lib-settings: Add support for $ENV:name

Expands into given environment variable

diff --git a/src/lib-settings/settings.c b/src/lib-settings/settings.c
index 134c765040f1c6cdd59f87fc915feedbcef84f13..228fab787a251d24f2dc5834006c0d9c3a556a76 100644 (file)
--- a/src/lib-settings/settings.c
+++ b/src/lib-settings/settings.c
@@ -50,6 +50,45 @@ static const char *get_uint(const char *value, unsigned int *result)
        return NULL;
 }
 
+#define IS_WHITE(c) ((c) == ' ' || (c) == '\t')
+
+static const char *expand_environment_vars(const char *value)
+{
+       const char *pvalue = value, *p;
+
+       /* Fast path when there are no candidates */
+       if ((pvalue = strchr(pvalue, '$')) == NULL)
+               return value;
+
+       string_t *expanded_value = t_str_new(strlen(value));
+       str_append_data(expanded_value, value, pvalue - value);
+
+       while (pvalue != NULL && (p = strchr(pvalue, '$')) != NULL) {
+               const char *var_end;
+               str_append_data(expanded_value, pvalue, p - pvalue);
+               if ((p == value || IS_WHITE(p[-1])) &&
+                   str_begins(p, "$ENV:")) {
+                       const char *var_name, *envval;
+                       var_end = strchr(p, ' ');
+                       if (var_end == NULL)
+                               var_name = p + 5;
+                       else
+                               var_name = t_strdup_until(p + 5, var_end);
+                       if ((envval = getenv(var_name)) != NULL)
+                               str_append(expanded_value, envval);
+               } else {
+                       str_append_c(expanded_value, '$');
+                       var_end = p + 1;
+               }
+               pvalue = var_end;
+       }
+
+       if (pvalue != NULL)
+               str_append(expanded_value, pvalue);
+
+       return str_c(expanded_value);
+}
+
 const char *
 parse_setting_from_defs(pool_t pool, const struct setting_def *defs, void *base,
                        const char *key, const char *value)
@@ -165,8 +204,6 @@ settings_include(const char *pattern, struct input_stack **inputp,
 #endif
 }
 
-#define IS_WHITE(c) ((c) == ' ' || (c) == '\t')
-
 bool settings_read_i(const char *path, const char *section,
                     settings_callback_t *callback,
                     settings_section_callback_t *sect_callback, void *context,
@@ -259,6 +296,7 @@ prevfile:
                        line = str_c_modifiable(full_line);
                }
 
+               bool quoted = FALSE;
                /* a) key = value
                   b) section_type [section_name] {
                   c) } */
@@ -288,8 +326,14 @@ prevfile:
                             (*line == '\'' && line[len-1] == '\''))) {
                                line[len-1] = '\0';
                                line = str_unescape(line+1);
+                               quoted = TRUE;
                        }
 
+                       /* @UNSAFE: Cast to modifiable datastack value,
+                          but it will not be actually modified after this. */
+                       if (!quoted)
+                               line = (char *)expand_environment_vars(line);
+
                        errormsg = skip > 0 ? NULL :
                                callback(key, line, context);
                } else if (strcmp(key, "}") != 0 || *line != '\0') {