Skip to content

Commit

Permalink
Apply suggestions from code review
Browse files Browse the repository at this point in the history 
Co-authored-by: Natalie Weizenbaum <[email protected]>
  • Loading branch information
@ntkme @nex3
ntkme and nex3 committed Jul 31, 2024
1 parent 7e4abcd commit fa91d91
Show file tree
Hide file tree
Showing 2 changed files with 60 additions and 54 deletions.
17 changes: 12 additions & 5 deletions lib/src/compiler-path.ts
View file
Original file line number Diff line number Diff line change
Expand Up @@ -4,17 +4,24 @@

import * as fs from 'fs';
import * as p from 'path';
import {getELFInterpreter} from './elf';
import {getElfInterpreter} from './elf';
import {isErrnoException} from './utils';

/**
* Detect if the given binary is linked with musl libc by checking if
* the interpreter basename starts with "ld-musl-"
*/
const isLinuxMusl = function (path: string): boolean {
const interpreter = getELFInterpreter(path);
return p.basename(interpreter).startsWith('ld-musl-');
};
function isLinuxMusl(path: string): boolean {
try {
const interpreter = getElfInterpreter(path);
return p.basename(interpreter).startsWith('ld-musl-');
} catch (error) {
console.warn(
`Warning: Failed to detect linux-musl, fallback to linux-gnu: ${error.message}`
);
return false;
}
}

/** The full command for the embedded compiler executable. */
export const compilerCommand = (() => {
Expand Down
97 changes: 48 additions & 49 deletions lib/src/elf.ts
View file
Original file line number Diff line number Diff line change
Expand Up @@ -4,10 +4,8 @@

import * as fs from 'fs';

/**
* Read chunk of data from a file descriptor into a new Buffer.
*/
const readFileDescriptor = function (
/** Read a chunk of data from a file descriptor into a new Buffer. */
function readFileDescriptor(
fd: number,
position: number,
length: number
Expand All @@ -26,74 +24,75 @@ const readFileDescriptor = function (
offset += bytesRead;
}
return buffer;
};
}

/**
* Parse an ELF file and return its interpreter.
*/
export const getELFInterpreter = function (path: string): string {
/** Parse an ELF file and return its interpreter. */
export function getElfInterpreter(path: string): string {
const fd = fs.openSync(path, 'r');
try {
const eIdent = new DataView(readFileDescriptor(fd, 0, 64).buffer);
const elfIdentification = new DataView(
readFileDescriptor(fd, 0, 64).buffer
);

if (
eIdent.getUint8(0) !== 0x7f ||
eIdent.getUint8(1) !== 0x45 ||
eIdent.getUint8(2) !== 0x4c ||
eIdent.getUint8(3) !== 0x46
elfIdentification.getUint8(0) !== 0x7f ||
elfIdentification.getUint8(1) !== 0x45 ||
elfIdentification.getUint8(2) !== 0x4c ||
elfIdentification.getUint8(3) !== 0x46
) {
throw new Error(`${path} is not an elf file.`);
throw new Error(`${path} is not an ELF file.`);
}

const eIdentClass = eIdent.getUint8(4);
if (eIdentClass !== 1 && eIdentClass !== 2) {
throw new Error(`${path} has an invalid elf class.`);
const elfIdentificationClass = elfIdentification.getUint8(4);
if (elfIdentificationClass !== 1 && elfIdentificationClass !== 2) {
throw new Error(`${path} has an invalid ELF class.`);
}
const class32 = eIdentClass === 1;
const class32 = elfIdentificationClass === 1;

const eIdentData = eIdent.getUint8(5);
if (eIdentData !== 1 && eIdentData !== 2) {
const elfIdentificationData = elfIdentification.getUint8(5);
if (elfIdentificationData !== 1 && elfIdentificationData !== 2) {
throw new Error(`${path} has an invalid endianness.`);
}
const littleEndian = eIdentData === 1;
const littleEndian = elfIdentificationData === 1;

const e_phoff = class32
? eIdent.getUint32(28, littleEndian)
: Number(eIdent.getBigUint64(32, littleEndian));
const e_phentsize = class32
? eIdent.getUint16(42, littleEndian)
: eIdent.getUint16(54, littleEndian);
const e_phnum = class32
? eIdent.getUint16(44, littleEndian)
: eIdent.getUint16(56, littleEndian);
// Converting BigUint64 to Number because node Buffer length has to be
// number type, and we don't expect any elf we check with this method to
// be larger than 9007199254740991 bytes.
const ePhoff = class32
? elfIdentification.getUint32(28, littleEndian)
: Number(elfIdentification.getBigUint64(32, littleEndian));
const ePhentsize = class32
? elfIdentification.getUint16(42, littleEndian)
: elfIdentification.getUint16(54, littleEndian);
const ePhnum = class32
? elfIdentification.getUint16(44, littleEndian)
: elfIdentification.getUint16(56, littleEndian);

const proghdrs = new DataView(
readFileDescriptor(fd, e_phoff, e_phentsize * e_phnum).buffer
const programHeaders = new DataView(
readFileDescriptor(fd, ePhoff, ePhentsize * ePhnum).buffer
);
for (let i = 0; i < e_phnum; i++) {
const byteOffset = i * e_phentsize;
const p_type = proghdrs.getUint32(byteOffset, littleEndian);
if (p_type !== 3) {
continue;
}
for (let i = 0; i < ePhnum; i++) {
const byteOffset = i * ePhentsize;
const pType = programHeaders.getUint32(byteOffset, littleEndian);
if (pType !== 3) continue; // 3 is PT_INTERP, the interpreter

const p_offset = class32
? proghdrs.getUint32(byteOffset + 4, littleEndian)
: Number(proghdrs.getBigUint64(byteOffset + 8, littleEndian));
const p_filesz = class32
? proghdrs.getUint32(byteOffset + 16, littleEndian)
: Number(proghdrs.getBigUint64(byteOffset + 32, littleEndian));
const pOffset = class32
? programHeaders.getUint32(byteOffset + 4, littleEndian)
: Number(programHeaders.getBigUint64(byteOffset + 8, littleEndian));
const pFilesz = class32
? programHeaders.getUint32(byteOffset + 16, littleEndian)
: Number(programHeaders.getBigUint64(byteOffset + 32, littleEndian));

const buffer = readFileDescriptor(fd, p_offset, p_filesz);
if (buffer[p_filesz - 1] !== 0) {
const buffer = readFileDescriptor(fd, pOffset, pFilesz);
if (buffer[pFilesz - 1] !== 0) {
throw new Error(`${path} is corrupted.`);
}

return buffer.toString('utf8', 0, p_filesz - 1);
return buffer.toString('utf8', 0, pFilesz - 1);
}

throw new Error(`${path} does not contain an interpreter entry.`);
} finally {
fs.closeSync(fd);
}
};
}

0 comments on commit fa91d91

Please sign in to comment.