user-util: add get{pw,gr}{uid,gid,name}_malloc() helpers
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
+197
-61
@@ -431,31 +431,11 @@ char* uid_to_name(uid_t uid) {
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return strdup(NOBODY_USER_NAME);
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if (uid_is_valid(uid)) {
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long bufsize;
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_cleanup_free_ struct passwd *pw = NULL;
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bufsize = sysconf(_SC_GETPW_R_SIZE_MAX);
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if (bufsize <= 0)
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bufsize = 4096;
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for (;;) {
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struct passwd pwbuf, *pw = NULL;
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_cleanup_free_ char *buf = NULL;
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buf = malloc(bufsize);
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if (!buf)
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return NULL;
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r = getpwuid_r(uid, &pwbuf, buf, (size_t) bufsize, &pw);
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if (r == 0 && pw)
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return strdup(pw->pw_name);
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if (r != ERANGE)
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break;
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if (bufsize > LONG_MAX/2) /* overflow check */
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return NULL;
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bufsize *= 2;
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}
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r = getpwuid_malloc(uid, &pw);
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if (r >= 0)
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return strdup(pw->pw_name);
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}
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if (asprintf(&ret, UID_FMT, uid) < 0)
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@@ -474,31 +454,11 @@ char* gid_to_name(gid_t gid) {
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return strdup(NOBODY_GROUP_NAME);
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if (gid_is_valid(gid)) {
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long bufsize;
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_cleanup_free_ struct group *gr = NULL;
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bufsize = sysconf(_SC_GETGR_R_SIZE_MAX);
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if (bufsize <= 0)
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bufsize = 4096;
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for (;;) {
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struct group grbuf, *gr = NULL;
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_cleanup_free_ char *buf = NULL;
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buf = malloc(bufsize);
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if (!buf)
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return NULL;
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r = getgrgid_r(gid, &grbuf, buf, (size_t) bufsize, &gr);
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if (r == 0 && gr)
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return strdup(gr->gr_name);
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if (r != ERANGE)
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break;
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if (bufsize > LONG_MAX/2) /* overflow check */
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return NULL;
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bufsize *= 2;
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}
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r = getgrgid_malloc(gid, &gr);
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if (r >= 0)
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return strdup(gr->gr_name);
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}
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if (asprintf(&ret, GID_FMT, gid) < 0)
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@@ -609,9 +569,10 @@ int getgroups_alloc(gid_t** gids) {
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}
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int get_home_dir(char **ret) {
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struct passwd *p;
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_cleanup_free_ struct passwd *p = NULL;
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const char *e;
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uid_t u;
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int r;
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assert(ret);
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@@ -626,19 +587,17 @@ int get_home_dir(char **ret) {
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e = "/root";
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goto found;
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}
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if (u == UID_NOBODY && synthesize_nobody()) {
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e = "/";
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goto found;
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}
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/* Check the database... */
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errno = 0;
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p = getpwuid(u);
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if (!p)
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return errno_or_else(ESRCH);
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e = p->pw_dir;
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r = getpwuid_malloc(u, &p);
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if (r < 0)
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return r;
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e = p->pw_dir;
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if (!path_is_valid(e) || !path_is_absolute(e))
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return -EINVAL;
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@@ -647,9 +606,10 @@ int get_home_dir(char **ret) {
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}
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int get_shell(char **ret) {
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struct passwd *p;
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_cleanup_free_ struct passwd *p = NULL;
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const char *e;
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uid_t u;
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int r;
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assert(ret);
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@@ -670,12 +630,11 @@ int get_shell(char **ret) {
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}
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/* Check the database... */
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errno = 0;
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p = getpwuid(u);
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if (!p)
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return errno_or_else(ESRCH);
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e = p->pw_shell;
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r = getpwuid_malloc(u, &p);
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if (r < 0)
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return r;
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e = p->pw_shell;
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if (!path_is_valid(e) || !path_is_absolute(e))
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return -EINVAL;
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@@ -1089,3 +1048,180 @@ const char* get_home_root(void) {
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return "/home";
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}
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static size_t getpw_buffer_size(void) {
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long bufsize = sysconf(_SC_GETPW_R_SIZE_MAX);
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return bufsize <= 0 ? 4096U : (size_t) bufsize;
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}
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static bool errno_is_user_doesnt_exist(int error) {
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/* See getpwnam(3) and getgrnam(3): those codes and others can be returned if the user or group are
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* not found. */
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return IN_SET(abs(error), ENOENT, ESRCH, EBADF, EPERM);
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}
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int getpwnam_malloc(const char *name, struct passwd **ret) {
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size_t bufsize = getpw_buffer_size();
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int r;
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/* A wrapper around getpwnam_r() that allocates the necessary buffer on the heap. The caller must
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* free() the returned sructured! */
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if (isempty(name))
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return -EINVAL;
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for (;;) {
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_cleanup_free_ void *buf = NULL;
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buf = malloc(ALIGN(sizeof(struct passwd)) + bufsize);
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if (!buf)
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return -ENOMEM;
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struct passwd *pw = NULL;
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r = getpwnam_r(name, buf, (char*) buf + ALIGN(sizeof(struct passwd)), (size_t) bufsize, &pw);
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if (r == 0) {
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if (pw) {
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if (ret)
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*ret = TAKE_PTR(buf);
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return 0;
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}
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return -ESRCH;
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}
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assert(r > 0);
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/* getpwnam() may fail with ENOENT if /etc/passwd is missing. For us that is equivalent to
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* the name not being defined. */
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if (errno_is_user_doesnt_exist(r))
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return -ESRCH;
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if (r != ERANGE)
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return -r;
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if (bufsize > SIZE_MAX/2 - ALIGN(sizeof(struct passwd)))
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return -ENOMEM;
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bufsize *= 2;
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}
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}
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int getpwuid_malloc(uid_t uid, struct passwd **ret) {
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size_t bufsize = getpw_buffer_size();
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int r;
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if (!uid_is_valid(uid))
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return -EINVAL;
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for (;;) {
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_cleanup_free_ void *buf = NULL;
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buf = malloc(ALIGN(sizeof(struct passwd)) + bufsize);
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if (!buf)
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return -ENOMEM;
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struct passwd *pw = NULL;
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r = getpwuid_r(uid, buf, (char*) buf + ALIGN(sizeof(struct passwd)), (size_t) bufsize, &pw);
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if (r == 0) {
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if (pw) {
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if (ret)
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*ret = TAKE_PTR(buf);
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return 0;
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}
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return -ESRCH;
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}
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assert(r > 0);
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if (errno_is_user_doesnt_exist(r))
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return -ESRCH;
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if (r != ERANGE)
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return -r;
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if (bufsize > SIZE_MAX/2 - ALIGN(sizeof(struct passwd)))
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return -ENOMEM;
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bufsize *= 2;
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}
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}
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static size_t getgr_buffer_size(void) {
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long bufsize = sysconf(_SC_GETGR_R_SIZE_MAX);
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return bufsize <= 0 ? 4096U : (size_t) bufsize;
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}
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int getgrnam_malloc(const char *name, struct group **ret) {
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size_t bufsize = getgr_buffer_size();
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int r;
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if (isempty(name))
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return -EINVAL;
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for (;;) {
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_cleanup_free_ void *buf = NULL;
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buf = malloc(ALIGN(sizeof(struct group)) + bufsize);
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if (!buf)
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return -ENOMEM;
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struct group *gr = NULL;
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r = getgrnam_r(name, buf, (char*) buf + ALIGN(sizeof(struct group)), (size_t) bufsize, &gr);
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if (r == 0) {
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if (gr) {
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if (ret)
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*ret = TAKE_PTR(buf);
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return 0;
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}
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return -ESRCH;
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}
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assert(r > 0);
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if (errno_is_user_doesnt_exist(r))
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return -ESRCH;
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if (r != ERANGE)
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return -r;
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if (bufsize > SIZE_MAX/2 - ALIGN(sizeof(struct group)))
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return -ENOMEM;
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bufsize *= 2;
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}
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}
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int getgrgid_malloc(gid_t gid, struct group **ret) {
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size_t bufsize = getgr_buffer_size();
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int r;
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if (!gid_is_valid(gid))
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return -EINVAL;
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for (;;) {
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_cleanup_free_ void *buf = NULL;
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buf = malloc(ALIGN(sizeof(struct group)) + bufsize);
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if (!buf)
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return -ENOMEM;
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struct group *gr = NULL;
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r = getgrgid_r(gid, buf, (char*) buf + ALIGN(sizeof(struct group)), (size_t) bufsize, &gr);
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if (r == 0) {
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if (gr) {
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if (ret)
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*ret = TAKE_PTR(buf);
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return 0;
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}
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return -ESRCH;
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}
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assert(r > 0);
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if (errno_is_user_doesnt_exist(r))
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return -ESRCH;
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if (r != ERANGE)
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return -r;
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if (bufsize > SIZE_MAX/2 - ALIGN(sizeof(struct group)))
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return -ENOMEM;
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bufsize *= 2;
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}
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}
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@@ -158,3 +158,9 @@ static inline bool hashed_password_is_locked_or_invalid(const char *password) {
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* Also see https://github.com/systemd/systemd/pull/24680#pullrequestreview-1439464325.
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*/
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#define PASSWORD_UNPROVISIONED "!unprovisioned"
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int getpwuid_malloc(uid_t uid, struct passwd **ret);
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int getpwnam_malloc(const char *name, struct passwd **ret);
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int getgrnam_malloc(const char *name, struct group **ret);
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int getgrgid_malloc(gid_t gid, struct group **ret);
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