tcb_chkpwd: Enhance the functionality of the helper program.

The tcb_chkpwd helper binary is now able to also perform verifications
for the expiration of user accounts.

Signed-off-by: Björn Esser <[email protected]>

Author: besser82

ChangeLog

@@ -114,6 +114,8 @@
 	around unix_run_helper_binary().
 	* pam_tcb/support.c (unix_verify_password_plain):
 	Replace call to unix_run_helper_binary() with run_chkpwd_binary().
+	* progs/tcb_chkpwd.c: Refactor the helper program to also perform
+	verifications for the expiration of user accounts.
 
 2021-09-30  Björn Esser  <besser82 at fedoraproject.org>
 

progs/tcb_chkpwd.c

@@ -12,6 +12,7 @@
 #include <string.h>
 #include <unistd.h>
 #include <syslog.h>
+#include <time.h>
 #include <pwd.h>
 #include <shadow.h>
 
@@ -25,12 +26,90 @@ IO_LOOP(write_loop, write, const)
 #define AUTH_PASSED			TCB_MAGIC
 #define AUTH_FAILED			1
 
+enum {
+	ACCT_0 = 0,
+	ACCT_1,
+	ACCT_2,
+	ACCT_3,
+	ACCT_4,
+	ACCT_5,
+	ACCT_6,
+	ACCT_7,
+	ACCT_SUCCESS = 255
+};
+
 static void zeroise(char *str)
 {
 	while (*str)
 		*(str++) = '\0';
 }
 
+static int unix_getspnam(struct spwd **spw, const struct passwd *pw, int shadow)
+{
+	if (shadow) {
+		*spw = getspnam(pw->pw_name);
+		endspent();
+		return 0;
+	}
+
+	return 1;
+}
+
+static int acct_shadow(const void *void_user, int shadow)
+{
+	int daysleft;
+	time_t curdays;
+	const char *user = void_user;
+	struct passwd *pw;
+	struct spwd *spw = NULL;
+
+	pw = getpwnam(user);
+	endpwent();
+	if (pw) {
+		uid_t uid = getuid();
+		if (uid != pw->pw_uid && uid != 0)
+			return ACCT_1;
+	}
+	if (!pw)
+		return ACCT_1; /* shouldn't happen */
+	if (!shadow && strcmp(pw->pw_passwd, "x")
+	    && strcmp(pw->pw_passwd, "*NP*"))
+		return ACCT_SUCCESS;
+
+	if (unix_getspnam(&spw, pw, shadow))
+		return ACCT_1;
+
+	if (!spw)
+		return ACCT_2;
+
+	curdays = time(NULL) / (60 * 60 * 24);
+	syslog(LOG_DEBUG, "today is %ld, last change %ld",
+		curdays, spw->sp_lstchg);
+	if ((curdays > spw->sp_expire) && (spw->sp_expire != -1))
+		return ACCT_3;
+
+	if ((curdays > (spw->sp_lstchg + spw->sp_max + spw->sp_inact)) &&
+	    (spw->sp_max != -1) && (spw->sp_inact != -1) &&
+	    (spw->sp_lstchg != 0))
+		return ACCT_4;
+
+	syslog(LOG_DEBUG, "when was the last change");
+	if (spw->sp_lstchg == 0)
+		return ACCT_5;
+
+	if (((spw->sp_lstchg + spw->sp_max) < curdays) &&
+	    (spw->sp_max != -1))
+		return ACCT_6;
+
+	if ((curdays > (spw->sp_lstchg + spw->sp_max - spw->sp_warn)) &&
+	    (spw->sp_max != -1) && (spw->sp_warn != -1)) {
+		daysleft = (spw->sp_lstchg + spw->sp_max) - curdays;
+		return ACCT_7 + 256 * daysleft;
+	}
+
+	return ACCT_SUCCESS;
+}
+
 static int unix_verify_password(const char *user, const char *pass, int nullok)
 {
 	struct passwd *pw;
@@ -89,27 +168,36 @@ static int is_two_strings(char *data, unsigned int len)
 	return (1 + strlen(data) < len);
 }
 
-int main(void)
+static int acctverify(int shadow)
 {
-	char option[8];
-	char userandpass[MAX_DATA_LENGTH + 1];
-	int datalen, nullok, retval;
+	int datalen, retval;
+	char username[MAX_DATA_LENGTH + 1];
 
-	openlog("tcb_chkpwd", LOG_CONS | LOG_PID, LOG_AUTH);
+	retval = ACCT_0;
 
-	if (isatty(STDIN_FILENO) || isatty(STDOUT_FILENO)) {
-		syslog(LOG_NOTICE, "inappropriate use by UID %d", getuid());
-		return 1;
-	}
+	/* read the user from stdin (a pipe from the PAM module) */
+	datalen = read_loop(STDIN_FILENO, username, MAX_DATA_LENGTH);
+	if (datalen < 0)
+		syslog(LOG_DEBUG, "no username supplied");
+	else if (datalen >= MAX_DATA_LENGTH)
+		syslog(LOG_DEBUG, "username too long");
+	else
+		retval = acct_shadow(username, shadow);
 
-	/* read the nullok/nonull option */
-	memset(option, 0, sizeof(option));
-	if (read_loop(STDIN_FILENO, option, sizeof(option)) <= 0) {
-		syslog(LOG_DEBUG, "no option supplied");
+	memset(username, 0, sizeof(username));
+
+	/* return pass or fail */
+	if (write_loop(STDOUT_FILENO, (char *)&retval, sizeof(retval)) ==
+	    sizeof(retval))
+		return retval == ACCT_SUCCESS ? 0 : 1;
+	else
 		return 1;
-	}
-	option[sizeof(option) - 1] = '\0';
-	nullok = !strcmp(option, "nullok");
+}
+
+static int passverify(int nullok)
+{
+	int datalen, retval;
+	char userandpass[MAX_DATA_LENGTH + 1];
 
 	retval = AUTH_FAILED;
 
@@ -134,3 +222,38 @@ int main(void)
 	else
 		return 1;
 }
+
+int main(int argc, char* argv[])
+{
+	char option[8];
+	int flag, retval = 1;
+
+	openlog("tcb_chkpwd", LOG_CONS | LOG_PID, LOG_AUTH);
+
+	if (argc != 2 || isatty(STDIN_FILENO) || isatty(STDOUT_FILENO)) {
+		syslog(LOG_NOTICE, "inappropriate use by UID %d", getuid());
+		goto out;
+	}
+
+	/* read the applicable option from pipe */
+	memset(option, 0, sizeof(option));
+	if (read_loop(STDIN_FILENO, option, sizeof(option)) <= 0) {
+		syslog(LOG_DEBUG, "no option supplied");
+		goto out;
+	}
+	option[sizeof(option) - 1] = '\0';
+
+	if (!strcmp(argv[1], "chkacct")) {
+		flag = !strcmp(option, "shadow");
+		retval = acctverify(flag);
+		goto out;
+	}
+
+	if (!strcmp(argv[1], "chkpwd")) {
+		flag = !strcmp(option, "nullok");
+		retval = passverify(flag);
+	}
+
+out:
+	return retval;
+}