diff --git a/mozilla/nsprpub/lib/libc/src/base64.c b/mozilla/nsprpub/lib/libc/src/base64.c
index 234d60d8fbf..0f6127574f0 100644
--- a/mozilla/nsprpub/lib/libc/src/base64.c
+++ b/mozilla/nsprpub/lib/libc/src/base64.c
@@ -155,7 +155,13 @@ PL_Base64Encode
 
     if( (char *)0 == dest )
     {
-        PRUint32 destlen = ((srclen + 2)/3) * 4;
+        PRUint32 destlen;
+        /* Ensure all PRUint32 values stay within range. */
+        if( srclen > (PR_UINT32_MAX/4) * 3 )
+        {
+            return (char *)0;
+        }
+        destlen = ((srclen + 2)/3) * 4;
         dest = (char *)PR_MALLOC(destlen + 1);
         if( (char *)0 == dest )
         {
@@ -403,7 +409,9 @@ PL_Base64Decode
 
     if( (char *)0 == dest )
     {
-        PRUint32 destlen = ((srclen * 3) / 4);
+        /* The following computes ((srclen * 3) / 4) without overflow. */
+        PRUint32 rem = srclen % 4;
+        PRUint32 destlen = (srclen / 4) * 3 + (rem * 3) / 4;
         dest = (char *)PR_MALLOC(destlen + 1);
         if( (char *)0 == dest )
         {
diff --git a/mozilla/nsprpub/lib/libc/src/strlen.c b/mozilla/nsprpub/lib/libc/src/strlen.c
index 6c47677727b..5cbc2b7ab1d 100644
--- a/mozilla/nsprpub/lib/libc/src/strlen.c
+++ b/mozilla/nsprpub/lib/libc/src/strlen.c
@@ -53,7 +53,7 @@ PL_strlen(const char *str)
      * we don't have ultra long strings that overflow an int32
      */ 
     if( sizeof(PRUint32) < sizeof(size_t) )
-        PR_ASSERT(l < 2147483647);
+        PR_ASSERT(l <= PR_INT32_MAX);
 
     return (PRUint32)l;
 }