Fix a read of uninitialized memory in next_token() of hba.c, spotted via

valgrind: a buffer passed to strncmp() had to be NUL-terminated. Original
report and patch from Dennis Bjorkland, some cleanup by Andrew Dunstan,
and finally some editorializing from Neil Conway.

src/backend/libpq/hba.c

@@ -10,7 +10,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/libpq/hba.c,v 1.119 2003/12/25 03:44:04 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/libpq/hba.c,v 1.120 2004/02/02 16:58:30 neilc Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -37,12 +37,23 @@
 #include "storage/fd.h"
 
 
-#define IDENT_USERNAME_MAX 512
 /* Max size of username ident server can return */
+#define IDENT_USERNAME_MAX 512
+
+/* Standard TCP port number for Ident service.  Assigned by IANA */
+#define IDENT_PORT 113
+
+/* Name of the config file  */
+#define CONF_FILE "pg_hba.conf"
+
+/* Name of the usermap file */
+#define USERMAP_FILE "pg_ident.conf"
 
 /* This is used to separate values in multi-valued column strings */
 #define MULTI_VALUE_SEP "\001"
 
+#define MAX_TOKEN	256
+
 /*
  * These variables hold the pre-parsed contents of the hba and ident
  * configuration files.  Each is a list of sublists, one sublist for
@@ -83,16 +94,16 @@ pg_isblank(const char c)
  * Grab one token out of fp. Tokens are strings of non-blank
  * characters bounded by blank characters, beginning of line, and
  * end of line. Blank means space or tab. Return the token as
- *	 *buf. Leave file positioned to character immediately after the
+ * *buf. Leave file positioned at the character immediately after the
  * token or EOF, whichever comes first. If no more tokens on line,
- *	 return null string as *buf and position file to beginning of
- *	 next line or EOF, whichever comes first. Allow spaces in quoted
- *	 strings. Terminate on unquoted commas. Handle comments. Treat
- *   unquoted keywords that might be user names or database names 
- *   specially, by appending a newline to them.
+ * return empty string as *buf and position the file to the beginning
+ * of the next line or EOF, whichever comes first. Allow spaces in
+ * quoted strings. Terminate on unquoted commas. Handle
+ * comments. Treat unquoted keywords that might be user names or
+ * database names specially, by appending a newline to them.
  */
-void
-next_token(FILE *fp, char *buf, const int bufsz)
+static void
+next_token(FILE *fp, char *buf, int bufsz)
 {
 	int			c;
 	char	   *start_buf = buf;
@@ -101,12 +112,18 @@ next_token(FILE *fp, char *buf, const int bufsz)
 	bool		was_quote = false;
 	bool        saw_quote = false;
 
+	Assert(end_buf > start_buf);
+
 	/* Move over initial whitespace and commas */
 	while ((c = getc(fp)) != EOF && (pg_isblank(c) || c == ','))
 		;
 
-	if (c != EOF && c != '\n')
+	if (c == EOF || c == '\n')
 	{
+		*buf = '\0';
+		return;
+	}
+
 	/*
 	 * Build a token in buf of next characters up to EOF, EOL,
 	 * unquoted comma, or unquoted whitespace.
@@ -166,23 +183,18 @@ next_token(FILE *fp, char *buf, const int bufsz)
 	 */
 	if (c != EOF)
 		ungetc(c, fp);
-	}
 
+	*buf = '\0';
 
-	if ( !saw_quote && 
-	     (
-			 strncmp(start_buf,"all",3) == 0  ||
-			 strncmp(start_buf,"sameuser",8) == 0  ||
-			 strncmp(start_buf,"samegroup",9) == 0 
-		 )
-		)
+	if (!saw_quote && 
+	     (strcmp(start_buf, "all") == 0 ||
+		  strcmp(start_buf, "sameuser") == 0 ||
+		  strcmp(start_buf, "samegroup") == 0))
 	{
 		/* append newline to a magical keyword */
 		*buf++ = '\n';
-	}
-
 		*buf = '\0';
-
+	}
 }
 
 /*

src/include/libpq/hba.h

@@ -4,7 +4,7 @@
  *	  Interface to hba.c
  *
  *
- * $PostgreSQL: pgsql/src/include/libpq/hba.h,v 1.34 2003/11/29 22:41:03 pgsql Exp $
+ * $PostgreSQL: pgsql/src/include/libpq/hba.h,v 1.35 2004/02/02 16:58:30 neilc Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -17,15 +17,6 @@
 
 #include "nodes/pg_list.h"
 
-#define CONF_FILE "pg_hba.conf"
- /* Name of the config file  */
-
-#define USERMAP_FILE "pg_ident.conf"
- /* Name of the usermap file */
-
-#define IDENT_PORT 113
- /* Standard TCP port number for Ident service.  Assigned by IANA */
-
 typedef enum UserAuth
 {
 	uaReject,
@@ -43,9 +34,6 @@ typedef enum UserAuth
 
 typedef struct Port hbaPort;
 
-#define MAX_TOKEN	256
-
-extern void next_token(FILE *fp, char *buf, const int bufsz);
 extern List **get_user_line(const char *user);
 extern void load_hba(void);
 extern void load_ident(void);