1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
|
#include "lock.hh"
#include "globals.hh"
#include "pathlocks.hh"
#include <pwd.h>
#include <grp.h>
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;
uid_t uid;
gid_t gid;
std::vector<gid_t> supplementaryGIDs;
uid_t getUID() override { assert(uid); return uid; }
uid_t getUIDCount() override { return 1; }
gid_t getGID() override { assert(gid); return gid; }
std::vector<gid_t> getSupplementaryGIDs() override { return supplementaryGIDs; }
static std::unique_ptr<UserLock> acquire()
{
assert(settings.buildUsersGroup != "");
createDirs(settings.nixStateDir + "/userpool");
/* Get the members of the build-users-group. */
struct group * gr = getgrnam(settings.buildUsersGroup.get().c_str());
if (!gr)
throw Error("the group '%s' specified in 'build-users-group' does not exist", settings.buildUsersGroup);
/* Copy the result of getgrnam. */
Strings users;
for (char * * p = gr->gr_mem; *p; ++p) {
debug("found build user '%s'", *p);
users.push_back(*p);
}
if (users.empty())
throw Error("the build users group '%s' has no members", settings.buildUsersGroup);
/* Find a user account that isn't currently in use for another
build. */
for (auto & i : users) {
debug("trying user '%s'", i);
struct passwd * pw = getpwnam(i.c_str());
if (!pw)
throw Error("the user '%s' in the group '%s' does not exist", i, settings.buildUsersGroup);
auto fnUserLock = fmt("%s/userpool/%s", settings.nixStateDir,pw->pw_uid);
AutoCloseFD fd{open(fnUserLock.c_str(), O_RDWR | O_CREAT | O_CLOEXEC, 0600)};
if (!fd)
throw SysError("opening user lock '%s'", fnUserLock);
if (lockFile(fd.get(), ltWrite, false)) {
auto lock = std::make_unique<SimpleUserLock>();
lock->fdUserLock = std::move(fd);
lock->uid = pw->pw_uid;
lock->gid = gr->gr_gid;
/* Sanity check... */
if (lock->uid == getuid() || lock->uid == geteuid())
throw Error("the Nix user should not be a member of '%s'", settings.buildUsersGroup);
#if __linux__
/* 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 gid : get_group_list(pw->pw_name, pw->pw_gid)) {
if (gid != lock->gid)
lock->supplementaryGIDs.push_back(gid);
}
#endif
return lock;
}
}
return nullptr;
}
};
struct AutoUserLock : UserLock
{
AutoCloseFD fdUserLock;
uid_t firstUid = 0;
gid_t firstGid = 0;
uid_t nrIds = 1;
uid_t getUID() override { assert(firstUid); return firstUid; }
gid_t getUIDCount() override { return nrIds; }
gid_t getGID() override { assert(firstGid); return firstGid; }
std::vector<gid_t> getSupplementaryGIDs() override { return {}; }
static std::unique_ptr<UserLock> acquire(uid_t nrIds, bool useUserNamespace)
{
#if !defined(__linux__)
useUserNamespace = false;
#endif
experimentalFeatureSettings.require(Xp::AutoAllocateUids);
assert(settings.startId > 0);
assert(settings.uidCount % maxIdsPerBuild == 0);
assert((uint64_t) settings.startId + (uint64_t) settings.uidCount <= std::numeric_limits<uid_t>::max());
assert(nrIds <= maxIdsPerBuild);
createDirs(settings.nixStateDir + "/userpool2");
size_t nrSlots = settings.uidCount / maxIdsPerBuild;
for (size_t i = 0; i < nrSlots; i++) {
debug("trying user slot '%d'", i);
createDirs(settings.nixStateDir + "/userpool2");
auto fnUserLock = fmt("%s/userpool2/slot-%d", settings.nixStateDir, i);
AutoCloseFD fd{open(fnUserLock.c_str(), O_RDWR | O_CREAT | O_CLOEXEC, 0600)};
if (!fd)
throw SysError("opening user lock '%s'", fnUserLock);
if (lockFile(fd.get(), ltWrite, false)) {
auto firstUid = settings.startId + i * maxIdsPerBuild;
auto pw = getpwuid(firstUid);
if (pw)
throw Error("auto-allocated UID %d clashes with existing user account '%s'", firstUid, pw->pw_name);
auto lock = std::make_unique<AutoUserLock>();
lock->fdUserLock = std::move(fd);
lock->firstUid = firstUid;
if (useUserNamespace)
lock->firstGid = firstUid;
else {
struct group * gr = getgrnam(settings.buildUsersGroup.get().c_str());
if (!gr)
throw Error("the group '%s' specified in 'build-users-group' does not exist", settings.buildUsersGroup);
lock->firstGid = gr->gr_gid;
}
lock->nrIds = nrIds;
return lock;
}
}
return nullptr;
}
};
std::unique_ptr<UserLock> acquireUserLock(uid_t nrIds, bool useUserNamespace)
{
if (settings.autoAllocateUids)
return AutoUserLock::acquire(nrIds, useUserNamespace);
else
return SimpleUserLock::acquire();
}
bool useBuildUsers()
{
#if __linux__
static bool b = (settings.buildUsersGroup != "" || settings.autoAllocateUids) && getuid() == 0;
return b;
#elif __APPLE__
static bool b = settings.buildUsersGroup != "" && getuid() == 0;
return b;
#else
return false;
#endif
}
}
|
