user: a primitive login utility

1 files changed, 95 insertions, 0 deletions

diff --git a/src/user/app/login/login.c b/src/user/app/login/login.c
new file mode 100644
index 0000000..c1fab3f
--- /dev/null
+++ b/src/user/app/login/login.c
@@ -0,0 +1,95 @@
+#include <camellia/flags.h>
+#include <camellia/syscalls.h>
+#include <errno.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+#include <user/lib/fs/misc.h>
+
+static const char *shell = "/bin/shell";
+
+static void cutspace(char *s) {
+	for (; *s; s++) {
+		if (isspace(*s)) {
+			*s = '\0';
+			break;
+		}
+	}
+}
+
+static bool accesscheck(const char *path) {
+	const char *prefix = "/Users/";
+	if (strlen(path) < strlen(prefix) || memcmp(path, prefix, strlen(prefix)))
+		return true; /* not an user dir - access allowed */
+	path += strlen(prefix);
+
+	/* skip username */
+	path = strchr(path, '/');
+	if (!path) return true;
+	path++;
+
+	/* inside an user dir */
+	const char *private = "private/";
+	return strlen(path) < strlen(private) || memcmp(path, private, strlen(private));
+}
+
+static void drv(const char *prefix) {
+	struct fs_wait_response res;
+	size_t prefixlen = strlen(prefix);
+	char buf[128];
+	while (!_syscall_fs_wait(buf, sizeof buf, &res)) {
+		switch (res.op) {
+			handle_t h;
+			case VFSOP_OPEN:
+				if (res.len == sizeof buf) {
+					_syscall_fs_respond(NULL, -1, 0);
+					break;
+				}
+				buf[res.len] = '\0';
+
+				if (res.len >= prefixlen && !memcmp(prefix, buf, prefixlen)) {
+					h = _syscall_open(buf, res.len, res.flags);
+				} else if (accesscheck(buf)) {
+					h = _syscall_open(buf, res.len, res.flags | OPEN_RO);
+				} else {
+					h = -EACCES;
+				}
+				_syscall_fs_respond(NULL, h, FSR_DELEGATE);
+				break;
+
+			default:
+				_syscall_fs_respond(NULL, -1, 0);
+				break;
+		}
+	}
+}
+
+static void trylogin(const char *user) {
+	if (strcmp(user, "root")) {
+		char buf[128];
+		snprintf(buf, sizeof buf, "/Users/%s/", user);
+		if (chdir(buf) < 0) {
+			printf("no such user: %s\n", user);
+			return;
+		}
+		MOUNT_AT("/") { drv(buf); }
+	}
+
+	execv(shell, NULL);
+	fprintf(stderr, "login: couldn't launch %s\n", shell);
+	exit(1);
+}
+
+int main(void) {
+	char user[64];
+	printf("\nCamellia\n");
+	for (;;) {
+		printf("login: ");
+		fgets(user, sizeof user, stdin);
+		if (ferror(stdin)) return -1;
+
+		cutspace(user);
+		if (user[0]) trylogin(user);
+	}
+}