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Clean up code style of Mastodon::TimestampId module (#5232)

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* Clean up code style of Mastodon::TimestampId module

* Update brakeman config
This commit is contained in:
Eugen Rochko 2017-10-06 03:42:21 +02:00 committed by GitHub
parent a5143df303
commit eb5ac23434
3 changed files with 124 additions and 119 deletions
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42
config/brakeman.ignore
View File

@ -57,6 +57,26 @@
"confidence": "Weak",
"note": ""
},
{
"warning_type": "SQL Injection",
"warning_code": 0,
"fingerprint": "34efc76883080f8b1110a30c34ec4f903946ee56651aae46c62477f45d4fc412",
"check_name": "SQL",
"message": "Possible SQL injection",
"file": "lib/mastodon/timestamp_ids.rb",
"line": 63,
"link": "http://brakemanscanner.org/docs/warning_types/sql_injection/",
"code": "connection.execute(\" CREATE OR REPLACE FUNCTION timestamp_id(table_name text)\\n RETURNS bigint AS\\n $$\\n DECLARE\\n time_part bigint;\\n sequence_base bigint;\\n tail bigint;\\n BEGIN\\n time_part := (\\n -- Get the time in milliseconds\\n ((date_part('epoch', now()) * 1000))::bigint\\n -- And shift it over two bytes\\n << 16);\\n\\n sequence_base := (\\n 'x' ||\\n -- Take the first two bytes (four hex characters)\\n substr(\\n -- Of the MD5 hash of the data we documented\\n md5(table_name ||\\n '#{SecureRandom.hex(16)}' ||\\n time_part::text\\n ),\\n 1, 4\\n )\\n -- And turn it into a bigint\\n )::bit(16)::bigint;\\n\\n -- Finally, add our sequence number to our base, and chop\\n -- it to the last two bytes\\n tail := (\\n (sequence_base + nextval(table_name || '_id_seq'))\\n & 65535);\\n\\n -- Return the time part and the sequence part. OR appears\\n -- faster here than addition, but they're equivalent:\\n -- time_part has no trailing two bytes, and tail is only\\n -- the last two bytes.\\n RETURN time_part | tail;\\n END\\n $$ LANGUAGE plpgsql VOLATILE;\\n\")",
"render_path": null,
"location": {
"type": "method",
"class": "Mastodon::TimestampIds",
"method": "define_timestamp_id"
},
"user_input": "SecureRandom.hex(16)",
"confidence": "Medium",
"note": ""
},
{
"warning_type": "Dynamic Render Path",
"warning_code": 15,
@ -210,26 +230,6 @@
"confidence": "Weak",
"note": ""
},
{
"warning_type": "SQL Injection",
"warning_code": 0,
"fingerprint": "cd440d9d0bcb76225f4142030cec0bdec6ad119c537c108c9d514bf87bc34d29",
"check_name": "SQL",
"message": "Possible SQL injection",
"file": "lib/mastodon/timestamp_ids.rb",
"line": 69,
"link": "http://brakemanscanner.org/docs/warning_types/sql_injection/",
"code": "ActiveRecord::Base.connection.execute(\" CREATE OR REPLACE FUNCTION timestamp_id(table_name text)\\n RETURNS bigint AS\\n $$\\n DECLARE\\n time_part bigint;\\n sequence_base bigint;\\n tail bigint;\\n BEGIN\\n -- Our ID will be composed of the following:\\n -- 6 bytes (48 bits) of millisecond-level timestamp\\n -- 2 bytes (16 bits) of sequence data\\n\\n -- The 'sequence data' is intended to be unique within a\\n -- given millisecond, yet obscure the 'serial number' of\\n -- this row.\\n\\n -- To do this, we hash the following data:\\n -- * Table name (if provided, skipped if not)\\n -- * Secret salt (should not be guessable)\\n -- * Timestamp (again, millisecond-level granularity)\\n\\n -- We then take the first two bytes of that value, and add\\n -- the lowest two bytes of the table ID sequence number\\n -- (`table_name`_id_seq). This means that even if we insert\\n -- two rows at the same millisecond, they will have\\n -- distinct 'sequence data' portions.\\n\\n -- If this happens, and an attacker can see both such IDs,\\n -- they can determine which of the two entries was inserted\\n -- first, but not the total number of entries in the table\\n -- (even mod 2**16).\\n\\n -- The table name is included in the hash to ensure that\\n -- different tables derive separate sequence bases so rows\\n -- inserted in the same millisecond in different tables do\\n -- not reveal the table ID sequence number for one another.\\n\\n -- The secret salt is included in the hash to ensure that\\n -- external users cannot derive the sequence base given the\\n -- timestamp and table name, which would allow them to\\n -- compute the table ID sequence number.\\n\\n time_part := (\\n -- Get the time in milliseconds\\n ((date_part('epoch', now()) * 1000))::bigint\\n -- And shift it over two bytes\\n << 16);\\n\\n sequence_base := (\\n 'x' ||\\n -- Take the first two bytes (four hex characters)\\n substr(\\n -- Of the MD5 hash of the data we documented\\n md5(table_name ||\\n '#{SecureRandom.hex(16)}' ||\\n time_part::text\\n ),\\n 1, 4\\n )\\n -- And turn it into a bigint\\n )::bit(16)::bigint;\\n\\n -- Finally, add our sequence number to our base, and chop\\n -- it to the last two bytes\\n tail := (\\n (sequence_base + nextval(table_name || '_id_seq'))\\n & 65535);\\n\\n -- Return the time part and the sequence part. OR appears\\n -- faster here than addition, but they're equivalent:\\n -- time_part has no trailing two bytes, and tail is only\\n -- the last two bytes.\\n RETURN time_part | tail;\\n END\\n $$ LANGUAGE plpgsql VOLATILE;\\n\")",
"render_path": null,
"location": {
"type": "method",
"class": "Mastodon::TimestampIds",
"method": "s(:self).define_timestamp_id"
},
"user_input": "SecureRandom.hex(16)",
"confidence": "Medium",
"note": ""
},
{
"warning_type": "Cross-Site Scripting",
"warning_code": 4,
@ -269,6 +269,6 @@
"note": ""
}
],
"updated": "2017-10-05 20:06:40 +0200",
"updated": "2017-10-06 03:27:46 +0200",
"brakeman_version": "4.0.1"
}

199
lib/mastodon/timestamp_ids.rb
View File

@ -1,120 +1,111 @@
# frozen_string_literal: true
module Mastodon
module TimestampIds
def self.define_timestamp_id
conn = ActiveRecord::Base.connection
module Mastodon::TimestampIds
DEFAULT_REGEX = /timestamp_id\('(?<seq_prefix>\w+)'/
# Make sure we don't already have a `timestamp_id` function.
unless conn.execute(<<~SQL).values.first.first
SELECT EXISTS(
SELECT * FROM pg_proc WHERE proname = 'timestamp_id'
);
class << self
# Our ID will be composed of the following:
# 6 bytes (48 bits) of millisecond-level timestamp
# 2 bytes (16 bits) of sequence data
#
# The 'sequence data' is intended to be unique within a
# given millisecond, yet obscure the 'serial number' of
# this row.
#
# To do this, we hash the following data:
# * Table name (if provided, skipped if not)
# * Secret salt (should not be guessable)
# * Timestamp (again, millisecond-level granularity)
#
# We then take the first two bytes of that value, and add
# the lowest two bytes of the table ID sequence number
# (`table_name`_id_seq). This means that even if we insert
# two rows at the same millisecond, they will have
# distinct 'sequence data' portions.
#
# If this happens, and an attacker can see both such IDs,
# they can determine which of the two entries was inserted
# first, but not the total number of entries in the table
# (even mod 2**16).
#
# The table name is included in the hash to ensure that
# different tables derive separate sequence bases so rows
# inserted in the same millisecond in different tables do
# not reveal the table ID sequence number for one another.
#
# The secret salt is included in the hash to ensure that
# external users cannot derive the sequence base given the
# timestamp and table name, which would allow them to
# compute the table ID sequence number.
def define_timestamp_id
return if already_defined?
connection.execute(<<~SQL)
CREATE OR REPLACE FUNCTION timestamp_id(table_name text)
RETURNS bigint AS
$$
DECLARE
time_part bigint;
sequence_base bigint;
tail bigint;
BEGIN
time_part := (
-- Get the time in milliseconds
((date_part('epoch', now()) * 1000))::bigint
-- And shift it over two bytes
<< 16);
sequence_base := (
'x' ||
-- Take the first two bytes (four hex characters)
substr(
-- Of the MD5 hash of the data we documented
md5(table_name ||
'#{SecureRandom.hex(16)}' ||
time_part::text
),
1, 4
)
-- And turn it into a bigint
)::bit(16)::bigint;
-- Finally, add our sequence number to our base, and chop
-- it to the last two bytes
tail := (
(sequence_base + nextval(table_name || '_id_seq'))
& 65535);
-- Return the time part and the sequence part. OR appears
-- faster here than addition, but they're equivalent:
-- time_part has no trailing two bytes, and tail is only
-- the last two bytes.
RETURN time_part | tail;
END
$$ LANGUAGE plpgsql VOLATILE;
SQL
# The function doesn't exist, so we'll define it.
conn.execute(<<~SQL)
CREATE OR REPLACE FUNCTION timestamp_id(table_name text)
RETURNS bigint AS
$$
DECLARE
time_part bigint;
sequence_base bigint;
tail bigint;
BEGIN
-- Our ID will be composed of the following:
-- 6 bytes (48 bits) of millisecond-level timestamp
-- 2 bytes (16 bits) of sequence data
-- The 'sequence data' is intended to be unique within a
-- given millisecond, yet obscure the 'serial number' of
-- this row.
-- To do this, we hash the following data:
-- * Table name (if provided, skipped if not)
-- * Secret salt (should not be guessable)
-- * Timestamp (again, millisecond-level granularity)
-- We then take the first two bytes of that value, and add
-- the lowest two bytes of the table ID sequence number
-- (`table_name`_id_seq). This means that even if we insert
-- two rows at the same millisecond, they will have
-- distinct 'sequence data' portions.
-- If this happens, and an attacker can see both such IDs,
-- they can determine which of the two entries was inserted
-- first, but not the total number of entries in the table
-- (even mod 2**16).
-- The table name is included in the hash to ensure that
-- different tables derive separate sequence bases so rows
-- inserted in the same millisecond in different tables do
-- not reveal the table ID sequence number for one another.
-- The secret salt is included in the hash to ensure that
-- external users cannot derive the sequence base given the
-- timestamp and table name, which would allow them to
-- compute the table ID sequence number.
time_part := (
-- Get the time in milliseconds
((date_part('epoch', now()) * 1000))::bigint
-- And shift it over two bytes
<< 16);
sequence_base := (
'x' ||
-- Take the first two bytes (four hex characters)
substr(
-- Of the MD5 hash of the data we documented
md5(table_name ||
'#{SecureRandom.hex(16)}' ||
time_part::text
),
1, 4
)
-- And turn it into a bigint
)::bit(16)::bigint;
-- Finally, add our sequence number to our base, and chop
-- it to the last two bytes
tail := (
(sequence_base + nextval(table_name || '_id_seq'))
& 65535);
-- Return the time part and the sequence part. OR appears
-- faster here than addition, but they're equivalent:
-- time_part has no trailing two bytes, and tail is only
-- the last two bytes.
RETURN time_part | tail;
END
$$ LANGUAGE plpgsql VOLATILE;
SQL
end
end
def self.ensure_id_sequences_exist
conn = ActiveRecord::Base.connection
def ensure_id_sequences_exist
# Find tables using timestamp IDs.
default_regex = /timestamp_id\('(?<seq_prefix>\w+)'/
conn.tables.each do |table|
connection.tables.each do |table|
# We're only concerned with "id" columns.
next unless (id_col = conn.columns(table).find { |col| col.name == 'id' })
next unless (id_col = connection.columns(table).find { |col| col.name == 'id' })
# And only those that are using timestamp_id.
next unless (data = default_regex.match(id_col.default_function))
next unless (data = DEFAULT_REGEX.match(id_col.default_function))
seq_name = data[:seq_prefix] + '_id_seq'
# If we were on Postgres 9.5+, we could do CREATE SEQUENCE IF
# NOT EXISTS, but we can't depend on that. Instead, catch the
# possible exception and ignore it.
# Note that seq_name isn't a column name, but it's a
# relation, like a column, and follows the same quoting rules
# in Postgres.
conn.execute(<<~SQL)
connection.execute(<<~SQL)
DO $$
BEGIN
CREATE SEQUENCE #{conn.quote_column_name(seq_name)};
CREATE SEQUENCE #{connection.quote_column_name(seq_name)};
EXCEPTION WHEN duplicate_table THEN
-- Do nothing, we have the sequence already.
END
@ -122,5 +113,19 @@ module Mastodon
SQL
end
end
private
def already_defined?
connection.execute(<<~SQL).values.first.first
SELECT EXISTS(
SELECT * FROM pg_proc WHERE proname = 'timestamp_id'
);
SQL
end
def connection
ActiveRecord::Base.connection
end
end
end

2
lib/tasks/db.rake
View File

@ -20,10 +20,10 @@ def each_schema_load_environment
if Rails.env == 'development'
test_conf = ActiveRecord::Base.configurations['test']
if test_conf['database']&.present?
ActiveRecord::Base.establish_connection(:test)
yield
ActiveRecord::Base.establish_connection(Rails.env.to_sym)
end
end