535 lines
21 KiB
Python
535 lines
21 KiB
Python
"""passlib.handlers.sha2_crypt - SHA256-Crypt / SHA512-Crypt"""
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#=============================================================================
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# imports
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#=============================================================================
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# core
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import hashlib
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import logging; log = logging.getLogger(__name__)
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# site
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# pkg
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from passlib.utils import safe_crypt, test_crypt, \
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repeat_string, to_unicode
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from passlib.utils.binary import h64
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from passlib.utils.compat import byte_elem_value, u, \
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uascii_to_str, unicode
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import passlib.utils.handlers as uh
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# local
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__all__ = [
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"sha512_crypt",
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"sha256_crypt",
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]
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#=============================================================================
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# pure-python backend, used by both sha256_crypt & sha512_crypt
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# when crypt.crypt() backend is not available.
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#=============================================================================
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_BNULL = b'\x00'
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# pre-calculated offsets used to speed up C digest stage (see notes below).
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# sequence generated using the following:
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##perms_order = "p,pp,ps,psp,sp,spp".split(",")
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##def offset(i):
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## key = (("p" if i % 2 else "") + ("s" if i % 3 else "") +
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## ("p" if i % 7 else "") + ("" if i % 2 else "p"))
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## return perms_order.index(key)
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##_c_digest_offsets = [(offset(i), offset(i+1)) for i in range(0,42,2)]
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_c_digest_offsets = (
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(0, 3), (5, 1), (5, 3), (1, 2), (5, 1), (5, 3), (1, 3),
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(4, 1), (5, 3), (1, 3), (5, 0), (5, 3), (1, 3), (5, 1),
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(4, 3), (1, 3), (5, 1), (5, 2), (1, 3), (5, 1), (5, 3),
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)
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# map used to transpose bytes when encoding final sha256_crypt digest
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_256_transpose_map = (
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20, 10, 0, 11, 1, 21, 2, 22, 12, 23, 13, 3, 14, 4, 24, 5,
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25, 15, 26, 16, 6, 17, 7, 27, 8, 28, 18, 29, 19, 9, 30, 31,
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)
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# map used to transpose bytes when encoding final sha512_crypt digest
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_512_transpose_map = (
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42, 21, 0, 1, 43, 22, 23, 2, 44, 45, 24, 3, 4, 46, 25, 26,
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5, 47, 48, 27, 6, 7, 49, 28, 29, 8, 50, 51, 30, 9, 10, 52,
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31, 32, 11, 53, 54, 33, 12, 13, 55, 34, 35, 14, 56, 57, 36, 15,
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16, 58, 37, 38, 17, 59, 60, 39, 18, 19, 61, 40, 41, 20, 62, 63,
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)
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def _raw_sha2_crypt(pwd, salt, rounds, use_512=False):
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"""perform raw sha256-crypt / sha512-crypt
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this function provides a pure-python implementation of the internals
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for the SHA256-Crypt and SHA512-Crypt algorithms; it doesn't
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handle any of the parsing/validation of the hash strings themselves.
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:arg pwd: password chars/bytes to hash
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:arg salt: salt chars to use
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:arg rounds: linear rounds cost
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:arg use_512: use sha512-crypt instead of sha256-crypt mode
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:returns:
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encoded checksum chars
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"""
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#===================================================================
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# init & validate inputs
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#===================================================================
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# NOTE: the setup portion of this algorithm scales ~linearly in time
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# with the size of the password, making it vulnerable to a DOS from
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# unreasonably large inputs. the following code has some optimizations
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# which would make things even worse, using O(pwd_len**2) memory
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# when calculating digest P.
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#
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# to mitigate these two issues: 1) this code switches to a
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# O(pwd_len)-memory algorithm for passwords that are much larger
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# than average, and 2) Passlib enforces a library-wide max limit on
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# the size of passwords it will allow, to prevent this algorithm and
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# others from being DOSed in this way (see passlib.exc.PasswordSizeError
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# for details).
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# validate secret
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if isinstance(pwd, unicode):
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# XXX: not sure what official unicode policy is, using this as default
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pwd = pwd.encode("utf-8")
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assert isinstance(pwd, bytes)
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if _BNULL in pwd:
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raise uh.exc.NullPasswordError(sha512_crypt if use_512 else sha256_crypt)
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pwd_len = len(pwd)
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# validate rounds
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assert 1000 <= rounds <= 999999999, "invalid rounds"
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# NOTE: spec says out-of-range rounds should be clipped, instead of
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# causing an error. this function assumes that's been taken care of
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# by the handler class.
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# validate salt
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assert isinstance(salt, unicode), "salt not unicode"
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salt = salt.encode("ascii")
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salt_len = len(salt)
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assert salt_len < 17, "salt too large"
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# NOTE: spec says salts larger than 16 bytes should be truncated,
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# instead of causing an error. this function assumes that's been
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# taken care of by the handler class.
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# load sha256/512 specific constants
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if use_512:
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hash_const = hashlib.sha512
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transpose_map = _512_transpose_map
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else:
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hash_const = hashlib.sha256
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transpose_map = _256_transpose_map
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#===================================================================
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# digest B - used as subinput to digest A
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#===================================================================
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db = hash_const(pwd + salt + pwd).digest()
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#===================================================================
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# digest A - used to initialize first round of digest C
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#===================================================================
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# start out with pwd + salt
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a_ctx = hash_const(pwd + salt)
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a_ctx_update = a_ctx.update
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# add pwd_len bytes of b, repeating b as many times as needed.
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a_ctx_update(repeat_string(db, pwd_len))
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# for each bit in pwd_len: add b if it's 1, or pwd if it's 0
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i = pwd_len
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while i:
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a_ctx_update(db if i & 1 else pwd)
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i >>= 1
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# finish A
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da = a_ctx.digest()
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#===================================================================
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# digest P from password - used instead of password itself
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# when calculating digest C.
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#===================================================================
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if pwd_len < 96:
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# this method is faster under python, but uses O(pwd_len**2) memory;
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# so we don't use it for larger passwords to avoid a potential DOS.
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dp = repeat_string(hash_const(pwd * pwd_len).digest(), pwd_len)
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else:
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# this method is slower under python, but uses a fixed amount of memory.
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tmp_ctx = hash_const(pwd)
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tmp_ctx_update = tmp_ctx.update
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i = pwd_len-1
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while i:
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tmp_ctx_update(pwd)
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i -= 1
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dp = repeat_string(tmp_ctx.digest(), pwd_len)
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assert len(dp) == pwd_len
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#===================================================================
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# digest S - used instead of salt itself when calculating digest C
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#===================================================================
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ds = hash_const(salt * (16 + byte_elem_value(da[0]))).digest()[:salt_len]
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assert len(ds) == salt_len, "salt_len somehow > hash_len!"
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#===================================================================
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# digest C - for a variable number of rounds, combine A, S, and P
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# digests in various ways; in order to burn CPU time.
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#===================================================================
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# NOTE: the original SHA256/512-Crypt specification performs the C digest
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# calculation using the following loop:
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#
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##dc = da
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##i = 0
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##while i < rounds:
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## tmp_ctx = hash_const(dp if i & 1 else dc)
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## if i % 3:
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## tmp_ctx.update(ds)
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## if i % 7:
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## tmp_ctx.update(dp)
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## tmp_ctx.update(dc if i & 1 else dp)
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## dc = tmp_ctx.digest()
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## i += 1
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#
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# The code Passlib uses (below) implements an equivalent algorithm,
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# it's just been heavily optimized to pre-calculate a large number
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# of things beforehand. It works off of a couple of observations
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# about the original algorithm:
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#
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# 1. each round is a combination of 'dc', 'ds', and 'dp'; determined
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# by the whether 'i' a multiple of 2,3, and/or 7.
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# 2. since lcm(2,3,7)==42, the series of combinations will repeat
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# every 42 rounds.
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# 3. even rounds 0-40 consist of 'hash(dc + round-specific-constant)';
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# while odd rounds 1-41 consist of hash(round-specific-constant + dc)
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#
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# Using these observations, the following code...
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# * calculates the round-specific combination of ds & dp for each round 0-41
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# * runs through as many 42-round blocks as possible
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# * runs through as many pairs of rounds as possible for remaining rounds
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# * performs once last round if the total rounds should be odd.
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#
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# this cuts out a lot of the control overhead incurred when running the
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# original loop 40,000+ times in python, resulting in ~20% increase in
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# speed under CPython (though still 2x slower than glibc crypt)
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# prepare the 6 combinations of ds & dp which are needed
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# (order of 'perms' must match how _c_digest_offsets was generated)
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dp_dp = dp+dp
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dp_ds = dp+ds
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perms = [dp, dp_dp, dp_ds, dp_ds+dp, ds+dp, ds+dp_dp]
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# build up list of even-round & odd-round constants,
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# and store in 21-element list as (even,odd) pairs.
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data = [ (perms[even], perms[odd]) for even, odd in _c_digest_offsets]
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# perform as many full 42-round blocks as possible
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dc = da
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blocks, tail = divmod(rounds, 42)
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while blocks:
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for even, odd in data:
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dc = hash_const(odd + hash_const(dc + even).digest()).digest()
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blocks -= 1
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# perform any leftover rounds
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if tail:
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# perform any pairs of rounds
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pairs = tail>>1
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for even, odd in data[:pairs]:
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dc = hash_const(odd + hash_const(dc + even).digest()).digest()
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# if rounds was odd, do one last round (since we started at 0,
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# last round will be an even-numbered round)
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if tail & 1:
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dc = hash_const(dc + data[pairs][0]).digest()
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#===================================================================
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# encode digest using appropriate transpose map
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#===================================================================
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return h64.encode_transposed_bytes(dc, transpose_map).decode("ascii")
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#=============================================================================
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# handlers
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#=============================================================================
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_UROUNDS = u("rounds=")
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_UDOLLAR = u("$")
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_UZERO = u("0")
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class _SHA2_Common(uh.HasManyBackends, uh.HasRounds, uh.HasSalt,
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uh.GenericHandler):
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"""class containing common code shared by sha256_crypt & sha512_crypt"""
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#===================================================================
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# class attrs
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#===================================================================
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# name - set by subclass
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setting_kwds = ("salt", "rounds", "implicit_rounds", "salt_size")
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# ident - set by subclass
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checksum_chars = uh.HASH64_CHARS
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# checksum_size - set by subclass
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max_salt_size = 16
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salt_chars = uh.HASH64_CHARS
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min_rounds = 1000 # bounds set by spec
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max_rounds = 999999999 # bounds set by spec
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rounds_cost = "linear"
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_cdb_use_512 = False # flag for _calc_digest_builtin()
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_rounds_prefix = None # ident + _UROUNDS
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#===================================================================
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# methods
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#===================================================================
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implicit_rounds = False
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def __init__(self, implicit_rounds=None, **kwds):
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super(_SHA2_Common, self).__init__(**kwds)
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# if user calls hash() w/ 5000 rounds, default to compact form.
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if implicit_rounds is None:
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implicit_rounds = (self.use_defaults and self.rounds == 5000)
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self.implicit_rounds = implicit_rounds
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def _parse_salt(self, salt):
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# required per SHA2-crypt spec -- truncate config salts rather than throwing error
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return self._norm_salt(salt, relaxed=self.checksum is None)
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def _parse_rounds(self, rounds):
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# required per SHA2-crypt spec -- clip config rounds rather than throwing error
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return self._norm_rounds(rounds, relaxed=self.checksum is None)
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@classmethod
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def from_string(cls, hash):
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# basic format this parses -
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# $5$[rounds=<rounds>$]<salt>[$<checksum>]
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# TODO: this *could* use uh.parse_mc3(), except that the rounds
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# portion has a slightly different grammar.
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# convert to unicode, check for ident prefix, split on dollar signs.
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hash = to_unicode(hash, "ascii", "hash")
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ident = cls.ident
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if not hash.startswith(ident):
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raise uh.exc.InvalidHashError(cls)
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assert len(ident) == 3
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parts = hash[3:].split(_UDOLLAR)
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# extract rounds value
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if parts[0].startswith(_UROUNDS):
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assert len(_UROUNDS) == 7
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rounds = parts.pop(0)[7:]
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if rounds.startswith(_UZERO) and rounds != _UZERO:
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raise uh.exc.ZeroPaddedRoundsError(cls)
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rounds = int(rounds)
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implicit_rounds = False
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else:
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rounds = 5000
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implicit_rounds = True
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# rest should be salt and checksum
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if len(parts) == 2:
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salt, chk = parts
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elif len(parts) == 1:
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salt = parts[0]
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chk = None
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else:
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raise uh.exc.MalformedHashError(cls)
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# return new object
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return cls(
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rounds=rounds,
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salt=salt,
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checksum=chk or None,
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implicit_rounds=implicit_rounds,
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)
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def to_string(self):
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if self.rounds == 5000 and self.implicit_rounds:
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hash = u("%s%s$%s") % (self.ident, self.salt,
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self.checksum or u(''))
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else:
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hash = u("%srounds=%d$%s$%s") % (self.ident, self.rounds,
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self.salt, self.checksum or u(''))
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return uascii_to_str(hash)
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#===================================================================
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# backends
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#===================================================================
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backends = ("os_crypt", "builtin")
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#---------------------------------------------------------------
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# os_crypt backend
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#---------------------------------------------------------------
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#: test hash for OS detection -- provided by subclass
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_test_hash = None
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@classmethod
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def _load_backend_os_crypt(cls):
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if test_crypt(*cls._test_hash):
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cls._set_calc_checksum_backend(cls._calc_checksum_os_crypt)
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return True
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else:
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return False
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def _calc_checksum_os_crypt(self, secret):
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config = self.to_string()
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hash = safe_crypt(secret, config)
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if hash is None:
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# py3's crypt.crypt() can't handle non-utf8 bytes.
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# fallback to builtin alg, which is always available.
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return self._calc_checksum_builtin(secret)
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# NOTE: avoiding full parsing routine via from_string().checksum,
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# and just extracting the bit we need.
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cs = self.checksum_size
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if not hash.startswith(self.ident) or hash[-cs-1] != _UDOLLAR:
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raise uh.exc.CryptBackendError(self, config, hash)
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return hash[-cs:]
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#---------------------------------------------------------------
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# builtin backend
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#---------------------------------------------------------------
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@classmethod
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def _load_backend_builtin(cls):
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cls._set_calc_checksum_backend(cls._calc_checksum_builtin)
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return True
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def _calc_checksum_builtin(self, secret):
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return _raw_sha2_crypt(secret, self.salt, self.rounds,
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self._cdb_use_512)
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#===================================================================
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# eoc
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#===================================================================
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class sha256_crypt(_SHA2_Common):
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"""This class implements the SHA256-Crypt password hash, and follows the :ref:`password-hash-api`.
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It supports a variable-length salt, and a variable number of rounds.
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The :meth:`~passlib.ifc.PasswordHash.using` method accepts the following optional keywords:
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:type salt: str
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:param salt:
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Optional salt string.
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If not specified, one will be autogenerated (this is recommended).
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If specified, it must be 0-16 characters, drawn from the regexp range ``[./0-9A-Za-z]``.
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:type rounds: int
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:param rounds:
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Optional number of rounds to use.
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Defaults to 535000, must be between 1000 and 999999999, inclusive.
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.. note::
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per the official specification, when the rounds parameter is set to 5000,
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it may be omitted from the hash string.
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:type relaxed: bool
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:param relaxed:
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By default, providing an invalid value for one of the other
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keywords will result in a :exc:`ValueError`. If ``relaxed=True``,
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and the error can be corrected, a :exc:`~passlib.exc.PasslibHashWarning`
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will be issued instead. Correctable errors include ``rounds``
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that are too small or too large, and ``salt`` strings that are too long.
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.. versionadded:: 1.6
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..
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commented out, currently only supported by :meth:`hash`, and not via :meth:`using`:
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:type implicit_rounds: bool
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:param implicit_rounds:
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this is an internal option which generally doesn't need to be touched.
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this flag determines whether the hash should omit the rounds parameter
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when encoding it to a string; this is only permitted by the spec for rounds=5000,
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and the flag is ignored otherwise. the spec requires the two different
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encodings be preserved as they are, instead of normalizing them.
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"""
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#===================================================================
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# class attrs
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#===================================================================
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name = "sha256_crypt"
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ident = u("$5$")
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checksum_size = 43
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# NOTE: using 25/75 weighting of builtin & os_crypt backends
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default_rounds = 535000
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#===================================================================
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# backends
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#===================================================================
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_test_hash = ("test", "$5$rounds=1000$test$QmQADEXMG8POI5W"
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"Dsaeho0P36yK3Tcrgboabng6bkb/")
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#===================================================================
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# eoc
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#===================================================================
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#=============================================================================
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# sha 512 crypt
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#=============================================================================
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class sha512_crypt(_SHA2_Common):
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"""This class implements the SHA512-Crypt password hash, and follows the :ref:`password-hash-api`.
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It supports a variable-length salt, and a variable number of rounds.
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The :meth:`~passlib.ifc.PasswordHash.using` method accepts the following optional keywords:
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:type salt: str
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:param salt:
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Optional salt string.
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If not specified, one will be autogenerated (this is recommended).
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If specified, it must be 0-16 characters, drawn from the regexp range ``[./0-9A-Za-z]``.
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:type rounds: int
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:param rounds:
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Optional number of rounds to use.
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Defaults to 656000, must be between 1000 and 999999999, inclusive.
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.. note::
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per the official specification, when the rounds parameter is set to 5000,
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it may be omitted from the hash string.
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:type relaxed: bool
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:param relaxed:
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By default, providing an invalid value for one of the other
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keywords will result in a :exc:`ValueError`. If ``relaxed=True``,
|
|
and the error can be corrected, a :exc:`~passlib.exc.PasslibHashWarning`
|
|
will be issued instead. Correctable errors include ``rounds``
|
|
that are too small or too large, and ``salt`` strings that are too long.
|
|
|
|
.. versionadded:: 1.6
|
|
|
|
..
|
|
commented out, currently only supported by :meth:`hash`, and not via :meth:`using`:
|
|
|
|
:type implicit_rounds: bool
|
|
:param implicit_rounds:
|
|
this is an internal option which generally doesn't need to be touched.
|
|
|
|
this flag determines whether the hash should omit the rounds parameter
|
|
when encoding it to a string; this is only permitted by the spec for rounds=5000,
|
|
and the flag is ignored otherwise. the spec requires the two different
|
|
encodings be preserved as they are, instead of normalizing them.
|
|
"""
|
|
|
|
#===================================================================
|
|
# class attrs
|
|
#===================================================================
|
|
name = "sha512_crypt"
|
|
ident = u("$6$")
|
|
checksum_size = 86
|
|
_cdb_use_512 = True
|
|
# NOTE: using 25/75 weighting of builtin & os_crypt backends
|
|
default_rounds = 656000
|
|
|
|
#===================================================================
|
|
# backend
|
|
#===================================================================
|
|
_test_hash = ("test", "$6$rounds=1000$test$2M/Lx6Mtobqj"
|
|
"Ljobw0Wmo4Q5OFx5nVLJvmgseatA6oMn"
|
|
"yWeBdRDx4DU.1H3eGmse6pgsOgDisWBG"
|
|
"I5c7TZauS0")
|
|
|
|
#===================================================================
|
|
# eoc
|
|
#===================================================================
|
|
|
|
#=============================================================================
|
|
# eof
|
|
#=============================================================================
|