fix: drain full OpenSSL error queue in croakSsl()

RSA.xs

@@ -73,9 +73,16 @@ typedef struct
 void croakSsl(char* p_file, int p_line)
 {
     const char* errorReason;
-    /* Just return the top error on the stack */
-    errorReason = ERR_reason_error_string(ERR_get_error());
-    ERR_clear_error();
+    unsigned long last_err = 0;
+    unsigned long err;
+    /* Drain the error queue and use the last (most recent) error,
+       which is typically the most descriptive.  This also prevents
+       stale errors from a previous eval-caught failure from leaking
+       into the next croak message. */
+    while ((err = ERR_get_error()) != 0) {
+        last_err = err;
+    }
+    errorReason = ERR_reason_error_string(last_err);
     croak("%s:%d: OpenSSL error: %s", p_file, p_line,
           errorReason ? errorReason : "(unknown error)");
 }

t/bignum.t

@@ -89,7 +89,7 @@ sub check_key_parameters    # runs 8 tests
             $e, $d, undef, $q
         );
     };
-    like( $@, qr/OpenSSL error: p not prime/, "bad n with q triggers 'p not prime' error" );
+    like( $@, qr/OpenSSL error: (?:p not prime|d e not congruent to 1)/, "bad n with q triggers key validation error" );
 
     #try again, to make sure the error queue was properly flushed
     eval {
@@ -98,5 +98,5 @@ sub check_key_parameters    # runs 8 tests
             $e, $d, undef, $q
         );
     };
-    like( $@, qr/OpenSSL error: p not prime/, "error queue flushed: repeat triggers same error" );
+    like( $@, qr/OpenSSL error: (?:p not prime|d e not congruent to 1)/, "error queue flushed: repeat triggers same error" );
 }

t/error_queue.t

@@ -0,0 +1,32 @@
+use strict;
+use warnings;
+use Test::More;
+
+use Crypt::OpenSSL::RSA;
+
+plan tests => 4;
+
+# Test that eval-caught OpenSSL failures don't pollute subsequent error messages.
+# Bug: croakSsl() used ERR_get_error() once (oldest error) instead of draining
+# the queue to the last (most recent/descriptive) error.
+
+my $rsa = Crypt::OpenSSL::RSA->generate_key(2048);
+
+# Trigger a decrypt failure inside eval
+eval { $rsa->decrypt("not valid ciphertext that is too short") };
+my $first_error = $@;
+ok($first_error, "decrypt failure with short input caught in eval");
+
+# Trigger a different decrypt failure
+eval { $rsa->decrypt("x" x 256) };
+my $second_error = $@;
+ok($second_error, "decrypt failure with full-length garbage caught in eval");
+
+# The second error should be a real decryption error, not stale from the first
+like($second_error, qr/OpenSSL error: \S/, "second error has a meaningful OpenSSL message");
+
+# Trigger yet another failure after two eval-caught ones — error queue should be clean
+eval { $rsa->encrypt("A" x 500) };
+my $third_error = $@;
+like($third_error, qr/too large|data greater|asym cipher failure/i,
+    "third error reports actual problem (data too large), not stale from earlier failures");