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user-util: add get{pw,gr}{uid,gid,name}_malloc() helpers

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These are wrappers around getpwuid_r() and friends, and will allocate the
right-sized buffer for this call.

We so far had multiple implementations of a buffer allocation loop
around getpwuid_r() and friends, and they all suck in some way. Let's
clean this up and add a common implementation, and use it everywhere.

Also, be more careful with error numbers, in particular systematically
turn ENOENT into ENOSRCH (the former is what is returned if /etc/passwd
is absent, which we want to consider identical to user not existing,
which is ENOSRCH). We so far did this at some invocations, but not all.

There are some invocations of getpwuid() left in the codebase. We really
should fix those too, and have a single unified implementation of the
logic, but those are not as trivial to convert, so left for another
time.
This commit is contained in:
Lennart Poettering
2024-01-22 17:55:07 +01:00
parent 829854afa5
commit 75673cd8ae
10 changed files with 311 additions and 255 deletions
Download Patch File Download Diff File Expand all files Collapse all files
src/sysusers/sysusers.c
+30 -42
View File
@@ -141,12 +141,6 @@ static void context_done(Context *c) {
uid_range_free(c->uid_range);
}
static int errno_is_not_exists(int code) {
/* See getpwnam(3) and getgrnam(3): those codes and others can be returned if the user or group are
* not found. */
return IN_SET(code, 0, ENOENT, ESRCH, EBADF, EPERM);
}
/* Note: the lifetime of the compound literal is the immediately surrounding block,
* see C11 §6.5.2.5, and
* https://stackoverflow.com/questions/34880638/compound-literal-lifetime-and-if-blocks */
@@ -1028,6 +1022,7 @@ static int uid_is_ok(
const char *name,
bool check_with_gid) {
int r;
assert(c);
/* Let's see if we already have assigned the UID a second time */
@@ -1058,24 +1053,21 @@ static int uid_is_ok(
/* Let's also check via NSS, to avoid UID clashes over LDAP and such, just in case */
if (!arg_root) {
struct passwd *p;
struct group *g;
_cleanup_free_ struct group *g = NULL;
errno = 0;
p = getpwuid(uid);
if (p)
r = getpwuid_malloc(uid, /* ret= */ NULL);
if (r >= 0)
return 0;
if (!IN_SET(errno, 0, ENOENT))
return -errno;
if (r != -ESRCH)
return r;
if (check_with_gid) {
errno = 0;
g = getgrgid((gid_t) uid);
if (g) {
r = getgrgid_malloc((gid_t) uid, &g);
if (r >= 0) {
if (!streq(g->gr_name, name))
return 0;
} else if (!IN_SET(errno, 0, ENOENT))
return -errno;
} else if (r != -ESRCH)
return r;
}
}
@@ -1164,12 +1156,11 @@ static int add_user(Context *c, Item *i) {
}
if (!arg_root) {
struct passwd *p;
_cleanup_free_ struct passwd *p = NULL;
/* Also check NSS */
errno = 0;
p = getpwnam(i->name);
if (p) {
r = getpwnam_malloc(i->name, &p);
if (r >= 0) {
log_debug("User %s already exists.", i->name);
i->uid = p->pw_uid;
i->uid_set = true;
@@ -1180,8 +1171,8 @@ static int add_user(Context *c, Item *i) {
return 0;
}
if (!errno_is_not_exists(errno))
return log_error_errno(errno, "Failed to check if user %s already exists: %m", i->name);
if (r != -ESRCH)
return log_error_errno(r, "Failed to check if user %s already exists: %m", i->name);
}
/* Try to use the suggested numeric UID */
@@ -1270,10 +1261,9 @@ static int gid_is_ok(
const char *groupname,
bool check_with_uid) {
struct group *g;
struct passwd *p;
Item *user;
char *username;
int r;
assert(c);
assert(groupname);
@@ -1298,20 +1288,18 @@ static int gid_is_ok(
}
if (!arg_root) {
errno = 0;
g = getgrgid(gid);
if (g)
r = getgrgid_malloc(gid, /* ret= */ NULL);
if (r >= 0)
return 0;
if (!IN_SET(errno, 0, ENOENT))
return -errno;
if (r != -ESRCH)
return r;
if (check_with_uid) {
errno = 0;
p = getpwuid((uid_t) gid);
if (p)
r = getpwuid_malloc(gid, /* ret= */ NULL);
if (r >= 0)
return 0;
if (!IN_SET(errno, 0, ENOENT))
return -errno;
if (r != -ESRCH)
return r;
}
}
@@ -1324,6 +1312,7 @@ static int get_gid_by_name(
gid_t *ret_gid) {
void *z;
int r;
assert(c);
assert(ret_gid);
@@ -1337,16 +1326,15 @@ static int get_gid_by_name(
/* Also check NSS */
if (!arg_root) {
struct group *g;
_cleanup_free_ struct group *g = NULL;
errno = 0;
g = getgrnam(name);
if (g) {
r = getgrnam_malloc(name, &g);
if (r >= 0) {
*ret_gid = g->gr_gid;
return 0;
}
if (!errno_is_not_exists(errno))
return log_error_errno(errno, "Failed to check if group %s already exists: %m", name);
if (r != -ESRCH)
return log_error_errno(r, "Failed to check if group %s already exists: %m", name);
}
return -ENOENT;