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LibCore: Define and use a fallible, OS-independent getpwent(_r) wrapper

Rather than maintaining a list of #ifdef guards to check systems that do
not provide the reentrant version of getpwent, we can use C++ concepts
to let the compiler perform this check for us.

While we're at it, we can also provide this wrapper as fallible to let
the caller TRY calling it.
This commit is contained in:
Timothy Flynn 2022-12-13 14:49:32 -05:00 committed by Tim Flynn
parent b367da592c
commit 1ee808fae6
3 changed files with 58 additions and 27 deletions

View file

@ -128,40 +128,31 @@ ErrorOr<Account> Account::from_uid(uid_t uid, [[maybe_unused]] Read options)
ErrorOr<Vector<Account>> Account::all([[maybe_unused]] Read options)
{
Vector<Account> accounts;
#ifndef AK_OS_MACOS
struct passwd pwd;
struct passwd* ptr = nullptr;
char buffer[1024] = { 0 };
#endif
ScopeGuard pwent_guard([] { endpwent(); });
setpwent();
errno = 0;
#ifndef AK_OS_MACOS
while (getpwent_r(&pwd, buffer, sizeof(buffer), &ptr) == 0 && ptr) {
#else
while (auto const* ptr = getpwent()) {
#endif
while (true) {
auto pwd = TRY(Core::System::getpwent({ buffer, sizeof(buffer) }));
if (!pwd.has_value())
break;
spwd spwd = {};
#ifndef AK_OS_BSD_GENERIC
ScopeGuard spent_guard([] { endspent(); });
if (options != Read::PasswdOnly) {
auto maybe_spwd = TRY(Core::System::getspnam({ ptr->pw_name, strlen(ptr->pw_name) }));
auto maybe_spwd = TRY(Core::System::getspnam({ pwd->pw_name, strlen(pwd->pw_name) }));
if (!maybe_spwd.has_value())
return Error::from_string_literal("No shadow entry for user");
spwd = maybe_spwd.release_value();
}
#endif
accounts.append({ *ptr, spwd, get_extra_gids(*ptr) });
accounts.append({ *pwd, spwd, get_extra_gids(*pwd) });
}
if (errno)
return Error::from_errno(errno);
return accounts;
}
@ -226,13 +217,17 @@ Account::Account(passwd const& pwd, spwd const& spwd, Vector<gid_t> extra_gids)
ErrorOr<DeprecatedString> Account::generate_passwd_file() const
{
StringBuilder builder;
char buffer[1024] = { 0 };
ScopeGuard pwent_guard([] { endpwent(); });
setpwent();
struct passwd* p;
errno = 0;
while ((p = getpwent())) {
if (p->pw_name == m_username) {
while (true) {
auto pwd = TRY(Core::System::getpwent({ buffer, sizeof(buffer) }));
if (!pwd.has_value())
break;
if (pwd->pw_name == m_username) {
builder.appendff("{}:!:{}:{}:{}:{}:{}\n",
m_username,
m_uid, m_gid,
@ -242,15 +237,11 @@ ErrorOr<DeprecatedString> Account::generate_passwd_file() const
} else {
builder.appendff("{}:!:{}:{}:{}:{}:{}\n",
p->pw_name, p->pw_uid,
p->pw_gid, p->pw_gecos, p->pw_dir,
p->pw_shell);
pwd->pw_name, pwd->pw_uid,
pwd->pw_gid, pwd->pw_gecos, pwd->pw_dir,
pwd->pw_shell);
}
}
endpwent();
if (errno)
return Error::from_errno(errno);
return builder.to_deprecated_string();
}

View file

@ -52,6 +52,40 @@ static int memfd_create(char const* name, unsigned int flags)
} \
return success_value;
// clang-format off
template<typename T>
concept SupportsReentrantGetpwent = requires(T passwd, T* ptr)
{
getpwent_r(&passwd, nullptr, 0, &ptr);
};
// clang-format on
// Note: This has to be in the global namespace for the extern declaration to trick the compiler
// into finding a declaration of getpwent_r when it doesn't actually exist.
static ErrorOr<Optional<struct passwd>> getpwent_impl(Span<char> buffer)
{
if constexpr (SupportsReentrantGetpwent<struct passwd>) {
struct passwd passwd;
struct passwd* ptr = nullptr;
extern int getpwent_r(struct passwd*, char*, size_t, struct passwd**);
auto result = getpwent_r(&passwd, buffer.data(), buffer.size(), &ptr);
if (result == 0 && ptr)
return passwd;
if (result != 0 && result != ENOENT)
return Error::from_errno(result);
} else {
errno = 0;
if (auto const* passwd = ::getpwent())
return *passwd;
if (errno)
return Error::from_errno(errno);
}
return Optional<struct passwd> {};
}
namespace Core::System {
#ifndef HOST_NAME_MAX
@ -627,6 +661,11 @@ ErrorOr<void> chown(StringView pathname, uid_t uid, gid_t gid)
#endif
}
ErrorOr<Optional<struct passwd>> getpwent(Span<char> buffer)
{
return getpwent_impl(buffer);
}
ErrorOr<Optional<struct passwd>> getpwuid(uid_t uid)
{
errno = 0;

View file

@ -122,6 +122,7 @@ ErrorOr<int> tcsetpgrp(int fd, pid_t pgrp);
ErrorOr<void> chmod(StringView pathname, mode_t mode);
ErrorOr<void> lchown(StringView pathname, uid_t uid, gid_t gid);
ErrorOr<void> chown(StringView pathname, uid_t uid, gid_t gid);
ErrorOr<Optional<struct passwd>> getpwent(Span<char> buffer);
ErrorOr<Optional<struct passwd>> getpwnam(StringView name);
ErrorOr<Optional<struct group>> getgrnam(StringView name);
ErrorOr<Optional<struct passwd>> getpwuid(uid_t);