From a3a7598c8ec6efb0eb9c0b786d80c4d2a3751b70 Mon Sep 17 00:00:00 2001

From: Hugo van der Sanden <hv@crypt.org>

Date: Tue, 18 Feb 2020 13:51:16 +0000

Subject: [PATCH v528 2/3] study_chunk: extract rck_elide_nothing

(CVE-2020-10878)

---

 embed.fnc |  1 +

 embed.h   |  1 +

 proto.h   |  3 +++

 regcomp.c | 70 ++++++++++++++++++++++++++++++++++---------------------

 4 files changed, 48 insertions(+), 27 deletions(-)

diff --git a/embed.fnc b/embed.fnc

index e762fe1eec..cf89277163 100644

--- a/embed.fnc

+++ b/embed.fnc

@@ -2398,6 +2398,7 @@ Es	|SSize_t|study_chunk	|NN RExC_state_t *pRExC_state \

                                 |I32 stopparen|U32 recursed_depth \

 				|NULLOK regnode_ssc *and_withp \

 				|U32 flags|U32 depth|bool was_mutate_ok

+Es	|void	|rck_elide_nothing|NN regnode *node

 EsRn	|U32	|add_data	|NN RExC_state_t* const pRExC_state \

 				|NN const char* const s|const U32 n

 rs	|void	|re_croak2	|bool utf8|NN const char* pat1|NN const char* pat2|...

diff --git a/embed.h b/embed.h

index a5416a1148..886551ce5c 100644

--- a/embed.h

+++ b/embed.h

@@ -1046,6 +1046,7 @@

 #define output_or_return_posix_warnings(a,b,c)	S_output_or_return_posix_warnings(aTHX_ a,b,c)

 #define parse_lparen_question_flags(a)	S_parse_lparen_question_flags(aTHX_ a)

 #define populate_ANYOF_from_invlist(a,b)	S_populate_ANYOF_from_invlist(aTHX_ a,b)

+#define rck_elide_nothing(a)	S_rck_elide_nothing(aTHX_ a)

 #define reg(a,b,c,d)		S_reg(aTHX_ a,b,c,d)

 #define reg2Lanode(a,b,c,d)	S_reg2Lanode(aTHX_ a,b,c,d)

 #define reg_node(a,b)		S_reg_node(aTHX_ a,b)

diff --git a/proto.h b/proto.h

index 66bb29b132..d3f8802c1d 100644

--- a/proto.h

+++ b/proto.h

@@ -5150,6 +5150,9 @@ STATIC void	S_parse_lparen_question_flags(pTHX_ RExC_state_t *pRExC_state);

 STATIC void	S_populate_ANYOF_from_invlist(pTHX_ regnode *node, SV** invlist_ptr);

 #define PERL_ARGS_ASSERT_POPULATE_ANYOF_FROM_INVLIST	\

 	assert(node); assert(invlist_ptr)

+STATIC void	S_rck_elide_nothing(pTHX_ regnode *node);

+#define PERL_ARGS_ASSERT_RCK_ELIDE_NOTHING	\

+	assert(node)

 PERL_STATIC_NO_RET void	S_re_croak2(pTHX_ bool utf8, const char* pat1, const char* pat2, ...)

 			__attribute__noreturn__;

 #define PERL_ARGS_ASSERT_RE_CROAK2	\

diff --git a/regcomp.c b/regcomp.c

index dd18add1db..0a9c6a8085 100644

--- a/regcomp.c

+++ b/regcomp.c

@@ -4094,6 +4094,43 @@ S_unwind_scan_frames(pTHX_ const void *p)

     } while (f);

 }

+/* Follow the next-chain of the current node and optimize away

+   all the NOTHINGs from it.

+ */

+STATIC void

+S_rck_elide_nothing(pTHX_ regnode *node)

+{

+    dVAR;

+

+    PERL_ARGS_ASSERT_RCK_ELIDE_NOTHING;

+

+    if (OP(node) != CURLYX) {

+        const int max = (reg_off_by_arg[OP(node)]

+                        ? I32_MAX

+                          /* I32 may be smaller than U16 on CRAYs! */

+                        : (I32_MAX < U16_MAX ? I32_MAX : U16_MAX));

+        int off = (reg_off_by_arg[OP(node)] ? ARG(node) : NEXT_OFF(node));

+        int noff;

+        regnode *n = node;

+

+        /* Skip NOTHING and LONGJMP. */

+        while (

+            (n = regnext(n))

+            && (

+                (PL_regkind[OP(n)] == NOTHING && (noff = NEXT_OFF(n)))

+                || ((OP(n) == LONGJMP) && (noff = ARG(n)))

+            )

+            && off + noff < max

+        ) {

+            off += noff;

+        }

+        if (reg_off_by_arg[OP(node)])

+            ARG(node) = off;

+        else

+            NEXT_OFF(node) = off;

+    }

+    return;

+}

 STATIC SSize_t

 S_study_chunk(pTHX_ RExC_state_t *pRExC_state, regnode **scanp,

@@ -4197,28 +4234,10 @@ S_study_chunk(pTHX_ RExC_state_t *pRExC_state, regnode **scanp,

         if (mutate_ok)

             JOIN_EXACT(scan,&min_subtract, &unfolded_multi_char, 0);

-	/* Follow the next-chain of the current node and optimize

-	   away all the NOTHINGs from it.  */

-	if (OP(scan) != CURLYX) {

-	    const int max = (reg_off_by_arg[OP(scan)]

-		       ? I32_MAX

-		       /* I32 may be smaller than U16 on CRAYs! */

-		       : (I32_MAX < U16_MAX ? I32_MAX : U16_MAX));

-	    int off = (reg_off_by_arg[OP(scan)] ? ARG(scan) : NEXT_OFF(scan));

-	    int noff;

-	    regnode *n = scan;

-

-	    /* Skip NOTHING and LONGJMP. */

-	    while ((n = regnext(n))

-		   && ((PL_regkind[OP(n)] == NOTHING && (noff = NEXT_OFF(n)))

-		       || ((OP(n) == LONGJMP) && (noff = ARG(n))))

-		   && off + noff < max)

-		off += noff;

-	    if (reg_off_by_arg[OP(scan)])

-		ARG(scan) = off;

-	    else

-		NEXT_OFF(scan) = off;

-	}

+        /* Follow the next-chain of the current node and optimize

+           away all the NOTHINGs from it.

+         */

+        rck_elide_nothing(scan);

 	/* The principal pseudo-switch.  Cannot be a switch, since we

 	   look into several different things.  */

@@ -5348,11 +5367,7 @@ Perl_re_printf( aTHX_  "LHS=%" UVuf " RHS=%" UVuf "\n",

 		if (data && (fl & SF_HAS_EVAL))

 		    data->flags |= SF_HAS_EVAL;

 	      optimize_curly_tail:

-		if (OP(oscan) != CURLYX) {

-		    while (PL_regkind[OP(next = regnext(oscan))] == NOTHING

-			   && NEXT_OFF(next))

-			NEXT_OFF(oscan) += NEXT_OFF(next);

-		}

+		rck_elide_nothing(oscan);

 		continue;

 	    default:

-- 

2.20.1