Ensure we check i2d_X509 return val

The i2d_X509() function can return a negative value on error. Therefore
we should make sure we check it.

Issue reported by Yuan Jochen Kang.

(Imported from upstream's 8f43c80bfac15544820739bf035df946eeb603e8)

Change-Id: If247d5bf1d792eb7c6dc179b606ed21ea0ccdbb8
Reviewed-on: https://boringssl-review.googlesource.com/7743
Reviewed-by: David Benjamin <davidben@google.com>

1 files changed, 13 insertions, 3 deletions

diff --git a/crypto/x509/x_x509.c b/crypto/x509/x_x509.c
index 1ae37c4b..9d242348 100644
--- a/crypto/x509/x_x509.c
+++ b/crypto/x509/x_x509.c
@@ -206,10 +206,20 @@ X509 *d2i_X509_AUX(X509 **a, const unsigned char **pp, long length)
 
 int i2d_X509_AUX(X509 *a, unsigned char **pp)
 {
-    int length;
+    int length, tmplen;
+    unsigned char *start = *pp;
     length = i2d_X509(a, pp);
-    if (a)
-        length += i2d_X509_CERT_AUX(a->aux, pp);
+    if (length < 0 || a == NULL) {
+        return length;
+    }
+
+    tmplen = i2d_X509_CERT_AUX(a->aux, pp);
+    if (tmplen < 0) {
+        *pp = start;
+        return tmplen;
+    }
+    length += tmplen;
+
     return length;
 }