Bug #15847: SecureRandom#gen_random becomes private after first invocation

• Status: Closed
• Assignee: -
• Target version: -
• ruby -v: ruby 2.5.5p157 (2019-03-15 revision 67260) [x86_64-linux]
• Backport: 2.4: DONTNEED, 2.5: DONE, 2.6: DONE

[graywolf (Gray Wolf)]

There seems to be an issue with SecureRandom#gen_random becoming private after first invocation:

+   $ /tmp/my_ruby/bin/ruby -v
ruby 2.7.0dev (2019-05-13 trunk 082bbdc92e) [x86_64-linux]

$ /tmp/my_ruby/bin/ruby \
	-e 'require "securerandom"' \
	-e 'SecureRandom.gen_random(1)'

$ /tmp/my_ruby/bin/ruby \
	-e 'require "securerandom"' \
	-e 'SecureRandom.gen_random(1)' \
	-e 'SecureRandom.gen_random(1)'
Traceback (most recent call last):
-e:3:in `<main>': private method `gen_random' called for SecureRandom:Module (NoMethodError)

This is caused by using alias since 2.5 ruby in secure random class. Both
.gen_random_openssl and .gen_random_urandom are private class method. Using
the alias on them does not remove the private property, so new .gen_random
is private as well. Patch fixing the issue:

diff --git a/lib/securerandom.rb b/lib/securerandom.rb
index 37835bf7df..2b0f3753b3 100644
--- a/lib/securerandom.rb
+++ b/lib/securerandom.rb
@@ -84,7 +84,8 @@ def gen_random(n)
           @rng_chooser.synchronize do
             class << self
               remove_method :gen_random
-              alias gen_random gen_random_openssl
+              alias_method(:gen_random, :gen_random_openssl)
+              public(:gen_random)
             end
           end
           return gen_random(n)
@@ -93,7 +94,8 @@ class << self
         @rng_chooser.synchronize do
           class << self
             remove_method :gen_random
-            alias gen_random gen_random_urandom
+            alias_method(:gen_random, :gen_random_urandom)
+            public(:gen_random)
           end
         end
         return gen_random(n)

This bug is not present in 2.4.6. First noticed on 2.5.5. Examples in this
ticket are from current trunk.

[shyouhei (Shyouhei Urabe)]

• Status changed from Open to Closed

Applied in changeset git|5bab1304af25a843728dbcd2f3594913740aecb0.

---

fix visibility of SecureRandom.gen_random

Aliasing a method preserves its visibility. These aliases turn
formerly-public methods into private. Should make them public
again. [Bug #15847]

[shyouhei (Shyouhei Urabe)]

Thank you for reporting! It was my fault. have just pushed a fix.

[nagachika (Tomoyuki Chikanaga)]

• Backport changed from 2.4: UNKNOWN, 2.5: UNKNOWN, 2.6: UNKNOWN to 2.4: DONTNEED, 2.5: REQUIRED, 2.6: REQUIRED

[nagachika (Tomoyuki Chikanaga)]

• Backport changed from 2.4: DONTNEED, 2.5: REQUIRED, 2.6: REQUIRED to 2.4: DONTNEED, 2.5: REQUIRED, 2.6: DONE

ruby_2_6 r67723 merged revision(s) 5bab1304af25a843728dbcd2f3594913740aecb0.

[usa (Usaku NAKAMURA)]

• Backport changed from 2.4: DONTNEED, 2.5: REQUIRED, 2.6: DONE to 2.4: DONTNEED, 2.5: DONE, 2.6: DONE

ruby_2_5 r67762 merged revision(s) 5bab1304af25a843728dbcd2f3594913740aecb0.