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commit    20dbc84bd002c5ef2b5439ac29b6a5b24b0a3d69
Author:   Michael Paquier <michael@paquier.xyz>
Date:     Wed Apr 24 00:05:30 2019 +0000
First released in: 9.4.22, 9.5.17, 9.6.13

    Fix detection of passwords hashed with MD5
    
    This commit fixes an issue related to the way password verifiers hashed
    with MD5 are detected, leading to possibly detect that plain passwords
    are legit MD5 hashes.  A MD5-hashed entry was checked based on if its
    header uses "md5" and if the string length matches what is expected.
    Unfortunately the code never checked if the hash only used hexadecimal
    characters after the three-character prefix.
    
    Fix 9.6 down to 9.4, where this code is present.  This area of the code
    has changed in 10 and upwards with the introduction of SCRAM, which led
    to a different fix committed as of ccae190.
    
    Reported-by: Tom Lane
    Author: Michael Paquier
    Reviewed-by: Jonathan Katz
    Discussion: https://postgr.es/m/016deb6b-1f0a-8e9f-1833-a8675b170aa9@postgresql.org
    Backpatch-through: 9.4


 src/include/libpq/md5.h | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/include/libpq/md5.h b/src/include/libpq/md5.h
index cb5883c4a54..72d0f9eb814 100644
--- a/src/include/libpq/md5.h
+++ b/src/include/libpq/md5.h
@@ -16,10 +16,12 @@
 #ifndef PG_MD5_H
 #define PG_MD5_H
 
+#define MD5_PASSWD_CHARSET "0123456789abcdef"
 #define MD5_PASSWD_LEN	35
 
 #define isMD5(passwd)	(strncmp(passwd, "md5", 3) == 0 && \
-						 strlen(passwd) == MD5_PASSWD_LEN)
+						 strlen(passwd) == MD5_PASSWD_LEN && \
+						 strspn(passwd + 3, MD5_PASSWD_CHARSET) == MD5_PASSWD_LEN - 3)
 
 
 extern bool pg_md5_hash(const void *buff, size_t len, char *hexsum);


[parent: 74589026f79f]