[OATH-Toolkit-help] catching errors from strcmp_otp

[Daniel Pocock]

The user callback strcmp_otp may need to return an error rather than 
just rejecting an OTP value.

response = 0: OTP accepted
response > 0: OTP mismatch
response < 0: internal failure (e.g. memory allocation), don't try again

I propose the patch below to allow this

The callback could potentially put details of the error in the 
strcmp_handle, for use by user code





diff --git a/liboath/hotp.c b/liboath/hotp.c
index 00c5b20..6647ce6 100644
--- a/liboath/hotp.c
+++ b/liboath/hotp.c
@@ -192,8 +192,10 @@ oath_hotp_validate_callback (const char *secret,
       if (rc != OATH_OK)
        return rc;

-      if (strcmp_otp (strcmp_handle, tmp_otp) == 0)
+      if ((rc = strcmp_otp (strcmp_handle, tmp_otp)) == 0)
        return iter;
+      if (rc < 0)
+        return OATH_STRCMP_ERROR;
     }
   while (window - iter++ > 0);

diff --git a/liboath/oath.h.in b/liboath/oath.h.in
index a934828..050ee34 100644
--- a/liboath/oath.h.in
+++ b/liboath/oath.h.in
@@ -79,6 +79,7 @@
  * @OATH_FILE_RENAME_ERROR: System error when renaming file
  * @OATH_FILE_UNLINK_ERROR: System error when removing file
  * @OATH_TIME_ERROR: System error for time manipulation
+ * @OATH_STRCMP_ERROR: A strcmp callback returned an error
  *
  * Return codes for OATH functions.  All return codes are negative
  * except for the successful code OATH_OK which are guaranteed to be
@@ -107,7 +108,8 @@ typedef enum
   OATH_FILE_LOCK_ERROR = -15,
   OATH_FILE_RENAME_ERROR = -16,
   OATH_FILE_UNLINK_ERROR = -17,
-  OATH_TIME_ERROR = -18
+  OATH_TIME_ERROR = -18,
+  OATH_STRCMP_ERROR = -19
 } oath_rc;

 /* Global */
@@ -163,7 +165,8 @@ oath_hotp_validate (const char *secret,
  * test_otp OTP using the same hash, and then compare the results.
  *
  * Return value: 0 if and only if @test_otp is identical to the OTP to
- *   be validated.
+ *   be validated.  Negative value if an internal failure occurs.
+ *   Positive value if the test_otp simply doesn't match.
  *
  * Since: 1.6.0
  **/
diff --git a/liboath/totp.c b/liboath/totp.c
index 70a92c8..d414622 100644
--- a/liboath/totp.c
+++ b/liboath/totp.c
@@ -302,12 +302,14 @@ oath_totp_validate2_callback (const char *secret,
          if (rc != OATH_OK)
            return rc;

-         if (strcmp_otp (strcmp_handle, tmp_otp) == 0)
+         if ((rc = (strcmp_otp (strcmp_handle, tmp_otp)) == 0)
            {
              if (otp_pos)
                *otp_pos = -iter;
              return iter;
            }
+          if (rc < 0)
+            return OATH_STRCMP_ERROR;
        }
     }
   while (window - iter++ > 0);