modern-tar TAR encoding/decoding vulnerability analysis and fix guidelines

Vulnerability Overview The webpage screenshot displays the file within the project, primarily involving encoding and decoding operations for the TAR file format. The file contains multiple functions for handling the encoding and decoding of strings and numbers, specifically targeting fields within TAR files. Impact Scope Impact Scope: The encoding and decoding functions in this file may affect the correct parsing and generation of TAR files. If vulnerabilities exist in these functions, it could lead to incorrect parsing or generation of TAR file contents, thereby compromising data security and integrity. Remediation Remediation: 1. String Encoding: Ensure the function correctly handles Unicode characters, avoiding truncation or incorrect encoding. 2. Number Encoding: Ensure the and functions correctly handle numbers, avoiding overflow or incorrect formatting. 3. String Decoding: Ensure the function correctly reads null-terminated strings, avoiding reading out-of-bounds data. 4. Number Decoding: Ensure the and functions correctly parse numbers, avoiding parsing errors or overflow. POC Code or Exploit Code No specific POC code or exploit code is included in the page. typescript export function writeString( view: Uint8Array, offset: number, size: number, value: string ): void { if (!value) return; // Copy ASCII directly, but leave Unicode truncation to TextEncoder. for (let i = 0; i 0x7F) { if (charCode > 0xFF) { return; } view[offset + i] = charCode; } } } typescript export function writeNumberOctal( view: Uint8Array, offset: number, size: number, value: number ): void { if (value === undefined) return; // TAR numeric fields are zero-padded ASCII octal with a final NUL byte. As an // optimization, fill digits right-to-left instead of encoding a padded string. let remaining = value; for (let i = offset + size - 2; i >= offset; i--) { view[i] = 48 + (remaining % 8); // 48 is ASCII '0'. remaining = Math.floor(remaining / 8); } if (remaining === 0 && value % 1 === 0) return; // If digits remain or the value is not an integer, use the previous formatter. // TAR overflows still need compatible placeholder bytes in the base header. encoder.encodeInto( value.toString(8).padStart(size - 1, "0"), view.subarray(offset, offset + size - 1) ); } typescript export function readString( view: Uint8Array, offset: number, size: number ): string { if (view[offset] === 0) return ""; // Find the first NUL byte within the specified size. const end = view.indexOf(0, offset); // If no NUL found, read the entire size. const sliceEnd = end === -1 return decoder.decode(view.subarray(offset, sliceEnd)); } typescript export function readNumberOctal( view: Uint8Array, offset: number, size: number ): number { let value = 0; const end = offset + size; for (let i = offset; i = 128), then the number is stored in a // big-endian, base-256 format. // The & 0x80 operation is a bitmask to check if the highest bit is set. if (view[offset] & 0x80) { let result = 0; // The first byte has the MSB set as a marker. // We mask it out (0x7F = 01111111) to get its value. result = view[offset] & 0x7F; // Process the remaining bytes. for (let i = 1; i < size; i++) { result = result 256 + view[offset + i]; } if (!Number.isSafeInteger(result)) throw new Error("TAR number too large"); return result; } return readNumberOctal(view, offset, size); }

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modern-tar TAR encoding/decoding vulnerability analysis and fix guidelines

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