michael/exif-rs
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exif-rs
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Wrap TIFF parser functions into a struct.

This commit is contained in:
KAMADA Ken'ichi 2021-06-05 19:32:24 +09:00
parent 8232c6cd51
commit 7365bc564f
3 changed files with 123 additions and 108 deletions
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2
src/lib.rs
View File

@ -94,7 +94,7 @@ pub use jpeg::get_exif_attr as get_exif_attr_from_jpeg;
pub use reader::{Exif, Reader};
pub use tag::{Context, Tag};
pub use tiff::{DateTime, Field, In};
pub use tiff::parse_exif_compat03 as parse_exif;
pub use tiff::parse_exif;
pub use value::Value;
pub use value::{Rational, SRational};

13
src/reader.rs
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@ -71,16 +71,15 @@ impl Reader {
/// Parses the Exif attributes from raw Exif data.
/// If an error occurred, `exif::Error` is returned.
pub fn read_raw(&self, data: Vec<u8>) -> Result<Exif, Error> {
let buf = data;
let (entries, le) = tiff::parse_exif(&buf)?;
let entry_map = entries.iter().enumerate()
let mut parser = tiff::Parser::new();
parser.parse(&data)?;
let entry_map = parser.entries.iter().enumerate()
.map(|(i, e)| (e.ifd_num_tag(), i)).collect();
Ok(Exif {
buf: buf,
entries: entries,
buf: data,
entries: parser.entries,
entry_map: entry_map,
little_endian: le,
little_endian: parser.little_endian,
})
}

216
src/tiff.rs
View File

@ -150,118 +150,135 @@ impl fmt::Display for In {
/// Returns a Vec of Exif fields and a bool.
/// The boolean value is true if the data is little endian.
/// If an error occurred, `exif::Error` is returned.
pub fn parse_exif_compat03(data: &[u8]) -> Result<(Vec<Field>, bool), Error> {
parse_exif(data).map(|(entries, le)| {
let fields = entries.into_iter()
.map(|e| e.into_field(data, le)).collect();
(fields, le)
})
pub fn parse_exif(data: &[u8]) -> Result<(Vec<Field>, bool), Error> {
let mut parser = Parser::new();
parser.parse(data)?;
let (entries, le) = (parser.entries, parser.little_endian);
Ok((entries.into_iter().map(|e| e.into_field(data, le)).collect(), le))
}
pub fn parse_exif(data: &[u8]) -> Result<(Vec<IfdEntry>, bool), Error> {
// Check the byte order and call the real parser.
if data.len() < 8 {
return Err(Error::InvalidFormat("Truncated TIFF header"));
}
match BigEndian::loadu16(data, 0) {
TIFF_BE => parse_exif_sub::<BigEndian>(data).map(|v| (v, false)),
TIFF_LE => parse_exif_sub::<LittleEndian>(data).map(|v| (v, true)),
_ => Err(Error::InvalidFormat("Invalid TIFF byte order")),
}
#[derive(Debug)]
pub struct Parser {
pub entries: Vec<IfdEntry>,
pub little_endian: bool,
}
fn parse_exif_sub<E>(data: &[u8])
-> Result<Vec<IfdEntry>, Error> where E: Endian {
// Parse the rest of the header (42 and the IFD offset).
if E::loadu16(data, 2) != TIFF_FORTY_TWO {
return Err(Error::InvalidFormat("Invalid forty two"));
impl Parser {
pub fn new() -> Self {
Self { entries: Vec::new(), little_endian: false }
}
let mut ifd_offset = E::loadu32(data, 4) as usize;
let mut ifd_num_ck = Some(0);
let mut entries = Vec::new();
while ifd_offset != 0 {
let ifd_num = ifd_num_ck.ok_or(Error::InvalidFormat("Too many IFDs"))?;
// Limit the number of IFDs to defend against resource exhaustion
// attacks.
if ifd_num >= 8 {
return Err(Error::InvalidFormat("Limit the IFD count to 8"));
pub fn parse(&mut self, data: &[u8]) -> Result<(), Error> {
// Check the byte order and call the real parser.
if data.len() < 8 {
return Err(Error::InvalidFormat("Truncated TIFF header"));
}
match BigEndian::loadu16(data, 0) {
TIFF_BE => {
self.little_endian = false;
self.parse_sub::<BigEndian>(data)
},
TIFF_LE => {
self.little_endian = true;
self.parse_sub::<LittleEndian>(data)
},
_ => Err(Error::InvalidFormat("Invalid TIFF byte order")),
}
ifd_offset = parse_ifd::<E>(
&mut entries, data, ifd_offset, Context::Tiff, ifd_num)?;
ifd_num_ck = ifd_num.checked_add(1);
}
Ok(entries)
}
// Parse IFD [EXIF23 4.6.2].
fn parse_ifd<E>(entries: &mut Vec<IfdEntry>, data: &[u8],
offset: usize, ctx: Context, ifd_num: u16)
-> Result<usize, Error> where E: Endian {
// Count (the number of the entries).
if data.len() < offset || data.len() - offset < 2 {
return Err(Error::InvalidFormat("Truncated IFD count"));
}
let count = E::loadu16(data, offset) as usize;
// Array of entries. (count * 12) never overflows.
if data.len() - offset - 2 < count * 12 {
return Err(Error::InvalidFormat("Truncated IFD"));
}
for i in 0..count as usize {
let tag = E::loadu16(data, offset + 2 + i * 12);
let typ = E::loadu16(data, offset + 2 + i * 12 + 2);
let cnt = E::loadu32(data, offset + 2 + i * 12 + 4);
let valofs_at = offset + 2 + i * 12 + 8;
let (unitlen, _parser) = get_type_info::<E>(typ);
let vallen = unitlen.checked_mul(cnt as usize).ok_or(
Error::InvalidFormat("Invalid entry count"))?;
let mut val = if vallen <= 4 {
Value::Unknown(typ, cnt, valofs_at as u32)
} else {
let ofs = E::loadu32(data, valofs_at) as usize;
if data.len() < ofs || data.len() - ofs < vallen {
return Err(Error::InvalidFormat("Truncated field value"));
fn parse_sub<E>(&mut self, data: &[u8])
-> Result<(), Error> where E: Endian {
// Parse the rest of the header (42 and the IFD offset).
if E::loadu16(data, 2) != TIFF_FORTY_TWO {
return Err(Error::InvalidFormat("Invalid forty two"));
}
let mut ifd_offset = E::loadu32(data, 4) as usize;
let mut ifd_num_ck = Some(0);
while ifd_offset != 0 {
let ifd_num = ifd_num_ck
.ok_or(Error::InvalidFormat("Too many IFDs"))?;
// Limit the number of IFDs to defend against resource exhaustion
// attacks.
if ifd_num >= 8 {
return Err(Error::InvalidFormat("Limit the IFD count to 8"));
}
Value::Unknown(typ, cnt, ofs as u32)
};
// No infinite recursion will occur because the context is not
// recursively defined.
let tag = Tag(ctx, tag);
match tag {
Tag::ExifIFDPointer => parse_child_ifd::<E>(
entries, data, &mut val, Context::Exif, ifd_num)?,
Tag::GPSInfoIFDPointer => parse_child_ifd::<E>(
entries, data, &mut val, Context::Gps, ifd_num)?,
Tag::InteropIFDPointer => parse_child_ifd::<E>(
entries, data, &mut val, Context::Interop, ifd_num)?,
_ => entries.push(IfdEntry { field: Field {
tag: tag, ifd_num: In(ifd_num), value: val }.into()}),
ifd_offset = self.parse_ifd::<E>(
data, ifd_offset, Context::Tiff, ifd_num)?;
ifd_num_ck = ifd_num.checked_add(1);
}
Ok(())
}
// Offset to the next IFD.
if data.len() - offset - 2 - count * 12 < 4 {
return Err(Error::InvalidFormat("Truncated next IFD offset"));
// Parse IFD [EXIF23 4.6.2].
fn parse_ifd<E>(&mut self, data: &[u8],
offset: usize, ctx: Context, ifd_num: u16)
-> Result<usize, Error> where E: Endian {
// Count (the number of the entries).
if data.len() < offset || data.len() - offset < 2 {
return Err(Error::InvalidFormat("Truncated IFD count"));
}
let count = E::loadu16(data, offset) as usize;
// Array of entries. (count * 12) never overflows.
if data.len() - offset - 2 < count * 12 {
return Err(Error::InvalidFormat("Truncated IFD"));
}
for i in 0..count as usize {
let tag = E::loadu16(data, offset + 2 + i * 12);
let typ = E::loadu16(data, offset + 2 + i * 12 + 2);
let cnt = E::loadu32(data, offset + 2 + i * 12 + 4);
let valofs_at = offset + 2 + i * 12 + 8;
let (unitlen, _parser) = get_type_info::<E>(typ);
let vallen = unitlen.checked_mul(cnt as usize).ok_or(
Error::InvalidFormat("Invalid entry count"))?;
let mut val = if vallen <= 4 {
Value::Unknown(typ, cnt, valofs_at as u32)
} else {
let ofs = E::loadu32(data, valofs_at) as usize;
if data.len() < ofs || data.len() - ofs < vallen {
return Err(Error::InvalidFormat("Truncated field value"));
}
Value::Unknown(typ, cnt, ofs as u32)
};
// No infinite recursion will occur because the context is not
// recursively defined.
let tag = Tag(ctx, tag);
match tag {
Tag::ExifIFDPointer => self.parse_child_ifd::<E>(
data, &mut val, Context::Exif, ifd_num)?,
Tag::GPSInfoIFDPointer => self.parse_child_ifd::<E>(
data, &mut val, Context::Gps, ifd_num)?,
Tag::InteropIFDPointer => self.parse_child_ifd::<E>(
data, &mut val, Context::Interop, ifd_num)?,
_ => self.entries.push(IfdEntry { field: Field {
tag: tag, ifd_num: In(ifd_num), value: val }.into()}),
}
}
// Offset to the next IFD.
if data.len() - offset - 2 - count * 12 < 4 {
return Err(Error::InvalidFormat("Truncated next IFD offset"));
}
let next_ifd_offset = E::loadu32(data, offset + 2 + count * 12);
Ok(next_ifd_offset as usize)
}
let next_ifd_offset = E::loadu32(data, offset + 2 + count * 12) as usize;
Ok(next_ifd_offset)
}
fn parse_child_ifd<E>(entries: &mut Vec<IfdEntry>, data: &[u8],
pointer: &mut Value, ctx: Context, ifd_num: u16)
-> Result<(), Error> where E: Endian {
// The pointer is not yet parsed, so do it here.
IfdEntry::parse_value::<E>(pointer, data);
fn parse_child_ifd<E>(&mut self, data: &[u8],
pointer: &mut Value, ctx: Context, ifd_num: u16)
-> Result<(), Error> where E: Endian {
// The pointer is not yet parsed, so do it here.
IfdEntry::parse_value::<E>(pointer, data);
// A pointer field has type == LONG and count == 1, so the
// value (IFD offset) must be embedded in the "value offset"
// element of the field.
let ofs = pointer.get_uint(0).ok_or(
Error::InvalidFormat("Invalid pointer"))? as usize;
match parse_ifd::<E>(entries, data, ofs, ctx, ifd_num)? {
0 => Ok(()),
_ => Err(Error::InvalidFormat("Unexpected next IFD")),
// A pointer field has type == LONG and count == 1, so the
// value (IFD offset) must be embedded in the "value offset"
// element of the field.
let ofs = pointer.get_uint(0).ok_or(
Error::InvalidFormat("Invalid pointer"))? as usize;
match self.parse_ifd::<E>(data, ofs, ctx, ifd_num)? {
0 => Ok(()),
_ => Err(Error::InvalidFormat("Unexpected next IFD")),
}
}
}
@ -567,10 +584,9 @@ mod tests {
fn unknown_field() {
let data = b"MM\0\x2a\0\0\0\x08\
\0\x01\x01\0\xff\xff\0\0\0\x01\0\x14\0\0\0\0\0\0";
let (v, le) = parse_exif(data).unwrap();
let (v, _le) = parse_exif(data).unwrap();
assert_eq!(v.len(), 1);
assert_pat!(v[0].ref_field(data, le).value,
Value::Unknown(0xffff, 1, 0x12));
assert_pat!(v[0].value, Value::Unknown(0xffff, 1, 0x12));
}
#[test]