SSL_CTX_set_default_passwd_cb 3 2002-06-09 0.9.9-dev OpenSSL

NAME

SSL_CTX_set_default_passwd_cb, SSL_CTX_set_default_passwd_cb_userdata - set passwd callback for encrypted PEM file handling

LIBRARY

libcrypto, -lcrypto

SYNOPSIS


 #include 


 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

_S_S_L___C_T_X___s_e_t___d_e_f_a_u_l_t___p_a_s_s_w_d___c_b_(_) sets the default password callback called when loading/storing a PEM certificate with encryption.

_S_S_L___C_T_X___s_e_t___d_e_f_a_u_l_t___p_a_s_s_w_d___c_b___u_s_e_r_d_a_t_a_(_) sets a pointer to uusseerrddaattaa which will be provided to the password callback on invocation.

The _p_e_m___p_a_s_s_w_d___c_b_(_), which must be provided by the application, hands back the password to be used during decryption. On invocation a pointer to uusseerrddaattaa is provided. The pem_passwd_cb must write the password into the provided buffer bbuuff which is of size ssiizzee. The actual length of the password must be returned to the calling function. rrwwffllaagg 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 _p_e_m___p_a_s_s_w_d___c_b_(_) 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 uusseerrddaattaa storage and the _p_e_m___p_a_s_s_w_d___c_b_(_) only returns the password already stored.

When asking for the password interactively, _p_e_m___p_a_s_s_w_d___c_b_(_) can use rrwwffllaagg 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

_S_S_L___C_T_X___s_e_t___d_e_f_a_u_l_t___p_a_s_s_w_d___c_b_(_) and _S_S_L___C_T_X___s_e_t___d_e_f_a_u_l_t___p_a_s_s_w_d___c_b___u_s_e_r_d_a_t_a_(_) do not provide diagnostic information.

EXAMPLES

The following example returns the password provided as uusseerrddaattaa 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));
 }

SEE ALSO

_s_s_l(3), _S_S_L___C_T_X___u_s_e___c_e_r_t_i_f_i_c_a_t_e(3)