From e3e479fc9c51e0b6f2c21087e2e78e7c6f55169c Mon Sep 17 00:00:00 2001

From: Lennart Poettering <lennart@poettering.net>

Date: Mon, 25 May 2020 00:34:58 +0200

Subject: [PATCH] unit-name: tighten checks for building valid unit names

Let's be more thorough that whenever we build a unit name based on

parameters, that the result is actually a valid user name. If it isn't

fail early.

This should allows us to catch various issues earlier, in particular

when we synthesize mount units from /proc/self/mountinfo: instead of

actually attempting to allocate a mount unit we will fail much earlier

when we build the name to synthesize the unit under. Failing early is a

good thing generally.

(cherry picked from commit ab19db01ae1826efb3cbdf6dcb6a14412f8844d4)

Related: #1940973

---

 src/basic/unit-name.c | 61 ++++++++++++++++++++++++++++++-------------

 1 file changed, 43 insertions(+), 18 deletions(-)

diff --git a/src/basic/unit-name.c b/src/basic/unit-name.c

index 614eb8649b..f9b3fafd4d 100644

--- a/src/basic/unit-name.c

+++ b/src/basic/unit-name.c

@@ -207,8 +207,9 @@ UnitType unit_name_to_type(const char *n) {

 }

 int unit_name_change_suffix(const char *n, const char *suffix, char **ret) {

-        char *e, *s;

+        _cleanup_free_ char *s = NULL;

         size_t a, b;

+        char *e;

         assert(n);

         assert(suffix);

@@ -230,8 +231,12 @@ int unit_name_change_suffix(const char *n, const char *suffix, char **ret) {

                 return -ENOMEM;

         strcpy(mempcpy(s, n, a), suffix);

-        *ret = s;

+        /* Make sure the name is still valid (i.e. didn't grow too large due to longer suffix) */

+        if (!unit_name_is_valid(s, UNIT_NAME_ANY))

+                return -EINVAL;

+

+        *ret = TAKE_PTR(s);

         return 0;

 }

@@ -253,8 +258,8 @@ int unit_name_build(const char *prefix, const char *instance, const char *suffix

 }

 int unit_name_build_from_type(const char *prefix, const char *instance, UnitType type, char **ret) {

+        _cleanup_free_ char *s = NULL;

         const char *ut;

-        char *s;

         assert(prefix);

         assert(type >= 0);

@@ -264,19 +269,23 @@ int unit_name_build_from_type(const char *prefix, const char *instance, UnitType

         if (!unit_prefix_is_valid(prefix))

                 return -EINVAL;

-        if (instance && !unit_instance_is_valid(instance))

-                return -EINVAL;

-

         ut = unit_type_to_string(type);

-        if (!instance)

-                s = strjoin(prefix, ".", ut);

-        else

+        if (instance) {

+                if (!unit_instance_is_valid(instance))

+                        return -EINVAL;

+

                 s = strjoin(prefix, "@", instance, ".", ut);

+        } else

+                s = strjoin(prefix, ".", ut);

         if (!s)

                 return -ENOMEM;

-        *ret = s;

+        /* Verify that this didn't grow too large (or otherwise is invalid) */

+        if (!unit_name_is_valid(s, instance ? UNIT_NAME_INSTANCE : UNIT_NAME_PLAIN))

+                return -EINVAL;

+

+        *ret = TAKE_PTR(s);

         return 0;

 }

@@ -445,8 +454,8 @@ int unit_name_path_unescape(const char *f, char **ret) {

 }

 int unit_name_replace_instance(const char *f, const char *i, char **ret) {

+        _cleanup_free_ char *s = NULL;

         const char *p, *e;

-        char *s;

         size_t a, b;

         assert(f);

@@ -470,7 +479,11 @@ int unit_name_replace_instance(const char *f, const char *i, char **ret) {

         strcpy(mempcpy(mempcpy(s, f, a + 1), i, b), e);

-        *ret = s;

+        /* Make sure the resulting name still is valid, i.e. didn't grow too large */

+        if (!unit_name_is_valid(s, UNIT_NAME_INSTANCE))

+                return -EINVAL;

+

+        *ret = TAKE_PTR(s);

         return 0;

 }

@@ -501,8 +514,7 @@ int unit_name_template(const char *f, char **ret) {

 }

 int unit_name_from_path(const char *path, const char *suffix, char **ret) {

-        _cleanup_free_ char *p = NULL;

-        char *s = NULL;

+        _cleanup_free_ char *p = NULL, *s = NULL;

         int r;

         assert(path);

@@ -520,7 +532,11 @@ int unit_name_from_path(const char *path, const char *suffix, char **ret) {

         if (!s)

                 return -ENOMEM;

-        *ret = s;

+        /* Refuse this if this got too long or for some other reason didn't result in a valid name */

+        if (!unit_name_is_valid(s, UNIT_NAME_PLAIN))

+                return -EINVAL;

+

+        *ret = TAKE_PTR(s);

         return 0;

 }

@@ -548,6 +564,10 @@ int unit_name_from_path_instance(const char *prefix, const char *path, const cha

         if (!s)

                 return -ENOMEM;

+        /* Refuse this if this got too long or for some other reason didn't result in a valid name */

+        if (!unit_name_is_valid(s, UNIT_NAME_INSTANCE))

+                return -EINVAL;

+

         *ret = s;

         return 0;

 }

@@ -601,7 +621,7 @@ static bool do_escape_mangle(const char *f, bool allow_globs, char *t) {

  *  If @allow_globs, globs characters are preserved. Otherwise, they are escaped.

  */

 int unit_name_mangle_with_suffix(const char *name, UnitNameMangle flags, const char *suffix, char **ret) {

-        char *s;

+        _cleanup_free_ char *s = NULL;

         int r;

         bool mangled;

@@ -656,7 +676,12 @@ int unit_name_mangle_with_suffix(const char *name, UnitNameMangle flags, const c

         if ((!(flags & UNIT_NAME_MANGLE_GLOB) || !string_is_glob(s)) && unit_name_to_type(s) < 0)

                 strcat(s, suffix);

-        *ret = s;

+        /* Make sure mangling didn't grow this too large (but don't do this check if globbing is allowed,

+         * since globs generally do not qualify as valid unit names) */

+        if (!FLAGS_SET(flags, UNIT_NAME_MANGLE_GLOB) && !unit_name_is_valid(s, UNIT_NAME_ANY))

+                return -EINVAL;

+

+        *ret = TAKE_PTR(s);

         return 1;

 good:

@@ -664,7 +689,7 @@ good:

         if (!s)

                 return -ENOMEM;

-        *ret = s;

+        *ret = TAKE_PTR(s);

         return 0;

 }