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🐛 Parse resp-text with invalid resp-text-code #601

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Merged
nevans merged 2 commits into from
Feb 10, 2026
+40 −2
Merged

🐛 Parse resp-text with invalid resp-text-code #601

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74acaaa
🥅 Add very basic backtracking to the parser
nevans Feb 5, 2026
7fb8b57
🐛 Parse `resp-text` with invalid `resp-text-code`
nevans Feb 3, 2026
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5 changes: 5 additions & 0 deletions lib/net/imap/response_parser.rb
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Original file line number Diff line number Diff line change
Expand Up @@ -1888,12 +1888,17 @@ def text?
# We leniently re-interpret this as
# resp-text = ["[" resp-text-code "]" [SP [text]] / [text]
def resp_text
state = current_state
if lbra?
code = resp_text_code; rbra
ResponseText.new(code, SP? && text? || "")
else
ResponseText.new(nil, text? || "")
end
rescue ResponseParseError => error
raise if /\buid-set\b/i.match? error.message
restore_state state
text
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@nevans nevans Feb 11, 2026

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Oops. This is a bug. It should be ResponseText.new(nil, text? || "")

end

# RFC3501 (See https://www.rfc-editor.org/errata/rfc3501):
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10 changes: 8 additions & 2 deletions lib/net/imap/response_parser/parser_utils.rb
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Expand Up @@ -221,8 +221,14 @@ def exception(message) = ResponseParseError.new(
message, parser_state:, parser_class: self.class
)

def current_state = [@lex_state, @pos, @token]
def parser_state = [@str, *current_state]
# This can be used to backtrack after a parse error, and re-attempt to
# parse using a fallback.
#
# NOTE: Reckless backtracking could lead to O(n²) situations, so this
# should very rarely be used. Ideally, fallbacks should not backtrack.
def restore_state(state) = (@lex_state, @pos, @token = state)
def current_state = [@lex_state, @pos, @token]
def parser_state = [@str, *current_state]

end
end
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27 changes: 27 additions & 0 deletions test/net/imap/fixtures/response_parser/quirky_behaviors.yml
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Expand Up @@ -31,6 +31,33 @@
unparsed_data: "froopy snood"
raw_data: "* 86 NOOP froopy snood\r\n"

"Microsoft Exchange issues an invalid resp-text-code":
comment: |
net-imap issue: https://github.com/ruby/net-imap/issues/597

Microsoft Exchange is issuing an invalid resp-text-code, but net-imap
should fallback to `resp-text = text` when resp-text-code fails to parse.
:debug: false # current version of backtracking still prints parse_errors
:response: "RUBY0001 OK [Error=\"Microsoft.Exchange.Data.Storage.WrongServerException:
Cross Server access is not allowed for mailbox xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx\"
AuthResultFromPopImapEnd=0 Proxy=XXXXXXXXXXXXX.EURXXXX.PROD.OUTLOOK.COM:1993:SSL
MailboxBE=XXXXXXXXXXXXX.EURXXXX.PROD.OUTLOOK.COM
Service=Imap4] AUTHENTICATE completed.\r\n"
:expected: !ruby/struct:Net::IMAP::TaggedResponse
tag: RUBY0001
name: OK
data: '[Error="Microsoft.Exchange.Data.Storage.WrongServerException: Cross Server
access is not allowed for mailbox xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx"
AuthResultFromPopImapEnd=0
Proxy=XXXXXXXXXXXXX.EURXXXX.PROD.OUTLOOK.COM:1993:SSL
MailboxBE=XXXXXXXXXXXXX.EURXXXX.PROD.OUTLOOK.COM Service=Imap4]
AUTHENTICATE completed.'
raw_data: "RUBY0001 OK [Error=\"Microsoft.Exchange.Data.Storage.WrongServerException:
Cross Server access is not allowed for mailbox xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx\"
AuthResultFromPopImapEnd=0 Proxy=XXXXXXXXXXXXX.EURXXXX.PROD.OUTLOOK.COM:1993:SSL
MailboxBE=XXXXXXXXXXXXX.EURXXXX.PROD.OUTLOOK.COM Service=Imap4] AUTHENTICATE
completed.\r\n"

outlook.com puts an extra SP in ENVELOPE address lists:
comment: |
An annoying bug from outlook.com. They've had the bug for years, and
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