在pg_shadow中加密密码加盐 [英] Salt in encrypted password in pg_shadow
问题描述
我读到pg_shadow中的密码哈希是用用户名加密的。
这仍然是这样吗？如果是这样，因为可能99％的PostgreSQL都有
" postgres"作为超级用户名，使用标准的
Unix / Apache MD5哈希不是更好吗？
-
dave
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David Garamond< li *** @ zara.6.isreserved.com>写道：我读到pg_shadow中的密码哈希是用用户名加密的。
这仍然是这样吗？如果是这样，因为大约99％的PostgreSQL都有postgres。作为超级用户名，使用标准的Unix / Apache MD5哈希不是更好吗？
如何改进？如果我们在其中添加一个随机盐，我们将要求b
必须将盐存储在pg_shadow中，所以不会有任何保密
加上---一个可以阅读pg_shadow的攻击者也可以看到盐。
（实际上，能够读取pg_shadow的攻击者已经是超级用户，
所以它是'不清楚还有什么可以躲避他的。）
问候，汤姆小巷
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< blockquote> Tom Lane写道：
我读到pg_shadow中的密码哈希是用用户名加密的。
这仍然是这样吗？如果是这样，因为大约99％的PostgreSQL都有postgres。作为超级用户名，使用标准的Unix / Apache MD5哈希不是更好吗？
如何改进任何东西？如果我们在其中添加一个随机盐，我们就必须将盐存储在pg_shadow中，这样就不会增加任何保密性 - 一个可以阅读pg_shadow的攻击者可以看到盐也是。
考虑一下创建一个长列表的人：
MD5（postgres+" aaaaaaaa）
MD5（postgres+aaaaaaab）
MD5（postgres+aaaaaaac）
...
现在，如果他可以访问其他人的pg_shadow，他可以将
哈希与他的字典进行比较。替换postgres随机盐
击败这个字典攻击（因此他将不得不求助于粗暴的
力量）。
（实际上，攻击者谁能读懂pg_shadow已经是超级用户了，所以不清楚还有什么东西可以躲避他。）
但是考虑一下找到包含数据库的硬盘或磁带的人
备份......然后他可以访问真实的在线数据库。
-
dave
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David Garamond写道：考虑一下谁创建了一个很长的列表：
MD5（postgres） +aaaaaaaa ）MD5（postgres+aaaaaaab）
MD5（postgres+aaaaaaac）
现在如果他可以访问其他人的pg_shadow，他可以将
哈希与他的字典进行比较。替换postgres用一个随意的盐
击败这个字典攻击（因此他将不得不求助于粗暴的力量）。
但你肯定必须将随机盐存储在pg_shadow中？或者我是否b $ b缺少一些东西？
-
Richard Huxton
Archonet Ltd
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I read that the password hash in pg_shadow is salted with username. Is
this still the case? If so, since probably 99% of all PostgreSQL has
"postgres" as the superuser name, wouldn''t it be better to use standard
Unix/Apache MD5 hash instead?
--
dave
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David Garamond <li***@zara.6.isreserved.com> writes:I read that the password hash in pg_shadow is salted with username. Is
this still the case? If so, since probably 99% of all PostgreSQL has
"postgres" as the superuser name, wouldn''t it be better to use standard
Unix/Apache MD5 hash instead?
How does that improve anything? If we add a random salt into it, we''d
have to store the salt in pg_shadow, so there wouldn''t be any secrecy
added --- an attacker who can read pg_shadow could see the salt too.
(Actually, an attacker who can read pg_shadow is already superuser,
so it''s not clear there''s anything left to hide from him anyway.)
regards, tom lane
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Tom Lane wrote:I read that the password hash in pg_shadow is salted with username. Is
this still the case? If so, since probably 99% of all PostgreSQL has
"postgres" as the superuser name, wouldn''t it be better to use standard
Unix/Apache MD5 hash instead?
How does that improve anything? If we add a random salt into it, we''d
have to store the salt in pg_shadow, so there wouldn''t be any secrecy
added --- an attacker who can read pg_shadow could see the salt too.
Consider someone who creates a long list of:
MD5( "postgres" + "aaaaaaaa" )
MD5( "postgres" + "aaaaaaab" )
MD5( "postgres" + "aaaaaaac" )
...
Now if he has access to other people''s pg_shadow, he can compare the
hashes with his dictionary. Replacing "postgres" with a random salt
defeats this dictionary attack (and thus he will have to resort to brute
force).
(Actually, an attacker who can read pg_shadow is already superuser,
so it''s not clear there''s anything left to hide from him anyway.)
But consider someone who finds a harddisk or tape containing a database
backup... he can then gain access to the real, online database.
--
dave
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David Garamond wrote:Consider someone who creates a long list of:
MD5( "postgres" + "aaaaaaaa" )
MD5( "postgres" + "aaaaaaab" )
MD5( "postgres" + "aaaaaaac" )
...
Now if he has access to other people''s pg_shadow, he can compare the
hashes with his dictionary. Replacing "postgres" with a random salt
defeats this dictionary attack (and thus he will have to resort to brute
force).
But surely you have to store the random salt in pg_shadow too? Or am I
missing something?
--
Richard Huxton
Archonet Ltd
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