1 files changed, 157 insertions, 0 deletions
diff --git a/contrib/passwordcheck/passwordcheck.c b/contrib/passwordcheck/passwordcheck.c
new file mode 100644
index 0000000..d5f9d14
--- /dev/null
+++ b/contrib/passwordcheck/passwordcheck.c
@@ -0,0 +1,157 @@
+/*-------------------------------------------------------------------------
+ *
+ * passwordcheck.c
+ *
+ *
+ * Copyright (c) 2009-2020, PostgreSQL Global Development Group
+ *
+ * Author: Laurenz Albe <laurenz.albe@wien.gv.at>
+ *
+ * IDENTIFICATION
+ *	  contrib/passwordcheck/passwordcheck.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include <ctype.h>
+
+#ifdef USE_CRACKLIB
+#include <crack.h>
+#endif
+
+#include "commands/user.h"
+#include "fmgr.h"
+#include "libpq/crypt.h"
+
+PG_MODULE_MAGIC;
+
+/* Saved hook value in case of unload */
+static check_password_hook_type prev_check_password_hook = NULL;
+
+/* passwords shorter than this will be rejected */
+#define MIN_PWD_LENGTH 8
+
+extern void _PG_init(void);
+extern void _PG_fini(void);
+
+/*
+ * check_password
+ *
+ * performs checks on an encrypted or unencrypted password
+ * ereport's if not acceptable
+ *
+ * username: name of role being created or changed
+ * password: new password (possibly already encrypted)
+ * password_type: PASSWORD_TYPE_* code, to indicate if the password is
+ *			in plaintext or encrypted form.
+ * validuntil_time: password expiration time, as a timestamptz Datum
+ * validuntil_null: true if password expiration time is NULL
+ *
+ * This sample implementation doesn't pay any attention to the password
+ * expiration time, but you might wish to insist that it be non-null and
+ * not too far in the future.
+ */
+static void
+check_password(const char *username,
+			   const char *shadow_pass,
+			   PasswordType password_type,
+			   Datum validuntil_time,
+			   bool validuntil_null)
+{
+	if (prev_check_password_hook)
+		prev_check_password_hook(username, shadow_pass,
+								 password_type, validuntil_time,
+								 validuntil_null);
+
+	if (password_type != PASSWORD_TYPE_PLAINTEXT)
+	{
+		/*
+		 * Unfortunately we cannot perform exhaustive checks on encrypted
+		 * passwords - we are restricted to guessing. (Alternatively, we could
+		 * insist on the password being presented non-encrypted, but that has
+		 * its own security disadvantages.)
+		 *
+		 * We only check for username = password.
+		 */
+		char	   *logdetail;
+
+		if (plain_crypt_verify(username, shadow_pass, username, &logdetail) == STATUS_OK)
+			ereport(ERROR,
+					(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+					 errmsg("password must not equal user name")));
+	}
+	else
+	{
+		/*
+		 * For unencrypted passwords we can perform better checks
+		 */
+		const char *password = shadow_pass;
+		int			pwdlen = strlen(password);
+		int			i;
+		bool		pwd_has_letter,
+					pwd_has_nonletter;
+
+		/* enforce minimum length */
+		if (pwdlen < MIN_PWD_LENGTH)
+			ereport(ERROR,
+					(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+					 errmsg("password is too short")));
+
+		/* check if the password contains the username */
+		if (strstr(password, username))
+			ereport(ERROR,
+					(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+					 errmsg("password must not contain user name")));
+
+		/* check if the password contains both letters and non-letters */
+		pwd_has_letter = false;
+		pwd_has_nonletter = false;
+		for (i = 0; i < pwdlen; i++)
+		{
+			/*
+			 * isalpha() does not work for multibyte encodings but let's
+			 * consider non-ASCII characters non-letters
+			 */
+			if (isalpha((unsigned char) password[i]))
+				pwd_has_letter = true;
+			else
+				pwd_has_nonletter = true;
+		}
+		if (!pwd_has_letter || !pwd_has_nonletter)
+			ereport(ERROR,
+					(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+					 errmsg("password must contain both letters and nonletters")));
+
+#ifdef USE_CRACKLIB
+		/* call cracklib to check password */
+		if (FascistCheck(password, CRACKLIB_DICTPATH))
+			ereport(ERROR,
+					(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+					 errmsg("password is easily cracked")));
+#endif
+	}
+
+	/* all checks passed, password is ok */
+}
+
+/*
+ * Module initialization function
+ */
+void
+_PG_init(void)
+{
+	/* activate password checks when the module is loaded */
+	prev_check_password_hook = check_password_hook;
+	check_password_hook = check_password;
+}
+
+/*
+ * Module unload function
+ */
+void
+_PG_fini(void)
+{
+	/* uninstall hook */
+	check_password_hook = prev_check_password_hook;
+}