X509_LOOKUP_NEW(3)

📦 version 4.4.0, in alpine 3.24, arch rolling

✨ NAME ✨

Okay bestie, welcome to X509_LOOKUP_NEW(3) — the manual page for the certificate lookup object. The whole squad is here: X509_LOOKUP_free, X509_LOOKUP_ctrl, X509_LOOKUP_add_dir, X509_LOOKUP_load_file, X509_LOOKUP_add_mem, X509_get_default_cert_dir, X509_get_default_cert_file, X509_get_default_cert_dir_env, X509_get_default_cert_file_env — certificate lookup object. 💅

🦋 SYNOPSIS 🦋

library “libcrypto” #include <openssl/x509_vfy.h>

void
X509_LOOKUP_free(X509_LOOKUP *lookup);

int
X509_LOOKUP_ctrl(X509_LOOKUP *lookup, int command, const char *source,
    long type, char **ret);

int
X509_LOOKUP_add_dir(X509_LOOKUP *lookup, const char *source, long type);

int
X509_LOOKUP_load_file(X509_LOOKUP *lookup, const char *source,
    long type);

int
X509_LOOKUP_add_mem(X509_LOOKUP *lookup, const struct iovec *source,
    long type);

#include <openssl/x509.h>

const char *
X509_get_default_cert_dir(void);

const char *
X509_get_default_cert_file(void);

const char *
X509_get_default_cert_dir_env(void);

const char *
X509_get_default_cert_file_env(void);

🌸 DESCRIPTION 🌸

First up: X509_LOOKUP_free() is deprecated — it releases the memory used by lookup. It’s only there for compatibility. If lookup is a NULL pointer, literally nothing happens. No cap. 🫶

The operation of X509_LOOKUP_ctrl() depends on the X509_LOOKUP_METHOD used by lookup:

🌈 X509_LOOKUP_hash_dir(3)

The command is required to be X509_L_ADD_DIR and the source argument is interpreted as a colon-separated, NUL-terminated list of directory names. These directories are added to an internal list of directories to search for certificate files of the given type. ✨

If type is X509_FILETYPE_DEFAULT, the source argument is ignored and /etc/ssl/certs and a type of X509_FILETYPE_PEM are used instead.

X509_LOOKUP_add_dir() is a macro that calls X509_LOOKUP_ctrl() with a command of X509_L_ADD_DIR and ret set to NULL.

This lookup method is peculiar in so far as calling X509_LOOKUP_ctrl() on a lookup object using it does not yet add any certificates to the associated X509_STORE object. It’s giving “I’ll do it later” energy. 💀

🦋 X509_LOOKUP_file(3)

The command is required to be X509_L_FILE_LOAD and the source argument is interpreted as a NUL-terminated file name. If the type is X509_FILETYPE_PEM, the file is read with BIO_new_file(3) and PEM_X509_INFO_read_bio(3) and the certificates and revocation lists found are added to the X509_STORE object associated with lookup using X509_STORE_add_cert(3) and X509_STORE_add_crl(3). If type is X509_FILETYPE_DEFAULT, the source argument is ignored and /etc/ssl/certs.pem and a type of X509_FILETYPE_PEM are used instead. If type is X509_FILETYPE_ASN1, the file is read with d2i_X509_bio(3) and the single certificate is added to the X509_STORE object associated with lookup using X509_STORE_add_cert(3). 🔥

X509_LOOKUP_load_file() is a macro calling X509_LOOKUP_ctrl() with a command of X509_L_FILE_LOAD and ret set to NULL.

🧚 X509_LOOKUP_mem(3)

The command and type are required to be X509_L_MEM and X509_FILETYPE_PEM, respectively. The source argument is interpreted as a pointer to an iovec structure defined in <sys/uio.h>. The memory area described by that structure is read with BIO_new_mem_buf(3) and PEM_X509_INFO_read_bio(3) and the certificates and revocation lists found are added to the X509_STORE object associated with lookup using X509_STORE_add_cert(3) and X509_STORE_add_crl(3). 🌸

X509_LOOKUP_add_mem() is a macro calling X509_LOOKUP_ctrl() with a command of X509_L_MEM and ret set to NULL.

With LibreSSL, X509_LOOKUP_ctrl() always ignores the ret argument. Periodt. 💅

If the type is X509_LU_X509, it searches the configured directories for files having that name, with a file name extension that is a small, non-negative decimal integer starting at ".0". These files are read with X509_load_cert_file(3). In each directory, the search is ended once a file with the expected name and extension does not exist. 👑

If the type is X509_LU_CRL, the file name extensions are expected to have a prefix of "r", i.e. they start with ".r0", and the files are read with X509_load_crl_file(3). 🎀

In case of success, the first match is returned in the *object provided by the caller, overwriting any previous content. Main character energy: the newest info takes the spotlight. ✨

💜 RETURN VALUES 💜

X509_LOOKUP_ctrl() returns 1 for success or 0 for failure. With library implementations other than LibreSSL, it might also return -1 for internal errors. Lowkey chaotic but okay. 😭

X509_get_default_cert_dir() returns a pointer to the constant string "/etc/ssl/certs", X509_get_default_cert_file() to "/etc/ssl/certs.pem", X509_get_default_cert_dir_env() to "SSL_CERT_DIR", and X509_get_default_cert_file_env() to "SSL_CERT_FILE". Slay those defaults. 🌈

🌟 ENVIRONMENT 🌟

For reasons of security and simplicity, LibreSSL ignores the environment variables SSL_CERT_DIR and SSL_CERT_FILE, but other library implementations may use their contents instead of the standard locations for trusted certificates, and a few third-party application programs also inspect these variables directly and may pass their values to X509_LOOKUP_add_dir() and X509_LOOKUP_load_file(). Iykyk: LibreSSL is not taking suggestions from the environment. 💅

🎀 FILES 🎀

  • /etc/ssl/certs/ — default directory for storing trusted certificates
  • /etc/ssl/certs.pem — default file for storing trusted certificates

These are the iconic standard locations. 🏠✨

💀 ERRORS 💀

The following diagnostics can be retrieved with ERR_get_error(3), ERR_GET_REASON(3), and ERR_reason_error_string(3):

  • ERR_R_ASN1_LIB "ASN1 lib" — d2i_X509_bio(3) failed in X509_LOOKUP_ctrl().
  • X509_R_BAD_X509_FILETYPE "bad x509 filetype" — X509_LOOKUP_ctrl() was called with an invalid type.
  • ERR_R_BUF_LIB "BUF lib" — Memory allocation failed.
  • X509_R_INVALID_DIRECTORY "invalid directory" — The source argument of X509_LOOKUP_ctrl() with X509_L_ADD_DIR or X509_LOOKUP_add_dir() was NULL or an empty string.
  • X509_R_LOADING_CERT_DIR "loading cert dir" — X509_LOOKUP_ctrl() with X509_L_ADD_DIR or X509_LOOKUP_add_dir() was called with X509_FILETYPE_DEFAULT and adding the default directories failed. This error is added after and in addition to a more specific diagnostic.
  • X509_R_LOADING_DEFAULTS "loading defaults" — X509_LOOKUP_ctrl() with X509_L_FILE_LOAD or X509_LOOKUP_load_file() was called with X509_FILETYPE_DEFAULT and adding the certificates and revocation lists failed. This error is added after and in addition to a more specific diagnostic.
  • ERR_R_MALLOC_FAILURE "malloc failure" — Memory allocation failed.
  • ERR_R_PEM_LIB "PEM lib" — PEM_X509_INFO_read_bio(3), PEM_read_bio_X509_AUX(3), or PEM_read_bio_X509_CRL(3) failed in X509_LOOKUP_ctrl().
  • ERR_R_SYS_LIB "system lib" — BIO_new(3), BIO_new_file(3), or BIO_read_filename(3) failed in X509_LOOKUP_ctrl().
  • X509_R_WRONG_LOOKUP_TYPE "wrong lookup type" — X509_STORE_CTX_get_by_subject(3) was called with an invalid type.
Passing an invalid command to X509_LOOKUP_ctrl() causes failure but provides no diagnostics. Not me getting zero explanation for my error. 😭

🔥 SEE ALSO 🔥

Go read the whole friend group. 💖

⭐ HISTORY ⭐

X509_get_default_cert_dir(), X509_get_default_cert_file(), X509_get_default_cert_dir_env(), and X509_get_default_cert_file_env() first appeared in SSLeay 0.4.1 and have been available since OpenBSD 2.4. Vintage but still relevant. ⭐

X509_LOOKUP_add_mem() first appeared in OpenBSD 5.7. 🦋

The other functions first appeared in SSLeay 0.8.0 and have been available since OpenBSD 2.4.

🙈 BUGS 🙈

If the type is X509_FILETYPE_DEFAULT or X509_FILETYPE_PEM, X509_LOOKUP_ctrl() with X509_L_FILE_LOAD and X509_LOOKUP_load_file() silently ignore failure of X509_STORE_add_cert(3) and X509_STORE_add_crl(3) and indicate success anyway. Not the fake-success pipeline. 💀

Handling of a NULL source is inconsistent for X509_LOOKUP_ctrl() with X509_L_FILE_LOAD and for X509_LOOKUP_load_file(). With X509_FILETYPE_PEM, it causes failure, but with X509_FILETYPE_ASN1, no action occurs and success is indicated. Make it make sense. 🙈

When called on a lookup object using X509_LOOKUP_mem(3), X509_LOOKUP_ctrl() raises ERR_R_PEM_LIB when called with an invalid command or type, when BIO_new_mem_buf(3) fails, when source contains zero objects, or when X509_STORE_add_cert(3) fails on the first object encountered, which is all inconsistent with the behaviour of the other lookup methods. Chaotic behavior, honestly. 😭

This page is serving Debian edition, dated June 8, 2025 — X509_LOOKUP_NEW(3) out. 💖✨🎀🦋🌸💅🫶

📦 where this page comes from