From 5b44c818b96193b3e240f38f61985fa2bc780eb7 Mon Sep 17 00:00:00 2001
From: Jakub Martisko <jamartis@redhat.com>
Date: Tue, 30 Nov 2021 15:42:17 +0100
Subject: [PATCH] Add an option to disable the zipbomb detection
This can be done by settting a newly introduced environment variable
UNZIP_DISABLE_ZIPBOMB_DETECTION to {TRUE,True,true}. If the variable is unset, or
set to any other value the zipbomb detection is left enabled.
Example:
UNZIP_DISABLE_ZIPBOMB_DETECTION=True unzip ./zbsm.zip -d ./test
---
extract.c | 85 ++++++++++++++++++++++++++++++-------------------------
unzip.c | 15 ++++++++--
unzip.h | 1 +
3 files changed, 60 insertions(+), 41 deletions(-)
diff --git a/extract.c b/extract.c
index 878817d..3e58071 100644
--- a/extract.c
+++ b/extract.c
@@ -322,7 +322,8 @@ static ZCONST char Far BadExtraFieldCRC[] =
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";
+ "error: invalid zip file with overlapped components (possible zip bomb)\n \
+To unzip the file anyway, rerun the command with UNZIP_DISABLE_ZIPBOMB_DETECTION=TRUE environmnent variable\n";
@@ -502,35 +503,37 @@ int extract_or_test_files(__G) /* return PK-type error code */
the end of central directory record (including the Zip64 end of central
directory locator, if present), and the Zip64 end of central directory
record, if present. */
- if (G.cover == NULL) {
+ if (uO.zipbomb == TRUE) {
+ if (G.cover == NULL) {
G.cover = malloc(sizeof(cover_t));
if (G.cover == NULL) {
- Info(slide, 0x401, ((char *)slide,
- LoadFarString(NotEnoughMemCover)));
- return PK_MEM;
+ 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 (cover_add((cover_t *)G.cover,
- G.extra_bytes + G.ecrec.offset_start_central_directory,
- G.extra_bytes + G.ecrec.offset_start_central_directory +
- G.ecrec.size_central_directory) != 0) {
+ }
+ ((cover_t *)G.cover)->num = 0;
+ if (cover_add((cover_t *)G.cover,
+ G.extra_bytes + G.ecrec.offset_start_central_directory,
+ G.extra_bytes + G.ecrec.offset_start_central_directory +
+ G.ecrec.size_central_directory) != 0) {
Info(slide, 0x401, ((char *)slide,
- LoadFarString(NotEnoughMemCover)));
+ LoadFarString(NotEnoughMemCover)));
return PK_MEM;
- }
- if ((G.extra_bytes != 0 &&
- cover_add((cover_t *)G.cover, 0, G.extra_bytes) != 0) ||
- (G.ecrec.have_ecr64 &&
- cover_add((cover_t *)G.cover, G.ecrec.ec64_start,
- G.ecrec.ec64_end) != 0) ||
- cover_add((cover_t *)G.cover, G.ecrec.ec_start,
- G.ecrec.ec_end) != 0) {
+ }
+ if ((G.extra_bytes != 0 &&
+ cover_add((cover_t *)G.cover, 0, G.extra_bytes) != 0) ||
+ (G.ecrec.have_ecr64 &&
+ cover_add((cover_t *)G.cover, G.ecrec.ec64_start,
+ G.ecrec.ec64_end) != 0) ||
+ cover_add((cover_t *)G.cover, G.ecrec.ec_start,
+ G.ecrec.ec_end) != 0) {
Info(slide, 0x401, ((char *)slide,
- LoadFarString(OverlappedComponents)));
+ LoadFarString(OverlappedComponents)));
return PK_BOMB;
+ }
}
/*---------------------------------------------------------------------------
@@ -1222,10 +1225,12 @@ 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)) {
+ if (uO.zipbomb == TRUE) {
+ if (cover_within((cover_t *)G.cover, request)) {
Info(slide, 0x401, ((char *)slide,
- LoadFarString(OverlappedComponents)));
+ LoadFarString(OverlappedComponents)));
return PK_BOMB;
+ }
}
inbuf_offset = request % INBUFSIZ;
bufstart = request - inbuf_offset;
@@ -1758,17 +1763,19 @@ 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) {
+ if (uO.zipbomb == TRUE) {
+ 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)));
+ LoadFarString(NotEnoughMemCover)));
return PK_MEM;
- }
- if (error != 0) {
+ }
+ if (error != 0) {
Info(slide, 0x401, ((char *)slide,
- LoadFarString(OverlappedComponents)));
+ LoadFarString(OverlappedComponents)));
return PK_BOMB;
+ }
}
#ifdef MACOS /* MacOS is no preemptive OS, thus call event-handling by hand */
UserStop();
@@ -2171,8 +2178,8 @@ static int extract_or_test_member(__G) /* return PK-type error code */
}
undefer_input(__G);
-
- if ((G.lrec.general_purpose_bit_flag & 8) != 0) {
+ if (uO.zipbomb == TRUE) {
+ if ((G.lrec.general_purpose_bit_flag & 8) != 0) {
/* skip over data descriptor (harder than it sounds, due to signature
* ambiguity)
*/
@@ -2189,16 +2196,16 @@ static int extract_or_test_member(__G) /* return PK-type error code */
((G.lrec.csize & LOW) != SIG || /* if not SIG, have signature */
(ulen == SIG && /* if not SIG, no signature */
(G.pInfo->zip64 ? G.lrec.csize >> 32 : G.lrec.ucsize) != SIG
- /* if not SIG, have signature */
+ /* if not SIG, have signature */
)))))
- /* skip four more bytes to account for signature */
- shy += 4 - readbuf((char *)buf, 4);
+ /* skip four more bytes to account for signature */
+ shy += 4 - readbuf((char *)buf, 4);
if (G.pInfo->zip64)
- shy += 8 - readbuf((char *)buf, 8); /* skip eight more for ZIP64 */
+ shy += 8 - readbuf((char *)buf, 8); /* skip eight more for ZIP64 */
if (shy)
- error = PK_ERR;
+ error = PK_ERR;
+ }
}
-
return error;
} /* end function extract_or_test_member() */
diff --git a/unzip.c b/unzip.c
index 8dbfc95..abb3644 100644
--- a/unzip.c
+++ b/unzip.c
@@ -1329,10 +1329,9 @@ int uz_opts(__G__ pargc, pargv)
int *pargc;
char ***pargv;
{
- char **argv, *s;
+ char **argv, *s, *zipbomb_envar;
int argc, c, error=FALSE, negative=0, showhelp=0;
-
argc = *pargc;
argv = *pargv;
@@ -1923,6 +1922,18 @@ opts_done: /* yes, very ugly...but only used by UnZipSFX with -x xlist */
else
G.extract_flag = TRUE;
+ /* Disable the zipbomb detection, this is the only option set only via the shell variables but it should at least not clash with something in the future. */
+ zipbomb_envar = getenv("UNZIP_DISABLE_ZIPBOMB_DETECTION");
+ uO.zipbomb = TRUE;
+ if (zipbomb_envar != NULL) {
+ /* strcasecmp might be a better approach here but it is POSIX-only */
+ if ((strcmp ("TRUE", zipbomb_envar) == 0)
+ || (strcmp ("True", zipbomb_envar) == 0)
+ || (strcmp ("true",zipbomb_envar) == 0)) {
+ uO.zipbomb = FALSE;
+ }
+ }
+
*pargc = argc;
*pargv = argv;
return PK_OK;
diff --git a/unzip.h b/unzip.h
index ed24a5b..e7665e8 100644
--- a/unzip.h
+++ b/unzip.h
@@ -559,6 +559,7 @@ typedef struct _UzpOpts {
#ifdef UNIX
int cflxflag; /* -^: allow control chars in extracted filenames */
#endif
+ int zipbomb;
#endif /* !FUNZIP */
} UzpOpts;
--
2.33.0