🚨 [security] Update net-imap 0.5.12 → 0.5.14 (minor)

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🚨 Your current dependencies have known security vulnerabilities 🚨

This dependency update fixes known security vulnerabilities. Please see the details below and assess their impact carefully. We recommend to merge and deploy this as soon as possible!

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Here is everything you need to know about this update. Please take a good look at what changed and the test results before merging this pull request.

What changed?

✳️ net-imap (0.5.12 → 0.5.14) · Repo · Changelog

Security Advisories 🚨

🚨 net-imap vulnerable to STARTTLS stripping via invalid response timing

Summary

A man-in-the-middle attacker can cause Net::IMAP#starttls to return "successfully", without starting TLS.

Details

When using Net::IMAP#starttls to upgrade a plaintext connection to use TLS, a man-in-the-middle attacker can inject a tagged OK response with an easily predictable tag. By sending the response before the client finishes sending the command, the command completes "successfully" before the response handler is registered. This allows #starttls to return without error, but the response handler is never invoked, the TLS connection is never established, and the socket remains unencrypted.

This allows man-in-the-middle attackers to perform a STARTTLS stripping attack, unless the client code explicitly checks Net::IMAP#tls_verified?.

Impact

TLS bypass, leading to cleartext transmission of sensitive information.

Mitigation

• Upgrade to a patched version of net-imap that raises an exception whenever #starttls does not establish TLS.
• Connect to an implicit TLS port, rather than use STARTTLS with a cleartext port.
  This is strongly recommended anyway:
  • RFC 8314: Cleartext Considered Obsolete: Use of Transport Layer Security (TLS) for Email Submission and Access
  • NO STARTTLS: Why TLS is better without STARTTLS, A Security Analysis of STARTTLS in the Email Context
• Explicitly verify Net::IMAP#tls_verified? is true, before using the connection after #starttls.

🚨 net-imap has quadratic complexity when reading response literals

Summary

Net::IMAP::ResponseReader has quadratic time complexity when reading large responses containing many string literals. A hostile server can send responses which are crafted to exhaust the client's CPU for a denial of service attack.

Details

For each literal in a response, ResponseReader rescans the entire growing response buffer. The regular expression that is used to scan the response buffer runs in linear time. With many literals, this becomes O(n²) total work. The regular expression should run in constant time: it is anchored to the end and only the last 23 bytes of the buffer are relevant.

Because the algorithmic complexity is super-linear, this bypasses protection from max_response_size: a response can stay well below the default size limit while still causing very large CPU cost.

Net::IMAP::ResponseReader runs continuously in the receiver thread until the connection closes.

Impact

This consumes disproportionate CPU time in the client's receiver thread. A hostile server could use this to exhaust the client's CPU for a denial of service attack.

For a response near the default max_response_size, each individual regexp scan could take between 100 to 200ms on common modern hardware, and this may be repeated 200k times per megabyte of response. While the regexp is scanning, it retains the Global VM lock, preventing other threads from running.

Although other threads should not be completely blocked, their run time will be significantly impacted.

Mitigation

• Upgrade to a patched version of net-imap that reads responses more efficiently.
• Do not connect to untrusted IMAP servers.
• When connecting to untrusted servers, a much smaller max_response_size (for example: 8KiB) will limit the impact. Although this is too small for fetching unpaginated message bodies, it should be enough for most other operations.

🚨 net-imap vulnerable to denial of service via high iteration count for `SCRAM-*` authentication

Summary

When authenticating a connection with SCRAM-SHA1 or SCRAM-SHA256, a hostile server can perform a computational denial-of-service attack on the client process by sending a big iteration count value.

Details

A hostile IMAP server can send an arbitrarily large PBKDF2 iteration count in the SCRAM server-first-message, causing the client to perform an expensive OpenSSL::KDF.pbkdf2_hmac call. Because the PBKDF2 function is a blocking C extension and holds onto Ruby’s Global VM Lock, it can freeze the entire Ruby VM for the duration of the computation.

OpenSSL enforces an effective maximum by using a 32-bit signed integer for the iteration count, Depending on hardware capabilities and OpenSSL version, this iteration count may be sufficient for to block all Ruby threads in the process for over seven minutes.

This is listed as one of the "Security Considerations", in RFC 7804:

A hostile server can perform a computational denial-of-service attack on clients by sending a big iteration count value. In order to defend against that, a client implementation can pick a maximum iteration count that it is willing to use and reject any values that exceed that threshold (in such cases, the client, of course, has to fail the authentication).

Impact

During SCRAM authentication to a hostile server, the entire Ruby VM will be locked for the duration of the computation. Depending on hardware capabilities and OpenSSL version, this may take many minutes.

OpenSSL::KDF.pbkdf2_hmac is a blocking C function, so Timeout cannot be used to guard against this. And it retains the Global VM lock, so other ruby threads will also be unable to run.

Mitigation

• Upgrade to a patched version of net-imap that adds the max_iterations option to the SASL-* authenticators, and call Net::IMAP#authenticate with a max_iterations keyword argument.

  NOTE: The default max_iterations is 2³¹ - 1, the maximum signed 32 bit integer, the maximum allowed by OpenSSL.
  To prevent a denial of service attack, this must be set to a safe value, depending on hardware and version of OpenSSL.
  It is the user's responsibility to enforce minimum and maximum iteration counts that are appropriate for their security context.

• Alternatively, avoid SCRAM-* mechanisms when authenticating to untrusted servers.

🚨 net-imap vulnerable to command Injection via unvalidated Symbol inputs

Summary

Symbol arguments to commands are vulnerable to a CRLF Injection / IMAP Command injection via Symbol arguments passed to IMAP commands.

Details

Symbol arguments represent IMAP "system flags", which are formatted as "atoms" (with no quoting) with a "\" prefix. Vulnerable versions of Net::IMAP sends the symbol name directly to the socket, with no validation.

Because the Symbol input is unvalidated, it could contain invalid flag characters, including SP and CRLF, which could be used to finish the current command and inject new commands.

Although IMAP flag arguments are only valid input for a few IMAP commands, most Net::IMAP commands use generic argument handling, and will allow Symbol (flag) inputs.

Note also that the list of valid symbol inputs should be restricted to an enumerated set of standard RFC defined flag types, which have each been given specific defined semantics. Any user-provided values outside of that list of standard "system flags" needs to use the IMAP keyword syntax, which are sent as atoms, i.e: string inputs. Under no circumstances should #to_sym ever be called on unvetted user-provided input: that will always be a bug in the calling code for the simple reason that user_input_atom is as \user_input_atom.

For forward compatibility with future IMAP extentions, Net::IMAP, does not restrict flag inputs to an enumerated list. That is the responsibility of the calling application code, which knows which flag semantics are valid for its context.

Impact

If a developer passes user-controlled input as a Symbol to most Net::IMAP commands, an attacker can append CRLF sequence followed by a new IMAP command (like DELETE mailbox).

Mitigation

• Upgrade to a version of Net::IMAP that validates Symbols are valid as an IMAP flag.

• User-provided input should never be able to control calling #to_sym on string arguments.

  For example, do not unsafely serialize and deserialize command arguments (e.g. with YAML or Marshal) in a way that could create unvetted Symbol arguments.

• For the few IMAP commands which do allow flag arguments, it may be appropriate to hard-code Symbol arguments or restrict them to an enumerated list which is valid for the calling application.

🚨 net-imap vulnerable to command Injection via "raw" arguments to multiple commands

Summary

Several Net::IMAP commands accept a raw string argument that is sent to the server without validation or escaping. If this string is derived from user-controlled input, it may contain contain CRLF sequences, which an attacker can use to inject arbitrary IMAP commands.

Details

Net::IMAP's generic argument handling, used by most command arguments, interprets string arguments as an IMAP astring. Depending on the string contents and the connection's UTF-8 support, this encodes strings as either a atom, quoted, or literal. These are safe from command or argument injection.

But the following commands transform specific String arguments to Net::IMAP::RawData, which bypasses normal argument validation and encoding and prints the string directly to the socket:

• #uid_search, #search
  • when criteria is a String, it is sent raw
• #uid_fetch, #fetch
  • when attr is a String, it is sent raw
  • when attr is an Array, each String in attr is sent raw
• #uid_store, #store
  • when attr is a String, it is sent raw
• #setquota:
  • limit is interpolated with #to_s and that string is sent raw

Because these string arguments are sent without any neutralization, they serve as a direct vector for command splitting. Any user controlled data interpolated into these strings can be used to break out of the intended command context.

Using "raw data" arguments for #uid_store, #store, and #setquota I both inappropriate and unnecessary. Net::IMAP's generic argument handling is sufficient to safely validate and encode their arguments. Users of the library probably do not expect arguments to these commands to be sent raw and might not be wary of passing unvalidated input.

The API for search criteria and fetch attributes is intentionally low-level and "close to the wire". It allows developers to use some IMAP extensions without requiring explicit support from the library and allows developers to use complex IMAP grammar without complex argument translation. Even so, basic validation is appropriate and could neutralize command injection.

Although this was explicitly documented for search criteria, it was insufficiently documented for fetch attr. So developers may not have realized that the attr argument to #fetch and #uid_fetch is sent as "raw data".

Impact

If a developer passes an unvalidated user-controlled input for one of these method arguments, an attacker can append CRLF sequence followed by a new IMAP command (like DELETE mailbox). Although this does not directly enable data exfiltration, it could be combined with other attack vectors or knowledge of the target system's attributes, e.g.: shared mail folders or the application's installed response handlers.

The SEARCH, STORE, and FETCH commands, and their UID variants are some of the most commonly used features of the library. Applications that build search queries or fetch attributes dynamically based on user input (e.g., mail clients or archival tools) may be at significant risk.

Expected use of Net::IMAP#setquota is much more limited: SETQUOTA is often only usable by users with special administrative privileges. Depending on the server, quota administration might be managed through server configuration rather than via the IMAP protocol SETQUOTA command. It is expected to be uncommonly used in system administration scripts or in interactive sessions, it should be completely controlled by trusted users, and should only use trusted inputs. Calling #setquota with untrusted user input is expected to be a very uncommon use case. Please note however this might be combined with other attacks, for example CSRF, which provide unauthorized access to trusted inputs, and may specifically target users or scripts with administrator privileges.

Mitigation

• Update to a patched version of net-imap which:
  • validates that Net::IMAP::RawData is composed of well-formed IMAP text, literal, and literal8 values, with no unescaped NULL, CR, or LF bytes.
  • does not use Net::IMAP::RawData for #store, #uid_store, or #setquota.
• Prefer to send search criteria as an array of key value pairs. Avoid sending it as an interpolated string.
• If an immediate upgrade is not possible:
  • String inputs to search criteria and fetch attributes can be validated against command injection by checking for \r and \n characters.
  • Hard-coding the store attr argument is often appropriate. Alternatively, user controlled inputs can be restricted to a small enumerated list which is valid for the calling application.
  • Use Kernel#Integer to coerce and validate user controlled inputs to #setquota limit.

Commits

See the full diff on Github. The new version differs by 46 commits:

• 🔖 Bump version to 0.5.14
• 🔀 Merge pull request #665 from ruby/backport/v0.5/STARTTLS-stripping
• 🍒 pick 24d5c773d: 🔒🥅 Handle tagged "OK" to incomplete command [backport #664]
• 🍒 pick 62eea6ffe: 🔒🥅 Ensure STARTTLS tagged response was handled [backport #664]
• 🍒 pick 46636cae8: ❌🔒 Add failing test for STARTTLS stripping [backport #664]
• 🔀 Merge pull request #662 from ruby/backport/v0.5/raw_data-warnings
• 🍒 pick be32e712e: 📚 Improve documentation of RawData arguments [backports #661]
• 🍒 pick 47c72186d: 🐛 Validate RawData and wait to continue literals [backports #660]
• 🍒 pick 0ec4fd351: 🥅 Validate `#setquota` storage limit argument [backports #659]
• 🍒 pick 0ea729c78: 📚 Update QUOTA rdoc, params, attrs to match RFCs [backports #636]
• 🍒 pick 654630528: ✅ Test current `#setquota` behavior [backports #636]
• 🍒 pick a4f7649c3: 🥅 Validate and send STORE `attr` as an `atom` [backports #658]
• 🍒 pick 9db3e9d60: 🥅 Strictly validate symbol (\flag) arguments [backports #657]
• 🔀 Merge pull request #656 from ruby/backport/v0.5/scram-maximum_iterations
• 🔒 Add `max_iterations` to ScramAuthenticator
• ✅ Add test for ScramAuthenticator#min_iterations
• ⚡️ Memoize salted_password for AUTHENTICATE SCRAM
• ♻️ Assign ScramAuthenticator ivars in initialize
• 🔀 Merge pull request #652 from ruby/backport/v0.5/internally-support-non-synchronizing-literals
• 🔀 Merge pull request #650 from ruby/backport/v0.5/response_reader-nonlinear-performance
• 🍒 pick 6f82e28f7: ⚡️ Faster ResponseReader: parse literal from line
• 🍒 pick 49c516d62: ⚡️ Faster ResponseParser: short-circuit no literal
• 🍒 pick 341ab6281: ⚡️🔒️ Fix non-linear performance in ResponseReader
• 🍒 pick 348db835f: ✅ Use binary mode in ResponseReader tests' IO
• 🍒 pick f4b5bf22c: 📚 Workaround rdoc parsing bugs
• 🍒 pick 96fb12823: ♻️ Add ability to send non-synchronizing literals
• 🍒 pick 282604486: ✅ Improve send literal tests
• 🍒 pick 154e67862: ✅ Refactor CommandData tests
• 🍒 pick 1eabb757e: ♻️ Add internal binary literal support
• 🍒 pick de70825ca: 🥅 Validate `Literal` data doesn't contain NULL
• 🐛 Config `version_defaults` should be attr_reader
• ✅ Fix Data polyfill tests for ruby 4.1
• 📦 Drop digest from Gemfile (workaround for #576)
• 🐛 Fix `#responses()` freezing internal arrays
• 🔖 Bump version to 0.5.13
• 🐛 Fix SequenceSet#max(n), cardinality < n <= size
• 🐛 Fix SequenceSet#delete?(num..num) to return set
• 🔀 Merge pull request #584 from ruby/backport-0.5/config/defaults
• ♻️ Compile Config.default using AttrVersionDefaults
• ♻️ Define config defaults with the attr definitions
• 🚚 Compile Config[:defaults] in AttrVersionDefaults
• ♻️ Allow Config[version] to work up to v1.0
• ♻️ Compile version_defaults hashes into configs
• 🚚 Assign config aliases in AttrVersionDefaults
• 🚚 Extract Config::AttrVersionDefaults module
• 📚 Improve rdoc example for uid_fetch with partial

↗️ date (indirect, 3.5.0 → 3.5.1) · Repo · Changelog

Release Notes

3.5.1

What's Changed

• Remove archaic conditions by @nobu in #144
• [DOC] Remove the name from same file references by @nobu in #147
• Call rb_gc_register_mark_object after object allocation by @peterzhu2118 in #149

New Contributors

• @peterzhu2118 made their first contribution in #149

Full Changelog: v3.5.0...v3.5.1

Does any of this look wrong? Please let us know.

Commits

See the full diff on Github. The new version differs by 16 commits:

• v3.5.1
• Reorganize page documentations (#15154)
• Merge pull request #150 from ruby/dependabot/github_actions/step-security/harden-runner-2.13.3
• Bump step-security/harden-runner from 2.13.2 to 2.13.3
• Merge pull request #149 from ruby/pz-init-register-mark-obj
• Call rb_gc_register_mark_object after object allocation
• Merge pull request #148 from ruby/dependabot/github_actions/actions/checkout-6
• Bump actions/checkout from 5 to 6
• [DOC] Remove the name from same file references
• Merge pull request #146 from ruby/dependabot/github_actions/step-security/harden-runner-2.13.2
• Bump step-security/harden-runner from 2.13.1 to 2.13.2
• Exclude dependabot updates from release note
• Merge pull request #144 from nobu/master
• Remove archaic conditions
• Prefer `method_defined?` over `allocate.respond_to?`
• Use rake build instead of compile for JRuby

↗️ timeout (indirect, 0.4.4 → 0.6.1) · Repo · Changelog

Release Notes

0.6.1

What's Changed

• add test case for string argument by @t-mangoe in #90
• Improve Timeout.timeout documentation formatting and typos by @ybiquitous in #92
• [DOC] document the private instance method by @nobu in #94
• Compatibility with Fiber scheduler. by @ioquatix in #97
• Remove warnings by @etiennebarrie in #99

New Contributors

• @t-mangoe made their first contribution in #90
• @ybiquitous made their first contribution in #92
• @ioquatix made their first contribution in #97
• @etiennebarrie made their first contribution in #99

Full Changelog: v0.6.0...v0.6.1

0.6.0

What's Changed

• Suppress warnings in two tests by @olleolleolle in #71
• Revert "Suppress warnings in two tests" by @nobu in #74
• Only the timeout method should be public on the Timeout module by @eregon in #76
• support Ractor by @ko1 in #75
• Test that Timeout does not expose extra constants by @eregon in #77
• Revert "Exclude constantly-failing test on x86_64-darwin" by @ko1 in #79
• Reset the interrupt mask when creating the Timeout thread by @eregon in #80
• Make Timeout.timeout work in a trap handler on CRuby by @eregon in #81
• Skip signal test on windows by @byroot in #82
• Add windows to CI matrix by @byroot in #83
• Fix failing timeout test by @luke-gruber in #85
• Restore original signal handler in test_timeout_in_trap_handler by @eregon in #87
• Run on Windows for all versions and remove old excludes by @eregon in #84

New Contributors

• @ko1 made their first contribution in #75
• @byroot made their first contribution in #82
• @luke-gruber made their first contribution in #85

Full Changelog: v0.4.4...v0.6.0

0.5.0

What's Changed

• Suppress warnings in two tests by @olleolleolle in #71
• Revert "Suppress warnings in two tests" by @nobu in #74
• Only the timeout method should be public on the Timeout module by @eregon in #76
• support Ractor by @ko1 in #75
• Test that Timeout does not expose extra constants by @eregon in #77

New Contributors

• @ko1 made their first contribution in #75

Full Changelog: v0.4.4...v0.5.0

Does any of this look wrong? Please let us know.

Commits

See the full diff on Github. The new version differs by 47 commits:

• Bump version to 0.6.1
• Remove warnings
• Fix timing-dependent test
• Compatibility with Fiber scheduler. (#97)
• Merge pull request #98 from ruby/dependabot/github_actions/step-security/harden-runner-2.15.1
• Bump step-security/harden-runner from 2.15.0 to 2.15.1
• Merge pull request #96 from ruby/dependabot/github_actions/step-security/harden-runner-2.15.0
• Bump step-security/harden-runner from 2.14.2 to 2.15.0
• Merge pull request #95 from ruby/dependabot/github_actions/step-security/harden-runner-2.14.2
• Bump step-security/harden-runner from 2.14.1 to 2.14.2
• [DOC] document the private instance method
• Merge pull request #93 from ruby/dependabot/github_actions/step-security/harden-runner-2.14.1
• Bump step-security/harden-runner from 2.14.0 to 2.14.1
• Improve Timeout.timeout documentation formatting and typos
• add test case for string argument
• v0.6.0
• Merge pull request #88 from ruby/dependabot/github_actions/step-security/harden-runner-2.14.0
• Bump step-security/harden-runner from 2.13.3 to 2.14.0
• Run on Windows for all versions and remove old excludes
• Restore original signal handler in test_timeout_in_trap_handler
• Fix failing timeout test
• Merge pull request #83 from byroot/test-on-windows
• Add windows to CI matrix
• Merge pull request #82 from byroot/no-sigusr1-win32
• Skip signal test on windows
• Make Timeout.timeout work in a trap handler on CRuby
• Encapsulate adding a timeout Request
• Revise Timeout.timeout docs and add a section about `ensure`
• Reset the interrupt mask when creating the Timeout thread
• Merge pull request #79 from ko1/revert_45816b1b2602278b6d6e069d36b24fd5e3437bdd
• Revert "Exclude constantly-failing test on x86_64-darwin"
• v0.5.0
• Exclude dependabot updates from release note
• Merge pull request #78 from ruby/dependabot/github_actions/step-security/harden-runner-2.13.3
• Bump step-security/harden-runner from 2.13.2 to 2.13.3
• Test that Timeout does not expose extra constants
• Exclude constantly-failing test on x86_64-darwin
• Simplify logic to make GET_TIME shareable
• Fix logic for Ractor support
• Fix condition and fix test to catch that broken condition
• Minor tweaks
• support Ractor
• Only the timeout method should be public on the Timeout module
• Bump actions/checkout from 5 to 6
• Bump step-security/harden-runner from 2.13.1 to 2.13.2
• Revert "Suppress warnings in two tests"
• Suppress warnings in two tests

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