[PATCH v2 2/2] notmuch-config: replace config reading function

[Tomi Ollila]

On Sun, Nov 06 2016, Ioan-Adrian Ratiu <adi at adirat.com> wrote:

> Config files are currently read using glib's g_key_file_load_from_file
> function which is very inconvenient because it's limited by design to read
> only from "regular data files" in a filesystem. Because of this limitation
> notmuch can't read configs from pipes, fifos, sockets, stdin, etc. Not even
> "notmuch --config=/dev/stdin" works:
>
> Error reading configuration file /dev/stdin: Not a regular file
>
> So replace g_key_file_load_from_file with g_key_file_load_from_data which
> gives us much more freedom to read configs from multiple sources.
>
> This also helps the more security sensitive users: If someone has private
> information in the config file, it can be encrypted on disk, then decrypted
> in RAM and passed through a pipe directly to notmuch without the use of
> intermediate plain text files.
>
> Signed-off-by: Ioan-Adrian Ratiu <adi at adirat.com>

I'd suggest the reading loop be something like (error handling (mostly) missing,
untested):

    // #define BUF_SIZE 200 // test line (use debug code or strace(1) to verify)
    #define BUF_SIZE 4096
    char *config_str;
    int config_len = 0;
    int config_bufsize = BUF_SIZE;
    size_t len;
...
    FILE *fp = fopen (config->filename, "r");
...
    config_str = talloc_zero_array (config, char, config_bufsize);
...
    while ((len = fread (config_str + config_len, 1,
                         config_bufsize - config_len, fp)) > 0) {
          config_len += len;
          if (config_len == config_bufsize) {
              config_bufsize += BUF_SIZE;
	      config_str = talloc_realloc (config, config_str, char, config_bufsize);
          }     
    }
    if (ferror (fp)) {
	fprintf (stderr, "Error reading '%s': I/O error\n", config->filename);
        fclose (fp);
	return FALSE;
    }
    fclose (fp)
    if (g_key_file_load_from_data (config->key_file, config_str, config_len,
				   G_KEY_FILE_KEEP_COMMENTS, &error))
       return TRUE;


> ---
>  notmuch-config.c | 53 +++++++++++++++++++++++++++++++++++++++++------------
>  1 file changed, 41 insertions(+), 12 deletions(-)
>
> diff --git a/notmuch-config.c b/notmuch-config.c
> index bd52790..569cf0b 100644
> --- a/notmuch-config.c
> +++ b/notmuch-config.c
> @@ -205,33 +205,62 @@ get_username_from_passwd_file (void *ctx)
>  static notmuch_bool_t
>  get_config_from_file (notmuch_config_t *config, notmuch_bool_t create_new)
>  {
> +    #define BUF_SIZE 4096
> +    char buffer[BUF_SIZE];
> +    size_t content_size = 1; // includes NULL
> +    char *config_str = NULL;
>      GError *error = NULL;
> -    notmuch_bool_t ret = FALSE;
>  
> -    if (g_key_file_load_from_file (config->key_file, config->filename,
> -				   G_KEY_FILE_KEEP_COMMENTS, &error))
> -	return TRUE;
> -
> -    if (error->domain == G_FILE_ERROR && error->code == G_FILE_ERROR_NOENT) {
> +    FILE *fp = fopen(config->filename, "r");
> +    if (fp == NULL) {
>  	/* If create_new is true, then the caller is prepared for a
>  	 * default configuration file in the case of FILE NOT FOUND.
>  	 */
>  	if (create_new) {
>  	    config->is_new = TRUE;
> -	    ret = TRUE;
> +	    return TRUE;
>  	} else {
> -	    fprintf (stderr, "Configuration file %s not found.\n"
> +	    fprintf (stderr, "Error opening config file '%s': %s\n"
>  		     "Try running 'notmuch setup' to create a configuration.\n",
> +		     config->filename, strerror(errno));
> +	    return FALSE;
> +	}
> +    }
> +
> +    config_str = talloc_zero_array (config, char, BUF_SIZE);
> +    if (config_str == NULL) {
> +	fprintf (stderr, "Error reading '%s': Out of memory\n", config->filename);
> +	return FALSE;
> +    }
> +
> +    while (fgets (buffer, BUF_SIZE, fp)) {
> +	content_size += strlen(buffer);
> +	config_str = talloc_realloc(config, config_str, char, content_size);
> +	if (config_str == NULL)	{
> +	    fprintf (stderr, "Error reading '%s': Failed to reallocate memory\n",
>  		     config->filename);
> +	    return FALSE;
>  	}
> -    } else {
> -	fprintf (stderr, "Error reading configuration file %s: %s\n",
> -		 config->filename, error->message);
> +	strcat (config_str, buffer);
> +    }
> +
> +    if (ferror (fp)) {
> +	fprintf (stderr, "Error reading '%s': I/O error\n", config->filename);
> +	return FALSE;
>      }
>  
> +    fclose(fp);
> +
> +    if (g_key_file_load_from_data (config->key_file, config_str, strlen(config_str),
> +				   G_KEY_FILE_KEEP_COMMENTS, &error))
> +	return TRUE;
> +
> +    fprintf (stderr, "Error parsing config file '%s': %s\n",
> +	     config->filename, error->message);
> +
>      g_error_free (error);
>  
> -    return ret;
> +    return FALSE;
>  }
>  
>  /* Open the named notmuch configuration file. If the filename is NULL,
> -- 
> 2.10.2
>
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