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LibArchive: Support POSIX.1-1988 tar files

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These old tar files didn't have magic numbers, so I've also added a checksum
check to TarInputStream::valid()
This commit is contained in:
Peter Elliott 2021-04-04 18:29:47 -06:00 • committed by Andreas Kling
parent a09421f1be
commit dcee024fee
2 changed files with 33 additions and 11 deletions
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35
Userland/Libraries/LibArchive/Tar.h
View file

@ -49,10 +49,12 @@ enum class TarFileType : char {
};
constexpr size_t block_size = 512;
constexpr const char* gnu_magic = "ustar "; // gnu format magic
constexpr const char* gnu_version = " "; // gnu format version
constexpr const char* ustar_magic = "ustar"; // ustar format magic
constexpr const char* ustar_version = "00"; // ustar format version
constexpr const char* gnu_magic = "ustar "; // gnu format magic
constexpr const char* gnu_version = " "; // gnu format version
constexpr const char* ustar_magic = "ustar"; // ustar format magic
constexpr const char* ustar_version = "00"; // ustar format version
constexpr const char* posix1_tar_magic = ""; // POSIX.1-1988 format magic
constexpr const char* posix1_tar_version = ""; // POSIX.1-1988 format version
class [[gnu::packed]] TarFileHeader {
public:
@ -63,6 +65,7 @@ public:
// FIXME: support 2001-star size encoding
size_t size() const { return get_tar_field(m_size); }
time_t timestamp() const { return get_tar_field(m_timestamp); }
unsigned checksum() const { return get_tar_field(m_checksum); }
TarFileType type_flag() const { return TarFileType(m_type_flag); }
const StringView link_name() const { return m_link_name; }
const StringView magic() const { return StringView(m_magic, min(__builtin_strlen(m_magic), sizeof(m_magic))); } // in some cases this is a null terminated string, in others its not
@ -90,6 +93,7 @@ public:
void set_minor(int minor) { VERIFY(String::formatted("{:o}", minor).copy_characters_to_buffer(m_minor, sizeof(m_minor))); }
void set_prefix(const String& prefix) { VERIFY(prefix.copy_characters_to_buffer(m_prefix, sizeof(m_prefix))); }
unsigned expected_checksum() const;
void calculate_checksum();
private:
@ -128,14 +132,25 @@ size_t TarFileHeader::get_tar_field(const char (&field)[N])
}
return value;
}
unsigned TarFileHeader::expected_checksum() const
{
auto checksum = 0u;
const u8* u8_this = reinterpret_cast<const u8*>(this);
const u8* u8_m_checksum = reinterpret_cast<const u8*>(&m_checksum);
for (auto i = 0u; i < sizeof(TarFileHeader); ++i) {
if (u8_this + i >= u8_m_checksum && u8_this + i < u8_m_checksum + sizeof(m_checksum)) {
checksum += ' ';
} else {
checksum += u8_this[i];
}
}
return checksum;
}
void TarFileHeader::calculate_checksum()
{
memset(m_checksum, ' ', sizeof(m_checksum));
auto checksum = 0u;
for (auto i = 0u; i < sizeof(TarFileHeader); ++i) {
checksum += ((unsigned char*)this)[i];
}
VERIFY(String::formatted("{:o}", checksum).copy_characters_to_buffer(m_checksum, sizeof(m_checksum)));
VERIFY(String::formatted("{:06o}", expected_checksum()).copy_characters_to_buffer(m_checksum, sizeof(m_checksum)));
}
}

9
Userland/Libraries/LibArchive/TarStream.cpp
View file

@ -125,7 +125,14 @@ bool TarInputStream::valid() const
{
auto& header_magic = header().magic();
auto& header_version = header().version();
return (header_magic == gnu_magic && header_version == gnu_version) || (header_magic == ustar_magic && header_version == ustar_version);
if (!((header_magic == gnu_magic && header_version == gnu_version)
|| (header_magic == ustar_magic && header_version == ustar_version)
|| (header_magic == posix1_tar_magic && header_version == posix1_tar_version)))
return false;
// POSIX.1-1988 tar does not have magic numbers, so we also neet to verify the header checksum.
return header().checksum() == header().expected_checksum();
}
TarFileStream TarInputStream::file_contents()