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Commita7be2a6

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Add new function, PQchangePassword(), to libpq
Essentially this moves the non-interactive part of psql's "\password"command into an exported client function. The password is not sent to theserver in cleartext because it is "encrypted" (in the case of scram and md5it is actually hashed, but we have called these encrypted passwords for along time now) on the client side. This is good because it ensures thecleartext password is never known by the server, and therefore won't end upin logs, pg_stat displays, etc.In other words, it exists for the same reason as PQencryptPasswordConn(), butis more convenient as it both builds and runs the "ALTER USER" command foryou. PQchangePassword() uses PQencryptPasswordConn() to do the passwordencryption. PQencryptPasswordConn() is passed a NULL for the algorithmargument, hence encryption is done according to the server'spassword_encryption setting.Also modify the psql client to use the new function. That provides a builtintest case. Ultimately drivers built on top of libpq should expose thisfunction and its use should be generally encouraged over doing ALTER USERdirectly for password changes.Author: Joe ConwayReviewed-by: Tom LaneDiscussion:https://postgr.es/m/flat/b75955f7-e8cc-4bbd-817f-ef536bacbe93%40joeconway.com
1 parentd596736 commita7be2a6

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5 files changed

+125
-17
lines changed

5 files changed

+125
-17
lines changed

‎doc/src/sgml/libpq.sgml

Lines changed: 39 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -7116,6 +7116,45 @@ char *PQencryptPasswordConn(PGconn *conn, const char *passwd, const char *user,
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</listitem>
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</varlistentry>
71187118

7119+
<varlistentry id="libpq-PQchangePassword">
7120+
<term><function>PQchangePassword</function><indexterm><primary>PQchangePassword</primary></indexterm></term>
7121+
7122+
<listitem>
7123+
<para>
7124+
Changes a <productname>PostgreSQL</productname> password.
7125+
<synopsis>
7126+
PGresult *PQchangePassword(PGconn *conn, const char *user, const char *passwd);
7127+
</synopsis>
7128+
This function uses <function>PQencryptPasswordConn</function>
7129+
to build and execute the command <literal>ALTER USER ... PASSWORD
7130+
'...'</literal>, thereby changing the user's password. It exists for
7131+
the same reason as <function>PQencryptPasswordConn</function>, but
7132+
is more convenient as it both builds and runs the command for you.
7133+
<xref linkend="libpq-PQencryptPasswordConn"/> is passed a
7134+
<symbol>NULL</symbol> for the algorithm argument, hence encryption is
7135+
done according to the server's <xref linkend="guc-password-encryption"/>
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setting.
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</para>
7138+
7139+
<para>
7140+
The <parameter>user</parameter> and <parameter>passwd</parameter> arguments
7141+
are the SQL name of the target user, and the new cleartext password.
7142+
</para>
7143+
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<para>
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Returns a <structname>PGresult</structname> pointer representing
7146+
the result of the <literal>ALTER USER</literal> command, or
7147+
a null pointer if the routine failed before issuing any command.
7148+
The <xref linkend="libpq-PQresultStatus"/> function should be called
7149+
to check the return value for any errors (including the value of a null
7150+
pointer, in which case it will return
7151+
<symbol>PGRES_FATAL_ERROR</symbol>). Use
7152+
<xref linkend="libpq-PQerrorMessage"/> to get more information about
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such errors.
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</para>
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</listitem>
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</varlistentry>
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71197158
<varlistentry id="libpq-PQencryptPassword">
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<term><function>PQencryptPassword</function><indexterm><primary>PQencryptPassword</primary></indexterm></term>
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‎src/bin/psql/command.c

Lines changed: 3 additions & 17 deletions
Original file line numberDiff line numberDiff line change
@@ -2158,29 +2158,15 @@ exec_command_password(PsqlScanState scan_state, bool active_branch)
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}
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else
21602160
{
2161-
char*encrypted_password;
2161+
PGresult*res=PQchangePassword(pset.db,user,pw1);
21622162

2163-
encrypted_password=PQencryptPasswordConn(pset.db,pw1,user,NULL);
2164-
2165-
if (!encrypted_password)
2163+
if (PQresultStatus(res)!=PGRES_COMMAND_OK)
21662164
{
21672165
pg_log_info("%s",PQerrorMessage(pset.db));
21682166
success= false;
21692167
}
2170-
else
2171-
{
2172-
PGresult*res;
21732168

2174-
printfPQExpBuffer(&buf,"ALTER USER %s PASSWORD ",
2175-
fmtId(user));
2176-
appendStringLiteralConn(&buf,encrypted_password,pset.db);
2177-
res=PSQLexec(buf.data);
2178-
if (!res)
2179-
success= false;
2180-
else
2181-
PQclear(res);
2182-
PQfreemem(encrypted_password);
2183-
}
2169+
PQclear(res);
21842170
}
21852171

21862172
free(user);

‎src/interfaces/libpq/exports.txt

Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -191,3 +191,4 @@ PQclosePrepared 188
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PQclosePortal 189
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PQsendClosePrepared 190
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PQsendClosePortal 191
194+
PQchangePassword 192

‎src/interfaces/libpq/fe-auth.c

Lines changed: 81 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -1372,3 +1372,84 @@ PQencryptPasswordConn(PGconn *conn, const char *passwd, const char *user,
13721372

13731373
returncrypt_pwd;
13741374
}
1375+
1376+
/*
1377+
* PQchangePassword -- exported routine to change a password
1378+
*
1379+
* This is intended to be used by client applications that wish to
1380+
* change the password for a user. The password is not sent in
1381+
* cleartext because it is encrypted on the client side. This is
1382+
* good because it ensures the cleartext password is never known by
1383+
* the server, and therefore won't end up in logs, pg_stat displays,
1384+
* etc. The password encryption is performed by PQencryptPasswordConn(),
1385+
* which is passed a NULL for the algorithm argument. Hence encryption
1386+
* is done according to the server's password_encryption
1387+
* setting. We export the function so that clients won't be dependent
1388+
* on the implementation specific details with respect to how the
1389+
* server changes passwords.
1390+
*
1391+
* Arguments are a connection object, the SQL name of the target user,
1392+
* and the cleartext password.
1393+
*
1394+
* Return value is the PGresult of the executed ALTER USER statement
1395+
* or NULL if we never get there. The caller is responsible to PQclear()
1396+
* the returned PGresult.
1397+
*
1398+
* PQresultStatus() should be called to check the return value for errors,
1399+
* and PQerrorMessage() used to get more information about such errors.
1400+
*/
1401+
PGresult*
1402+
PQchangePassword(PGconn*conn,constchar*user,constchar*passwd)
1403+
{
1404+
char*encrypted_password=PQencryptPasswordConn(conn,passwd,
1405+
user,NULL);
1406+
1407+
if (!encrypted_password)
1408+
{
1409+
/* PQencryptPasswordConn() already registered the error */
1410+
returnNULL;
1411+
}
1412+
else
1413+
{
1414+
char*fmtpw=PQescapeLiteral(conn,encrypted_password,
1415+
strlen(encrypted_password));
1416+
1417+
/* no longer needed, so clean up now */
1418+
PQfreemem(encrypted_password);
1419+
1420+
if (!fmtpw)
1421+
{
1422+
/* PQescapeLiteral() already registered the error */
1423+
returnNULL;
1424+
}
1425+
else
1426+
{
1427+
char*fmtuser=PQescapeIdentifier(conn,user,strlen(user));
1428+
1429+
if (!fmtuser)
1430+
{
1431+
/* PQescapeIdentifier() already registered the error */
1432+
PQfreemem(fmtpw);
1433+
returnNULL;
1434+
}
1435+
else
1436+
{
1437+
PQExpBufferDatabuf;
1438+
PGresult*res;
1439+
1440+
initPQExpBuffer(&buf);
1441+
printfPQExpBuffer(&buf,"ALTER USER %s PASSWORD %s",
1442+
fmtuser,fmtpw);
1443+
1444+
res=PQexec(conn,buf.data);
1445+
1446+
/* clean up */
1447+
termPQExpBuffer(&buf);
1448+
PQfreemem(fmtuser);
1449+
PQfreemem(fmtpw);
1450+
1451+
returnres;
1452+
}
1453+
}
1454+
}
1455+
}

‎src/interfaces/libpq/libpq-fe.h

Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -659,6 +659,7 @@ extern intPQenv2encoding(void);
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660660
externchar*PQencryptPassword(constchar*passwd,constchar*user);
661661
externchar*PQencryptPasswordConn(PGconn*conn,constchar*passwd,constchar*user,constchar*algorithm);
662+
externPGresult*PQchangePassword(PGconn*conn,constchar*user,constchar*passwd);
662663

663664
/* === in encnames.c === */
664665

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