SSL_CTX_SET_...ULT_PASSWD_CB(3ossl)

💅 SSL_CTX_SET_...ULT_PASSWD_CB(3ossl) ✨

okay so this is an OpenSSL manual page, bestie — buckle up, it's about the passwd callback for encrypted PEM file handling, and honestly? kinda iconic.

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🎀 NAME 🎀

So there's a whole squad of functions here, and they all do basically the set-or-get dance for the passwd callback when you're handling encrypted PEM files:

• 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

like, that's the whole roster 💖 set or get the passwd callback for encrypted PEM file handling. periodt.

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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 🌸

okay so, one by one:

• SSL_CTX_set_default_passwd_cb() — sets the default password callback, the one that gets called when you're loading or storing a PEM certificate with encryption. 🎀
• SSL_CTX_set_default_passwd_cb_userdata() — sets a pointer to userdata, u, which gets handed to the password callback whenever it's invoked. like a little gift bag for your callback 🫶
• SSL_CTX_get_default_passwd_cb() — returns a function pointer to the password callback currently set in ctx. no callback explicitly set? you get the NULL pointer back, sorry bestie 😭
• SSL_CTX_get_default_passwd_cb_userdata() — returns a pointer to the userdata currently set in ctx. again, no userdata explicitly set = NULL pointer 🙈
• SSL_set_default_passwd_cb(), SSL_set_default_passwd_cb_userdata(), SSL_get_default_passwd_cb() and SSL_get_default_passwd_cb_userdata() — same exact energy as their SSL_CTX counterparts, except they operate on an SSL object instead of an SSL_CTX. main character vs. main character's context, iykyk 💅

now, about the password callback itself — your application has to provide it, no cap. it hands back the password to be used during decryption. on invocation it gets a pointer to the userdata. the function must store the password into the provided buffer buf, which is of size size. and the actual length of the password must be returned to the calling function — don't forget the return, that's the whole vibe check 🔥

rwflag tells you whether the callback is being used for reading/decryption (rwflag=0) or writing/encryption (rwflag=1). for more deets, go look at pem_password_cb(3) ⭐

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🦋 NOTES 🦋

when you're loading or storing private keys, a password might be supplied to protect the private key. how that password gets supplied? totally depends on the application, bestie.

• one private key to handle? honestly kind of practical to have the callback do the password dialog interactively. 🍓
• several keys to handle? lowkey practical to ask for the password once, keep it in memory, and reuse it several times. 💜
• in that last case, the password could be stored into the userdata storage and then the callback just returns the password that's already stored. slay, efficient. ✨

when asking for the password interactively, the callback can use rwflag to check whether an item shall be encrypted (rwflag=1). and in that case, the password dialog may ask for the same password twice for comparison — purely to catch typos, because a typo would make decryption impossible 😭😭

other items in PEM formatting (certificates) can also be encrypted, but it's not usual, since certificate information is considered public. like, why hide what's already public, right? 🙈

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⭐ RETURN VALUES ⭐

these functions do not provide diagnostic information. that's it, that's the whole section. no diag, no drama 💀

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🧚 EXAMPLES 🧚

here's the glow-up example — it returns the password provided as userdata to the calling function. the password is considered to be a '\0' terminated string. and if the password doesn't fit into the buffer? it gets truncated. bestie it is what it is 🎀

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)

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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. the origin story 💫

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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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ngl this page is short but it's doing the most. set your callbacks, mind your rwflag, and always, always null-terminate your buffer. 🫶

and that's the tea, bestie — this was OpenSSL version 3.5.6, dated 2026-04-0. catch you in the next manpage 💅✨🎀