From 668c4c897671ed9d8a2836829c0e2744289d1a38 Mon Sep 17 00:00:00 2001
From: Bananymous <oskari.alaranta@bananymous.com>
Date: Wed, 3 Jan 2024 00:14:49 +0200
Subject: [PATCH] LibC: Implement getgrnam and getgrgid

---
 libc/CMakeLists.txt |   1 +
 libc/grp.cpp        | 162 ++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 163 insertions(+)
 create mode 100644 libc/grp.cpp

diff --git a/libc/CMakeLists.txt b/libc/CMakeLists.txt
index c7e3a21d..3b2d634d 100644
--- a/libc/CMakeLists.txt
+++ b/libc/CMakeLists.txt
@@ -7,6 +7,7 @@ set(LIBC_SOURCES
 	ctype.cpp
 	dirent.cpp
 	fcntl.cpp
+	grp.cpp
 	malloc.cpp
 	printf_impl.cpp
 	pwd.cpp
diff --git a/libc/grp.cpp b/libc/grp.cpp
new file mode 100644
index 00000000..b7547ee0
--- /dev/null
+++ b/libc/grp.cpp
@@ -0,0 +1,162 @@
+#include <BAN/StringView.h>
+#include <BAN/Vector.h>
+
+#include <ctype.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <grp.h>
+#include <stdlib.h>
+#include <sys/mman.h>
+#include <sys/types.h>
+
+static struct stat s_group_st;
+static char* s_group_mmap = nullptr;
+static int s_group_fd = -1;
+
+static struct group s_group;
+
+id_t parse_id(BAN::StringView string)
+{
+	id_t id = 0;
+	for (char c : string)
+	{
+		if (!isdigit(c))
+			return -1;
+		id = (id * 10) + (c - '0');
+	}
+	return id;
+}
+
+static bool open_group_file()
+{
+	if (s_group_fd == -1)
+		s_group_fd = open("/etc/group", O_RDONLY);
+	if (s_group_fd == -1)
+		return false;
+
+	if (fstat(s_group_fd, &s_group_st) == -1)
+		return false;
+
+	if (s_group_mmap == nullptr || s_group_mmap == MAP_FAILED)
+		s_group_mmap = (char*)mmap(nullptr, s_group_st.st_size, PROT_READ, MAP_PRIVATE, s_group_fd, 0);
+	if (s_group_mmap == MAP_FAILED)
+		return false;
+
+	s_group.gr_name = nullptr;
+	s_group.gr_mem = nullptr;
+
+	return true;
+}
+
+struct group* fill_group(const BAN::Vector<BAN::StringView>& parts)
+{
+	if (parts.size() != 4)
+		return nullptr;
+
+	if (s_group.gr_name)
+	{
+		free(s_group.gr_name);
+		s_group.gr_name = nullptr;
+	}
+
+	if (s_group.gr_mem)
+	{
+		for (size_t i = 0; s_group.gr_mem && s_group.gr_mem[i]; i++)
+			free(s_group.gr_mem[i]);
+		free(s_group.gr_mem);
+		s_group.gr_mem = nullptr;
+	}
+
+	auto groups_or_error = parts[3].split(',');	
+	if (groups_or_error.is_error())
+		return nullptr;
+	auto groups = groups_or_error.release_value();
+
+	s_group.gr_gid = parse_id(parts[2]);
+	if (s_group.gr_gid == -1)
+		return nullptr;
+
+	s_group.gr_name = (char*)malloc(parts[0].size() + 1);
+	if (s_group.gr_name == nullptr)
+		return nullptr;
+	memcpy(s_group.gr_name, parts[0].data(), parts[0].size());	
+	s_group.gr_name[parts[0].size()] = '\0';
+
+	s_group.gr_mem = (char**)malloc((groups.size() + 1) * sizeof(char*));
+	if (s_group.gr_mem == nullptr)
+		return nullptr;
+
+	for (size_t i = 0; i < groups.size(); i++)
+	{
+		s_group.gr_mem[i] = (char*)malloc(groups[i].size() + 1);
+		if (s_group.gr_mem[i] == nullptr)
+		{
+			for (size_t j = 0; j < i; j++)
+				free(s_group.gr_mem[j]);
+			free(s_group.gr_mem);
+			s_group.gr_mem = nullptr;
+			return nullptr;
+		}
+		memcpy(s_group.gr_mem[i], groups[i].data(), groups[i].size());
+		s_group.gr_mem[i][groups[i].size()] = '\0';
+	}	
+	s_group.gr_mem[groups.size()] = nullptr;
+
+	return &s_group;
+}
+
+struct group* getgrnam(const char* name)
+{
+	if (s_group_mmap == nullptr || s_group_mmap == MAP_FAILED)
+		if (!open_group_file())
+			return nullptr;
+	
+	off_t start = 0;
+	off_t end = 0;
+	while (start < s_group_st.st_size)
+	{
+		while (end < s_group_st.st_size && s_group_mmap[end] != '\n')
+			end++;
+
+		BAN::StringView line(s_group_mmap + start, end - start);
+		start = ++end;
+
+		auto parts_or_error = line.split(':', true);
+		if (parts_or_error.is_error())
+			return nullptr;
+
+		auto parts = parts_or_error.release_value();
+		if (parts.size() == 4 && parts[0] == name)
+			return fill_group(parts);
+	}
+
+	return nullptr;
+}
+
+struct group* getgrgid(gid_t gid)
+{
+	if (s_group_mmap == nullptr || s_group_mmap == MAP_FAILED)
+		if (!open_group_file())
+			return nullptr;
+	
+	off_t start = 0;
+	off_t end = 0;
+	while (start < s_group_st.st_size)
+	{
+		while (end < s_group_st.st_size && s_group_mmap[end] != '\n')
+			end++;
+
+		BAN::StringView line(s_group_mmap + start, end - start);
+		start = ++end;
+
+		auto parts_or_error = line.split(':', true);
+		if (parts_or_error.is_error())
+			return nullptr;
+
+		auto parts = parts_or_error.release_value();
+		if (parts.size() == 4 && parse_id(parts[2]) == gid)
+			return fill_group(parts);
+	}
+
+	return nullptr;
+}