Cleaning the linker environment as we initialize it requires less API.
Change-Id: I612fd699e46833a411589478564a1f859223c380
diff --git a/linker/linker_environ.cpp b/linker/linker_environ.cpp
index 357be6d..8ae5a9d 100644
--- a/linker/linker_environ.cpp
+++ b/linker/linker_environ.cpp
@@ -40,45 +40,6 @@
return _AT_SECURE_value;
}
-/* Returns 1 if 'str' points to a valid environment variable definition.
- * For now, we check that:
- * - It is smaller than MAX_ENV_LEN (to detect non-zero terminated strings)
- * - It contains at least one equal sign that is not the first character
- */
-static int _is_valid_definition(const char* str) {
- int pos = 0;
- int first_equal_pos = -1;
-
- // According to its sources, the kernel uses 32*PAGE_SIZE by default
- // as the maximum size for an env. variable definition.
- const int MAX_ENV_LEN = 32*4096;
-
- if (str == NULL) {
- return 0;
- }
-
- // Parse the string, looking for the first '=' there, and its size.
- while (pos < MAX_ENV_LEN) {
- if (str[pos] == '\0') {
- break;
- }
- if (str[pos] == '=' && first_equal_pos < 0) {
- first_equal_pos = pos;
- }
- pos++;
- }
-
- if (pos >= MAX_ENV_LEN) {
- return 0; // Too large.
- }
-
- if (first_equal_pos < 1) {
- return 0; // No equals sign, or it's the first character.
- }
-
- return 1;
-}
-
static void __init_AT_SECURE(unsigned* auxv) {
// Check auxv for AT_SECURE first to see if program is setuid, setgid,
// has file caps, or caused a SELinux/AppArmor domain transition.
@@ -96,7 +57,59 @@
exit(EXIT_FAILURE);
}
-static void __remove_unsafe_environment_variables() {
+// Check if the environment variable definition at 'envstr'
+// starts with '<name>=', and if so return the address of the
+// first character after the equal sign. Otherwise return NULL.
+static const char* env_match(const char* envstr, const char* name) {
+ size_t i = 0;
+
+ while (envstr[i] == name[i] && name[i] != '\0') {
+ ++i;
+ }
+
+ if (name[i] == '\0' && envstr[i] == '=') {
+ return envstr + i + 1;
+ }
+
+ return NULL;
+}
+
+static bool __is_valid_environment_variable(const char* name) {
+ // According to its sources, the kernel uses 32*PAGE_SIZE by default
+ // as the maximum size for an env. variable definition.
+ const int MAX_ENV_LEN = 32*4096;
+
+ if (name == NULL) {
+ return false;
+ }
+
+ // Parse the string, looking for the first '=' there, and its size.
+ int pos = 0;
+ int first_equal_pos = -1;
+ while (pos < MAX_ENV_LEN) {
+ if (name[pos] == '\0') {
+ break;
+ }
+ if (name[pos] == '=' && first_equal_pos < 0) {
+ first_equal_pos = pos;
+ }
+ pos++;
+ }
+
+ // Check that it's smaller than MAX_ENV_LEN (to detect non-zero terminated strings).
+ if (pos >= MAX_ENV_LEN) {
+ return false;
+ }
+
+ // Check that it contains at least one equal sign that is not the first character
+ if (first_equal_pos < 1) {
+ return false;
+ }
+
+ return true;
+}
+
+static bool __is_unsafe_environment_variable(const char* name) {
// None of these should be allowed in setuid programs.
static const char* const UNSAFE_VARIABLE_NAMES[] = {
"GCONV_PATH",
@@ -127,17 +140,24 @@
NULL
};
for (size_t i = 0; UNSAFE_VARIABLE_NAMES[i] != NULL; ++i) {
- linker_env_unset(UNSAFE_VARIABLE_NAMES[i]);
+ if (env_match(name, UNSAFE_VARIABLE_NAMES[i]) != NULL) {
+ return true;
+ }
}
+ return false;
}
-static void __remove_invalid_environment_variables() {
+static void __sanitize_environment_variables() {
char** src = _envp;
char** dst = _envp;
for (; src[0] != NULL; ++src) {
- if (!_is_valid_definition(src[0])) {
+ if (!__is_valid_environment_variable(src[0])) {
continue;
}
+ // Remove various unsafe environment variables if we're loading a setuid program.
+ if (get_AT_SECURE() && __is_unsafe_environment_variable(src[0])) {
+ continue;
+ }
dst[0] = src[0];
++dst;
}
@@ -156,42 +176,19 @@
}
++aux_vectors;
- __remove_invalid_environment_variables();
__init_AT_SECURE(aux_vectors);
-
- // Sanitize environment if we're loading a setuid program.
- if (get_AT_SECURE()) {
- __remove_unsafe_environment_variables();
- }
+ __sanitize_environment_variables();
return aux_vectors;
}
-/* Check if the environment variable definition at 'envstr'
- * starts with '<name>=', and if so return the address of the
- * first character after the equal sign. Otherwise return NULL.
- */
-static char* env_match(char* envstr, const char* name) {
- size_t i = 0;
-
- while (envstr[i] == name[i] && name[i] != '\0') {
- ++i;
- }
-
- if (name[i] == '\0' && envstr[i] == '=') {
- return envstr + i + 1;
- }
-
- return NULL;
-}
-
const char* linker_env_get(const char* name) {
if (name == NULL || name[0] == '\0') {
return NULL;
}
for (char** p = _envp; p[0] != NULL; ++p) {
- char* val = env_match(p[0], name);
+ const char* val = env_match(p[0], name);
if (val != NULL) {
if (val[0] == '\0') {
return NULL; // Return NULL for empty strings.
@@ -201,22 +198,3 @@
}
return NULL;
}
-
-void linker_env_unset(const char* name) {
- char** readp = _envp;
- char** writep = readp;
-
- if (name == NULL || name[0] == '\0') {
- return;
- }
-
- for ( ; readp[0] != NULL; readp++ ) {
- if (env_match(readp[0], name)) {
- continue;
- }
- writep[0] = readp[0];
- writep++;
- }
- /* end list with a NULL */
- writep[0] = NULL;
-}