have in the store several certificates with the same subject, or several CRLs with the same issuer (and, for example, different validity period). So versatile. 🎀

When checking for new CRLs once one CRL for a given hash value is loaded, the hash_dir lookup method checks only for certificates with sequence number greater than that of the already cached CRL.

⚠️ Heads up bestie: the hash algorithm used for subject name hashing changed in OpenSSL 1.0.0, and all certificate stores have to be rehashed when moving from OpenSSL 0.9.8 to 1.0.0. No skipping this one.

OpenSSL includes an openssl-rehash(1) utility which creates symlinks with hashed names for all files with .pem suffix in a given directory. Slay. 🌈

🛍️ OSSL_STORE Method 🛍️

X509_LOOKUP_store is a method that lets you access any store of certificates and CRLs through any loader supported by ossl_store(7). It works with the help of URIs — which can be direct references to certificates or CRLs, but can also be references to catalogues of such objects (and those behave like directories). 🦋

This method overlaps the "File Method" and "Hashed Directory Method" because of the file: scheme loader. It does no caching of its own, but it can use a caching ossl_store(7) loader, and therefore it depends on the loader's capability. 🤝

🎯 RETURN VALUES 🎯

X509_LOOKUP_hash_dir(), X509_LOOKUP_file() and X509_LOOKUP_store() always return a valid X509_LOOKUP_METHOD structure. Every single time. No cap. 💖

X509_load_cert_file(), X509_load_crl_file() and X509_load_cert_crl_file() return the number of loaded objects, or 0 on error. 😭

👀 SEE ALSO 👀

📜 HISTORY 📜

The functions X509_load_cert_file_ex(), X509_load_cert_crl_file_ex() and X509_LOOKUP_store() were added in OpenSSL 3.0. Newer era, newer functions. ✨

Copyright 2015-2021 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>.

okay that's the whole page bestie, ily, go forth and hash your directories 💅✨

this was X509_LOOKUP_HASH_DIR(3ossl) from OpenSSL 3.5.9, dated 2026-09-29 — mwah, take care of your certs 🎀🦋

📦 where this page comes from