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Nov 15, 2025
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refactor(docs): improve wording, fix section #1342

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6 changes: 5 additions & 1 deletion .github/actions/spelling/expect.txt
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Original file line number Diff line number Diff line change
Expand Up @@ -58,6 +58,7 @@ bayes
bcc
benumber
bernat
bigcrypt
bitfield
BITMIME
blitiri
Expand All @@ -68,6 +69,7 @@ boollist
Borenstein
bsd
bsdauth
bsdicrypt
bsearch
bugreport
bugzilla
Expand Down Expand Up @@ -138,6 +140,7 @@ delaycompress
deleteheader
DELETESCRIPT
dentries
descrypt
DESTNAME
destuser
dextended
Expand Down Expand Up @@ -259,6 +262,7 @@ gmatch
gno
gnomint
gnutls
gost
gss
gssapi
halon
Expand Down Expand Up @@ -893,7 +897,6 @@ vlast
vmail
vname
vnd
vpv
vsize
vsz
vuejs
Expand All @@ -916,6 +919,7 @@ xfs
xoauth
XRCPTFORWARD
xuidl
yescrypt
yourldap
zimbra
Zstandard
51 changes: 41 additions & 10 deletions docs/core/config/auth/schemes.md
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Expand Up @@ -72,6 +72,35 @@ algorithm as described in the hash, e.g, `{ARGON2}$argon2id$...` is
recognized and processed properly as ARGON2I/ARGON2ID (as long as
libsodium is recent enough to support it).

### CRYPT

This is an umbrella term for all password schemes libc's `crypt()` can verify.
On a current Linux system (2025) these are the following roughly in the order
from strongest to weakest:

| Scheme | Prefix | Maximum passphrase length |
|---------------|----------|----------------------------------|
| yescrypt | `$y$` | unlimited |
| gost-yescrypt | `$gy$` | unlimited |
| sm3-yescrypt | `$sm3y$` | unlimited |
| scrypt | `$7$` | unlimited |
| bcrypt | `$2b$` | 72 characters |
| sha512crypt | `$6$` | unlimited |
| sha256crypt | `$5$` | unlimited |
| sm3crypt | `$sm3$` | unlimited |
| sha1crypt | `$sha1` | unlimited |
| SunMD5 | `$md5` | unlimited |
| md5crypt | `$1$` | unlimited |
| bsdicrypt | `_` | (ignores 8th bit) |
| descrypt | | 8 characters (ignores 8th bit) |
| bigcrypt | | 128 characters (ignores 8th bit) |
| NT | `$3$` | unlimited |

::: warning
On older Linux distros `crypt()` might not include all of the schemes in the list above.
You can verify which ones are supported on your system by reading `man 5 crypt`
:::

### BLF-CRYPT

This is the Blowfish crypt (bcrypt) scheme. It is generally considered to
Expand All @@ -92,7 +121,9 @@ A strong scheme. The encrypted password will start with `$6$`.

A strong scheme. The encrypted password will start with `$5$`.

### MD5-CRYPT: A weak but common scheme often used in `/etc/shadow`. The
### MD5-CRYPT

A weak but common scheme often used in `/etc/shadow`. The
encrypted password will start with `$1$`.

## Generating Encrypted Passwords
Expand Down Expand Up @@ -165,16 +196,12 @@ Password is in cleartext.

### CRYPT

Traditional DES-crypted password in `/etc/passwd` (e.g.
"pass" = `vpvKh.SaNbR6s`.
Password is encrypted.

* Dovecot uses libc's `crypt()` function, which means that CRYPT is usually
able to recognize MD5-CRYPT and possibly also other password schemes. See
all of the `*-CRYPT` schemes at the top of this page.
Dovecot uses libc's `crypt()` function, which means that it is able to recognize
all password schemes available on your system (e.g. the ones used in `/etc/passwd`).

* The traditional DES-crypt scheme only uses the first 8 characters of the
password, the rest are ignored. Other schemes may have other password length
limitations (if they limit the password length at all).
See [CRYPT](#crypt) above for a list.

#### BLF-CRYPT

Expand All @@ -184,6 +211,10 @@ Bcrypt based hash. (`$2y$`)

Traditional DES based hash.

The DES-crypt scheme only uses the first 8 characters of the password, the rest
is ignored. Other schemes may have other password length limitations (if they
limit the password length at all).

::: warning [[changed,crypt_des_md5_schemes]]
Disabled by default.
:::
Expand All @@ -204,7 +235,7 @@ SHA-256 based hash (`$5$`)

SHA-512 based hash (`$6$`)

#### OTP
### OTP

[[rfc,2289]] based One-Time Password system.

Expand Down