From af92b565250adce354d1af936c0013d0175a5b81 Mon Sep 17 00:00:00 2001

From: Jitka Plesnikova <jplesnik@redhat.com>

Date: Mon, 1 Jun 2020 18:33:56 +0200

Subject: [PATCH 4/4] study_chunk: extract rck_elide_nothing

(CVE-2020-10878)

---

 embed.fnc |  1 +

 embed.h   |  1 +

 proto.h   |  4 ++++

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

 4 files changed, 49 insertions(+), 27 deletions(-)

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

index 9546555..aa6c886 100644

--- a/embed.fnc

+++ b/embed.fnc

@@ -1952,6 +1952,7 @@ Es	|I32	|study_chunk	|NN struct RExC_state_t *pRExC_state \

 				|I32 stopparen|NULLOK U8* recursed \

 				|NULLOK struct regnode_charclass_class *and_withp \

 				|U32 flags|U32 depth|bool was_mutate_ok

+Es	|void	|rck_elide_nothing|NN regnode *node

 EsRn	|U32	|add_data	|NN struct RExC_state_t *pRExC_state|U32 n \

 				|NN const char *s

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

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

index f7db1e0..555538d 100644

--- a/embed.h

+++ b/embed.h

@@ -933,6 +933,7 @@

 #define make_trie(a,b,c,d,e,f,g,h)	S_make_trie(aTHX_ a,b,c,d,e,f,g,h)

 #define make_trie_failtable(a,b,c,d)	S_make_trie_failtable(aTHX_ a,b,c,d)

 #define nextchar(a)		S_nextchar(aTHX_ a)

+#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 reg_namedseq(a,b,c,d)	S_reg_namedseq(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 143eee0..d7cba26 100644

--- a/proto.h

+++ b/proto.h

@@ -6477,6 +6477,10 @@ STATIC char *	S_nextchar(pTHX_ struct RExC_state_t *pRExC_state)

 #define PERL_ARGS_ASSERT_NEXTCHAR	\

 	assert(pRExC_state)

+STATIC void	S_rck_elide_nothing(pTHX_ regnode *node);

+#define PERL_ARGS_ASSERT_RCK_ELIDE_NOTHING	\

+        assert(node)

+

 STATIC void	S_re_croak2(pTHX_ const char* pat1, const char* pat2, ...)

 			__attribute__noreturn__

 			__attribute__nonnull__(pTHX_1)

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

index 9842a83..aa96980 100644

--- a/regcomp.c

+++ b/regcomp.c

@@ -2967,6 +2967,43 @@ case N ## nAmE:                                                    \

     break

+/* 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 I32

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

@@ -3034,27 +3071,9 @@ S_study_chunk(pTHX_ RExC_state_t *pRExC_state, regnode **scanp,

 	/* 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;

-	}

+           away all the NOTHINGs from it.

+         */

+        rck_elide_nothing(scan);

@@ -4057,11 +4094,7 @@ S_study_chunk(pTHX_ RExC_state_t *pRExC_state, regnode **scanp,

 		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:			/* REF, ANYOFV, and CLUMP only? */

 		if (flags & SCF_DO_SUBSTR) {

-- 

2.25.4