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Replace isMD5() with a more future-proof way to check if pw is encrypted. 

The rule is that if pg_authid.rolpassword begins with "md5" and has the
right length, it's an MD5 hash, otherwise it's a plaintext password. The
idiom has been to use isMD5() to check for that, but that gets awkward,
when we add new kinds of verifiers, like the verifiers for SCRAM
authentication in the pending SCRAM patch set. Replace isMD5() with a new
get_password_type() function, so that when new verifier types are added, we
don't need to remember to modify every place that currently calls isMD5(),
to also recognize the new kinds of verifiers.

Also, use the new plain_crypt_verify function in passwordcheck, so that it
doesn't need to know about MD5, or in the future, about other kinds of
hashes or password verifiers.

Reviewed by Michael Paquier and Peter Eisentraut.

Discussion: https://www.postgresql.org/message-id/2d07165c-1793-e243-a2a9-e45b624c7580@iki.fi
This commit is contained in:
Heikki Linnakangas 2017-02-01 13:11:37 +02:00
parent 7ac4a389a7
commit dbd69118c0
6 changed files with 219 additions and 158 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

134
contrib/passwordcheck/passwordcheck.c
View File

@ -21,7 +21,7 @@
#endif
#include "commands/user.h"
#include "common/md5.h"
#include "libpq/crypt.h"
#include "fmgr.h"
PG_MODULE_MAGIC;
@ -50,87 +50,77 @@ extern void _PG_init(void);
*/
static void
check_password(const char *username,
const char *password,
int password_type,
const char *shadow_pass,
PasswordType password_type,
Datum validuntil_time,
bool validuntil_null)
{
int namelen = strlen(username);
int pwdlen = strlen(password);
char encrypted[MD5_PASSWD_LEN + 1];
int i;
bool pwd_has_letter,
pwd_has_nonletter;
switch (password_type)
if (password_type != PASSWORD_TYPE_PLAINTEXT)
{
case PASSWORD_TYPE_MD5:
/*
* Unfortunately we cannot perform exhaustive checks on encrypted
* passwords - we are restricted to guessing. (Alternatively, we could
* insist on the password being presented non-encrypted, but that has
* its own security disadvantages.)
*
* We only check for username = password.
*/
char *logdetail;
if (plain_crypt_verify(username, shadow_pass, username, &logdetail) == STATUS_OK)
ereport(ERROR,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("password must not contain user name")));
}
else
{
/*
* For unencrypted passwords we can perform better checks
*/
const char *password = shadow_pass;
int pwdlen = strlen(password);
int i;
bool pwd_has_letter,
pwd_has_nonletter;
/* enforce minimum length */
if (pwdlen < MIN_PWD_LENGTH)
ereport(ERROR,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("password is too short")));
/* check if the password contains the username */
if (strstr(password, username))
ereport(ERROR,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("password must not contain user name")));
/* check if the password contains both letters and non-letters */
pwd_has_letter = false;
pwd_has_nonletter = false;
for (i = 0; i < pwdlen; i++)
{
/*
* Unfortunately we cannot perform exhaustive checks on encrypted
* passwords - we are restricted to guessing. (Alternatively, we
* could insist on the password being presented non-encrypted, but
* that has its own security disadvantages.)
*
* We only check for username = password.
* isalpha() does not work for multibyte encodings but let's
* consider non-ASCII characters non-letters
*/
if (!pg_md5_encrypt(username, username, namelen, encrypted))
elog(ERROR, "password encryption failed");
if (strcmp(password, encrypted) == 0)
ereport(ERROR,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("password must not contain user name")));
break;
case PASSWORD_TYPE_PLAINTEXT:
/*
* For unencrypted passwords we can perform better checks
*/
/* enforce minimum length */
if (pwdlen < MIN_PWD_LENGTH)
ereport(ERROR,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("password is too short")));
/* check if the password contains the username */
if (strstr(password, username))
ereport(ERROR,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("password must not contain user name")));
/* check if the password contains both letters and non-letters */
pwd_has_letter = false;
pwd_has_nonletter = false;
for (i = 0; i < pwdlen; i++)
{
/*
* isalpha() does not work for multibyte encodings but let's
* consider non-ASCII characters non-letters
*/
if (isalpha((unsigned char) password[i]))
pwd_has_letter = true;
else
pwd_has_nonletter = true;
}
if (!pwd_has_letter || !pwd_has_nonletter)
ereport(ERROR,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("password must contain both letters and nonletters")));
if (isalpha((unsigned char) password[i]))
pwd_has_letter = true;
else
pwd_has_nonletter = true;
}
if (!pwd_has_letter || !pwd_has_nonletter)
ereport(ERROR,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("password must contain both letters and nonletters")));
#ifdef USE_CRACKLIB
/* call cracklib to check password */
if (FascistCheck(password, CRACKLIB_DICTPATH))
ereport(ERROR,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("password is easily cracked")));
/* call cracklib to check password */
if (FascistCheck(password, CRACKLIB_DICTPATH))
ereport(ERROR,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("password is easily cracked")));
#endif
break;
default:
elog(ERROR, "unrecognized password type: %d", password_type);
break;
}
/* all checks passed, password is ok */

44
src/backend/commands/user.c
View File

@ -29,7 +29,7 @@
#include "commands/dbcommands.h"
#include "commands/seclabel.h"
#include "commands/user.h"
#include "common/md5.h"
#include "libpq/crypt.h"
#include "miscadmin.h"
#include "storage/lmgr.h"
#include "utils/acl.h"
@ -81,7 +81,6 @@ CreateRole(ParseState *pstate, CreateRoleStmt *stmt)
ListCell *option;
char *password = NULL; /* user password */
int password_type = Password_encryption;
char encrypted_password[MD5_PASSWD_LEN + 1];
bool issuper = false; /* Make the user a superuser? */
bool inherit = true; /* Auto inherit privileges? */
bool createrole = false; /* Can this user create roles? */
@ -370,7 +369,7 @@ CreateRole(ParseState *pstate, CreateRoleStmt *stmt)
if (check_password_hook && password)
(*check_password_hook) (stmt->role,
password,
isMD5(password) ? PASSWORD_TYPE_MD5 : PASSWORD_TYPE_PLAINTEXT,
get_password_type(password),
validUntil_datum,
validUntil_null);
@ -393,17 +392,12 @@ CreateRole(ParseState *pstate, CreateRoleStmt *stmt)
if (password)
{
if (password_type == PASSWORD_TYPE_PLAINTEXT || isMD5(password))
new_record[Anum_pg_authid_rolpassword - 1] =
CStringGetTextDatum(password);
else
{
if (!pg_md5_encrypt(password, stmt->role, strlen(stmt->role),
encrypted_password))
elog(ERROR, "password encryption failed");
new_record[Anum_pg_authid_rolpassword - 1] =
CStringGetTextDatum(encrypted_password);
}
/* Encrypt the password to the requested format. */
char *shadow_pass;
shadow_pass = encrypt_password(password_type, stmt->role, password);
new_record[Anum_pg_authid_rolpassword - 1] =
CStringGetTextDatum(shadow_pass);
}
else
new_record_nulls[Anum_pg_authid_rolpassword - 1] = true;
@ -505,7 +499,6 @@ AlterRole(AlterRoleStmt *stmt)
char *rolename = NULL;
char *password = NULL; /* user password */
int password_type = Password_encryption;
char encrypted_password[MD5_PASSWD_LEN + 1];
int issuper = -1; /* Make the user a superuser? */
int inherit = -1; /* Auto inherit privileges? */
int createrole = -1; /* Can this user create roles? */
@ -744,7 +737,7 @@ AlterRole(AlterRoleStmt *stmt)
if (check_password_hook && password)
(*check_password_hook) (rolename,
password,
isMD5(password) ? PASSWORD_TYPE_MD5 : PASSWORD_TYPE_PLAINTEXT,
get_password_type(password),
validUntil_datum,
validUntil_null);
@ -803,17 +796,12 @@ AlterRole(AlterRoleStmt *stmt)
/* password */
if (password)
{
if (password_type == PASSWORD_TYPE_PLAINTEXT || isMD5(password))
new_record[Anum_pg_authid_rolpassword - 1] =
CStringGetTextDatum(password);
else
{
if (!pg_md5_encrypt(password, rolename, strlen(rolename),
encrypted_password))
elog(ERROR, "password encryption failed");
new_record[Anum_pg_authid_rolpassword - 1] =
CStringGetTextDatum(encrypted_password);
}
/* Encrypt the password to the requested format. */
char *shadow_pass;
shadow_pass = encrypt_password(password_type, rolename, password);
new_record[Anum_pg_authid_rolpassword - 1] =
CStringGetTextDatum(shadow_pass);
new_record_repl[Anum_pg_authid_rolpassword - 1] = true;
}
@ -1228,7 +1216,7 @@ RenameRole(const char *oldname, const char *newname)
datum = heap_getattr(oldtuple, Anum_pg_authid_rolpassword, dsc, &isnull);
if (!isnull && isMD5(TextDatumGetCString(datum)))
if (!isnull && get_password_type(TextDatumGetCString(datum)) == PASSWORD_TYPE_MD5)
{
/* MD5 uses the username as salt, so just clear it on a rename */
repl_repl[Anum_pg_authid_rolpassword - 1] = true;

159
src/backend/libpq/crypt.c
View File

@ -1,10 +1,8 @@
/*-------------------------------------------------------------------------
*
* crypt.c
* Look into the password file and check the encrypted password with
* the one passed in from the frontend.
*
* Original coding by Todd A. Brandys
* Functions for dealing with encrypted passwords stored in
* pg_authid.rolpassword.
*
* Portions Copyright (c) 1996-2017, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
@ -105,6 +103,65 @@ get_role_password(const char *role, char **shadow_pass, char **logdetail)
return retval;
}
/*
* What kind of a password verifier is 'shadow_pass'?
*/
PasswordType
get_password_type(const char *shadow_pass)
{
if (strncmp(shadow_pass, "md5", 3) == 0 && strlen(shadow_pass) == MD5_PASSWD_LEN)
return PASSWORD_TYPE_MD5;
return PASSWORD_TYPE_PLAINTEXT;
}
/*
* Given a user-supplied password, convert it into a verifier of
* 'target_type' kind.
*
* If the password looks like a valid MD5 hash, it is stored as it is.
* We cannot reverse the hash, so even if the caller requested a plaintext
* plaintext password, the MD5 hash is returned.
*/
char *
encrypt_password(PasswordType target_type, const char *role,
const char *password)
{
PasswordType guessed_type = get_password_type(password);
char *encrypted_password;
switch (target_type)
{
case PASSWORD_TYPE_PLAINTEXT:
/*
* We cannot convert a hashed password back to plaintext, so just
* store the password as it was, whether it was hashed or not.
*/
return pstrdup(password);
case PASSWORD_TYPE_MD5:
switch (guessed_type)
{
case PASSWORD_TYPE_PLAINTEXT:
encrypted_password = palloc(MD5_PASSWD_LEN + 1);
if (!pg_md5_encrypt(password, role, strlen(role),
encrypted_password))
elog(ERROR, "password encryption failed");
return encrypted_password;
case PASSWORD_TYPE_MD5:
return pstrdup(password);
}
}
/*
* This shouldn't happen, because the above switch statements should
* handle every combination of source and target password types.
*/
elog(ERROR, "cannot encrypt password to requested type");
}
/*
* Check MD5 authentication response, and return STATUS_OK or STATUS_ERROR.
*
@ -135,32 +192,40 @@ md5_crypt_verify(const char *role, const char *shadow_pass,
* below: the only possible error is out-of-memory, which is unlikely, and
* if it did happen adding a psprintf call would only make things worse.
*/
if (isMD5(shadow_pass))
switch (get_password_type(shadow_pass))
{
/* stored password already encrypted, only do salt */
if (!pg_md5_encrypt(shadow_pass + strlen("md5"),
md5_salt, md5_salt_len,
crypt_pwd))
{
case PASSWORD_TYPE_MD5:
/* stored password already encrypted, only do salt */
if (!pg_md5_encrypt(shadow_pass + strlen("md5"),
md5_salt, md5_salt_len,
crypt_pwd))
{
return STATUS_ERROR;
}
break;
case PASSWORD_TYPE_PLAINTEXT:
/* stored password is plain, double-encrypt */
if (!pg_md5_encrypt(shadow_pass,
role,
strlen(role),
crypt_pwd2))
{
return STATUS_ERROR;
}
if (!pg_md5_encrypt(crypt_pwd2 + strlen("md5"),
md5_salt, md5_salt_len,
crypt_pwd))
{
return STATUS_ERROR;
}
break;
default:
/* unknown password hash format. */
*logdetail = psprintf(_("User \"%s\" has a password that cannot be used with MD5 authentication."),
role);
return STATUS_ERROR;
}
}
else
{
/* stored password is plain, double-encrypt */
if (!pg_md5_encrypt(shadow_pass,
role,
strlen(role),
crypt_pwd2))
{
return STATUS_ERROR;
}
if (!pg_md5_encrypt(crypt_pwd2 + strlen("md5"),
md5_salt, md5_salt_len,
crypt_pwd))
{
return STATUS_ERROR;
}
}
if (strcmp(client_pass, crypt_pwd) == 0)
@ -198,22 +263,36 @@ plain_crypt_verify(const char *role, const char *shadow_pass,
* the password the client sent, and compare the hashes. Otherwise
* compare the plaintext passwords directly.
*/
if (isMD5(shadow_pass))
switch (get_password_type(shadow_pass))
{
if (!pg_md5_encrypt(client_pass,
role,
strlen(role),
crypt_client_pass))
{
case PASSWORD_TYPE_MD5:
if (!pg_md5_encrypt(client_pass,
role,
strlen(role),
crypt_client_pass))
{
/*
* We do not bother setting logdetail for pg_md5_encrypt
* failure: the only possible error is out-of-memory, which is
* unlikely, and if it did happen adding a psprintf call would
* only make things worse.
*/
return STATUS_ERROR;
}
client_pass = crypt_client_pass;
break;
case PASSWORD_TYPE_PLAINTEXT:
break;
default:
/*
* We do not bother setting logdetail for pg_md5_encrypt failure:
* the only possible error is out-of-memory, which is unlikely,
* and if it did happen adding a psprintf call would only make
* things worse.
* This shouldn't happen. Plain "password" authentication should
* be possible with any kind of stored password hash.
*/
*logdetail = psprintf(_("Password of user \"%s\" is in unrecognized format."),
role);
return STATUS_ERROR;
}
client_pass = crypt_client_pass;
}
if (strcmp(client_pass, shadow_pass) == 0)

17
src/include/commands/user.h
View File

@ -12,24 +12,15 @@
#define USER_H
#include "catalog/objectaddress.h"
#include "libpq/crypt.h"
#include "nodes/parsenodes.h"
#include "parser/parse_node.h"
/*
* Types of password, for Password_encryption GUC and the password_type
* argument of the check-password hook.
*/
typedef enum PasswordType
{
PASSWORD_TYPE_PLAINTEXT = 0,
PASSWORD_TYPE_MD5
} PasswordType;
extern int Password_encryption; /* GUC */
/* GUC. Is actually of type PasswordType. */
extern int Password_encryption;
/* Hook to check passwords in CreateRole() and AlterRole() */
typedef void (*check_password_hook_type) (const char *username, const char *password, int password_type, Datum validuntil_time, bool validuntil_null);
typedef void (*check_password_hook_type) (const char *username, const char *shadow_pass, PasswordType password_type, Datum validuntil_time, bool validuntil_null);
extern PGDLLIMPORT check_password_hook_type check_password_hook;

4
src/include/common/md5.h
View File

@ -18,10 +18,6 @@
#define MD5_PASSWD_LEN 35
#define isMD5(passwd) (strncmp(passwd, "md5", 3) == 0 && \
strlen(passwd) == MD5_PASSWD_LEN)
extern bool pg_md5_hash(const void *buff, size_t len, char *hexsum);
extern bool pg_md5_binary(const void *buff, size_t len, void *outbuf);
extern bool pg_md5_encrypt(const char *passwd, const char *salt,

19
src/include/libpq/crypt.h
View File

@ -15,7 +15,24 @@
#include "datatype/timestamp.h"
extern int get_role_password(const char *role, char **shadow_pass, char **logdetail);
/*
* Types of password hashes or verifiers that can be stored in
* pg_authid.rolpassword.
*
* This is also used for the password_encryption GUC.
*/
typedef enum PasswordType
{
PASSWORD_TYPE_PLAINTEXT = 0,
PASSWORD_TYPE_MD5
} PasswordType;
extern PasswordType get_password_type(const char *shadow_pass);
extern char *encrypt_password(PasswordType target_type, const char *role,
const char *password);
extern int get_role_password(const char *role, char **shadow_pass,
char **logdetail);
extern int md5_crypt_verify(const char *role, const char *shadow_pass,
const char *client_pass, const char *md5_salt,