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path-util: some updates to path_make_relative()

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Don't miscount number of "../" to generate, if we "." is included in an
input path.

Also, refuse if we encounter "../" since we can't possibly follow that
up properly, without file system access.

Some other modernizations.
This commit is contained in:
Lennart Poettering
2017-10-02 17:41:44 +02:00
parent 091e9efed3
commit 2a5beb669f
2 changed files with 19 additions and 8 deletions
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src/basic/path-util.c
+17 -8
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@@ -131,8 +131,7 @@ int path_make_relative(const char *from_dir, const char *to_path, char **_r) {
/* Skip the common part. */
for (;;) {
size_t a;
size_t b;
size_t a, b;
from_dir += strspn(from_dir, "/");
to_path += strspn(to_path, "/");
@@ -144,7 +143,6 @@ int path_make_relative(const char *from_dir, const char *to_path, char **_r) {
else
/* from_dir is a parent directory of to_path. */
r = strdup(to_path);
if (!r)
return -ENOMEM;
@@ -175,21 +173,32 @@ int path_make_relative(const char *from_dir, const char *to_path, char **_r) {
/* Count the number of necessary ".." elements. */
for (n_parents = 0;;) {
size_t w;
from_dir += strspn(from_dir, "/");
if (!*from_dir)
break;
from_dir += strcspn(from_dir, "/");
n_parents++;
w = strcspn(from_dir, "/");
/* If this includes ".." we can't do a simple series of "..", refuse */
if (w == 2 && from_dir[0] == '.' && from_dir[1] == '.')
return -EINVAL;
/* Count number of elements, except if they are "." */
if (w != 1 || from_dir[0] != '.')
n_parents++;
from_dir += w;
}
r = malloc(n_parents * 3 + strlen(to_path) + 1);
r = new(char, n_parents * 3 + strlen(to_path) + 1);
if (!r)
return -ENOMEM;
for (p = r; n_parents > 0; n_parents--, p += 3)
memcpy(p, "../", 3);
for (p = r; n_parents > 0; n_parents--)
p = mempcpy(p, "../", 3);
strcpy(p, to_path);
path_kill_slashes(r);