lib/env: add function to save and restore unwanted variables

Signed-off-by: Karel Zak <kzak@redhat.com>

include/env.h

@@ -4,7 +4,14 @@
 #include "c.h"
 #include "nls.h"
 
+struct ul_env_list;
+
 extern void sanitize_env(void);
+extern void __sanitize_env(struct ul_env_list **org);
+
+extern int env_list_setenv(struct ul_env_list *ls);
+extern void env_list_free(struct ul_env_list *ls);
+
 extern char *safe_getenv(const char *arg);
 
 

lib/env.c

@@ -50,8 +50,73 @@ static char * const noslash[] = {
         (char *) 0
 };
 
-void
-sanitize_env(void)
+
+struct ul_env_list {
+	char *env;
+	struct ul_env_list *next;
+};
+
+/*
+ * Saves @name env.varable to @ls, returns pointer to the new head of the list.
+ */
+static struct ul_env_list *env_list_add(struct ul_env_list *ls0, const char *str)
+{
+	struct ul_env_list *ls;
+	char *p;
+	size_t sz = 0;
+
+	if (!str || !*str)
+		return ls0;
+
+	sz = strlen(str) + 1;
+	p = malloc(sizeof(struct ul_env_list) + sz);
+
+	ls = (struct ul_env_list *) p;
+	p += sizeof(struct ul_env_list);
+	memcpy(p, str, sz);
+	ls->env = p;
+
+	ls->next = ls0;
+	return ls;
+}
+
+/*
+ * Use setenv() for all stuff in @ls.
+ *
+ * It would be possible to use putenv(), but we want to keep @ls free()-able.
+ */
+int env_list_setenv(struct ul_env_list *ls)
+{
+	int rc = 0;
+
+	while (ls && rc == 0) {
+		if (ls->env) {
+			char *val = strchr(ls->env, '=');
+			if (!val)
+				continue;
+			*val = '\0';
+			rc = setenv(ls->env, val + 1, 0);
+			*val = '=';
+		}
+		ls = ls->next;
+	}
+	return rc;
+}
+
+void env_list_free(struct ul_env_list *ls)
+{
+	while (ls) {
+		struct ul_env_list *x = ls;
+		ls = ls->next;
+		free(x);
+	}
+}
+
+/*
+ * Removes unwanted variables from environ[]. If @ls is not NULL than stores
+ * unwnated variables to the list.
+ */
+void __sanitize_env(struct ul_env_list **org)
 {
         char **envp = environ;
         char * const *bad;
@@ -64,6 +129,8 @@ sanitize_env(void)
         for (cur = envp; *cur; cur++) {
                 for (bad = forbid; *bad; bad++) {
                         if (strncmp(*cur, *bad, strlen(*bad)) == 0) {
+				if (org)
+					*org = env_list_add(*org, *cur);
                                 last = remote_entry(envp, cur - envp, last);
                                 cur--;
                                 break;
@@ -77,6 +144,8 @@ sanitize_env(void)
                                 continue;
                         if (!strchr(*cur, '/'))
                                 continue;  /* OK */
+			if (org)
+				*org = env_list_add(*org, *cur);
                         last = remote_entry(envp, cur - envp, last);
                         cur--;
                         break;
@@ -84,6 +153,10 @@ sanitize_env(void)
         }
 }
 
+void sanitize_env(void)
+{
+	__sanitize_env(NULL);
+}
 
 char *safe_getenv(const char *arg)
 {
@@ -116,6 +189,7 @@ int main(void)
 	char copy[32];
 	char *p;
 	int retval = EXIT_SUCCESS;
+	struct ul_env_list *removed = NULL;
 
 	for (bad = forbid; *bad; bad++) {
 		strcpy(copy, *bad);
@@ -124,7 +198,11 @@ int main(void)
 			*p = '\0';
 		setenv(copy, copy, 1);
 	}
-	sanitize_env();
+
+	/* removed */
+	__sanitize_env(&removed);
+
+	/* check removal */
 	for (bad = forbid; *bad; bad++) {
 		strcpy(copy, *bad);
 		p = strchr(copy, '=');
@@ -136,6 +214,25 @@ int main(void)
 			retval = EXIT_FAILURE;
 		}
 	}
+
+	/* restore removed */
+	env_list_setenv(removed);
+
+	/* check restore */
+	for (bad = forbid; *bad; bad++) {
+		strcpy(copy, *bad);
+		p = strchr(copy, '=');
+		if (p)
+			*p = '\0';
+		p = getenv(copy);
+		if (!p) {
+			warnx("%s was not restored", copy);
+			retval = EXIT_FAILURE;
+		}
+	}
+
+	env_list_free(removed);
+
 	return retval;
 }
 #endif