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read/archive: locate members by table in AIX archive #467

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merged 4 commits into from
Sep 30, 2022
Merged

read/archive: locate members by table in AIX archive #467

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f3279e8
read/archive: locate members by tablein AIX archive
ecnelises Sep 21, 2022
c58b6aa
Check string table offset for overflow
ecnelises Sep 22, 2022
48cbed4
Run cargo format
ecnelises Sep 27, 2022
098dac5
Format archive.rs
ecnelises Sep 29, 2022
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80 changes: 64 additions & 16 deletions src/read/archive.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -74,14 +74,11 @@ impl<'data, R: ReadRef<'data>> ArchiveFile<'data, R> {

if file.kind == ArchiveKind::AixBig {
// The fixed length header is located just after magic number.
let file_header = data.read::<archive::AIXFileHeader>(&mut tail)
let file_header = data
.read::<archive::AIXFileHeader>(&mut tail)
.read_error("Invalid AIX big archive file header")?;
file.offset = parse_u64_digits(&file_header.fstmoff, 10)
.read_error("Invalid offset for first archive member in AIX big archive")?;

// Member table is located just after all archive members.
file.len = parse_u64_digits(&file_header.memoff, 10)
.read_error("Invalid offset for member table of AIX big archive")?;
// Read the span of symbol table.
let symtbl64 = parse_u64_digits(&file_header.gst64off, 10)
.read_error("Invalid offset to 64-bit symbol table in AIX big archive")?;
if symtbl64 > 0 {
Expand All @@ -93,6 +90,56 @@ impl<'data, R: ReadRef<'data>> ArchiveFile<'data, R> {
file.symbols = (symtbl, len);
}
}

// Big archive member table lists file entries with offsets and names. To avoid
// potential infinite loop (members are double-linked list), the iterator goes
// through the table instead of real members.
let mut member_table_offset = parse_u64_digits(&file_header.memoff, 10)
.read_error("Invalid offset for member table of AIX big archive")?;
if member_table_offset > 0 {
// The table itself is also a file with header.
let header = data
.read::<archive::AixHeader>(&mut member_table_offset)
.read_error("Invalid AIX big archive member header")?;
let terminator = data
.read_bytes(&mut member_table_offset, 2)
.read_error("Invalid AIX big archive terminator")?;
if terminator != archive::TERMINATOR {
return Err(Error("Invalid AIX big archive terminator"));
}

// Structure of member table:
// Number of entries (20 bytes)
// Offsets of each entry (20*N bytes)
// Names string table (the rest of bytes to fill size defined in header)
let table_size = parse_u64_digits(&header.size, 10)
.read_error("Invalid AIX big archive member size")?;
let members_count = data
.read_bytes_at(member_table_offset, 30)
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Should this have been a length of 20?

I'll do a followup PR for some other things, so I'll change this if needed.

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Ah, it should be 20, Thanks!

.ok()
.and_then(|bytes| parse_u64_digits(bytes, 10))
.read_error("Invalid member count in AIX big archive")?;
file.offset = member_table_offset
.checked_add(20)
.read_error("AIX big archive offset overflow")?;
let member_offsets_size = members_count
.checked_mul(20)
.read_error("AIX big archive length overflow")?;
file.len = member_offsets_size
.checked_add(file.offset)
.read_error("AIX big archive length overflow")?;
let names_size = table_size
.checked_sub(member_offsets_size)
.and_then(|size| size.checked_sub(20))
.read_error("AIX big archive string table size overflow")?;
file.names = data
.read_bytes_at(file.len, names_size)
.read_error("Invalid AIX big archive member name list")?;
} else {
// The offset would be zero if archive contains no file.
file.offset = 0;
file.len = 0;
}
return Ok(file);
} else if tail < len {
// The first few members may be special, so parse them.
Expand Down Expand Up @@ -303,34 +350,34 @@ impl<'data> ArchiveMember<'data> {
) -> read::Result<Self> {
// The format was described at
// https://www.ibm.com/docs/en/aix/7.3?topic=formats-ar-file-format-big
let file_offset_dec = data
.read_bytes(offset, 20)
.read_error("Invalid AIX big archive file member offset")?;
let mut file_offset = parse_u64_digits(file_offset_dec, 10)
.read_error("Invalid AIX big archive file member offset")?;
let header = data
.read::<archive::AixHeader>(offset)
.read::<archive::AixHeader>(&mut file_offset)
.read_error("Invalid AIX big archive member header")?;
let name_length = parse_u64_digits(&header.namlen, 10)
.read_error("Invalid AIX big archive member name length")?;
let name = data
.read_bytes(offset, name_length)
.read_bytes(&mut file_offset, name_length)
.read_error("Invalid AIX big archive member name")?;

// The actual data for a file member begins at the first even-byte boundary beyond the
// member header and continues for the number of bytes specified by the ar_size field. The
// ar command inserts null bytes for padding where necessary.
if *offset & 1 != 0 {
*offset = offset.saturating_add(1);
if file_offset & 1 != 0 {
file_offset = file_offset.saturating_add(1);
}
// Because of the even-byte boundary, we have to read and check terminator after header.
let terminator = data
.read_bytes(offset, 2)
.read_bytes(&mut file_offset, 2)
.read_error("Invalid AIX big archive head terminator")?;
if terminator != archive::TERMINATOR {
return Err(Error("Invalid AIX big archive terminator"));
}
let file_offset = *offset;
let nextmbroff = parse_u64_digits(&header.nxtmem, 10)
.read_error("Invalid next member offset in AIX big archive")?;

// Move the offset to next member offset
*offset = nextmbroff;
let file_size = parse_u64_digits(&header.size, 10)
.read_error("Invalid archive member size in AIX big archive")?;
Ok(ArchiveMember {
Expand Down Expand Up @@ -654,6 +701,7 @@ mod tests {
let data = &data[..];
let archive = ArchiveFile::parse(data).unwrap();
assert_eq!(archive.kind(), ArchiveKind::AixBig);
assert_eq!(archive.names, b"0123456789abcdef\0fedcba9876543210\0");
let mut members = archive.members();

let member = members.next().unwrap().unwrap();
Expand Down