Mail: fixed s->arg_start clearing on invalid IMAP commands. Previously, s->arg_start was left intact after invalid IMAP commands, and this might result in an argument incorrectly added to the following command. Similarly, s->backslash was left intact as well, leading to unneeded backslash removal. For example (LFs from the client are explicitly shown as "<LF>"): S: * OK IMAP4 ready C: a01 login "\<LF> S: a01 BAD invalid command C: a0000000000\2 authenticate <LF> S: a00000000002 aBAD invalid command The backslash followed by LF generates invalid command with s->arg_start and s->backslash set, the following command incorrectly treats anything from the old s->arg_start to the space after the command as an argument, and removes the backslash from the tag. If there is no space, s->arg_end will be NULL. Both things seem to be harmless though. In particular: - This can be used to provide an incorrect argument to a command without arguments. The only command which seems to look at the single argument is AUTHENTICATE, and it checks the argument length before trying to access it. - Backslash removal uses the "end" pointer, and stops due to "src < end" condition instead of scanning all the process memory if s->arg_end is NULL (and arg[0].len is huge). - There should be no backslashes in unquoted strings. An obvious fix is to clear s->arg_start and s->backslash on invalid commands, similarly to how it is done in POP3 parsing (added in 810:e3aa8f305d21) and SMTP parsing. This, however, makes it clear that s->arg_start handling in the "done" label is wrong: s->arg_start cannot be legitimately set there, as it is expected to be cleared in all possible cases when the "done" label is reached. The relevant code is dead and will be removed by the following change.

/*
 * Copyright (C) Igor Sysoev
 * Copyright (C) Nginx, Inc.
 */


#ifndef _NGX_MAIL_SSL_H_INCLUDED_
#define _NGX_MAIL_SSL_H_INCLUDED_


#include <ngx_config.h>
#include <ngx_core.h>
#include <ngx_mail.h>


#define NGX_MAIL_STARTTLS_OFF   0
#define NGX_MAIL_STARTTLS_ON    1
#define NGX_MAIL_STARTTLS_ONLY  2


typedef struct {
    ngx_flag_t       enable;
    ngx_flag_t       prefer_server_ciphers;

    ngx_ssl_t        ssl;

    ngx_uint_t       starttls;
    ngx_uint_t       listen;
    ngx_uint_t       protocols;

    ngx_uint_t       verify;
    ngx_uint_t       verify_depth;

    ssize_t          builtin_session_cache;

    time_t           session_timeout;

    ngx_array_t     *certificates;
    ngx_array_t     *certificate_keys;

    ngx_str_t        dhparam;
    ngx_str_t        ecdh_curve;
    ngx_str_t        client_certificate;
    ngx_str_t        trusted_certificate;
    ngx_str_t        crl;

    ngx_str_t        ciphers;

    ngx_array_t     *passwords;
    ngx_array_t     *conf_commands;

    ngx_shm_zone_t  *shm_zone;

    ngx_flag_t       session_tickets;
    ngx_array_t     *session_ticket_keys;

    u_char          *file;
    ngx_uint_t       line;
} ngx_mail_ssl_conf_t;


extern ngx_module_t  ngx_mail_ssl_module;


#endif /* _NGX_MAIL_SSL_H_INCLUDED_ */