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Try harder to de-compress corrupted Mach-o file.

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https://github.com/upx/upx/issues/579
	modified:   p_mach.cpp
This commit is contained in:
John Reiser
2022-05-31 11:52:10 -07:00
committed by Markus F.X.J. Oberhumer
parent c1311c78a3
commit 05976ee1a7
1 changed files with 38 additions and 8 deletions
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src/p_mach.cpp
+38 -8
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@@ -1735,8 +1735,11 @@ int PackMachBase<T>::canUnpack()
fi->seek(offLINK - bufsize - sizeof(PackHeader), SEEK_SET); fi->seek(offLINK - bufsize - sizeof(PackHeader), SEEK_SET);
} }
MemBuffer buf(bufsize); MemBuffer buf(bufsize);
MemBuffer buf3(bufsize);
fi->readx(buf, bufsize); fi->readx(buf, bufsize);
// Do not overwrite buf[]; For scratch space, then use buf3 instead.
int i = bufsize; int i = bufsize;
while (i > small && 0 == buf[--i]) { } while (i > small && 0 == buf[--i]) { }
i -= small; i -= small;
@@ -1747,11 +1750,13 @@ int PackMachBase<T>::canUnpack()
upx_uint64_t const rip_off = ptrTEXT ? (rip - ptrTEXT->vmaddr) : 0; upx_uint64_t const rip_off = ptrTEXT ? (rip - ptrTEXT->vmaddr) : 0;
if (ptrTEXT && rip && rip_off < ptrTEXT->vmsize) { if (ptrTEXT && rip && rip_off < ptrTEXT->vmsize) {
fi->seek(ptrTEXT->fileoff + rip_off, SEEK_SET); fi->seek(ptrTEXT->fileoff + rip_off, SEEK_SET);
fi->readx(buf, bufsize); fi->readx(buf3, bufsize);
unsigned char const *b = &buf[0]; unsigned char const *b = &buf3[0];
unsigned disp = *(TE32 const *)&b[1]; unsigned disp = *(TE32 const *)&b[1];
// Emulate the code // Emulate the code
if (0xe8==b[0] && disp < bufsize if (0xe8==b[0] && disp < bufsize
// This has been obsoleted by amd64-darwin.macho-entry.S
// searching for "executable_path=" etc.
&& 0x5d==b[5+disp] && 0xe8==b[6+disp]) { && 0x5d==b[5+disp] && 0xe8==b[6+disp]) {
unsigned disp2 = 0u - *(TE32 const *)&b[7+disp]; unsigned disp2 = 0u - *(TE32 const *)&b[7+disp];
if (disp2 < (12+disp) && 0x5b==b[11+disp-disp2]) { if (disp2 < (12+disp) && 0x5b==b[11+disp-disp2]) {
@@ -1769,6 +1774,31 @@ int PackMachBase<T>::canUnpack()
} }
} }
} }
if (395 == style) { // Desperation
infoWarning("file corrupted");
fi->seek(file_size - bufsize, SEEK_SET);
fi->readx(buf3, bufsize);
unsigned const *p = (unsigned const *)&buf3[bufsize];
for (; buf3 < (void const *)--p; ) {
unsigned x = *p;
if (x) {
if (!(3& x) && x < bufsize) {
fi->seek(0, SEEK_SET);
fi->readx(buf3, bufsize);
p = (unsigned const *)&buf3[x];
if (0 == p[0] && 0 != p[1] && p[1] == p[2] // p_info
&& sz_mach_headers < p[3] && p[4] < p[3] // b_info
) {
overlay_offset = x;
infoWarning("attempting recovery, overlay_offset = %#x",
overlay_offset);
return true;
}
}
break;
}
}
}
} }
if (391==style) { if (391==style) {
TE32 const *uptr = (TE32 const *)&buf[bufsize]; TE32 const *uptr = (TE32 const *)&buf[bufsize];
@@ -1786,8 +1816,8 @@ int PackMachBase<T>::canUnpack()
// 0== .p_progid // 0== .p_progid
// .p_filesize == .p_blocksize // .p_filesize == .p_blocksize
fi->seek(overlay_offset, SEEK_SET); fi->seek(overlay_offset, SEEK_SET);
fi->readx(buf, bufsize); fi->readx(buf3, bufsize);
struct p_info const *const p_ptr = (struct p_info const *)&buf[0]; struct p_info const *const p_ptr = (struct p_info const *)&buf3[0];
struct b_info const *const b_ptr = (struct b_info const *)(1+ p_ptr); struct b_info const *const b_ptr = (struct b_info const *)(1+ p_ptr);
TE32 const *uptr = (TE32 const *)(1+ b_ptr); TE32 const *uptr = (TE32 const *)(1+ b_ptr);
if (b_ptr->sz_unc < 0x4000 if (b_ptr->sz_unc < 0x4000
@@ -1812,16 +1842,16 @@ int PackMachBase<T>::canUnpack()
// is the total length of compressed data which precedes it // is the total length of compressed data which precedes it
//(distance to l_info), so that's another method. //(distance to l_info), so that's another method.
fi->seek(offLINK - 0x1000, SEEK_SET); fi->seek(offLINK - 0x1000, SEEK_SET);
fi->readx(buf, 0x1000); fi->readx(buf3, 0x1000);
unsigned const *const lo = (unsigned const *)&buf[0]; unsigned const *const lo = (unsigned const *)&buf3[0];
unsigned const *p; unsigned const *p;
for (p = (unsigned const *)&buf[0x1000]; p > lo; ) if (*--p) { for (p = (unsigned const *)&buf3[0x1000]; p > lo; ) if (*--p) {
overlay_offset = *(TE32 const *)p; overlay_offset = *(TE32 const *)p;
if ((off_t)overlay_offset < offLINK) { if ((off_t)overlay_offset < offLINK) {
overlay_offset = ((char const *)p - (char const *)lo) + overlay_offset = ((char const *)p - (char const *)lo) +
(offLINK - 0x1000) - overlay_offset + sizeof(l_info); (offLINK - 0x1000) - overlay_offset + sizeof(l_info);
fi->seek(overlay_offset, SEEK_SET); fi->seek(overlay_offset, SEEK_SET);
fi->readx(buf, bufsize); fi->readx(buf3, bufsize);
if (b_ptr->sz_unc < 0x4000 if (b_ptr->sz_unc < 0x4000
&& b_ptr->sz_cpr < b_ptr->sz_unc ) { && b_ptr->sz_cpr < b_ptr->sz_unc ) {
return true; return true;