- djm@cvs.openbsd.org 2006/03/25 01:13:23

     [buffer.c channels.c deattack.c misc.c scp.c session.c sftp-client.c]
     [sftp-server.c ssh-agent.c ssh-rsa.c xmalloc.c xmalloc.h auth-pam.c]
     [uidswap.c]
     change OpenSSH's xrealloc() function from being xrealloc(p, new_size)
     to xrealloc(p, new_nmemb, new_itemsize).

     realloc is particularly prone to integer overflows because it is
     almost always allocating "n * size" bytes, so this is a far safer
     API; ok deraadt@

1 files changed, 11 insertions, 6 deletions

diff --git a/channels.c b/channels.c
index 0e7d5cf58..5706833a9 100644
--- a/channels.c
+++ b/channels.c
@@ -266,8 +266,8 @@ channel_new(char *ctype, int type, int rfd, int wfd, int efd,
                 if (channels_alloc > 10000)
                         fatal("channel_new: internal error: channels_alloc %d "
                             "too big.", channels_alloc);
-                channels = xrealloc(channels,
-                    (channels_alloc + 10) * sizeof(Channel *));
+                channels = xrealloc(channels, channels_alloc + 10,
+                    sizeof(Channel *));
                 channels_alloc += 10;
                 debug2("channel: expanding %d", channels_alloc);
                 for (i = found; i < channels_alloc; i++)
@@ -1789,15 +1789,20 @@ void
 channel_prepare_select(fd_set **readsetp, fd_set **writesetp, int *maxfdp,
     u_int *nallocp, int rekeying)
 {
-        u_int n, sz;
+        u_int n, sz, nfdset;
 
         n = MAX(*maxfdp, channel_max_fd);
 
-        sz = howmany(n+1, NFDBITS) * sizeof(fd_mask);
+        nfdset = howmany(n+1, NFDBITS);
+        /* Explicitly test here, because xrealloc isn't always called */
+        if (nfdset && SIZE_T_MAX / nfdset < sizeof(fd_mask))
+                fatal("channel_prepare_select: max_fd (%d) is too large", n);
+        sz = nfdset * sizeof(fd_mask);
+
         /* perhaps check sz < nalloc/2 and shrink? */
         if (*readsetp == NULL || sz > *nallocp) {
-                *readsetp = xrealloc(*readsetp, sz);
-                *writesetp = xrealloc(*writesetp, sz);
+                *readsetp = xrealloc(*readsetp, nfdset, sizeof(fd_mask));
+                *writesetp = xrealloc(*writesetp, nfdset, sizeof(fd_mask));
                 *nallocp = sz;
         }
         *maxfdp = n;