goblin_experimental/pe/
section_table.rs

1use crate::error::{self, Error};
2use crate::pe::relocation;
3use alloc::borrow::Cow;
4use alloc::string::{String, ToString};
5use alloc::vec::Vec;
6use scroll::{ctx, Pread, Pwrite};
7
8#[repr(C)]
9#[derive(Debug, PartialEq, Clone, Default)]
10pub struct SectionTable {
11    pub name: [u8; 8],
12    pub real_name: Option<String>,
13    pub virtual_size: u32,
14    pub virtual_address: u32,
15    pub size_of_raw_data: u32,
16    pub pointer_to_raw_data: u32,
17    pub pointer_to_relocations: u32,
18    pub pointer_to_linenumbers: u32,
19    pub number_of_relocations: u16,
20    pub number_of_linenumbers: u16,
21    pub characteristics: u32,
22}
23
24pub const SIZEOF_SECTION_TABLE: usize = 8 * 5;
25
26// Based on https://github.com/llvm-mirror/llvm/blob/af7b1832a03ab6486c42a40d21695b2c03b2d8a3/lib/Object/COFFObjectFile.cpp#L70
27// Decodes a string table entry in base 64 (//AAAAAA). Expects string without
28// prefixed slashes.
29fn base64_decode_string_entry(s: &str) -> Result<usize, ()> {
30    assert!(s.len() <= 6, "String too long, possible overflow.");
31
32    let mut val = 0;
33    for c in s.bytes() {
34        let v = if b'A' <= c && c <= b'Z' {
35            // 00..=25
36            c - b'A'
37        } else if b'a' <= c && c <= b'z' {
38            // 26..=51
39            c - b'a' + 26
40        } else if b'0' <= c && c <= b'9' {
41            // 52..=61
42            c - b'0' + 52
43        } else if c == b'+' {
44            // 62
45            62
46        } else if c == b'/' {
47            // 63
48            63
49        } else {
50            return Err(());
51        };
52        val = val * 64 + v as usize;
53    }
54    Ok(val)
55}
56
57impl SectionTable {
58    pub fn parse(
59        bytes: &[u8],
60        offset: &mut usize,
61        string_table_offset: usize,
62    ) -> error::Result<Self> {
63        let mut table = SectionTable::default();
64        let mut name = [0u8; 8];
65        name.copy_from_slice(bytes.gread_with(offset, 8)?);
66
67        table.name = name;
68        table.virtual_size = bytes.gread_with(offset, scroll::LE)?;
69        table.virtual_address = bytes.gread_with(offset, scroll::LE)?;
70        table.size_of_raw_data = bytes.gread_with(offset, scroll::LE)?;
71        table.pointer_to_raw_data = bytes.gread_with(offset, scroll::LE)?;
72        table.pointer_to_relocations = bytes.gread_with(offset, scroll::LE)?;
73        table.pointer_to_linenumbers = bytes.gread_with(offset, scroll::LE)?;
74        table.number_of_relocations = bytes.gread_with(offset, scroll::LE)?;
75        table.number_of_linenumbers = bytes.gread_with(offset, scroll::LE)?;
76        table.characteristics = bytes.gread_with(offset, scroll::LE)?;
77
78        if let Some(idx) = table.name_offset()? {
79            table.real_name = Some(bytes.pread::<&str>(string_table_offset + idx)?.to_string());
80        }
81        Ok(table)
82    }
83
84    pub fn data<'a, 'b: 'a>(&'a self, pe_bytes: &'b [u8]) -> error::Result<Option<Cow<[u8]>>> {
85        let section_start: usize = self.pointer_to_raw_data.try_into().map_err(|_| {
86            Error::Malformed(format!("Virtual address cannot fit in platform `usize`"))
87        })?;
88
89        // assert!(self.virtual_size <= self.size_of_raw_data);
90        // if vsize > size_of_raw_data, the section is zero padded.
91        let section_end: usize = section_start
92            + usize::try_from(self.size_of_raw_data).map_err(|_| {
93                Error::Malformed(format!("Virtual size cannot fit in platform `usize`"))
94            })?;
95
96        let original_bytes = pe_bytes.get(section_start..section_end).map(Cow::Borrowed);
97
98        if original_bytes.is_some() && self.virtual_size > self.size_of_raw_data {
99            let mut bytes: Vec<u8> = Vec::new();
100            bytes.resize(self.size_of_raw_data.try_into()?, 0);
101            bytes.copy_from_slice(&original_bytes.unwrap());
102            bytes.resize(self.virtual_size.try_into()?, 0);
103
104            Ok(Some(Cow::Owned(bytes)))
105        } else {
106            Ok(original_bytes)
107        }
108    }
109
110    pub fn name_offset(&self) -> error::Result<Option<usize>> {
111        // Based on https://github.com/llvm-mirror/llvm/blob/af7b1832a03ab6486c42a40d21695b2c03b2d8a3/lib/Object/COFFObjectFile.cpp#L1054
112        if self.name[0] == b'/' {
113            let idx: usize = if self.name[1] == b'/' {
114                let b64idx = self.name.pread::<&str>(2)?;
115                base64_decode_string_entry(b64idx).map_err(|_| {
116                    Error::Malformed(format!(
117                        "Invalid indirect section name //{}: base64 decoding failed",
118                        b64idx
119                    ))
120                })?
121            } else {
122                let name = self.name.pread::<&str>(1)?;
123                name.parse().map_err(|err| {
124                    Error::Malformed(format!("Invalid indirect section name /{}: {}", name, err))
125                })?
126            };
127            Ok(Some(idx))
128        } else {
129            Ok(None)
130        }
131    }
132
133    #[allow(clippy::useless_let_if_seq)]
134    pub fn set_name_offset(&mut self, mut idx: usize) -> error::Result<()> {
135        if idx <= 9_999_999 {
136            // 10^7 - 1
137            // write!(&mut self.name[1..], "{}", idx) without using io::Write.
138            // We write into a temporary since we calculate digits starting at the right.
139            let mut name = [0; 7];
140            let mut len = 0;
141            if idx == 0 {
142                name[6] = b'0';
143                len = 1;
144            } else {
145                while idx != 0 {
146                    let rem = (idx % 10) as u8;
147                    idx /= 10;
148                    name[6 - len] = b'0' + rem;
149                    len += 1;
150                }
151            }
152            self.name = [0; 8];
153            self.name[0] = b'/';
154            self.name[1..][..len].copy_from_slice(&name[7 - len..]);
155            Ok(())
156        } else if idx as u64 <= 0xfff_fff_fff {
157            // 64^6 - 1
158            self.name[0] = b'/';
159            self.name[1] = b'/';
160            for i in 0..6 {
161                let rem = (idx % 64) as u8;
162                idx /= 64;
163                let c = match rem {
164                    0..=25 => b'A' + rem,
165                    26..=51 => b'a' + rem - 26,
166                    52..=61 => b'0' + rem - 52,
167                    62 => b'+',
168                    63 => b'/',
169                    _ => unreachable!(),
170                };
171                self.name[7 - i] = c;
172            }
173            Ok(())
174        } else {
175            Err(Error::Malformed(format!(
176                "Invalid section name offset: {}",
177                idx
178            )))
179        }
180    }
181
182    pub fn name(&self) -> error::Result<&str> {
183        match self.real_name.as_ref() {
184            Some(s) => Ok(s),
185            None => Ok(self.name.pread(0)?),
186        }
187    }
188
189    pub fn relocations<'a>(&self, bytes: &'a [u8]) -> error::Result<relocation::Relocations<'a>> {
190        let offset = self.pointer_to_relocations as usize;
191        let number = self.number_of_relocations as usize;
192        relocation::Relocations::parse(bytes, offset, number)
193    }
194
195    /// Tests if `another_section` on-disk ranges will collide.
196    pub fn overlaps_with(&self, another_section: &SectionTable) -> bool {
197        let self_end = self.pointer_to_raw_data + self.size_of_raw_data;
198        let another_end = another_section.pointer_to_raw_data + another_section.size_of_raw_data;
199
200        !((self_end <= another_section.pointer_to_raw_data)
201            || (another_end <= self.pointer_to_raw_data))
202    }
203}
204
205impl ctx::SizeWith<scroll::Endian> for SectionTable {
206    fn size_with(_ctx: &scroll::Endian) -> usize {
207        SIZEOF_SECTION_TABLE
208    }
209}
210
211impl ctx::TryIntoCtx<scroll::Endian> for &SectionTable {
212    type Error = error::Error;
213    fn try_into_ctx(self, bytes: &mut [u8], ctx: scroll::Endian) -> Result<usize, Self::Error> {
214        let offset = &mut 0;
215        bytes.gwrite(&self.name[..], offset)?;
216        bytes.gwrite_with(self.virtual_size, offset, ctx)?;
217        bytes.gwrite_with(self.virtual_address, offset, ctx)?;
218        bytes.gwrite_with(self.size_of_raw_data, offset, ctx)?;
219        bytes.gwrite_with(self.pointer_to_raw_data, offset, ctx)?;
220        bytes.gwrite_with(self.pointer_to_relocations, offset, ctx)?;
221        bytes.gwrite_with(self.pointer_to_linenumbers, offset, ctx)?;
222        bytes.gwrite_with(self.number_of_relocations, offset, ctx)?;
223        bytes.gwrite_with(self.number_of_linenumbers, offset, ctx)?;
224        bytes.gwrite_with(self.characteristics, offset, ctx)?;
225        Ok(SIZEOF_SECTION_TABLE)
226    }
227}
228
229impl ctx::IntoCtx<scroll::Endian> for &SectionTable {
230    fn into_ctx(self, bytes: &mut [u8], ctx: scroll::Endian) {
231        bytes.pwrite_with(self, 0, ctx).unwrap();
232    }
233}
234
235/// The section should not be padded to the next boundary. This flag is obsolete and is replaced
236/// by `IMAGE_SCN_ALIGN_1BYTES`. This is valid only for object files.
237pub const IMAGE_SCN_TYPE_NO_PAD: u32 = 0x0000_0008;
238/// The section contains executable code.
239pub const IMAGE_SCN_CNT_CODE: u32 = 0x0000_0020;
240/// The section contains initialized data.
241pub const IMAGE_SCN_CNT_INITIALIZED_DATA: u32 = 0x0000_0040;
242///  The section contains uninitialized data.
243pub const IMAGE_SCN_CNT_UNINITIALIZED_DATA: u32 = 0x0000_0080;
244pub const IMAGE_SCN_LNK_OTHER: u32 = 0x0000_0100;
245/// The section contains comments or other information. The .drectve section has this type.
246/// This is valid for object files only.
247pub const IMAGE_SCN_LNK_INFO: u32 = 0x0000_0200;
248/// The section will not become part of the image. This is valid only for object files.
249pub const IMAGE_SCN_LNK_REMOVE: u32 = 0x0000_0800;
250/// The section contains COMDAT data. This is valid only for object files.
251pub const IMAGE_SCN_LNK_COMDAT: u32 = 0x0000_1000;
252/// The section contains data referenced through the global pointer (GP).
253pub const IMAGE_SCN_GPREL: u32 = 0x0000_8000;
254pub const IMAGE_SCN_MEM_PURGEABLE: u32 = 0x0002_0000;
255pub const IMAGE_SCN_MEM_16BIT: u32 = 0x0002_0000;
256pub const IMAGE_SCN_MEM_LOCKED: u32 = 0x0004_0000;
257pub const IMAGE_SCN_MEM_PRELOAD: u32 = 0x0008_0000;
258
259pub const IMAGE_SCN_ALIGN_1BYTES: u32 = 0x0010_0000;
260pub const IMAGE_SCN_ALIGN_2BYTES: u32 = 0x0020_0000;
261pub const IMAGE_SCN_ALIGN_4BYTES: u32 = 0x0030_0000;
262pub const IMAGE_SCN_ALIGN_8BYTES: u32 = 0x0040_0000;
263pub const IMAGE_SCN_ALIGN_16BYTES: u32 = 0x0050_0000;
264pub const IMAGE_SCN_ALIGN_32BYTES: u32 = 0x0060_0000;
265pub const IMAGE_SCN_ALIGN_64BYTES: u32 = 0x0070_0000;
266pub const IMAGE_SCN_ALIGN_128BYTES: u32 = 0x0080_0000;
267pub const IMAGE_SCN_ALIGN_256BYTES: u32 = 0x0090_0000;
268pub const IMAGE_SCN_ALIGN_512BYTES: u32 = 0x00A0_0000;
269pub const IMAGE_SCN_ALIGN_1024BYTES: u32 = 0x00B0_0000;
270pub const IMAGE_SCN_ALIGN_2048BYTES: u32 = 0x00C0_0000;
271pub const IMAGE_SCN_ALIGN_4096BYTES: u32 = 0x00D0_0000;
272pub const IMAGE_SCN_ALIGN_8192BYTES: u32 = 0x00E0_0000;
273pub const IMAGE_SCN_ALIGN_MASK: u32 = 0x00F0_0000;
274
275/// The section contains extended relocations.
276pub const IMAGE_SCN_LNK_NRELOC_OVFL: u32 = 0x0100_0000;
277/// The section can be discarded as needed.
278pub const IMAGE_SCN_MEM_DISCARDABLE: u32 = 0x0200_0000;
279/// The section cannot be cached.
280pub const IMAGE_SCN_MEM_NOT_CACHED: u32 = 0x0400_0000;
281/// The section is not pageable.
282pub const IMAGE_SCN_MEM_NOT_PAGED: u32 = 0x0800_0000;
283/// The section can be shared in memory.
284pub const IMAGE_SCN_MEM_SHARED: u32 = 0x1000_0000;
285/// The section can be executed as code.
286pub const IMAGE_SCN_MEM_EXECUTE: u32 = 0x2000_0000;
287/// The section can be read.
288pub const IMAGE_SCN_MEM_READ: u32 = 0x4000_0000;
289/// The section can be written to.
290pub const IMAGE_SCN_MEM_WRITE: u32 = 0x8000_0000;
291
292#[cfg(test)]
293mod tests {
294    use super::*;
295
296    #[test]
297    fn set_name_offset() {
298        let mut section = SectionTable::default();
299        for &(offset, name) in [
300            (0usize, b"/0\0\0\0\0\0\0"),
301            (1, b"/1\0\0\0\0\0\0"),
302            (9_999_999, b"/9999999"),
303            (10_000_000, b"//AAmJaA"),
304            #[cfg(target_pointer_width = "64")]
305            (0xfff_fff_fff, b"////////"),
306        ]
307        .iter()
308        {
309            section.set_name_offset(offset).unwrap();
310            assert_eq!(&section.name, name);
311            assert_eq!(section.name_offset().unwrap(), Some(offset));
312        }
313        #[cfg(target_pointer_width = "64")]
314        assert!(section.set_name_offset(0x1_000_000_000).is_err());
315    }
316}
goblin_experimental/pe/section_table.rs

goblin_experimental/pe/
section_table.rs
