SSL_CTX_SET_...ULT_PASSWD_CB(3ossl)

🎀 SSL_CTX_SET_...ULT_PASSWD_CB — bestie edition 💅

okay so this is from the 3ossl manual, and we're about to make password callbacks for encrypted PEM files make sense. no cap. let's go 🦋

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✨ NAME ✨

SSL_CTX_set_default_passwd_cb, SSL_CTX_set_default_passwd_cb_userdata, SSL_CTX_get_default_passwd_cb, SSL_CTX_get_default_passwd_cb_userdata, SSL_set_default_passwd_cb, SSL_set_default_passwd_cb_userdata, SSL_get_default_passwd_cb, SSL_get_default_passwd_cb_userdata — these girls set or get the passwd callback for encrypted PEM file handling. literally that's the whole job. 👑

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✨ SYNOPSIS ✨

#include <openssl/ssl.h>

void SSL_CTX_set_default_passwd_cb(SSL_CTX *ctx, pem_password_cb *cb);
void SSL_CTX_set_default_passwd_cb_userdata(SSL_CTX *ctx, void *u);
pem_password_cb *SSL_CTX_get_default_passwd_cb(SSL_CTX *ctx);
void *SSL_CTX_get_default_passwd_cb_userdata(SSL_CTX *ctx);

void SSL_set_default_passwd_cb(SSL *s, pem_password_cb *cb);
void SSL_set_default_passwd_cb_userdata(SSL *s, void *u);
pem_password_cb *SSL_get_default_passwd_cb(SSL *s);
void *SSL_get_default_passwd_cb_userdata(SSL *s);

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✨ DESCRIPTION ✨

so. SSL_CTX_set_default_passwd_cb() sets the default password callback — the lil function that gets called whenever you're loading or storing a PEM certificate with encryption. 🔐

SSL_CTX_set_default_passwd_cb_userdata() sets a pointer to userdata, u, and that pointer gets handed over to the password callback whenever it's invoked. like a little gift you pass along 🎁

SSL_CTX_get_default_passwd_cb() returns a function pointer to the password callback that's currently chilling in ctx. and if nobody ever explicitly set a callback? you get the NULL pointer. 🙈

SSL_CTX_get_default_passwd_cb_userdata() returns a pointer to the userdata currently set in ctx. and again — no explicit userdata? NULL pointer, bestie. 🙈

SSL_set_default_passwd_cb(), SSL_set_default_passwd_cb_userdata(), SSL_get_default_passwd_cb() and SSL_get_default_passwd_cb_userdata() do exactly the same thing as their SSL_CTX counterparts — the only glow-up is that they work on an SSL object instead. ✨

now for the callback itself: the password callback must be provided by the application, and its whole moment is handing back the password used during decryption. on invocation it gets a pointer to userdata. the function has to store the password into the provided buffer buf, which is of size size. the actual length of the password must be returned to the calling function — don't forget that part, it's giving consequences 💀

and rwflag tells you whether the callback is being used for reading/decryption (rwflag=0) or writing/encryption (rwflag=1). want the whole story? go read pem_password_cb(3). 📖

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✨ NOTES ✨

when you're loading or storing private keys, a password might be supplied to protect that private key. how you supply it? depends on the app, honestly.

• if you're only handling one private key, it can be practical to let the callback do the password dialog interactively. cute, personal, one-on-one 💬
• if you've got several keys to handle, it can be practical to ask for the password once, keep it in memory, and reuse it several times. efficiency, queen 👑
• in that last case, the password could be stored into the userdata storage, and the callback just returns the password that's already stored. lazy in the best way 🍓

when asking for the password interactively, the callback can use rwflag to check whether an item shall be encrypted (rwflag=1). in that case the password dialog may ask for the same password twice for comparison, so it catches typos — because a typo would make decryption impossible. and that's a tragedy nobody's signing up for 😭

also! other items in PEM formatting (certificates) can also be encrypted. it's just not usual, since certificate information is considered public. so like. you can. but why. 💅

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✨ RETURN VALUES ✨

these functions do not provide diagnostic information. that's it. that's the section. no notes. 🫶

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✨ EXAMPLES ✨

okay here's the example — it returns the password that was provided as userdata to the calling function. the password is treated as a '\0' terminated string. and if the password doesn't fit into the buffer, it gets truncated. 🩴

int my_cb(char *buf, int size, int rwflag, void *u)
{
    strncpy(buf, (char *)u, size);
    buf[size - 1] = '\0';
    return strlen(buf);
}

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✨ SEE ALSO ✨

ssl(7), SSL_CTX_use_certificate(3) — go read these too, bestie, they're part of the lore 🌸

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✨ HISTORY ✨

SSL_CTX_get_default_passwd_cb(), SSL_CTX_get_default_passwd_cb_userdata(), SSL_set_default_passwd_cb() and SSL_set_default_passwd_cb_userdata() were added in OpenSSL 1.1.0. glow-up era. ✨

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✨ COPYRIGHT ✨

Copyright 2000-2019 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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💜 that's the whole page, bestie. no detail left behind, every flag and callback intact, periodt.

signing off from the 3ossl manual, OpenSSL version 3.5.9, dated 2026-09-2 — mwah, go encrypt something responsibly 💅🎀🦋