ssl_ctx_set_default_passwd_cb(3)
NAME
SSL_CTX_set_default_passwd_cb, SSL_CTX_set_default_passwd_cb_userdata set passwd callback for encrypted PEM file handling
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); int pem_passwd_cb(char *buf, int size, int rwflag, void *userdata);
DESCRIPTION
SSL_CTX_set_default_passwd_cb() sets the default password callback
called when loading/storing a PEM certificate with encryption.
SSL_CTX_set_default_passwd_cb_userdata() sets a pointer to userdata
which will be provided to the password callback on invocation.
The pem_passwd_cb(), which must be provided by the application, hands
back the password to be used during decryption. On invocation a pointer
to userdata is provided. The pem_passwd_cb must write 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. rwflag indicates
whether the callback is used for reading/decryption (rwflag=0) or
writing/encryption (rwflag=1).
NOTES
When loading or storing private keys, a password might be supplied to
protect the private key. The way this password can be supplied may
depend on the application. If only one private key is handled, it can
be practical to have pem_passwd_cb() handle the password dialog
interactively. If several keys have to be handled, it can be practical
to ask for the password once, then keep it in memory and use it several
times. In the last case, the password could be stored into the userdata
storage and the pem_passwd_cb() only returns the password already
stored.
When asking for the password interactively, pem_passwd_cb() can use
rwflag to check, whether an item shall be encrypted (rwflag=1). In
this case the password dialog may ask for the same password twice for
comparison in order to catch typos, that would make decryption
impossible.
Other items in PEM formatting (certificates) can also be encrypted, it is however not usual, as certificate information is considered public.
RETURN VALUES
SSL_CTX_set_default_passwd_cb() and
SSL_CTX_set_default_passwd_cb_userdata() do not provide diagnostic
information.
EXAMPLES
- The following example returns the password provided as userdata to the
calling function. The password is considered to be a '\0' terminated
string. If the password does not fit into the buffer, the password is
truncated. - int pem_passwd_cb(char *buf, int size, int rwflag, void *password)
{strncpy(buf, (char *)(password), size);
buf[size - 1] = '\0';
return(strlen(buf)); - }