From e121dc35abafd9a2eda01b05aa5fa13b13e6196e Mon Sep 17 00:00:00 2001
From: Even Rouault <even.rouault@spatialys.com>
Date: Sun, 3 Feb 2019 15:16:01 +0100
Subject: Avoid division by zero in Ellipsoid::computeSemiMinorAxis(). Fixes
 https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=12867. Credit to OSS
 Fuzz. master only

---
 src/iso19111/datum.cpp   | 10 +++++++---
 test/unit/test_datum.cpp | 12 ++++++++++++
 2 files changed, 19 insertions(+), 3 deletions(-)

diff --git a/src/iso19111/datum.cpp b/src/iso19111/datum.cpp
index 4df1b319..66717f70 100644
--- a/src/iso19111/datum.cpp
+++ b/src/iso19111/datum.cpp
@@ -646,7 +646,8 @@ EllipsoidNNPtr Ellipsoid::createSphere(const util::PropertyMap &properties,
  * @param properties See \ref general_properties.
  * At minimum the name should be defined.
  * @param semiMajorAxisIn the semi-major axis.
- * @param invFlattening the inverse/reverse flattening.
+ * @param invFlattening the inverse/reverse flattening. If set to 0, this will
+ * be considered as a sphere.
  * @param celestialBody Name of the celestial body on which the ellipsoid refers
  * to.
  * @return new Ellipsoid.
@@ -654,8 +655,11 @@ EllipsoidNNPtr Ellipsoid::createSphere(const util::PropertyMap &properties,
 EllipsoidNNPtr Ellipsoid::createFlattenedSphere(
     const util::PropertyMap &properties, const common::Length &semiMajorAxisIn,
     const common::Scale &invFlattening, const std::string &celestialBody) {
-    auto ellipsoid(Ellipsoid::nn_make_shared<Ellipsoid>(
-        semiMajorAxisIn, invFlattening, celestialBody));
+    auto ellipsoid(invFlattening.value() == 0
+                       ? Ellipsoid::nn_make_shared<Ellipsoid>(semiMajorAxisIn,
+                                                              celestialBody)
+                       : Ellipsoid::nn_make_shared<Ellipsoid>(
+                             semiMajorAxisIn, invFlattening, celestialBody));
     ellipsoid->setProperties(properties);
     return ellipsoid;
 }
diff --git a/test/unit/test_datum.cpp b/test/unit/test_datum.cpp
index 18cf244a..c6ccf5cf 100644
--- a/test/unit/test_datum.cpp
+++ b/test/unit/test_datum.cpp
@@ -127,6 +127,18 @@ TEST(datum, ellipsoid_from_inverse_flattening) {
 
 // ---------------------------------------------------------------------------
 
+TEST(datum, ellipsoid_from_null_inverse_flattening) {
+
+    auto ellipsoid = Ellipsoid::createFlattenedSphere(
+        PropertyMap(), Length(6378137), Scale(0));
+    EXPECT_FALSE(ellipsoid->inverseFlattening().has_value());
+    EXPECT_FALSE(ellipsoid->semiMinorAxis().has_value());
+    EXPECT_FALSE(ellipsoid->semiMedianAxis().has_value());
+    EXPECT_TRUE(ellipsoid->isSphere());
+}
+
+// ---------------------------------------------------------------------------
+
 TEST(datum, ellipsoid_from_semi_minor_axis) {
 
     auto ellipsoid = Ellipsoid::createTwoAxis(PropertyMap(), Length(6378137),
-- 
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