| From 1aae47fa8935654a84403768f32c03ecbb1be470 Mon Sep 17 00:00:00 2001 |
| From: Mark Adler <madler@alumni.caltech.edu> |
| Date: Tue, 11 Jun 2019 22:01:18 -0700 |
| Subject: [PATCH 2/3] Detect and reject a zip bomb using overlapped entries. |
| |
| This detects an invalid zip file that has at least one entry that |
| overlaps with another entry or with the central directory to the |
| end of the file. A Fifield zip bomb uses overlapped local entries |
| to vastly increase the potential inflation ratio. Such an invalid |
| zip file is rejected. |
| |
| See https://www.bamsoftware.com/hacks/zipbomb/ for David Fifield's |
| analysis, construction, and examples of such zip bombs. |
| |
| The detection maintains a list of covered spans of the zip files |
| so far, where the central directory to the end of the file and any |
| bytes preceding the first entry at zip file offset zero are |
| considered covered initially. Then as each entry is decompressed |
| or tested, it is considered covered. When a new entry is about to |
| be processed, its initial offset is checked to see if it is |
| contained by a covered span. If so, the zip file is rejected as |
| invalid. |
| |
| This commit depends on a preceding commit: "Fix bug in |
| undefer_input() that misplaced the input state." |
| |
| CVE: CVE-2019-13232 |
| Upstream-Status: Backport |
| [https://github.com/madler/unzip/commit/47b3ceae397d21bf822bc2ac73052a4b1daf8e1c] |
| |
| Signed-off-by: Dan Tran <dantran@microsoft.com> |
| --- |
| extract.c | 190 +++++++++++++++++++++++++++++++++++++++++++++++++++++- |
| globals.c | 1 + |
| globals.h | 3 + |
| process.c | 10 +++ |
| unzip.h | 1 + |
| 5 files changed, 204 insertions(+), 1 deletion(-) |
| |
| diff --git a/extract.c b/extract.c |
| index 24db2a8..2bb72ba 100644 |
| --- a/extract.c |
| +++ b/extract.c |
| @@ -321,6 +321,125 @@ static ZCONST char Far UnsupportedExtraField[] = |
| "\nerror: unsupported extra-field compression type (%u)--skipping\n"; |
| static ZCONST char Far BadExtraFieldCRC[] = |
| "error [%s]: bad extra-field CRC %08lx (should be %08lx)\n"; |
| +static ZCONST char Far NotEnoughMemCover[] = |
| + "error: not enough memory for bomb detection\n"; |
| +static ZCONST char Far OverlappedComponents[] = |
| + "error: invalid zip file with overlapped components (possible zip bomb)\n"; |
| + |
| + |
| + |
| + |
| + |
| +/* A growable list of spans. */ |
| +typedef zoff_t bound_t; |
| +typedef struct { |
| + bound_t beg; /* start of the span */ |
| + bound_t end; /* one past the end of the span */ |
| +} span_t; |
| +typedef struct { |
| + span_t *span; /* allocated, distinct, and sorted list of spans */ |
| + size_t num; /* number of spans in the list */ |
| + size_t max; /* allocated number of spans (num <= max) */ |
| +} cover_t; |
| + |
| +/* |
| + * Return the index of the first span in cover whose beg is greater than val. |
| + * If there is no such span, then cover->num is returned. |
| + */ |
| +static size_t cover_find(cover, val) |
| + cover_t *cover; |
| + bound_t val; |
| +{ |
| + size_t lo = 0, hi = cover->num; |
| + while (lo < hi) { |
| + size_t mid = (lo + hi) >> 1; |
| + if (val < cover->span[mid].beg) |
| + hi = mid; |
| + else |
| + lo = mid + 1; |
| + } |
| + return hi; |
| +} |
| + |
| +/* Return true if val lies within any one of the spans in cover. */ |
| +static int cover_within(cover, val) |
| + cover_t *cover; |
| + bound_t val; |
| +{ |
| + size_t pos = cover_find(cover, val); |
| + return pos > 0 && val < cover->span[pos - 1].end; |
| +} |
| + |
| +/* |
| + * Add a new span to the list, but only if the new span does not overlap any |
| + * spans already in the list. The new span covers the values beg..end-1. beg |
| + * must be less than end. |
| + * |
| + * Keep the list sorted and merge adjacent spans. Grow the allocated space for |
| + * the list as needed. On success, 0 is returned. If the new span overlaps any |
| + * existing spans, then 1 is returned and the new span is not added to the |
| + * list. If the new span is invalid because beg is greater than or equal to |
| + * end, then -1 is returned. If the list needs to be grown but the memory |
| + * allocation fails, then -2 is returned. |
| + */ |
| +static int cover_add(cover, beg, end) |
| + cover_t *cover; |
| + bound_t beg; |
| + bound_t end; |
| +{ |
| + size_t pos; |
| + int prec, foll; |
| + |
| + if (beg >= end) |
| + /* The new span is invalid. */ |
| + return -1; |
| + |
| + /* Find where the new span should go, and make sure that it does not |
| + overlap with any existing spans. */ |
| + pos = cover_find(cover, beg); |
| + if ((pos > 0 && beg < cover->span[pos - 1].end) || |
| + (pos < cover->num && end > cover->span[pos].beg)) |
| + return 1; |
| + |
| + /* Check for adjacencies. */ |
| + prec = pos > 0 && beg == cover->span[pos - 1].end; |
| + foll = pos < cover->num && end == cover->span[pos].beg; |
| + if (prec && foll) { |
| + /* The new span connects the preceding and following spans. Merge the |
| + following span into the preceding span, and delete the following |
| + span. */ |
| + cover->span[pos - 1].end = cover->span[pos].end; |
| + cover->num--; |
| + memmove(cover->span + pos, cover->span + pos + 1, |
| + (cover->num - pos) * sizeof(span_t)); |
| + } |
| + else if (prec) |
| + /* The new span is adjacent only to the preceding span. Extend the end |
| + of the preceding span. */ |
| + cover->span[pos - 1].end = end; |
| + else if (foll) |
| + /* The new span is adjacent only to the following span. Extend the |
| + beginning of the following span. */ |
| + cover->span[pos].beg = beg; |
| + else { |
| + /* The new span has gaps between both the preceding and the following |
| + spans. Assure that there is room and insert the span. */ |
| + if (cover->num == cover->max) { |
| + size_t max = cover->max == 0 ? 16 : cover->max << 1; |
| + span_t *span = realloc(cover->span, max * sizeof(span_t)); |
| + if (span == NULL) |
| + return -2; |
| + cover->span = span; |
| + cover->max = max; |
| + } |
| + memmove(cover->span + pos + 1, cover->span + pos, |
| + (cover->num - pos) * sizeof(span_t)); |
| + cover->num++; |
| + cover->span[pos].beg = beg; |
| + cover->span[pos].end = end; |
| + } |
| + return 0; |
| +} |
| |
| |
| |
| @@ -376,6 +495,29 @@ int extract_or_test_files(__G) /* return PK-type error code */ |
| } |
| #endif /* !SFX || SFX_EXDIR */ |
| |
| + /* One more: initialize cover structure for bomb detection. Start with a |
| + span that covers the central directory though the end of the file. */ |
| + if (G.cover == NULL) { |
| + G.cover = malloc(sizeof(cover_t)); |
| + if (G.cover == NULL) { |
| + Info(slide, 0x401, ((char *)slide, |
| + LoadFarString(NotEnoughMemCover))); |
| + return PK_MEM; |
| + } |
| + ((cover_t *)G.cover)->span = NULL; |
| + ((cover_t *)G.cover)->max = 0; |
| + } |
| + ((cover_t *)G.cover)->num = 0; |
| + if ((G.extra_bytes != 0 && |
| + cover_add((cover_t *)G.cover, 0, G.extra_bytes) != 0) || |
| + cover_add((cover_t *)G.cover, |
| + G.extra_bytes + G.ecrec.offset_start_central_directory, |
| + G.ziplen) != 0) { |
| + Info(slide, 0x401, ((char *)slide, |
| + LoadFarString(NotEnoughMemCover))); |
| + return PK_MEM; |
| + } |
| + |
| /*--------------------------------------------------------------------------- |
| The basic idea of this function is as follows. Since the central di- |
| rectory lies at the end of the zipfile and the member files lie at the |
| @@ -593,7 +735,8 @@ int extract_or_test_files(__G) /* return PK-type error code */ |
| if (error > error_in_archive) |
| error_in_archive = error; |
| /* ...and keep going (unless disk full or user break) */ |
| - if (G.disk_full > 1 || error_in_archive == IZ_CTRLC) { |
| + if (G.disk_full > 1 || error_in_archive == IZ_CTRLC || |
| + error == PK_BOMB) { |
| /* clear reached_end to signal premature stop ... */ |
| reached_end = FALSE; |
| /* ... and cancel scanning the central directory */ |
| @@ -1062,6 +1205,11 @@ static int extract_or_test_entrylist(__G__ numchunk, |
| |
| /* seek_zipf(__G__ pInfo->offset); */ |
| request = G.pInfo->offset + G.extra_bytes; |
| + if (cover_within((cover_t *)G.cover, request)) { |
| + Info(slide, 0x401, ((char *)slide, |
| + LoadFarString(OverlappedComponents))); |
| + return PK_BOMB; |
| + } |
| inbuf_offset = request % INBUFSIZ; |
| bufstart = request - inbuf_offset; |
| |
| @@ -1593,6 +1741,18 @@ reprompt: |
| return IZ_CTRLC; /* cancel operation by user request */ |
| } |
| #endif |
| + error = cover_add((cover_t *)G.cover, request, |
| + G.cur_zipfile_bufstart + (G.inptr - G.inbuf)); |
| + if (error < 0) { |
| + Info(slide, 0x401, ((char *)slide, |
| + LoadFarString(NotEnoughMemCover))); |
| + return PK_MEM; |
| + } |
| + if (error != 0) { |
| + Info(slide, 0x401, ((char *)slide, |
| + LoadFarString(OverlappedComponents))); |
| + return PK_BOMB; |
| + } |
| #ifdef MACOS /* MacOS is no preemptive OS, thus call event-handling by hand */ |
| UserStop(); |
| #endif |
| @@ -1994,6 +2154,34 @@ static int extract_or_test_member(__G) /* return PK-type error code */ |
| } |
| |
| undefer_input(__G); |
| + |
| + if ((G.lrec.general_purpose_bit_flag & 8) != 0) { |
| + /* skip over data descriptor (harder than it sounds, due to signature |
| + * ambiguity) |
| + */ |
| +# define SIG 0x08074b50 |
| +# define LOW 0xffffffff |
| + uch buf[12]; |
| + unsigned shy = 12 - readbuf((char *)buf, 12); |
| + ulg crc = shy ? 0 : makelong(buf); |
| + ulg clen = shy ? 0 : makelong(buf + 4); |
| + ulg ulen = shy ? 0 : makelong(buf + 8); /* or high clen if ZIP64 */ |
| + if (crc == SIG && /* if not SIG, no signature */ |
| + (G.lrec.crc32 != SIG || /* if not SIG, have signature */ |
| + (clen == SIG && /* if not SIG, no signature */ |
| + ((G.lrec.csize & LOW) != SIG || /* if not SIG, have signature */ |
| + (ulen == SIG && /* if not SIG, no signature */ |
| + (G.zip64 ? G.lrec.csize >> 32 : G.lrec.ucsize) != SIG |
| + /* if not SIG, have signature */ |
| + ))))) |
| + /* skip four more bytes to account for signature */ |
| + shy += 4 - readbuf((char *)buf, 4); |
| + if (G.zip64) |
| + shy += 8 - readbuf((char *)buf, 8); /* skip eight more for ZIP64 */ |
| + if (shy) |
| + error = PK_ERR; |
| + } |
| + |
| return error; |
| |
| } /* end function extract_or_test_member() */ |
| diff --git a/globals.c b/globals.c |
| index fa8cca5..1e0f608 100644 |
| --- a/globals.c |
| +++ b/globals.c |
| @@ -181,6 +181,7 @@ Uz_Globs *globalsCtor() |
| # if (!defined(NO_TIMESTAMPS)) |
| uO.D_flag=1; /* default to '-D', no restoration of dir timestamps */ |
| # endif |
| + G.cover = NULL; /* not allocated yet */ |
| #endif |
| |
| uO.lflag=(-1); |
| diff --git a/globals.h b/globals.h |
| index 11b7215..2bdcdeb 100644 |
| --- a/globals.h |
| +++ b/globals.h |
| @@ -260,12 +260,15 @@ typedef struct Globals { |
| ecdir_rec ecrec; /* used in unzip.c, extract.c */ |
| z_stat statbuf; /* used by main, mapname, check_for_newer */ |
| |
| + int zip64; /* true if Zip64 info in extra field */ |
| + |
| int mem_mode; |
| uch *outbufptr; /* extract.c static */ |
| ulg outsize; /* extract.c static */ |
| int reported_backslash; /* extract.c static */ |
| int disk_full; |
| int newfile; |
| + void **cover; /* used in extract.c for bomb detection */ |
| |
| int didCRlast; /* fileio static */ |
| ulg numlines; /* fileio static: number of lines printed */ |
| diff --git a/process.c b/process.c |
| index a3c1a4d..208619c 100644 |
| --- a/process.c |
| +++ b/process.c |
| @@ -637,6 +637,13 @@ void free_G_buffers(__G) /* releases all memory allocated in global vars */ |
| } |
| #endif |
| |
| + /* Free the cover span list and the cover structure. */ |
| + if (G.cover != NULL) { |
| + free(*(G.cover)); |
| + free(G.cover); |
| + G.cover = NULL; |
| + } |
| + |
| } /* end function free_G_buffers() */ |
| |
| |
| @@ -1905,6 +1912,7 @@ int getZip64Data(__G__ ef_buf, ef_len) |
| |
| #define Z64FLGS 0xffff |
| #define Z64FLGL 0xffffffff |
| + G.zip64 = FALSE; |
| |
| if (ef_len == 0 || ef_buf == NULL) |
| return PK_COOL; |
| @@ -1964,6 +1972,8 @@ int getZip64Data(__G__ ef_buf, ef_len) |
| G.crec.disk_number_start = (zuvl_t)makelong(offset + ef_buf); |
| offset += 4; |
| } |
| + |
| + G.zip64 = TRUE; |
| #if 0 |
| break; /* Expect only one EF_PKSZ64 block. */ |
| #endif /* 0 */ |
| diff --git a/unzip.h b/unzip.h |
| index 5b2a326..ed24a5b 100644 |
| --- a/unzip.h |
| +++ b/unzip.h |
| @@ -645,6 +645,7 @@ typedef struct _Uzp_cdir_Rec { |
| #define PK_NOZIP 9 /* zipfile not found */ |
| #define PK_PARAM 10 /* bad or illegal parameters specified */ |
| #define PK_FIND 11 /* no files found */ |
| +#define PK_BOMB 12 /* likely zip bomb */ |
| #define PK_DISK 50 /* disk full */ |
| #define PK_EOF 51 /* unexpected EOF */ |
| |
| -- |
| 2.22.0.vfs.1.1.57.gbaf16c8 |