Implemented snprintf and similar functions. It took a lot of thinking,

but the modifications were relatively simple and straightforward.

diff --git a/lib/printf.c b/lib/printf.c
index 21453ddcb49c0ad507c10fb90fc6467b435f7662..8e6ec76eb984583b8bb76e017a8797544f70f30f 100644 (file)
--- a/lib/printf.c
+++ b/lib/printf.c
@@ -4,6 +4,7 @@
  *     (c) 1991, 1992 Lars Wirzenius & Linus Torvalds
  *
  *     Hacked up for BIRD by Martin Mares <mj@ucw.cz>
+ *     Buffer size limitation implemented by Martin Mares.
  */
 
 #include "nest/bird.h"
@@ -38,13 +39,15 @@ __res = ((unsigned long) n) % (unsigned) base; \
 n = ((unsigned long) n) / (unsigned) base; \
 __res; })
 
-static char * number(char * str, long num, int base, int size, int precision
-       ,int type)
+static char * number(char * str, long num, int base, int size, int precision,
+       int type, int remains)
 {
        char c,sign,tmp[66];
        const char *digits="0123456789abcdefghijklmnopqrstuvwxyz";
        int i;
 
+       if (size >= 0 && (remains -= size) < 0)
+               return NULL;
        if (type & LARGE)
                digits = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";
        if (type & LEFT)
@@ -80,6 +83,8 @@ static char * number(char * str, long num, int base, int size, int precision
        if (i > precision)
                precision = i;
        size -= precision;
+       if (size < 0 && -size > remains)
+               return NULL;
        if (!(type&(ZEROPAD+LEFT)))
                while(size-->0)
                        *str++ = ' ';
@@ -105,12 +110,12 @@ static char * number(char * str, long num, int base, int size, int precision
        return str;
 }
 
-int bvsprintf(char *buf, const char *fmt, va_list args)
+int bvsnprintf(char *buf, int size, const char *fmt, va_list args)
 {
        int len;
        unsigned long num;
        int i, base;
-       char * str;
+       char *str, *start;
        const char *s;
 
        int flags;              /* flags to number() */
@@ -120,8 +125,10 @@ int bvsprintf(char *buf, const char *fmt, va_list args)
                                   number of chars for from string */
        int qualifier;          /* 'h', 'l', or 'L' for integer fields */
 
-       for (str=buf ; *fmt ; ++fmt) {
+       for (start=str=buf ; *fmt ; ++fmt, size-=(str-start), start=str) {
                if (*fmt != '%') {
+                       if (!size)
+                               return -1;
                        *str++ = *fmt;
                        continue;
                }
@@ -177,6 +184,8 @@ int bvsprintf(char *buf, const char *fmt, va_list args)
                /* default base */
                base = 10;
 
+               if (field_width > size)
+                       return -1;
                switch (*fmt) {
                case 'c':
                        if (!(flags & LEFT))
@@ -199,6 +208,8 @@ int bvsprintf(char *buf, const char *fmt, va_list args)
                        len = strlen(s);
                        if (precision >= 0 && len > precision)
                                len = precision;
+                       if (len > size)
+                               return -1;
 
                        if (!(flags & LEFT))
                                while (len < field_width--)
@@ -216,7 +227,9 @@ int bvsprintf(char *buf, const char *fmt, va_list args)
                        }
                        str = number(str,
                                (unsigned long) va_arg(args, void *), 16,
-                               field_width, precision, flags);
+                               field_width, precision, flags, size);
+                       if (!str)
+                               return -1;
                        continue;
 
 
@@ -232,6 +245,8 @@ int bvsprintf(char *buf, const char *fmt, va_list args)
 
                /* IP address */
                case 'I':
+                       if (size < STD_ADDRESS_P_LENGTH)
+                               return -1;
                        if (flags & SPECIAL)
                                str = ip_ntox(va_arg(args, ip_addr), str);
                        else {
@@ -261,6 +276,8 @@ int bvsprintf(char *buf, const char *fmt, va_list args)
                        break;
 
                default:
+                       if (size < 2)
+                               return -1;
                        if (*fmt != '%')
                                *str++ = '%';
                        if (*fmt)
@@ -280,19 +297,39 @@ int bvsprintf(char *buf, const char *fmt, va_list args)
                        num = va_arg(args, int);
                else
                        num = va_arg(args, unsigned int);
-               str = number(str, num, base, field_width, precision, flags);
+               str = number(str, num, base, field_width, precision, flags, size);
+               if (!str)
+                       return -1;
        }
+       if (!size)
+               return -1;
        *str = '\0';
        return str-buf;
 }
 
+int bvsprintf(char *buf, const char *fmt, va_list args)
+{
+  return bvsnprintf(buf, 1000000000, fmt, args);
+}
+
 int bsprintf(char * buf, const char *fmt, ...)
 {
-       va_list args;
-       int i;
+  va_list args;
+  int i;
 
-       va_start(args, fmt);
-       i=bvsprintf(buf,fmt,args);
-       va_end(args);
-       return i;
+  va_start(args, fmt);
+  i=bvsnprintf(buf, 1000000000, fmt, args);
+  va_end(args);
+  return i;
+}
+
+int bsnprintf(char * buf, int size, const char *fmt, ...)
+{
+  va_list args;
+  int i;
+
+  va_start(args, fmt);
+  i=bvsnprintf(buf, size, fmt, args);
+  va_end(args);
+  return i;
 }

diff --git a/lib/string.h b/lib/string.h
index 9f72cb7980cb3403555b15ec68b12e1b03a87d64..202db0abf41fb9de681afb246ffa53fb569f525b 100644 (file)
--- a/lib/string.h
+++ b/lib/string.h
@@ -13,5 +13,7 @@
 
 int bsprintf(char *str, const char *fmt, ...);
 int bvsprintf(char *str, const char *fmt, va_list args);
+int bsnprintf(char *str, int size, const char *fmt, ...);
+int bvsnprintf(char *str, int size, const char *fmt, va_list args);
 
 #endif