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Commit3855e5b

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Ignore attempts to \gset into specially treated variables.
If an interactive psql session used \gset when querying a compromisedserver, the attacker could execute arbitrary code as the operatingsystem account running psql. Using a prefix not found among speciallytreated variables, e.g. every lowercase string, precluded the attack.Fix by issuing a warning and setting no variable for the column inquestion. Users wanting the old behavior can use a prefix and then ameta-command like "\set HISTSIZE :prefix_HISTSIZE". Back-patch to 9.5(all supported versions).Reviewed by Robert Haas. Reported by Nick Cleaton.Security:CVE-2020-25696
1 parentac8f624 commit3855e5b

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5 files changed

+41
-0
lines changed

5 files changed

+41
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lines changed

‎src/bin/psql/common.c

Lines changed: 7 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -921,6 +921,13 @@ StoreQueryTuple(const PGresult *result)
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/* concatenate prefix and column name */
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varname=psprintf("%s%s",pset.gset_prefix,colname);
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if (VariableHasHook(pset.vars,varname))
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{
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pg_log_warning("attempt to \\gset into specially treated variable \"%s\" ignored",
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varname);
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continue;
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}
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if (!PQgetisnull(result,0,i))
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value=PQgetvalue(result,0,i);
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else

‎src/bin/psql/variables.c

Lines changed: 26 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -362,6 +362,32 @@ SetVariableHooks(VariableSpace space, const char *name,
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(void) (*ahook) (current->value);
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}
364364

365+
/*
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* Return true iff the named variable has substitute and/or assign hook
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* functions.
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*/
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bool
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VariableHasHook(VariableSpacespace,constchar*name)
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{
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struct_variable*current;
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Assert(space);
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Assert(name);
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for (current=space->next;current;current=current->next)
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{
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intcmp=strcmp(current->name,name);
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if (cmp==0)
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return (current->substitute_hook!=NULL||
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current->assign_hook!=NULL);
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if (cmp>0)
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break;/* it's not there */
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}
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return false;
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}
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/*
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* Convenience function to set a variable's value to "on".
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*/

‎src/bin/psql/variables.h

Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -90,6 +90,7 @@ boolDeleteVariable(VariableSpace space, const char *name);
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voidSetVariableHooks(VariableSpacespace,constchar*name,
9191
VariableSubstituteHookshook,
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VariableAssignHookahook);
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boolVariableHasHook(VariableSpacespace,constchar*name);
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voidPsqlVarEnumError(constchar*name,constchar*value,constchar*suggestions);
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‎src/test/regress/expected/psql.out

Lines changed: 4 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -84,6 +84,10 @@ select 10 as test01, 20 as test02, 'Hello' as test03 \gset pref01_
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select 10 as "bad name"
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\gset
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invalid variable name: "bad name"
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select 97 as "EOF", 'ok' as _foo \gset IGNORE
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attempt to \gset into specially treated variable "IGNOREEOF" ignored
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\echo :IGNORE_foo :IGNOREEOF
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ok 0
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-- multiple backslash commands in one line
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select 1 as x, 2 as y \gset pref01_ \\ \echo :pref01_x
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1

‎src/test/regress/sql/psql.sql

Lines changed: 3 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -48,6 +48,9 @@ select 10 as test01, 20 as test02, 'Hello' as test03 \gset pref01_
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select10as"bad name"
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\gset
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select97as"EOF",'ok'as _foo \gset IGNORE
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\echo :IGNORE_foo :IGNOREEOF
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-- multiple backslash commands in one line
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select1as x,2as y \gset pref01_ \\ \echo :pref01_x
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select3as x,4as y \gset pref01_ \echo :pref01_x \echo :pref01_y

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