base+su+libc: Add support for a shadow file and use it by default

apps/su.cpp

@@ -3,6 +3,7 @@
 #include <grp.h>
 #include <os/ArgumentParser.h>
 #include <pwd.h>
+#include <shadow.h>
 #include <signal.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ -148,7 +149,25 @@ Result<int> luna_main(int argc, char** argv)
     {
         signal(SIGTTOU, SIG_IGN);
 
-        if (!strcmp(entry->pw_passwd, "!"))
+        const char* passwd = entry->pw_passwd;
+
+        // If the user's password entry is 'x', read their password from the shadow file instead.
+        if (!strcmp(entry->pw_passwd, "x"))
+        {
+            struct spwd* sp = getspnam(name.chars());
+
+            if (!sp)
+            {
+                fprintf(stderr, "%s: user %s not found in shadow file!\n", argv[0], name.chars());
+                return 1;
+            }
+
+            endspent();
+
+            passwd = sp->sp_pwdp;
+        }
+
+        if (!strcmp(passwd, "!"))
         {
             fprintf(stderr, "%s: %s's password is disabled!\n", argv[0], entry->pw_name);
             return 1;
@@ -157,7 +176,7 @@ Result<int> luna_main(int argc, char** argv)
         char* pass = getpass();
         if (!pass) return 1;
 
-        if (strcmp(pass, entry->pw_passwd))
+        if (strcmp(pass, passwd))
         {
             fprintf(stderr, "%s: wrong password!\n", argv[0]);
             return 1;

base/etc/passwd

@@ -1,3 +1,3 @@
-root:toor:0:0:Administrator:/:/usr/bin/sh
+root:x:0:0:Administrator:/:/usr/bin/sh
-wind:!:2:2:Window Manager:/:/usr/bin/init
+wind:x:2:2:Window Manager:/:/usr/bin/init
-selene:moon:1000:1000:User:/home/selene:/usr/bin/sh
+selene:x:1000:1000:User:/home/selene:/usr/bin/sh

base/etc/shadow

@@ -0,0 +1,3 @@
+root:toor:0:0:99999:7:::
+wind:!:0:0:99999:7:::
+selene:moon:0:0:99999:7:::

libc/CMakeLists.txt

@@ -27,6 +27,7 @@ set(SOURCES
     src/math.cpp
     src/pty.cpp
     src/utmp.cpp
+    src/shadow.cpp
     src/sys/stat.cpp
     src/sys/mman.cpp
     src/sys/wait.cpp

libc/include/shadow.h

@@ -0,0 +1,48 @@
+/* shadow.h: Password file parsing. */
+
+#ifndef _SHADOW_H
+#define _SHADOW_H
+
+#include <stdio.h>
+
+struct spwd
+{
+    char* sp_namp;
+    char* sp_pwdp;
+    long sp_lstchg;
+    long sp_min;
+    long sp_max;
+    long sp_warn;
+    long sp_inact;
+    long sp_expire;
+    unsigned long sp_flag;
+};
+
+#ifdef __cplusplus
+extern "C"
+{
+#endif
+
+    /* Read the next entry from the shadow file. */
+    struct spwd* getspent();
+
+    /* Find the entry with a matching username in the shadow file. */
+    struct spwd* getspnam(const char* name);
+
+    /* Read the next entry from the shadow file (reentrant version). */
+    int getspent_r(struct spwd* spbuf, char* buf, size_t buflen, struct spwd** spbufp);
+
+    /* Read the next entry from a shadow file (reentrant version). */
+    int fgetspent_r(FILE* stream, struct spwd* spbuf, char* buf, size_t buflen, struct spwd** spbufp);
+
+    /* Rewind the shadow file. */
+    void setspent(void);
+
+    /* End shadow file parsing. */
+    void endspent(void);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif

libc/src/shadow.cpp

@@ -0,0 +1,116 @@
+#include <fcntl.h>
+#include <shadow.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+static struct spwd spwd;
+static FILE* f { nullptr };
+static char s_buf[4096];
+
+extern char* _strtok_once(char* str, const char* delim);
+
+extern "C"
+{
+    struct spwd* getspent()
+    {
+        struct spwd* result;
+
+        getspent_r(&spwd, s_buf, sizeof(s_buf), &result);
+
+        return result;
+    }
+
+    int getspent_r(struct spwd* spbuf, char* buf, size_t buflen, struct spwd** spbufp)
+    {
+        *spbufp = nullptr;
+
+        if (!f)
+        {
+            f = fopen("/etc/shadow", "r");
+            if (!f) return 0;
+            fcntl(fileno(f), F_SETFD, FD_CLOEXEC);
+        }
+
+        return fgetspent_r(f, spbuf, buf, buflen, spbufp);
+    }
+
+    int fgetspent_r(FILE* stream, struct spwd* spbuf, char* buf, size_t buflen, struct spwd** spbufp)
+    {
+        *spbufp = nullptr;
+
+        while (true)
+        {
+            char* rc = fgets(buf, buflen, stream);
+            if (!rc) return -1;
+
+            char* name = _strtok_once(rc, ":\n");
+            if (!name) continue;
+
+            char* passwd = _strtok_once(nullptr, ":\n");
+            if (!passwd) continue;
+
+            char* lstchg = _strtok_once(nullptr, ":\n");
+            if (!lstchg) continue;
+
+            char* min = _strtok_once(nullptr, ":\n");
+            if (!min) continue;
+
+            char* max = _strtok_once(nullptr, ":\n");
+            if (!max) continue;
+
+            char* warn = _strtok_once(nullptr, ":\n");
+            if (!warn) continue;
+
+            char* inact = _strtok_once(nullptr, ":\n");
+            if (!inact) continue;
+
+            char* expire = _strtok_once(nullptr, ":\n");
+            if (!expire) continue;
+
+            char* flag = _strtok_once(nullptr, ":\n");
+            if (!flag) continue;
+
+            spbuf->sp_namp = name;
+            spbuf->sp_pwdp = passwd;
+            spbuf->sp_lstchg = (long)strtol(lstchg, nullptr, 10);
+            spbuf->sp_min = (long)strtol(min, nullptr, 10);
+            spbuf->sp_max = (long)strtol(max, nullptr, 10);
+            spbuf->sp_warn = (long)strtol(warn, nullptr, 10);
+            spbuf->sp_inact = (long)strtol(inact, nullptr, 10);
+            spbuf->sp_expire = (long)strtol(expire, nullptr, 10);
+            spbuf->sp_flag = (unsigned long)strtoul(flag, nullptr, 10);
+
+            *spbufp = spbuf;
+            return 0;
+        }
+    }
+
+    struct spwd* getspnam(const char* name)
+    {
+        setspent();
+
+        struct spwd* entry;
+
+        while ((entry = getspent()))
+        {
+            if (!strcmp(entry->sp_namp, name)) { return entry; }
+        }
+
+        return entry;
+    }
+
+    void setspent()
+    {
+        if (f) rewind(f);
+    }
+
+    void endspent()
+    {
+        if (f)
+        {
+            fclose(f);
+            f = nullptr;
+        }
+    }
+}

tools/install.sh

@@ -17,6 +17,8 @@ cmake --install $LUNA_BUILD_DIR
 
 chmod a+s base/usr/bin/su
 
+chmod 600 base/etc/shadow
+
 mkdir -p base/home/selene
 
 mkdir -p base/dev