76 lines
2.7 KiB
Text
76 lines
2.7 KiB
Text
=pod
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=head1 NAME
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SSL_CTX_set_default_passwd_cb, SSL_CTX_set_default_passwd_cb_userdata - set passwd callback for encrypted PEM file handling
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=head1 SYNOPSIS
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#include <openssl/ssl.h>
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void SSL_CTX_set_default_passwd_cb(SSL_CTX *ctx, pem_password_cb *cb);
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void SSL_CTX_set_default_passwd_cb_userdata(SSL_CTX *ctx, void *u);
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int pem_passwd_cb(char *buf, int size, int rwflag, void *userdata);
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=head1 DESCRIPTION
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SSL_CTX_set_default_passwd_cb() sets the default password callback called
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when loading/storing a PEM certificate with encryption.
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SSL_CTX_set_default_passwd_cb_userdata() sets a pointer to B<userdata> which
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will be provided to the password callback on invocation.
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The pem_passwd_cb(), which must be provided by the application, hands back the
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password to be used during decryption. On invocation a pointer to B<userdata>
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is provided. The pem_passwd_cb must write the password into the provided buffer
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B<buf> which is of size B<size>. The actual length of the password must
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be returned to the calling function. B<rwflag> indicates whether the
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callback is used for reading/decryption (rwflag=0) or writing/encryption
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(rwflag=1).
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=head1 NOTES
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When loading or storing private keys, a password might be supplied to
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protect the private key. The way this password can be supplied may depend
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on the application. If only one private key is handled, it can be practical
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to have pem_passwd_cb() handle the password dialog interactively. If several
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keys have to be handled, it can be practical to ask for the password once,
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then keep it in memory and use it several times. In the last case, the
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password could be stored into the B<userdata> storage and the
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pem_passwd_cb() only returns the password already stored.
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When asking for the password interactively, pem_passwd_cb() can use
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B<rwflag> to check, whether an item shall be encrypted (rwflag=1).
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In this case the password dialog may ask for the same password twice
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for comparison in order to catch typos, that would make decryption
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impossible.
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Other items in PEM formatting (certificates) can also be encrypted, it is
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however not usual, as certificate information is considered public.
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=head1 RETURN VALUES
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SSL_CTX_set_default_passwd_cb() and SSL_CTX_set_default_passwd_cb_userdata()
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do not provide diagnostic information.
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=head1 EXAMPLES
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The following example returns the password provided as B<userdata> to the
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calling function. The password is considered to be a '\0' terminated
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string. If the password does not fit into the buffer, the password is
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truncated.
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int pem_passwd_cb(char *buf, int size, int rwflag, void *password)
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{
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strncpy(buf, (char *)(password), size);
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buf[size - 1] = '\0';
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return(strlen(buf));
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}
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=head1 SEE ALSO
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L<ssl(3)|ssl(3)>,
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L<SSL_CTX_use_certificate(3)|SSL_CTX_use_certificate(3)>
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=cut
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