commit 37b45d8ff0f92a7ea0491dd61a0bceb951af332e Author: Tomas Korbar Date: Tue May 3 09:57:53 2022 +0200 Fix CVE-2022-25313 diff --git a/lib/xmlparse.c b/lib/xmlparse.c index 0948906..8e84b5a 100644 --- a/lib/xmlparse.c +++ b/lib/xmlparse.c @@ -7138,44 +7138,15 @@ nextScaffoldPart(XML_Parser parser) { return next; } -static void -build_node(XML_Parser parser, int src_node, XML_Content *dest, - XML_Content **contpos, XML_Char **strpos) { - DTD *const dtd = parser->m_dtd; /* save one level of indirection */ - dest->type = dtd->scaffold[src_node].type; - dest->quant = dtd->scaffold[src_node].quant; - if (dest->type == XML_CTYPE_NAME) { - const XML_Char *src; - dest->name = *strpos; - src = dtd->scaffold[src_node].name; - for (;;) { - *(*strpos)++ = *src; - if (! *src) - break; - src++; - } - dest->numchildren = 0; - dest->children = NULL; - } else { - unsigned int i; - int cn; - dest->numchildren = dtd->scaffold[src_node].childcnt; - dest->children = *contpos; - *contpos += dest->numchildren; - for (i = 0, cn = dtd->scaffold[src_node].firstchild; i < dest->numchildren; - i++, cn = dtd->scaffold[cn].nextsib) { - build_node(parser, cn, &(dest->children[i]), contpos, strpos); - } - dest->name = NULL; - } -} - static XML_Content * build_model(XML_Parser parser) { + /* Function build_model transforms the existing parser->m_dtd->scaffold + * array of CONTENT_SCAFFOLD tree nodes into a new array of + * XML_Content tree nodes followed by a gapless list of zero-terminated + * strings. */ DTD *const dtd = parser->m_dtd; /* save one level of indirection */ XML_Content *ret; - XML_Content *cpos; - XML_Char *str; + XML_Char *str; /* the current string writing location */ /* Detect and prevent integer overflow. * The preprocessor guard addresses the "always false" warning @@ -7201,10 +7172,96 @@ build_model(XML_Parser parser) { if (! ret) return NULL; - str = (XML_Char *)(&ret[dtd->scaffCount]); - cpos = &ret[1]; + /* What follows is an iterative implementation (of what was previously done + * recursively in a dedicated function called "build_node". The old recursive + * build_node could be forced into stack exhaustion from input as small as a + * few megabyte, and so that was a security issue. Hence, a function call + * stack is avoided now by resolving recursion.) + * + * The iterative approach works as follows: + * + * - We have two writing pointers, both walking up the result array; one does + * the work, the other creates "jobs" for its colleague to do, and leads + * the way: + * + * - The faster one, pointer jobDest, always leads and writes "what job + * to do" by the other, once they reach that place in the + * array: leader "jobDest" stores the source node array index (relative + * to array dtd->scaffold) in field "numchildren". + * + * - The slower one, pointer dest, looks at the value stored in the + * "numchildren" field (which actually holds a source node array index + * at that time) and puts the real data from dtd->scaffold in. + * + * - Before the loop starts, jobDest writes source array index 0 + * (where the root node is located) so that dest will have something to do + * when it starts operation. + * + * - Whenever nodes with children are encountered, jobDest appends + * them as new jobs, in order. As a result, tree node siblings are + * adjacent in the resulting array, for example: + * + * [0] root, has two children + * [1] first child of 0, has three children + * [3] first child of 1, does not have children + * [4] second child of 1, does not have children + * [5] third child of 1, does not have children + * [2] second child of 0, does not have children + * + * Or (the same data) presented in flat array view: + * + * [0] root, has two children + * + * [1] first child of 0, has three children + * [2] second child of 0, does not have children + * + * [3] first child of 1, does not have children + * [4] second child of 1, does not have children + * [5] third child of 1, does not have children + * + * - The algorithm repeats until all target array indices have been processed. + */ + XML_Content *dest = ret; /* tree node writing location, moves upwards */ + XML_Content *const destLimit = &ret[dtd->scaffCount]; + XML_Content *jobDest = ret; /* next free writing location in target array */ + str = (XML_Char *)&ret[dtd->scaffCount]; + + /* Add the starting job, the root node (index 0) of the source tree */ + (jobDest++)->numchildren = 0; + + for (; dest < destLimit; dest++) { + /* Retrieve source tree array index from job storage */ + const int src_node = (int)dest->numchildren; + + /* Convert item */ + dest->type = dtd->scaffold[src_node].type; + dest->quant = dtd->scaffold[src_node].quant; + if (dest->type == XML_CTYPE_NAME) { + const XML_Char *src; + dest->name = str; + src = dtd->scaffold[src_node].name; + for (;;) { + *str++ = *src; + if (! *src) + break; + src++; + } + dest->numchildren = 0; + dest->children = NULL; + } else { + unsigned int i; + int cn; + dest->name = NULL; + dest->numchildren = dtd->scaffold[src_node].childcnt; + dest->children = jobDest; + + /* Append scaffold indices of children to array */ + for (i = 0, cn = dtd->scaffold[src_node].firstchild; + i < dest->numchildren; i++, cn = dtd->scaffold[cn].nextsib) + (jobDest++)->numchildren = (unsigned int)cn; + } + } - build_node(parser, 0, ret, &cpos, &str); return ret; } diff --git a/tests/runtests.c b/tests/runtests.c index 7293d46..05f3083 100644 --- a/tests/runtests.c +++ b/tests/runtests.c @@ -2677,6 +2677,82 @@ START_TEST(test_dtd_elements) { } END_TEST +static void XMLCALL +element_decl_check_model(void *userData, const XML_Char *name, + XML_Content *model) { + UNUSED_P(userData); + uint32_t errorFlags = 0; + + /* Expected model array structure is this: + * [0] (type 6, quant 0) + * [1] (type 5, quant 0) + * [3] (type 4, quant 0, name "bar") + * [4] (type 4, quant 0, name "foo") + * [5] (type 4, quant 3, name "xyz") + * [2] (type 4, quant 2, name "zebra") + */ + errorFlags |= ((xcstrcmp(name, XCS("junk")) == 0) ? 0 : (1u << 0)); + errorFlags |= ((model != NULL) ? 0 : (1u << 1)); + + errorFlags |= ((model[0].type == XML_CTYPE_SEQ) ? 0 : (1u << 2)); + errorFlags |= ((model[0].quant == XML_CQUANT_NONE) ? 0 : (1u << 3)); + errorFlags |= ((model[0].numchildren == 2) ? 0 : (1u << 4)); + errorFlags |= ((model[0].children == &model[1]) ? 0 : (1u << 5)); + errorFlags |= ((model[0].name == NULL) ? 0 : (1u << 6)); + + errorFlags |= ((model[1].type == XML_CTYPE_CHOICE) ? 0 : (1u << 7)); + errorFlags |= ((model[1].quant == XML_CQUANT_NONE) ? 0 : (1u << 8)); + errorFlags |= ((model[1].numchildren == 3) ? 0 : (1u << 9)); + errorFlags |= ((model[1].children == &model[3]) ? 0 : (1u << 10)); + errorFlags |= ((model[1].name == NULL) ? 0 : (1u << 11)); + + errorFlags |= ((model[2].type == XML_CTYPE_NAME) ? 0 : (1u << 12)); + errorFlags |= ((model[2].quant == XML_CQUANT_REP) ? 0 : (1u << 13)); + errorFlags |= ((model[2].numchildren == 0) ? 0 : (1u << 14)); + errorFlags |= ((model[2].children == NULL) ? 0 : (1u << 15)); + errorFlags |= ((xcstrcmp(model[2].name, XCS("zebra")) == 0) ? 0 : (1u << 16)); + + errorFlags |= ((model[3].type == XML_CTYPE_NAME) ? 0 : (1u << 17)); + errorFlags |= ((model[3].quant == XML_CQUANT_NONE) ? 0 : (1u << 18)); + errorFlags |= ((model[3].numchildren == 0) ? 0 : (1u << 19)); + errorFlags |= ((model[3].children == NULL) ? 0 : (1u << 20)); + errorFlags |= ((xcstrcmp(model[3].name, XCS("bar")) == 0) ? 0 : (1u << 21)); + + errorFlags |= ((model[4].type == XML_CTYPE_NAME) ? 0 : (1u << 22)); + errorFlags |= ((model[4].quant == XML_CQUANT_NONE) ? 0 : (1u << 23)); + errorFlags |= ((model[4].numchildren == 0) ? 0 : (1u << 24)); + errorFlags |= ((model[4].children == NULL) ? 0 : (1u << 25)); + errorFlags |= ((xcstrcmp(model[4].name, XCS("foo")) == 0) ? 0 : (1u << 26)); + + errorFlags |= ((model[5].type == XML_CTYPE_NAME) ? 0 : (1u << 27)); + errorFlags |= ((model[5].quant == XML_CQUANT_PLUS) ? 0 : (1u << 28)); + errorFlags |= ((model[5].numchildren == 0) ? 0 : (1u << 29)); + errorFlags |= ((model[5].children == NULL) ? 0 : (1u << 30)); + errorFlags |= ((xcstrcmp(model[5].name, XCS("xyz")) == 0) ? 0 : (1u << 31)); + + XML_SetUserData(g_parser, (void *)(uintptr_t)errorFlags); + XML_FreeContentModel(g_parser, model); +} + +START_TEST(test_dtd_elements_nesting) { + // Payload inspired by a test in Perl's XML::Parser + const char *text = "\n" + "]>\n" + ""; + + XML_SetUserData(g_parser, (void *)(uintptr_t)-1); + + XML_SetElementDeclHandler(g_parser, element_decl_check_model); + if (XML_Parse(g_parser, text, (int)strlen(text), XML_TRUE) + == XML_STATUS_ERROR) + xml_failure(g_parser); + + if ((uint32_t)(uintptr_t)XML_GetUserData(g_parser) != 0) + fail("Element declaration model regression detected"); +} +END_TEST + /* Test foreign DTD handling */ START_TEST(test_set_foreign_dtd) { const char *text1 = "\n"; @@ -11487,6 +11563,7 @@ make_suite(void) { tcase_add_test(tc_basic, test_memory_allocation); tcase_add_test(tc_basic, test_default_current); tcase_add_test(tc_basic, test_dtd_elements); + tcase_add_test(tc_basic, test_dtd_elements_nesting); tcase_add_test__ifdef_xml_dtd(tc_basic, test_set_foreign_dtd); tcase_add_test__ifdef_xml_dtd(tc_basic, test_foreign_dtd_not_standalone); tcase_add_test__ifdef_xml_dtd(tc_basic, test_invalid_foreign_dtd);