jory/upx
1
0
Fork 0
Code Issues Pull Requests 1 Actions Packages Projects Releases Wiki Activity

WIP: de-compression of old-style shlib

Browse Source 
modified:   p_lx_elf.cpp
This commit is contained in:
John Reiser 2021-09-06 08:43:20 -07:00 committed by Markus F.X.J. Oberhumer
parent 02bd9cc403
commit bd441e83ae
1 changed files with 54 additions and 40 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

94
src/p_lx_elf.cpp
View File

@ -4673,7 +4673,7 @@ PackLinuxElf64::unRela64(
fo->rewrite(rela0, relasz);
}
// File layout of compressed .so shared library:
// File layout of compressed .so (new-style: 3 or 4 PT_LOAD) shared library:
// 1. new Elf headers: Ehdr, PT_LOAD (r-x), PT_LOAD (rw-, if any), non-PT_LOAD Phdrs
// 2. Space for (original - 2) PT_LOAD Phdr
// 3. Remaining original contents of file below xct_off
@ -4748,8 +4748,14 @@ void PackLinuxElf64::un_shlib_1(
}
}
// Decompress first Extent. Old style covers [0, xct_off);
// new style covers just Elf headers: the rest below xct_off is constant!
// Decompress first Extent. Old style covers [0, xct_off)
// which includes rtld constant data and eXecutable app code below DT_INIT.
// In old style, the first compressed Extent is redundant
// except for the compressed original Elf headers.
// New style covers just Elf headers: the rest below xct_off is
// rtld constant data: DT_*HASH, DT_SYMTAB, DT_STRTAB, etc.
// New style puts eXecutable app code in second PT_LOAD
// in order to mark Elf headers and rtld data as non-eXecutable.
fi->seek(xct_off, SEEK_SET);
struct {
struct l_info l;
@ -4774,52 +4780,60 @@ void PackLinuxElf64::un_shlib_1(
u_fi.readx((void *)o_elfhdrs,o_elfhdrs.getSize());
u_fi.close();
// New style: not compressed, up to xct_off
if (ph.u_len < xct_off) {
Elf64_Phdr const *t_phdr = (Elf64_Phdr const *)(1+ (Elf64_Ehdr const *)(void const *)o_elfhdrs);
unsigned t_flags = get_te32(&t_phdr->p_flags);
// New style: 1st PT_LOAD has no eXecutable code
if (!(Elf64_Phdr::PF_X & t_flags)) {
if (fo) {
fo->write(&ibuf[ph.u_len], xct_off - ph.u_len);
}
}
// Now handle compressed PT_LOADs
Elf64_Phdr const *i_phdr = phdri;
Elf64_Phdr const *o_phdr = (Elf64_Phdr const *)(1+ (Elf64_Ehdr const *)(void const *)o_elfhdrs);
int once = 0;
for (unsigned k = 0; k < e_phnum; ++k, ++i_phdr, ++o_phdr) {
unsigned type = get_te32(&o_phdr->p_type); // output side avoids PT_NULL
unsigned flags = get_te32(&o_phdr->p_flags);
unsigned vaddr = get_te64(&o_phdr->p_vaddr);
unsigned filesz = get_te64(&o_phdr->p_filesz);
unsigned o_offset = get_te64(&o_phdr->p_offset);
unsigned i_offset = get_te64(&i_phdr->p_offset);
if (xct_off <= vaddr) { // beyond rtld control info
if (PT_LOAD64==type
&& xct_off < (filesz + vaddr)) {
if (!(Elf64_Phdr::PF_W & flags)) { // Read-only, so was compressed
fi->readx(&hdr.b, sizeof(hdr.b));
fi->seek(-(off_t)sizeof(struct b_info), SEEK_CUR);
if (fo) {
// Now handle compressed PT_LOADs.
// Phdr are parallel from input to output, except perhaps PT_NULL.
Elf64_Phdr const *i_phdr = phdri;
Elf64_Phdr const *o_phdr = (Elf64_Phdr const *)(1+ (Elf64_Ehdr const *)(void const *)o_elfhdrs);
int once = 0;
for (unsigned k = 0; k < e_phnum; ++k, ++i_phdr, ++o_phdr) {
unsigned type = get_te32(&o_phdr->p_type); // output side avoids PT_NULL
unsigned flags = get_te32(&o_phdr->p_flags);
unsigned vaddr = get_te64(&o_phdr->p_vaddr);
unsigned filesz = get_te64(&o_phdr->p_filesz);
unsigned o_offset = get_te64(&o_phdr->p_offset);
unsigned i_offset = get_te64(&i_phdr->p_offset);
if (xct_off <= vaddr) { // beyond rtld control info
if (PT_LOAD64==type
&& xct_off < (filesz + vaddr)) {
if (!(Elf64_Phdr::PF_W & flags)) { // Read-only, so was compressed
fi->readx(&hdr.b, sizeof(hdr.b));
fi->seek(-(off_t)sizeof(struct b_info), SEEK_CUR);
if (fo) {
fo->seek(o_offset, SEEK_SET);
}
ph.c_len = get_te32(&hdr.b.sz_cpr);
ph.u_len = get_te32(&hdr.b.sz_unc);
unpackExtent(ph.u_len, fo, c_adler, u_adler, false, szb_info);
}
else { // Writeable, so might written by rtld, so not compressed.
if (!once++) {
funpad4(fi);
loader_offset = fi->tell();
}
fi->seek(i_offset, SEEK_SET);
fi->readx(ibuf, filesz);
total_in += filesz;
fo->seek(o_offset, SEEK_SET);
fo->write(ibuf, filesz);
total_out = filesz + o_offset; // high-water mark
}
ph.c_len = get_te32(&hdr.b.sz_cpr);
ph.u_len = get_te32(&hdr.b.sz_unc);
unpackExtent(ph.u_len, fo, c_adler, u_adler, false, szb_info);
}
else { // Writeable, so might written by rtld, so not compressed.
if (!once++) {
funpad4(fi);
loader_offset = fi->tell();
}
fi->seek(i_offset, SEEK_SET);
fi->readx(ibuf, filesz);
total_in += filesz;
fo->seek(o_offset, SEEK_SET);
fo->write(ibuf, filesz);
total_out = filesz + o_offset; // high-water mark
}
}
}
}
else { // Old style
Elf64_Phdr const *o_phdr = (Elf64_Phdr const *)(1+ (Elf64_Ehdr const *)(void const *)o_elfhdrs);
fi->seek(o_phdr->p_offset, SEEK_CUR); // DEBUG no-op
}
// position fi at loader offset
fi->seek(loader_offset, SEEK_SET);
}