EC_POINT_is_on_curve does not return a boolean

The function EC_POINT_is_on_curve does not return a boolean value.
It returns 1 if the point is on the curve, 0 if it is not, and -1
on error. Many usages within OpenSSL were incorrectly using this
function and therefore not correctly handling error conditions.

With thanks to the Open Crypto Audit Project for reporting this issue.

Reviewed-by: Kurt Roeckx <kurt@openssl.org>

5 files changed, 11 insertions, 4 deletions

diff --git a/crypto/ec/ec2_oct.c b/crypto/ec/ec2_oct.c
index 821c371009..33f703b168 100644
--- a/crypto/ec/ec2_oct.c
+++ b/crypto/ec/ec2_oct.c
@@ -384,7 +384,7 @@ int ec_GF2m_simple_oct2point(const EC_GROUP *group, EC_POINT *point,
     }
 
     /* test required by X9.62 */
-    if (!EC_POINT_is_on_curve(group, point, ctx)) {
+    if (EC_POINT_is_on_curve(group, point, ctx) <= 0) {
         ECerr(EC_F_EC_GF2M_SIMPLE_OCT2POINT, EC_R_POINT_IS_NOT_ON_CURVE);
         goto err;
     }
diff --git a/crypto/ec/ec_check.c b/crypto/ec/ec_check.c
index 1d44ad2283..bdbf91c470 100644
--- a/crypto/ec/ec_check.c
+++ b/crypto/ec/ec_check.c
@@ -85,7 +85,7 @@ int EC_GROUP_check(const EC_GROUP *group, BN_CTX *ctx)
         ECerr(EC_F_EC_GROUP_CHECK, EC_R_UNDEFINED_GENERATOR);
         goto err;
     }
-    if (!EC_POINT_is_on_curve(group, group->generator, ctx)) {
+    if (EC_POINT_is_on_curve(group, group->generator, ctx) <= 0) {
         ECerr(EC_F_EC_GROUP_CHECK, EC_R_POINT_IS_NOT_ON_CURVE);
         goto err;
     }
diff --git a/crypto/ec/ec_key.c b/crypto/ec/ec_key.c
index 07c33fe733..620860cad4 100644
--- a/crypto/ec/ec_key.c
+++ b/crypto/ec/ec_key.c
@@ -296,7 +296,7 @@ int EC_KEY_check_key(const EC_KEY *eckey)
         goto err;
 
     /* testing whether the pub_key is on the elliptic curve */
-    if (!EC_POINT_is_on_curve(eckey->group, eckey->pub_key, ctx)) {
+    if (EC_POINT_is_on_curve(eckey->group, eckey->pub_key, ctx) <= 0) {
         ECerr(EC_F_EC_KEY_CHECK_KEY, EC_R_POINT_IS_NOT_ON_CURVE);
         goto err;
     }
diff --git a/crypto/ec/ec_lib.c b/crypto/ec/ec_lib.c
index 9156943e20..3ddaa5d8fb 100644
--- a/crypto/ec/ec_lib.c
+++ b/crypto/ec/ec_lib.c
@@ -949,6 +949,13 @@ int EC_POINT_is_at_infinity(const EC_GROUP *group, const EC_POINT *point)
     return group->meth->is_at_infinity(group, point);
 }
 
+/*
+ * Check whether an EC_POINT is on the curve or not. Note that the return
+ * value for this function should NOT be treated as a boolean. Return values:
+ *  1: The point is on the curve
+ *  0: The point is not on the curve
+ * -1: An error occurred
+ */
 int EC_POINT_is_on_curve(const EC_GROUP *group, const EC_POINT *point,
                          BN_CTX *ctx)
 {
diff --git a/crypto/ec/ecp_oct.c b/crypto/ec/ecp_oct.c
index a68b559bc0..8bb7aa3090 100644
--- a/crypto/ec/ecp_oct.c
+++ b/crypto/ec/ecp_oct.c
@@ -410,7 +410,7 @@ int ec_GFp_simple_oct2point(const EC_GROUP *group, EC_POINT *point,
     }
 
     /* test required by X9.62 */
-    if (!EC_POINT_is_on_curve(group, point, ctx)) {
+    if (EC_POINT_is_on_curve(group, point, ctx) <= 0) {
         ECerr(EC_F_EC_GFP_SIMPLE_OCT2POINT, EC_R_POINT_IS_NOT_ON_CURVE);
         goto err;
     }