Dear Dochelp Team,
I need your help again :-)
I'm trying to implement SamrUnicodeChangePasswordUser4. However when I try to
run my implementation against Windows. I always get STATUS_WRONG_PASSWORD
returned.
For the SamrUnicodeChangePasswordUser4 method (section 3.1.5.10.4), the shared
secret is the plaintext old password and the CEK is generated as specified in
section 3.2.2.5.
3.2.2.5 Deriving an Encryption Key from a Plaintext Password
The client MUST derive the CEK in the following manner:
CEK :: = (PBKDF2(NT HASH of “OldPassword”, Salt, IterationCount, 512))
Looking at the RFC 8018 section 5.2:
PBKDF2 (P, S, c, dkLen)
Options: PRF underlying pseudorandom function (hLen
denotes the length in octets of the
pseudorandom function output)
Input: P password, an octet string
S salt, an octet string
c iteration count, a positive integer
dkLen intended length in octets of the derived
key, a positive integer, at most
(2^32 - 1) * hLen
Output: DK derived key, a dkLen-octet string
The MS-SAMR document doesn't say a word about the dkLen. Which would be how
many bytes the pbkdf2 function should return for the CEK.
I've used 16 bytes (same as the session key) as dkLen. However I get
STATUS_WRONG_PASSWORD
./bin/rpcclient ncacn_np:earth.milkyway.site -U'bob%Pa$$w0rd@3' -c 'chgpasswd4
bob Pa$$w0rd@3 Pa$$w0rd@6'
[...]
rpc_api_pipe: host earth.milkyway.site returned 4 bytes.
samr_ChangePasswordUser4: struct samr_ChangePasswordUser4
out: struct samr_ChangePasswordUser4
result : NT_STATUS_WRONG_PASSWORD
I've uploaded traces to:
https://support.microsoft.com/files?
workspace=eyJ0eXAiOiJKV1QiLCJhbGciOiJSUzI1NiJ9.eyJ3c2lkIjoiNTY5YjBlMTItMzYyNS00NjhlLWIwNjgtOTBiZDYyZDk2MTllIiwic3IiOiIyMjA3MTEwMDQwMDA4ODMyIiwiYXBwaWQiOiI0ZTc2ODkxZC04NDUwLTRlNWUtYmUzOC1lYTNiZDZlZjIxZTUiLCJzdiI6InYxIiwicnMiOiJFeHRlcm5hbCIsInd0aWQiOiJhYzUxMDFlOS1mMTExLTQ5MGUtOGVlYS04NWMxNGMyNzMyNmIiLCJpc3MiOiJodHRwczovL2FwaS5kdG1uZWJ1bGEubWljcm9zb2Z0LmNvbSIsImF1ZCI6Imh0dHA6Ly9zbWMiLCJleHAiOjE2NjU0MTQxMzEsIm5iZiI6MTY1NzYzODEzMX0.Oe0Nrl4WiClzTrLHTGeFVX6S-
oHNH4LjSGoiVF9eXNo9wN9w-
NyabVRaEUpWVvKheXcqukAuNYvxDGCnoj2ZbpPsE1JY4EByZfqC2l--8i6N0smD8Rtccd_YLg_hx9SqGO-
Dgr6Y5zLo6FMBUnfF6xQ8jhqB5a7ZJf4-
TfMnCgXDsltrLzB_JU1rLDsVGI5ZzZfN9BEOJeKxS9PJEB3azUy8lFvcMsyq8ZL5LOzyQyhg7H2CglwDjzNeGmg2Wov8vdVdh3Ahk0AZ08Otf7i-7tpggx0F9FsH13oS2j6IOzEni23z2G6AqNL4j7ss_23sCp5njIL70rvGv3LliynERA&wid=569b0e12-3625-468e-
b068-90bd62d9619e
Help here would be much appreciated. Thanks you dochelp team.
Best regards
Andreas
--
Andreas Schneider a...@samba.org
Samba Team www.samba.org
GPG-ID: 8DFF53E18F2ABC8D8F3C92237EE0FC4DCC014E3D
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