summary refs log tree commit diff
path: root/src/libstore/local-store.cc
blob: 704bb1a0660252d03057ce95e50f103c0eab905b (plain) (blame)
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
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
#include "config.h"
#include "local-store.hh"
#include "globals.hh"
#include "archive.hh"
#include "pathlocks.hh"
#include "aterm.hh"
#include "derivations-ast.hh"
#include "worker-protocol.hh"
    
#include <iostream>
#include <algorithm>

#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <utime.h>
#include <fcntl.h>
#include <errno.h>


namespace nix {

    
void checkStoreNotSymlink()
{
    if (getEnv("NIX_IGNORE_SYMLINK_STORE") == "1") return;
    Path path = nixStore;
    struct stat st;
    while (path != "/") {
        if (lstat(path.c_str(), &st))
            throw SysError(format("getting status of `%1%'") % path);
        if (S_ISLNK(st.st_mode))
            throw Error(format(
                "the path `%1%' is a symlink; "
                "this is not allowed for the Nix store and its parent directories")
                % path);
        path = dirOf(path);
    }
}


LocalStore::LocalStore()
{
    substitutablePathsLoaded = false;
    
    schemaPath = nixDBPath + "/schema";
    
    if (readOnlyMode) return;

    createDirs(nixStore);
    
    checkStoreNotSymlink();

    try {
        Path globalLockPath = nixDBPath + "/big-lock";
        globalLock = openLockFile(globalLockPath.c_str(), true);
    } catch (SysError & e) {
        if (e.errNo != EACCES) throw;
        readOnlyMode = true;
        return;
    }
    
    if (!lockFile(globalLock, ltRead, false)) {
        printMsg(lvlError, "waiting for the big Nix store lock...");
        lockFile(globalLock, ltRead, true);
    }

    createDirs(nixDBPath + "/info");
    createDirs(nixDBPath + "/referrer");
    createDirs(nixDBPath + "/failed");

    int curSchema = getSchema();
    if (curSchema > nixSchemaVersion)
        throw Error(format("current Nix store schema is version %1%, but I only support %2%")
            % curSchema % nixSchemaVersion);
    if (curSchema == 0) { /* new store */
        curSchema = nixSchemaVersion; 
        writeFile(schemaPath, (format("%1%") % nixSchemaVersion).str());
    }
    if (curSchema == 1) throw Error("your Nix store is no longer supported");
    if (curSchema < nixSchemaVersion) upgradeStore12();
}


LocalStore::~LocalStore()
{
    try {
        flushDelayedUpdates();

        foreach (RunningSubstituters::iterator, i, runningSubstituters) {
            i->second.to.close();
            i->second.from.close();
            i->second.pid.wait(true);
        }
                
    } catch (...) {
        ignoreException();
    }
}


int LocalStore::getSchema()
{
    int curSchema = 0;
    if (pathExists(schemaPath)) {
        string s = readFile(schemaPath);
        if (!string2Int(s, curSchema))
            throw Error(format("`%1%' is corrupt") % schemaPath);
    }
    return curSchema;
}


void canonicalisePathMetaData(const Path & path, bool recurse)
{
    checkInterrupt();

    struct stat st;
    if (lstat(path.c_str(), &st))
	throw SysError(format("getting attributes of path `%1%'") % path);

    /* Change ownership to the current uid.  If it's a symlink, use
       lchown if available, otherwise don't bother.  Wrong ownership
       of a symlink doesn't matter, since the owning user can't change
       the symlink and can't delete it because the directory is not
       writable.  The only exception is top-level paths in the Nix
       store (since that directory is group-writable for the Nix build
       users group); we check for this case below. */
    if (st.st_uid != geteuid()) {
#if HAVE_LCHOWN
        if (lchown(path.c_str(), geteuid(), (gid_t) -1) == -1)
#else
        if (!S_ISLNK(st.st_mode) &&
            chown(path.c_str(), geteuid(), (gid_t) -1) == -1)
#endif
            throw SysError(format("changing owner of `%1%' to %2%")
                % path % geteuid());
    }
    
    if (!S_ISLNK(st.st_mode)) {

        /* Mask out all type related bits. */
        mode_t mode = st.st_mode & ~S_IFMT;
        
        if (mode != 0444 && mode != 0555) {
            mode = (st.st_mode & S_IFMT)
                 | 0444
                 | (st.st_mode & S_IXUSR ? 0111 : 0);
            if (chmod(path.c_str(), mode) == -1)
                throw SysError(format("changing mode of `%1%' to %2$o") % path % mode);
        }

        if (st.st_mtime != 0) {
            struct utimbuf utimbuf;
            utimbuf.actime = st.st_atime;
            utimbuf.modtime = 1; /* 1 second into the epoch */
            if (utime(path.c_str(), &utimbuf) == -1) 
                throw SysError(format("changing modification time of `%1%'") % path);
        }

    }

    if (recurse && S_ISDIR(st.st_mode)) {
        Strings names = readDirectory(path);
	foreach (Strings::iterator, i, names)
	    canonicalisePathMetaData(path + "/" + *i, true);
    }
}


void canonicalisePathMetaData(const Path & path)
{
    canonicalisePathMetaData(path, true);

    /* On platforms that don't have lchown(), the top-level path can't
       be a symlink, since we can't change its ownership. */
    struct stat st;
    if (lstat(path.c_str(), &st))
	throw SysError(format("getting attributes of path `%1%'") % path);

    if (st.st_uid != geteuid()) {
        assert(S_ISLNK(st.st_mode));
        throw Error(format("wrong ownership of top-level store path `%1%'") % path);
    }
}


static Path infoFileFor(const Path & path)
{
    string baseName = baseNameOf(path);
    return (format("%1%/info/%2%") % nixDBPath % baseName).str();
}


static Path referrersFileFor(const Path & path)
{
    string baseName = baseNameOf(path);
    return (format("%1%/referrer/%2%") % nixDBPath % baseName).str();
}


static Path failedFileFor(const Path & path)
{
    string baseName = baseNameOf(path);
    return (format("%1%/failed/%2%") % nixDBPath % baseName).str();
}


static Path tmpFileForAtomicUpdate(const Path & path)
{
    return (format("%1%/.%2%.%3%") % dirOf(path) % getpid() % baseNameOf(path)).str();
}


static void appendReferrer(const Path & from, const Path & to, bool lock)
{
    Path referrersFile = referrersFileFor(from);
    
    PathLocks referrersLock;
    if (lock) {
        referrersLock.lockPaths(singleton<PathSet, Path>(referrersFile));
        referrersLock.setDeletion(true);
    }

    AutoCloseFD fd = open(referrersFile.c_str(), O_WRONLY | O_APPEND | O_CREAT, 0666);
    if (fd == -1) throw SysError(format("opening file `%1%'") % referrersFile);
    
    string s = " " + to;
    writeFull(fd, (const unsigned char *) s.c_str(), s.size());
}


/* Atomically update the referrers file.  If `purge' is true, the set
   of referrers is set to `referrers'.  Otherwise, the current set of
   referrers is purged of invalid paths. */
void LocalStore::rewriteReferrers(const Path & path, bool purge, PathSet referrers)
{
    Path referrersFile = referrersFileFor(path);
    
    PathLocks referrersLock(singleton<PathSet, Path>(referrersFile));
    referrersLock.setDeletion(true);

    if (purge)
        /* queryReferrers() purges invalid paths, so that's all we
           need. */
        queryReferrers(path, referrers);

    Path tmpFile = tmpFileForAtomicUpdate(referrersFile);
    
    AutoCloseFD fd = open(tmpFile.c_str(), O_WRONLY | O_TRUNC | O_CREAT, 0666);
    if (fd == -1) throw SysError(format("opening file `%1%'") % referrersFile);
    
    string s;
    foreach (PathSet::const_iterator, i, referrers) {
        s += " "; s += *i;
    }
    
    writeFull(fd, (const unsigned char *) s.c_str(), s.size());

    fd.close(); /* for Windows; can't rename open file */

    if (rename(tmpFile.c_str(), referrersFile.c_str()) == -1)
        throw SysError(format("cannot rename `%1%' to `%2%'") % tmpFile % referrersFile);
}


void LocalStore::flushDelayedUpdates()
{
    foreach (PathSet::iterator, i, delayedUpdates) {
        rewriteReferrers(*i, true, PathSet());
    }
    delayedUpdates.clear();
}


void LocalStore::registerValidPath(const Path & path,
    const Hash & hash, const PathSet & references,
    const Path & deriver)
{
    ValidPathInfo info;
    info.path = path;
    info.hash = hash;
    info.references = references;
    info.deriver = deriver;
    registerValidPath(info);
}


void LocalStore::registerValidPath(const ValidPathInfo & info, bool ignoreValidity)
{
    Path infoFile = infoFileFor(info.path);

    ValidPathInfo oldInfo;
    if (pathExists(infoFile)) oldInfo = queryPathInfo(info.path);

    /* Note that it's possible for infoFile to already exist. */

    /* Acquire a lock on each referrer file.  This prevents those
       paths from being invalidated.  (It would be a violation of the
       store invariants if we registered info.path as valid while some
       of its references are invalid.)  NB: there can be no deadlock
       here since we're acquiring the locks in sorted order. */
    PathSet lockNames;
    foreach (PathSet::const_iterator, i, info.references)
        if (*i != info.path) lockNames.insert(referrersFileFor(*i));
    PathLocks referrerLocks(lockNames);
    referrerLocks.setDeletion(true);
        
    string refs;
    foreach (PathSet::const_iterator, i, info.references) {
        if (!refs.empty()) refs += " ";
        refs += *i;

        if (!ignoreValidity && *i != info.path && !isValidPath(*i))
            throw Error(format("cannot register `%1%' as valid, because its reference `%2%' isn't valid")
                % info.path % *i);

        /* Update the referrer mapping for *i.  This must be done
           before the info file is written to maintain the invariant
           that if `path' is a valid path, then all its references
           have referrer mappings back to `path'.  A " " is prefixed
           to separate it from the previous entry.  It's not suffixed
           to deal with interrupted partial writes to this file. */
        if (oldInfo.references.find(*i) == oldInfo.references.end())
            appendReferrer(*i, info.path, false);
    }

    assert(info.hash.type == htSHA256);

    string s = (format(
        "Hash: sha256:%1%\n"
        "References: %2%\n"
        "Deriver: %3%\n"
        "Registered-At: %4%\n")
        % printHash(info.hash) % refs % info.deriver %
        (oldInfo.registrationTime ? oldInfo.registrationTime : time(0))).str();

    /* Atomically rewrite the info file. */
    Path tmpFile = tmpFileForAtomicUpdate(infoFile);
    writeFile(tmpFile, s);
    if (rename(tmpFile.c_str(), infoFile.c_str()) == -1)
        throw SysError(format("cannot rename `%1%' to `%2%'") % tmpFile % infoFile);

    pathInfoCache[info.path] = info;
}


void LocalStore::registerFailedPath(const Path & path)
{
    /* Write an empty file in the .../failed directory to denote the
       failure of the builder for `path'. */
    writeFile(failedFileFor(path), "");
}


bool LocalStore::hasPathFailed(const Path & path)
{
    return pathExists(failedFileFor(path));
}


Hash parseHashField(const Path & path, const string & s)
{
    string::size_type colon = s.find(':');
    if (colon == string::npos)
        throw Error(format("corrupt hash `%1%' in valid-path entry for `%2%'")
            % s % path);
    HashType ht = parseHashType(string(s, 0, colon));
    if (ht == htUnknown)
        throw Error(format("unknown hash type `%1%' in valid-path entry for `%2%'")
            % string(s, 0, colon) % path);
    return parseHash(ht, string(s, colon + 1));
}


ValidPathInfo LocalStore::queryPathInfo(const Path & path, bool ignoreErrors)
{
    ValidPathInfo res;
    res.path = path;

    assertStorePath(path);

    std::map<Path, ValidPathInfo>::iterator lookup = pathInfoCache.find(path);
    if (lookup != pathInfoCache.end()) return lookup->second;
    
    /* Read the info file. */
    Path infoFile = infoFileFor(path);
    if (!pathExists(infoFile))
        throw Error(format("path `%1%' is not valid") % path);
    string info = readFile(infoFile);

    /* Parse it. */
    Strings lines = tokenizeString(info, "\n");

    foreach (Strings::iterator, i, lines) {
        string::size_type p = i->find(':');
        if (p == string::npos) continue; /* bad line */
        string name(*i, 0, p);
        string value(*i, p + 2);
        if (name == "References") {
            Strings refs = tokenizeString(value, " ");
            res.references = PathSet(refs.begin(), refs.end());
        } else if (name == "Deriver") {
            res.deriver = value;
        } else if (name == "Hash") {
            try {
                res.hash = parseHashField(path, value);
            } catch (Error & e) {
                if (!ignoreErrors) throw;
                printMsg(lvlError, format("cannot parse hash field in `%1%': %2%") % infoFile % e.msg());
            }
        } else if (name == "Registered-At") {
            int n = 0;
            string2Int(value, n);
            res.registrationTime = n;
        }
    }

    return pathInfoCache[path] = res;
}


bool LocalStore::isValidPath(const Path & path)
{
    /* Files in the info directory starting with a `.' are temporary
       files. */
    if (baseNameOf(path).at(0) == '.') return false;
    return pathExists(infoFileFor(path));
}


PathSet LocalStore::queryValidPaths()
{
    PathSet paths;
    Strings entries = readDirectory(nixDBPath + "/info");
    foreach (Strings::iterator, i, entries)
        if (i->at(0) != '.') paths.insert(nixStore + "/" + *i);
    return paths;
}


void LocalStore::queryReferences(const Path & path,
    PathSet & references)
{
    ValidPathInfo info = queryPathInfo(path);
    references.insert(info.references.begin(), info.references.end());
}


bool LocalStore::queryReferrersInternal(const Path & path, PathSet & referrers)
{
    bool allValid = true;
    
    if (!isValidPath(path))
        throw Error(format("path `%1%' is not valid") % path);

    /* No locking is necessary here: updates are only done by
       appending or by atomically replacing the file.  When appending,
       there is a possibility that we see a partial entry, but it will
       just be filtered out below (the partially written path will not
       be valid, so it will be ignored). */

    Path referrersFile = referrersFileFor(path);
    if (!pathExists(referrersFile)) return true;
    
    AutoCloseFD fd = open(referrersFile.c_str(), O_RDONLY);
    if (fd == -1) throw SysError(format("opening file `%1%'") % referrersFile);

    Paths refs = tokenizeString(readFile(fd), " ");

    foreach (Paths::iterator, i, refs)
        /* Referrers can be invalid (see registerValidPath() for the
           invariant), so we only return one if it is valid. */
        if (isStorePath(*i) && isValidPath(*i)) referrers.insert(*i); else allValid = false;

    return allValid;
}


void LocalStore::queryReferrers(const Path & path, PathSet & referrers)
{
    queryReferrersInternal(path, referrers);
}


Path LocalStore::queryDeriver(const Path & path)
{
    return queryPathInfo(path).deriver;
}


void LocalStore::startSubstituter(const Path & substituter, RunningSubstituter & run)
{
    if (run.pid != -1) return;
    
    debug(format("starting substituter program `%1%'") % substituter);

    Pipe toPipe, fromPipe;
            
    toPipe.create();
    fromPipe.create();

    run.pid = fork();
            
    switch (run.pid) {

    case -1:
        throw SysError("unable to fork");

    case 0: /* child */
        try {
            fromPipe.readSide.close();
            toPipe.writeSide.close();
            if (dup2(toPipe.readSide, STDIN_FILENO) == -1)
                throw SysError("dupping stdin");
            if (dup2(fromPipe.writeSide, STDOUT_FILENO) == -1)
                throw SysError("dupping stdout");
            closeMostFDs(set<int>());
            execl(substituter.c_str(), substituter.c_str(), "--query", NULL);
            throw SysError(format("executing `%1%'") % substituter);
        } catch (std::exception & e) {
            std::cerr << "error: " << e.what() << std::endl;
        }
        quickExit(1);
    }

    /* Parent. */
    
    run.to = toPipe.writeSide.borrow();
    run.from = fromPipe.readSide.borrow();
}


template<class T> T getIntLine(int fd)
{
    string s = readLine(fd);
    T res;
    if (!string2Int(s, res)) throw Error("integer expected from stream");
    return res;
}


bool LocalStore::hasSubstitutes(const Path & path)
{
    foreach (Paths::iterator, i, substituters) {
        RunningSubstituter & run(runningSubstituters[*i]);
        startSubstituter(*i, run);
        writeLine(run.to, "have\n" + path);
        if (getIntLine<int>(run.from)) return true;
    }

    return false;
}


bool LocalStore::querySubstitutablePathInfo(const Path & substituter,
    const Path & path, SubstitutablePathInfo & info)
{
    RunningSubstituter & run(runningSubstituters[substituter]);
    startSubstituter(substituter, run);

    writeLine(run.to, "info\n" + path);

    if (!getIntLine<int>(run.from)) return false;
    
    info.deriver = readLine(run.from);
    if (info.deriver != "") assertStorePath(info.deriver);
    int nrRefs = getIntLine<int>(run.from);
    while (nrRefs--) {
        Path p = readLine(run.from);
        assertStorePath(p);
        info.references.insert(p);
    }
    info.downloadSize = getIntLine<long long>(run.from);
    
    return true;
}


bool LocalStore::querySubstitutablePathInfo(const Path & path,
    SubstitutablePathInfo & info)
{
    foreach (Paths::iterator, i, substituters)
        if (querySubstitutablePathInfo(*i, path, info)) return true;
    return false;
}


Hash LocalStore::queryPathHash(const Path & path)
{
    return queryPathInfo(path).hash;
}


static void dfsVisit(std::map<Path, ValidPathInfo> & infos,
    const Path & path, PathSet & visited, Paths & sorted)
{
    if (visited.find(path) != visited.end()) return;
    visited.insert(path);

    ValidPathInfo & info(infos[path]);
    
    foreach (PathSet::iterator, i, info.references)
        if (infos.find(*i) != infos.end())
            dfsVisit(infos, *i, visited, sorted);

    sorted.push_back(path);
}


void LocalStore::registerValidPaths(const ValidPathInfos & infos)
{
    std::map<Path, ValidPathInfo> infosMap;
    
    /* Sort the paths topologically under the references relation, so
       that if path A is referenced by B, then A is registered before
       B. */
    foreach (ValidPathInfos::const_iterator, i, infos)
        infosMap[i->path] = *i;

    PathSet visited;
    Paths sorted;
    foreach (ValidPathInfos::const_iterator, i, infos)
        dfsVisit(infosMap, i->path, visited, sorted);

    foreach (Paths::iterator, i, sorted)
        registerValidPath(infosMap[*i]);
}


/* Invalidate a path.  The caller is responsible for checking that
   there are no referrers. */
void LocalStore::invalidatePath(const Path & path)
{
    debug(format("invalidating path `%1%'") % path);

    ValidPathInfo info;

    if (pathExists(infoFileFor(path))) {
        info = queryPathInfo(path);

        /* Remove the info file. */
        Path p = infoFileFor(path);
        if (unlink(p.c_str()) == -1)
            throw SysError(format("unlinking `%1%'") % p);
    }

    /* Remove the referrers file for `path'. */
    Path p = referrersFileFor(path);
    if (pathExists(p) && unlink(p.c_str()) == -1)
        throw SysError(format("unlinking `%1%'") % p);

    /* Clear `path' from the info cache. */
    pathInfoCache.erase(path);
    delayedUpdates.erase(path);

    /* Cause the referrer files for each path referenced by this one
       to be updated.  This has to happen after removing the info file
       to preserve the invariant (see registerValidPath()).

       The referrer files are updated lazily in flushDelayedUpdates()
       to prevent quadratic performance in the garbage collector
       (i.e., when N referrers to some path X are deleted, we have to
       rewrite the referrers file for X N times, causing O(N^2) I/O).

       What happens if we die before the referrer file can be updated?
       That's not a problem, because stale (invalid) entries in the
       referrer file are ignored by queryReferrers().  Thus a referrer
       file is allowed to have stale entries; removing them is just an
       optimisation.  verifyStore() gets rid of them eventually.
    */
    foreach (PathSet::iterator, i, info.references)
        if (*i != path) delayedUpdates.insert(*i);
}


Path LocalStore::addToStoreFromDump(const string & dump, const string & name,
    bool recursive, HashType hashAlgo)
{
    Hash h = hashString(hashAlgo, dump);

    Path dstPath = makeFixedOutputPath(recursive, hashAlgo, h, name);

    addTempRoot(dstPath);

    if (!isValidPath(dstPath)) {

        /* The first check above is an optimisation to prevent
           unnecessary lock acquisition. */

        PathLocks outputLock(singleton<PathSet, Path>(dstPath));

        if (!isValidPath(dstPath)) {

            if (pathExists(dstPath)) deletePathWrapped(dstPath);

            if (recursive) {
                StringSource source(dump);
                restorePath(dstPath, source);
            } else
                writeStringToFile(dstPath, dump);

            canonicalisePathMetaData(dstPath);

            /* Register the SHA-256 hash of the NAR serialisation of
               the path in the database.  We may just have computed it
               above (if called with recursive == true and hashAlgo ==
               sha256); otherwise, compute it here. */
            registerValidPath(dstPath,
                (recursive && hashAlgo == htSHA256) ? h :
                (recursive ? hashString(htSHA256, dump) : hashPath(htSHA256, dstPath)),
                PathSet(), "");
        }

        outputLock.setDeletion(true);
    }

    return dstPath;
}


Path LocalStore::addToStore(const Path & _srcPath,
    bool recursive, HashType hashAlgo, PathFilter & filter)
{
    Path srcPath(absPath(_srcPath));
    debug(format("adding `%1%' to the store") % srcPath);

    /* Read the whole path into memory. This is not a very scalable
       method for very large paths, but `copyPath' is mainly used for
       small files. */
    StringSink sink;
    if (recursive) 
        dumpPath(srcPath, sink, filter);
    else
        sink.s = readFile(srcPath);

    return addToStoreFromDump(sink.s, baseNameOf(srcPath), recursive, hashAlgo);
}


Path LocalStore::addTextToStore(const string & name, const string & s,
    const PathSet & references)
{
    Path dstPath = computeStorePathForText(name, s, references);
    
    addTempRoot(dstPath);

    if (!isValidPath(dstPath)) {

        PathLocks outputLock(singleton<PathSet, Path>(dstPath));

        if (!isValidPath(dstPath)) {

            if (pathExists(dstPath)) deletePathWrapped(dstPath);

            writeStringToFile(dstPath, s);

            canonicalisePathMetaData(dstPath);
            
            registerValidPath(dstPath,
                hashPath(htSHA256, dstPath), references, "");
        }

        outputLock.setDeletion(true);
    }

    return dstPath;
}


struct HashAndWriteSink : Sink
{
    Sink & writeSink;
    HashSink hashSink;
    bool hashing;
    HashAndWriteSink(Sink & writeSink) : writeSink(writeSink), hashSink(htSHA256)
    {
        hashing = true;
    }
    virtual void operator ()
        (const unsigned char * data, unsigned int len)
    {
        writeSink(data, len);
        if (hashing) hashSink(data, len);
    }
};


#define EXPORT_MAGIC 0x4558494e


static void checkSecrecy(const Path & path)
{
    struct stat st;
    if (stat(path.c_str(), &st))
        throw SysError(format("getting status of `%1%'") % path);
    if ((st.st_mode & (S_IRWXG | S_IRWXO)) != 0)
        throw Error(format("file `%1%' should be secret (inaccessible to everybody else)!") % path);
}


void LocalStore::exportPath(const Path & path, bool sign,
    Sink & sink)
{
    assertStorePath(path);

    addTempRoot(path);
    if (!isValidPath(path))
        throw Error(format("path `%1%' is not valid") % path);

    HashAndWriteSink hashAndWriteSink(sink);
    
    dumpPath(path, hashAndWriteSink);

    writeInt(EXPORT_MAGIC, hashAndWriteSink);

    writeString(path, hashAndWriteSink);
    
    PathSet references;
    queryReferences(path, references);
    writeStringSet(references, hashAndWriteSink);

    Path deriver = queryDeriver(path);
    writeString(deriver, hashAndWriteSink);

    if (sign) {
        Hash hash = hashAndWriteSink.hashSink.finish();
        hashAndWriteSink.hashing = false;

        writeInt(1, hashAndWriteSink);
        
        Path tmpDir = createTempDir();
        AutoDelete delTmp(tmpDir);
        Path hashFile = tmpDir + "/hash";
        writeStringToFile(hashFile, printHash(hash));

        Path secretKey = nixConfDir + "/signing-key.sec";
        checkSecrecy(secretKey);

        Strings args;
        args.push_back("rsautl");
        args.push_back("-sign");
        args.push_back("-inkey");
        args.push_back(secretKey);
        args.push_back("-in");
        args.push_back(hashFile);
        string signature = runProgram(OPENSSL_PATH, true, args);

        writeString(signature, hashAndWriteSink);
        
    } else
        writeInt(0, hashAndWriteSink);
}


struct HashAndReadSource : Source
{
    Source & readSource;
    HashSink hashSink;
    bool hashing;
    HashAndReadSource(Source & readSource) : readSource(readSource), hashSink(htSHA256)
    {
        hashing = true;
    }
    virtual void operator ()
        (unsigned char * data, unsigned int len)
    {
        readSource(data, len);
        if (hashing) hashSink(data, len);
    }
};


Path LocalStore::importPath(bool requireSignature, Source & source)
{
    HashAndReadSource hashAndReadSource(source);
    
    /* We don't yet know what store path this archive contains (the
       store path follows the archive data proper), and besides, we
       don't know yet whether the signature is valid. */
    Path tmpDir = createTempDir(nixStore);
    AutoDelete delTmp(tmpDir); /* !!! could be GC'ed! */
    Path unpacked = tmpDir + "/unpacked";

    restorePath(unpacked, hashAndReadSource);

    unsigned int magic = readInt(hashAndReadSource);
    if (magic != EXPORT_MAGIC)
        throw Error("Nix archive cannot be imported; wrong format");

    Path dstPath = readStorePath(hashAndReadSource);

    PathSet references = readStorePaths(hashAndReadSource);

    Path deriver = readString(hashAndReadSource);
    if (deriver != "") assertStorePath(deriver);

    Hash hash = hashAndReadSource.hashSink.finish();
    hashAndReadSource.hashing = false;

    bool haveSignature = readInt(hashAndReadSource) == 1;

    if (requireSignature && !haveSignature)
        throw Error("imported archive lacks a signature");
    
    if (haveSignature) {
        string signature = readString(hashAndReadSource);

        if (requireSignature) {
            Path sigFile = tmpDir + "/sig";
            writeStringToFile(sigFile, signature);

            Strings args;
            args.push_back("rsautl");
            args.push_back("-verify");
            args.push_back("-inkey");
            args.push_back(nixConfDir + "/signing-key.pub");
            args.push_back("-pubin");
            args.push_back("-in");
            args.push_back(sigFile);
            string hash2 = runProgram(OPENSSL_PATH, true, args);

            /* Note: runProgram() throws an exception if the signature
               is invalid. */

            if (printHash(hash) != hash2)
                throw Error(
                    "signed hash doesn't match actual contents of imported "
                    "archive; archive could be corrupt, or someone is trying "
                    "to import a Trojan horse");
        }
    }

    /* Do the actual import. */

    /* !!! way too much code duplication with addTextToStore() etc. */
    addTempRoot(dstPath);

    if (!isValidPath(dstPath)) {

        PathLocks outputLock;

        /* Lock the output path.  But don't lock if we're being called
           from a build hook (whose parent process already acquired a
           lock on this path). */
        Strings locksHeld = tokenizeString(getEnv("NIX_HELD_LOCKS"));
        if (find(locksHeld.begin(), locksHeld.end(), dstPath) == locksHeld.end())
            outputLock.lockPaths(singleton<PathSet, Path>(dstPath));

        if (!isValidPath(dstPath)) {

            if (pathExists(dstPath)) deletePathWrapped(dstPath);

            if (rename(unpacked.c_str(), dstPath.c_str()) == -1)
                throw SysError(format("cannot move `%1%' to `%2%'")
                    % unpacked % dstPath);

            canonicalisePathMetaData(dstPath);
            
            /* !!! if we were clever, we could prevent the hashPath()
               here. */
            if (deriver != "" && !isValidPath(deriver)) deriver = "";
            registerValidPath(dstPath,
                hashPath(htSHA256, dstPath), references, deriver);
        }
        
        outputLock.setDeletion(true);
    }
    
    return dstPath;
}


void LocalStore::deleteFromStore(const Path & path, unsigned long long & bytesFreed,
    unsigned long long & blocksFreed)
{
    bytesFreed = 0;

    assertStorePath(path);

    if (isValidPath(path)) {
        /* Acquire a lock on the referrers file to prevent new
           referrers to this path from appearing while we're deleting
           it. */
        PathLocks referrersLock(singleton<PathSet, Path>(referrersFileFor(path)));
        referrersLock.setDeletion(true);
        PathSet referrers; queryReferrers(path, referrers);
        referrers.erase(path); /* ignore self-references */
        if (!referrers.empty())
            throw PathInUse(format("cannot delete path `%1%' because it is in use by `%2%'")
                % path % showPaths(referrers));
        invalidatePath(path);
    }

    deletePathWrapped(path, bytesFreed, blocksFreed);
}


void LocalStore::verifyStore(bool checkContents)
{
    /* Check whether all valid paths actually exist. */
    printMsg(lvlInfo, "checking path existence");

    PathSet validPaths2 = queryValidPaths(), validPaths;
    
    foreach (PathSet::iterator, i, validPaths2) {
        checkInterrupt();
        if (!isStorePath(*i)) {
            printMsg(lvlError, format("path `%1%' is not in the Nix store") % *i);
            invalidatePath(*i);
        } else if (!pathExists(*i)) {
            printMsg(lvlError, format("path `%1%' disappeared") % *i);
            invalidatePath(*i);
        } else
            validPaths.insert(*i);
    }


    /* Check the store path meta-information. */
    printMsg(lvlInfo, "checking path meta-information");

    std::map<Path, PathSet> referrersCache;
    
    foreach (PathSet::iterator, i, validPaths) {
        bool update = false;
        ValidPathInfo info = queryPathInfo(*i, true);

        /* Check the references: each reference should be valid, and
           it should have a matching referrer. */
        foreach (PathSet::iterator, j, info.references) {
            if (validPaths.find(*j) == validPaths.end()) {
                printMsg(lvlError, format("incomplete closure: `%1%' needs missing `%2%'")
                    % *i % *j);
                /* nothing we can do about it... */
            } else {
                if (referrersCache.find(*j) == referrersCache.end())
                    queryReferrers(*j, referrersCache[*j]);
                if (referrersCache[*j].find(*i) == referrersCache[*j].end()) {
                    printMsg(lvlError, format("adding missing referrer mapping from `%1%' to `%2%'")
                        % *j % *i);
                    appendReferrer(*j, *i, true);
                }
            }
        }

        /* Check the deriver.  (Note that the deriver doesn't have to
           be a valid path.) */
        if (!info.deriver.empty() && !isStorePath(info.deriver)) {
            info.deriver = "";
            update = true;
        }

        /* Check the content hash (optionally - slow). */
        if (info.hash.hashSize == 0) {
            printMsg(lvlError, format("re-hashing `%1%'") % *i);
            info.hash = hashPath(htSHA256, *i);
            update = true;
        } else if (checkContents) {
            debug(format("checking contents of `%1%'") % *i);
            Hash current = hashPath(info.hash.type, *i);
            if (current != info.hash) {
                printMsg(lvlError, format("path `%1%' was modified! "
                        "expected hash `%2%', got `%3%'")
                    % *i % printHash(info.hash) % printHash(current));
            }
        }

        if (update) registerValidPath(info);
    }

    referrersCache.clear();
    

    /* Check the referrers. */
    printMsg(lvlInfo, "checking referrers");

    std::map<Path, PathSet> referencesCache;
    
    Strings entries = readDirectory(nixDBPath + "/referrer");
    foreach (Strings::iterator, i, entries) {
        Path from = nixStore + "/" + *i;
        
        if (validPaths.find(from) == validPaths.end()) {
            /* !!! This removes lock files as well.  Need to check
               whether that's okay. */
            printMsg(lvlError, format("removing referrers file for invalid `%1%'") % from);
            Path p = referrersFileFor(from);
            if (unlink(p.c_str()) == -1)
                throw SysError(format("unlinking `%1%'") % p);
            continue;
        }

        PathSet referrers;
        bool allValid = queryReferrersInternal(from, referrers);
        bool update = false;

        if (!allValid) {
            printMsg(lvlError, format("removing some stale referrers for `%1%'") % from);
            update = true;
        }

        /* Each referrer should have a matching reference. */
        PathSet referrersNew;
        foreach (PathSet::iterator, j, referrers) {
            if (referencesCache.find(*j) == referencesCache.end())
                queryReferences(*j, referencesCache[*j]);
            if (referencesCache[*j].find(from) == referencesCache[*j].end()) {
                printMsg(lvlError, format("removing unexpected referrer mapping from `%1%' to `%2%'")
                    % from % *j);
                update = true;
            } else referrersNew.insert(*j);
        }

        if (update) rewriteReferrers(from, false, referrersNew);
    }
}


}