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Improve loop over gid container

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This commit is contained in:
Jacek Galowicz 2023-10-24 19:30:37 +02:00
parent b113d925de
commit f555c98a34
1 changed files with 31 additions and 29 deletions
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60
src/libstore/lock.cc
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@ -7,6 +7,31 @@
namespace nix {
#if __linux__
static std::vector<gid_t> get_group_list(const char *username, gid_t group_id)
{
std::vector<gid_t> gids;
gids.resize(32); // Initial guess
auto getgroupl_failed {[&] {
int ngroups = gids.size();
int err = getgrouplist(username, group_id, gids.data(), &ngroups);
gids.resize(ngroups);
return err == -1;
}};
// The first error means that the vector was not big enough.
// If it happens again, there is some different problem.
if (getgroupl_failed() && getgroupl_failed()) {
throw SysError("failed to get list of supplementary groups for '%s'", username);
}
return gids;
}
#endif
struct SimpleUserLock : UserLock
{
AutoCloseFD fdUserLock;
@ -67,37 +92,14 @@ struct SimpleUserLock : UserLock
throw Error("the Nix user should not be a member of '%s'", settings.buildUsersGroup);
#if __linux__
/* Get the list of supplementary groups of this build
user. This is usually either empty or contains a
group such as "kvm". */
int ngroups = 32; // arbitrary initial guess
std::vector<gid_t> gids;
gids.resize(ngroups);
int err = getgrouplist(
pw->pw_name, pw->pw_gid,
gids.data(),
&ngroups);
/* Our initial size of 32 wasn't sufficient, the
correct size has been stored in ngroups, so we try
again. */
if (err == -1) {
gids.resize(ngroups);
err = getgrouplist(
pw->pw_name, pw->pw_gid,
gids.data(),
&ngroups);
}
// If it failed once more, then something must be broken.
if (err == -1)
throw Error("failed to get list of supplementary groups for '%s'", pw->pw_name);
/* Get the list of supplementary groups of this user. This is
* usually either empty or contains a group such as "kvm". */
// Finally, trim back the GID list to its real size.
for (auto i = 0; i < ngroups; i++)
if (gids[i] != lock->gid)
lock->supplementaryGIDs.push_back(gids[i]);
for (auto gid : get_group_list(pw->pw_name, pw->pw_gid)) {
if (gid != lock->gid)
lock->supplementaryGIDs.push_back(gid);
}
#endif
return lock;