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0023-Detect-and-reject-a-zip-bomb-using-overlapped-entrie.patch (13171B)

    

  1. From 6cdb7b372b4d46e06a982c6f3494c086d2418c7b Mon Sep 17 00:00:00 2001
  2. From: Mark Adler <madler@alumni.caltech.edu>
  3. Date: Fri, 31 Jan 2020 22:05:59 -0800
  4. Subject: [PATCH] Detect and reject a zip bomb using overlapped entries.
  6.     Detect and reject a zip bomb using overlapped entries.
  8.     This detects an invalid zip file that has at least one entry that
  9.     overlaps with another entry or with the central directory to the
  10.     end of the file. A Fifield zip bomb uses overlapped local entries
  11.     to vastly increase the potential inflation ratio. Such an invalid
  12.     zip file is rejected.
  14.     See https://www.bamsoftware.com/hacks/zipbomb/ for David Fifield's
  15.     analysis, construction, and examples of such zip bombs.
  17.     The detection maintains a list of covered spans of the zip files
  18.     so far, where the central directory to the end of the file and any
  19.     bytes preceding the first entry at zip file offset zero are
  20.     considered covered initially. Then as each entry is decompressed
  21.     or tested, it is considered covered. When a new entry is about to
  22.     be processed, its initial offset is checked to see if it is
  23.     contained by a covered span. If so, the zip file is rejected as
  24.     invalid.
  26.     This commit depends on a preceding commit: "Fix bug in
  27.     undefer_input() that misplaced the input state."
  28. ---
  29.  extract.c | 190 +++++++++++++++++++++++++++++++++++++++++++++++++++++-
  30.  globals.c |   1 +
  31.  globals.h |   3 +
  32.  process.c |  11 ++++
  33.  unzip.h   |   1 +
  34.  5 files changed, 205 insertions(+), 1 deletion(-)
  36. diff --git a/extract.c b/extract.c
  37. index 549a5eb..1f078d1 100644
  38. --- a/extract.c
  39. +++ b/extract.c
  40. @@ -321,6 +321,125 @@ static ZCONST char Far UnsupportedExtraField[] =
  41.    "\nerror:  unsupported extra-field compression type (%u)--skipping\n";
  42.  static ZCONST char Far BadExtraFieldCRC[] =
  43.    "error [%s]:  bad extra-field CRC %08lx (should be %08lx)\n";
  44. +static ZCONST char Far NotEnoughMemCover[] =
  45. +  "error: not enough memory for bomb detection\n";
  46. +static ZCONST char Far OverlappedComponents[] =
  47. +  "error: invalid zip file with overlapped components (possible zip bomb)\n";
  48. +
  49. +
  50. +
  51. +
  52. +
  53. +/* A growable list of spans. */
  54. +typedef zoff_t bound_t;
  55. +typedef struct {
  56. +    bound_t beg;        /* start of the span */
  57. +    bound_t end;        /* one past the end of the span */
  58. +} span_t;
  59. +typedef struct {
  60. +    span_t *span;       /* allocated, distinct, and sorted list of spans */
  61. +    size_t num;         /* number of spans in the list */
  62. +    size_t max;         /* allocated number of spans (num <= max) */
  63. +} cover_t;
  64. +
  65. +/*
  66. + * Return the index of the first span in cover whose beg is greater than val.
  67. + * If there is no such span, then cover->num is returned.
  68. + */
  69. +static size_t cover_find(cover, val)
  70. +    cover_t *cover;
  71. +    bound_t val;
  72. +{
  73. +    size_t lo = 0, hi = cover->num;
  74. +    while (lo < hi) {
  75. +        size_t mid = (lo + hi) >> 1;
  76. +        if (val < cover->span[mid].beg)
  77. +            hi = mid;
  78. +        else
  79. +            lo = mid + 1;
  80. +    }
  81. +    return hi;
  82. +}
  83. +
  84. +/* Return true if val lies within any one of the spans in cover. */
  85. +static int cover_within(cover, val)
  86. +    cover_t *cover;
  87. +    bound_t val;
  88. +{
  89. +    size_t pos = cover_find(cover, val);
  90. +    return pos > 0 && val < cover->span[pos - 1].end;
  91. +}
  92. +
  93. +/*
  94. + * Add a new span to the list, but only if the new span does not overlap any
  95. + * spans already in the list. The new span covers the values beg..end-1. beg
  96. + * must be less than end.
  97. + *
  98. + * Keep the list sorted and merge adjacent spans. Grow the allocated space for
  99. + * the list as needed. On success, 0 is returned. If the new span overlaps any
  100. + * existing spans, then 1 is returned and the new span is not added to the
  101. + * list. If the new span is invalid because beg is greater than or equal to
  102. + * end, then -1 is returned. If the list needs to be grown but the memory
  103. + * allocation fails, then -2 is returned.
  104. + */
  105. +static int cover_add(cover, beg, end)
  106. +    cover_t *cover;
  107. +    bound_t beg;
  108. +    bound_t end;
  109. +{
  110. +    size_t pos;
  111. +    int prec, foll;
  112. +
  113. +    if (beg >= end)
  114. +    /* The new span is invalid. */
  115. +        return -1;
  116. +
  117. +    /* Find where the new span should go, and make sure that it does not
  118. +       overlap with any existing spans. */
  119. +    pos = cover_find(cover, beg);
  120. +    if ((pos > 0 && beg < cover->span[pos - 1].end) ||
  121. +        (pos < cover->num && end > cover->span[pos].beg))
  122. +        return 1;
  123. +
  124. +    /* Check for adjacencies. */
  125. +    prec = pos > 0 && beg == cover->span[pos - 1].end;
  126. +    foll = pos < cover->num && end == cover->span[pos].beg;
  127. +    if (prec && foll) {
  128. +        /* The new span connects the preceding and following spans. Merge the
  129. +           following span into the preceding span, and delete the following
  130. +           span. */
  131. +        cover->span[pos - 1].end = cover->span[pos].end;
  132. +        cover->num--;
  133. +        memmove(cover->span + pos, cover->span + pos + 1,
  134. +                (cover->num - pos) * sizeof(span_t));
  135. +    }
  136. +    else if (prec)
  137. +        /* The new span is adjacent only to the preceding span. Extend the end
  138. +           of the preceding span. */
  139. +        cover->span[pos - 1].end = end;
  140. +    else if (foll)
  141. +        /* The new span is adjacent only to the following span. Extend the
  142. +           beginning of the following span. */
  143. +        cover->span[pos].beg = beg;
  144. +    else {
  145. +        /* The new span has gaps between both the preceding and the following
  146. +           spans. Assure that there is room and insert the span.  */
  147. +        if (cover->num == cover->max) {
  148. +            size_t max = cover->max == 0 ? 16 : cover->max << 1;
  149. +            span_t *span = realloc(cover->span, max * sizeof(span_t));
  150. +            if (span == NULL)
  151. +                return -2;
  152. +            cover->span = span;
  153. +            cover->max = max;
  154. +        }
  155. +        memmove(cover->span + pos + 1, cover->span + pos,
  156. +                (cover->num - pos) * sizeof(span_t));
  157. +        cover->num++;
  158. +        cover->span[pos].beg = beg;
  159. +        cover->span[pos].end = end;
  160. +    }
  161. +    return 0;
  162. +}
  163.  
  164.  
  165.  
  166. @@ -376,6 +495,29 @@ int extract_or_test_files(__G)    /* return PK-type error code */
  167.      }
  168.  #endif /* !SFX || SFX_EXDIR */
  169.  
  170. +    /* One more: initialize cover structure for bomb detection. Start with a
  171. +       span that covers the central directory though the end of the file. */
  172. +    if (G.cover == NULL) {
  173. +        G.cover = malloc(sizeof(cover_t));
  174. +        if (G.cover == NULL) {
  175. +            Info(slide, 0x401, ((char *)slide,
  176. +              LoadFarString(NotEnoughMemCover)));
  177. +            return PK_MEM;
  178. +        }
  179. +        ((cover_t *)G.cover)->span = NULL;
  180. +        ((cover_t *)G.cover)->max = 0;
  181. +    }
  182. +    ((cover_t *)G.cover)->num = 0;
  183. +    if ((G.extra_bytes != 0 &&
  184. +         cover_add((cover_t *)G.cover, 0, G.extra_bytes) != 0) ||
  185. +        cover_add((cover_t *)G.cover,
  186. +                  G.extra_bytes + G.ecrec.offset_start_central_directory,
  187. +                  G.ziplen) != 0) {
  188. +        Info(slide, 0x401, ((char *)slide,
  189. +          LoadFarString(NotEnoughMemCover)));
  190. +        return PK_MEM;
  191. +    }
  192. +
  193.  /*---------------------------------------------------------------------------
  194.      The basic idea of this function is as follows.  Since the central di-
  195.      rectory lies at the end of the zipfile and the member files lie at the
  196. @@ -593,7 +735,8 @@ int extract_or_test_files(__G)    /* return PK-type error code */
  197.              if (error > error_in_archive)
  198.                  error_in_archive = error;
  199.              /* ...and keep going (unless disk full or user break) */
  200. -            if (G.disk_full > 1 || error_in_archive == IZ_CTRLC) {
  201. +            if (G.disk_full > 1 || error_in_archive == IZ_CTRLC ||
  202. +                error == PK_BOMB) {
  203.                  /* clear reached_end to signal premature stop ... */
  204.                  reached_end = FALSE;
  205.                  /* ... and cancel scanning the central directory */
  206. @@ -1062,6 +1205,11 @@ static int extract_or_test_entrylist(__G__ numchunk,
  207.  
  208.          /* seek_zipf(__G__ pInfo->offset);  */
  209.          request = G.pInfo->offset + G.extra_bytes;
  210. +        if (cover_within((cover_t *)G.cover, request)) {
  211. +            Info(slide, 0x401, ((char *)slide,
  212. +              LoadFarString(OverlappedComponents)));
  213. +            return PK_BOMB;
  214. +        }
  215.          inbuf_offset = request % INBUFSIZ;
  216.          bufstart = request - inbuf_offset;
  217.  
  218. @@ -1602,6 +1750,18 @@ reprompt:
  219.              return IZ_CTRLC;        /* cancel operation by user request */
  220.          }
  221.  #endif
  222. +        error = cover_add((cover_t *)G.cover, request,
  223. +                          G.cur_zipfile_bufstart + (G.inptr - G.inbuf));
  224. +        if (error < 0) {
  225. +            Info(slide, 0x401, ((char *)slide,
  226. +              LoadFarString(NotEnoughMemCover)));
  227. +            return PK_MEM;
  228. +        }
  229. +        if (error != 0) {
  230. +            Info(slide, 0x401, ((char *)slide,
  231. +              LoadFarString(OverlappedComponents)));
  232. +            return PK_BOMB;
  233. +        }
  234.  #ifdef MACOS  /* MacOS is no preemptive OS, thus call event-handling by hand */
  235.          UserStop();
  236.  #endif
  237. @@ -2003,6 +2163,34 @@ static int extract_or_test_member(__G)    /* return PK-type error code */
  238.      }
  239.  
  240.      undefer_input(__G);
  241. +
  242. +    if ((G.lrec.general_purpose_bit_flag & 8) != 0) {
  243. +        /* skip over data descriptor (harder than it sounds, due to signature
  244. +         * ambiguity)
  245. +         */
  246. +#       define SIG 0x08074b50
  247. +#       define LOW 0xffffffff
  248. +        uch buf[12];
  249. +        unsigned shy = 12 - readbuf((char *)buf, 12);
  250. +        ulg crc = shy ? 0 : makelong(buf);
  251. +        ulg clen = shy ? 0 : makelong(buf + 4);
  252. +        ulg ulen = shy ? 0 : makelong(buf + 8); /* or high clen if ZIP64 */
  253. +        if (crc == SIG &&                       /* if not SIG, no signature */
  254. +            (G.lrec.crc32 != SIG ||             /* if not SIG, have signature */
  255. +             (clen == SIG &&                    /* if not SIG, no signature */
  256. +              ((G.lrec.csize & LOW) != SIG ||   /* if not SIG, have signature */
  257. +               (ulen == SIG &&                  /* if not SIG, no signature */
  258. +                (G.zip64 ? G.lrec.csize >> 32 : G.lrec.ucsize) != SIG
  259. +                                                /* if not SIG, have signature */
  260. +                )))))
  261. +                   /* skip four more bytes to account for signature */
  262. +                   shy += 4 - readbuf((char *)buf, 4);
  263. +        if (G.zip64)
  264. +            shy += 8 - readbuf((char *)buf, 8); /* skip eight more for ZIP64 */
  265. +        if (shy)
  266. +            error = PK_ERR;
  267. +    }
  268. +
  269.      return error;
  270.  
  271.  } /* end function extract_or_test_member() */
  272. diff --git a/globals.c b/globals.c
  273. index fa8cca5..1e0f608 100644
  274. --- a/globals.c
  275. +++ b/globals.c
  276. @@ -181,6 +181,7 @@ Uz_Globs *globalsCtor()
  277.  # if (!defined(NO_TIMESTAMPS))
  278.      uO.D_flag=1;    /* default to '-D', no restoration of dir timestamps */
  279.  # endif
  280. +    G.cover = NULL;     /* not allocated yet */
  281.  #endif
  282.  
  283.      uO.lflag=(-1);
  284. diff --git a/globals.h b/globals.h
  285. index 11b7215..2bdcdeb 100644
  286. --- a/globals.h
  287. +++ b/globals.h
  288. @@ -260,12 +260,15 @@ typedef struct Globals {
  289.      ecdir_rec       ecrec;         /* used in unzip.c, extract.c */
  290.      z_stat   statbuf;              /* used by main, mapname, check_for_newer */
  291.  
  292. +    int zip64;                     /* true if Zip64 info in extra field */
  293. +
  294.      int      mem_mode;
  295.      uch      *outbufptr;           /* extract.c static */
  296.      ulg      outsize;              /* extract.c static */
  297.      int      reported_backslash;   /* extract.c static */
  298.      int      disk_full;
  299.      int      newfile;
  300. +    void     **cover;              /* used in extract.c for bomb detection */
  301.  
  302.      int      didCRlast;            /* fileio static */
  303.      ulg      numlines;             /* fileio static: number of lines printed */
  304. diff --git a/process.c b/process.c
  305. index e4f2405..e4e7aee 100644
  306. --- a/process.c
  307. +++ b/process.c
  308. @@ -637,6 +637,13 @@ void free_G_buffers(__G)     /* releases all memory allocated in global vars */
  309.      }
  310.  #endif
  311.  
  312. +    /* Free the cover span list and the cover structure. */
  313. +    if (G.cover != NULL) {
  314. +        free(*(G.cover));
  315. +        free(G.cover);
  316. +        G.cover = NULL;
  317. +    }
  318. +
  319.  } /* end function free_G_buffers() */
  320.  
  321.  
  322. @@ -1913,6 +1920,8 @@ int getZip64Data(__G__ ef_buf, ef_len)
  323.  #define Z64FLGS 0xffff
  324.  #define Z64FLGL 0xffffffff
  325.  
  326. +    G.zip64 = FALSE;
  327. +
  328.      if (ef_len == 0 || ef_buf == NULL)
  329.          return PK_COOL;
  330.  
  331. @@ -2084,6 +2093,8 @@ int getUnicodeData(__G__ ef_buf, ef_len)
  332.                      (ZCONST char *)(offset + ef_buf), ULen);
  333.              G.unipath_filename[ULen] = '\0';
  334.            }
  335. +
  336. +          G.zip64 = TRUE;
  337.          }
  338.  
  339.          /* Skip this extra field block */
  340. diff --git a/unzip.h b/unzip.h
  341. index 5b2a326..ed24a5b 100644
  342. --- a/unzip.h
  343. +++ b/unzip.h
  344. @@ -645,6 +645,7 @@ typedef struct _Uzp_cdir_Rec {
  345.  #define PK_NOZIP           9   /* zipfile not found */
  346.  #define PK_PARAM          10   /* bad or illegal parameters specified */
  347.  #define PK_FIND           11   /* no files found */
  348. +#define PK_BOMB           12   /* likely zip bomb */
  349.  #define PK_DISK           50   /* disk full */
  350.  #define PK_EOF            51   /* unexpected EOF */
  351.  
  352. -- 
  353. 2.25.0