SSL_CTX_USE_CERTIFICATE(3ossl)

✨ NAME ✨

okay bestie, this is the manual page for SSL_CTX_USE_CERTIFICATE(3ossl) from the OpenSSL fam 💖 — and it's the one that loads your certificate and key data. Like, all of it. It's giving "here's every single way to hand OpenSSL a cert and a private key."

The whole squad of functions living on this page:

• SSL_CTX_use_certificate, SSL_CTX_use_certificate_ASN1, SSL_CTX_use_certificate_file, SSL_use_certificate, SSL_use_certificate_ASN1, SSL_use_certificate_file, SSL_CTX_use_certificate_chain_file, SSL_use_certificate_chain_file
• SSL_CTX_use_PrivateKey, SSL_CTX_use_PrivateKey_ASN1, SSL_CTX_use_PrivateKey_file, SSL_CTX_use_RSAPrivateKey, SSL_CTX_use_RSAPrivateKey_ASN1, SSL_CTX_use_RSAPrivateKey_file
• SSL_use_PrivateKey_file, SSL_use_PrivateKey_ASN1, SSL_use_PrivateKey, SSL_use_RSAPrivateKey, SSL_use_RSAPrivateKey_ASN1, SSL_use_RSAPrivateKey_file
• SSL_CTX_check_private_key, SSL_check_private_key
• SSL_CTX_use_cert_and_key, SSL_use_cert_and_key

and their collective job description is: load certificate and key data. that's it. that's the vibe. 🎀

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🌸 SYNOPSIS 🌸

like, just include the header and go, bestie:

#include <openssl/ssl.h>

int SSL_CTX_use_certificate(SSL_CTX *ctx, X509 *x);
int SSL_CTX_use_certificate_ASN1(SSL_CTX *ctx, int len, const unsigned char *d);
int SSL_CTX_use_certificate_file(SSL_CTX *ctx, const char *file, int type);
int SSL_use_certificate(SSL *ssl, X509 *x);
int SSL_use_certificate_ASN1(SSL *ssl, const unsigned char *d, int len);
int SSL_use_certificate_file(SSL *ssl, const char *file, int type);

int SSL_CTX_use_certificate_chain_file(SSL_CTX *ctx, const char *file);
int SSL_use_certificate_chain_file(SSL *ssl, const char *file);

int SSL_CTX_use_PrivateKey(SSL_CTX *ctx, EVP_PKEY *pkey);
int SSL_CTX_use_PrivateKey_ASN1(int pk, SSL_CTX *ctx, const unsigned char *d,
                                long len);
int SSL_CTX_use_PrivateKey_file(SSL_CTX *ctx, const char *file, int type);
int SSL_CTX_use_RSAPrivateKey(SSL_CTX *ctx, RSA *rsa);
int SSL_CTX_use_RSAPrivateKey_ASN1(SSL_CTX *ctx, const unsigned char *d, long len);
int SSL_CTX_use_RSAPrivateKey_file(SSL_CTX *ctx, const char *file, int type);
int SSL_use_PrivateKey(SSL *ssl, EVP_PKEY *pkey);
int SSL_use_PrivateKey_ASN1(int pk, SSL *ssl, const unsigned char *d, long len);
int SSL_use_PrivateKey_file(SSL *ssl, const char *file, int type);
int SSL_use_RSAPrivateKey(SSL *ssl, RSA *rsa);
int SSL_use_RSAPrivateKey_ASN1(SSL *ssl, const unsigned char *d, long len);
int SSL_use_RSAPrivateKey_file(SSL *ssl, const char *file, int type);

int SSL_CTX_check_private_key(const SSL_CTX *ctx);
int SSL_check_private_key(const SSL *ssl);

int SSL_CTX_use_cert_and_key(SSL_CTX *ctx, X509 *x, EVP_PKEY *pkey, STACK_OF(X509) *chain, int override);
int SSL_use_cert_and_key(SSL *ssl, X509 *x, EVP_PKEY *pkey, STACK_OF(X509) *chain, int override);

ok but the way there are so many of these? iconic honestly 👑

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💅 DESCRIPTION 💅

So the tea is: these functions load certificates and private keys into either the SSL_CTX object or the SSL object, depending on which one you picked. 💖

The SSL_CTX_* crew loads certificates and keys into the SSL_CTX object ctx. And here's the important part — that info gets passed to SSL objects ssl created from ctx with SSL_new(3) by copying, which means changes you apply to ctx afterwards do not propagate to SSL objects that already exist. no take-backs, bestie. 🙈

The SSL_* crew only loads certificates and keys into one specific SSL object. And the specific info is kept when SSL_clear(3) is called on that SSL object. main character energy fr. ✨

SSL_CTX_use_certificate() loads the certificate x into ctx, and SSL_use_certificate() loads x into ssl. The rest of the certificates you need to form the complete certificate chain can be specified with the SSL_CTX_add_extra_chain_cert(3) function. On success the reference counter of the x is incremented. 🎀

SSL_CTX_use_certificate_ASN1() loads the ASN1 encoded certificate from the memory location d (with length len) into ctx, and SSL_use_certificate_ASN1() loads the ASN1 encoded certificate into ssl.

SSL_CTX_use_certificate_file() loads the first certificate stored in file into ctx. You must specify the formatting type of the certificate, from the known types SSL_FILETYPE_PEM and SSL_FILETYPE_ASN1. SSL_use_certificate_file() loads the certificate from file into ssl. Also, pls check the NOTES section for why SSL_CTX_use_certificate_chain_file() should be preferred. (spoiler: it's the better one, lowkey.)

SSL_CTX_use_certificate_chain_file() loads a certificate chain from file into ctx. The certificates must be in PEM format and must be sorted starting with the subject's certificate (the actual client or server certificate), followed by intermediate CA certificates if applicable, and ending at the highest level (root) CA. SSL_use_certificate_chain_file() is the same vibe except it loads the certificate chain into ssl. 🦋

SSL_CTX_use_PrivateKey() adds pkey as private key to ctx. And listen — ctx MUST NOT be NULL. SSL_CTX_use_RSAPrivateKey() adds the private key rsa of type RSA to ctx. SSL_use_PrivateKey() adds pkey as private key to ssl; SSL_use_RSAPrivateKey() adds rsa as private key of type RSA to ssl. If a certificate has already been set and the private key does not belong to that certificate, an error is returned. 🚨 And if you wanna change a [certificate/private-key] pair, you have to set the new certificate first with SSL_use_certificate() or SSL_CTX_use_certificate() before setting the private key with SSL_CTX_use_PrivateKey() or SSL_use_PrivateKey(). order matters, periodt. On success the reference counter of the pkey/rsa is incremented.

SSL_CTX_use_cert_and_key() and SSL_use_cert_and_key() assign the X.509 certificate x, private key key, and certificate chain onto the corresponding ssl or ctx. The pkey argument must be the private key of the X.509 certificate x. If the override argument is 0, then x, pkey and chain are set only if all were not previously set. If override is non-0, then the certificate, private key and chain certs are always set. If pkey is NULL, then the public key of x is used as the private key. This is intended to be used with hardware (via the ENGINE interface) that stores the private key securely, such that it cannot be accessed by OpenSSL. The reference count of the public key is incremented (twice if there is no private key); it is not copied nor duplicated. This allows all private key validation checks to succeed without an actual private key being assigned via SSL_CTX_use_PrivateKey(), etc. 🤯

SSL_CTX_use_PrivateKey_ASN1() adds the private key of type pk stored at memory location d (length len) to ctx. SSL_CTX_use_RSAPrivateKey_ASN1() adds the private key of type RSA stored at memory location d (length len) to ctx. SSL_use_PrivateKey_ASN1() and SSL_use_RSAPrivateKey_ASN1() add the private key to ssl. 🧚

SSL_CTX_use_PrivateKey_file() adds the first private key found in file to ctx. You have to specify the formatting type of the private key from the known types SSL_FILETYPE_PEM and SSL_FILETYPE_ASN1. SSL_CTX_use_RSAPrivateKey_file() adds the first private RSA key found in file to ctx. SSL_use_PrivateKey_file() adds the first private key found in file to ssl; SSL_use_RSAPrivateKey_file() adds the first private RSA key found to ssl. And again: ctx MUST NOT be NULL. 💀

SSL_CTX_check_private_key() checks the consistency of a private key against the corresponding certificate loaded into ctx. If more than one key/certificate pair (RSA/DSA) is installed, the last item installed will be checked. If, e.g., the last item was an RSA certificate or key, then the RSA key/certificate pair will be checked. SSL_check_private_key() does the same check for ssl. And if no key/certificate was explicitly added for that ssl, then the last item added into ctx will be checked. 👑

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🎀 NOTES 🎀

The internal certificate store of OpenSSL can hold several private key/certificate pairs at a time. Which certificate actually gets used depends on the cipher selected — see also SSL_CTX_set_cipher_list(3). 🌈

When reading certificates and private keys from a file, files of type SSL_FILETYPE_ASN1 (also known as DER, binary encoding) can only contain one certificate or private key, which is why SSL_CTX_use_certificate_chain_file() is only applicable to PEM formatting. Files of type SSL_FILETYPE_PEM can contain more than one item. 🍓

SSL_CTX_use_certificate_chain_file() adds the first certificate found in the file to the certificate store. The other certificates are added to the store of chain certificates using SSL_CTX_add1_chain_cert(3). Note: versions of OpenSSL before 1.0.2 only had a single certificate chain store for all certificate types, while OpenSSL 1.0.2 and later have a separate chain store for each type. SSL_CTX_use_certificate_chain_file() should be used instead of the SSL_CTX_use_certificate_file() function, so you can use complete certificate chains even when no trusted CA storage is used, or when the CA issuing the certificate shall not be added to the trusted CA storage. 💜

If additional certificates are needed to complete the chain during the TLS negotiation, CA certificates are additionally looked up in the locations of trusted CA certificates — see SSL_CTX_load_verify_locations(3). 🌸

The private keys loaded from file can be encrypted. To successfully load encrypted keys, a function returning the passphrase must have been supplied — see SSL_CTX_set_default_passwd_cb(3). (Certificate files might be encrypted too from a purely technical point of view, but it lowkey does not make sense, since the data in the certificate is considered public anyway. 🤷♀️)

All of the functions that set a new certificate will replace any existing certificate of the same type that has already been set. Same energy for all the functions that set a new private key — they replace any private key that's already been set. So after loading a new certificate and private key, applications should call SSL_CTX_check_private_key(3) or SSL_check_private_key(3) as appropriate, to confirm that the certificate and the key actually match. do not skip this step bestie, it's the vibe check. 💅

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💖 RETURN VALUES 💖

On success, the functions return 1. Otherwise, go check out the error stack to find out the reason. 😭

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🦋 SEE ALSO 🦋

ssl(7), SSL_new(3), SSL_clear(3), SSL_CTX_load_verify_locations(3), SSL_CTX_set_default_passwd_cb(3), SSL_CTX_set_cipher_list(3), SSL_CTX_set_client_CA_list(3), SSL_CTX_set_client_cert_cb(3), SSL_CTX_add_extra_chain_cert(3)

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👑 COPYRIGHT 👑

Copyright 2000-2024 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 🫶 this was SSL_CTX_USE_CERTIFICATE(3ossl) from OpenSSL 3.5.9, dated 2026-09-29 — go forth and load those certs, you absolute icon ✨💜