I forgot the patch of course... -- Robin Haberkorn Senior Software Engineer
B1 Systems GmbH Osterfeldstraße 7 / 85088 Vohburg / https://www.b1-systems.de GF: Ralph Dehner / Unternehmenssitz: Vohburg / AG: Ingolstadt, HRB 3537
From cc5be302aa4305403b8131f6c22c39e4dfb75bd1 Mon Sep 17 00:00:00 2001 From: Robin Haberkorn <haberk...@b1-systems.de> Date: Thu, 17 Apr 2025 13:15:48 +0300 Subject: [PATCH] contrib/xml2: xslt_process() now reports XSLT-related error details * It sets (and restores) the libxslt error handler (xsltSetGenericErrorFunc()). Since it only supports old-school "generic" error handlers, which are no longer used in PG's libxml code, we reintroduced a "generic" error handler xml_generic_error_handler() in xml.c. * The alternative would have been to expose PgXmlErrorContext in xml.h, so we could implement a generic handler in xslt_proc.c. This is obviously not desirable, as it would depend on USE_LIBXML. * No longer use the PG_XML_STRICTNESS_LEGACY for error handling, but query the error_occurred-flag via pg_xml_error_occurred(). The existance of this getter is another hint, that we are not supposed to expose PgXmlErrorContext in xml.h. * This change means that xslt_process() now reports not only details about XML parsing errors, but XSLT-schema deviations and missing stylesheet parameters as well. * The XSLT error messages now also contain line numbers. For that to work, we had to set a dummy "SQL" URL when parsing XML strings. This is important, since xsltPrintErrorContext() includes line numbers only if an URL is set. * The xsltSaveResultToString() error handling has been removed. It can practically only fail in OOM situations and there is no reason to handle them any different than with the other libxslt functions. * Updated test suite and added test case for detecting missing stylesheet parameters. This was initially reported here but has obviously been fixed in the meantime: https://www.postgresql.org/message-id/4C5ECEF9.3030806%40mlfowler.com --- contrib/xml2/expected/xml2.out | 17 +++++++++++++++ contrib/xml2/sql/xml2.sql | 8 +++++++ contrib/xml2/xslt_proc.c | 40 ++++++++++++++++++++++++---------- src/backend/utils/adt/xml.c | 37 +++++++++++++++++++++++++++++++ src/include/utils/xml.h | 2 ++ 5 files changed, 92 insertions(+), 12 deletions(-) diff --git a/contrib/xml2/expected/xml2.out b/contrib/xml2/expected/xml2.out index 3d97b14..157d584 100644 --- a/contrib/xml2/expected/xml2.out +++ b/contrib/xml2/expected/xml2.out @@ -261,3 +261,20 @@ $$<xsl:stylesheet version="1.0" </xsl:template> </xsl:stylesheet>$$); ERROR: failed to apply stylesheet +DETAIL: runtime error: file SQL line 7 element output +File write for 0wn3d.txt refused +runtime error: file SQL line 7 element output +xsltDocumentElem: write rights for 0wn3d.txt denied +-- detecting missing stylesheet parameter +SELECT xslt_process('<xml/>', +$$<stylesheet version="1.0" xmlns="http://www.w3.org/1999/XSL/Transform";> + <template match="/"> + <value-of select="$n1"/> + </template> +</stylesheet>$$)::xml; +ERROR: failed to apply stylesheet +DETAIL: runtime error: file SQL line 3 element value-of +Variable 'n1' has not been declared. +Undefined variable +runtime error: file SQL line 3 element value-of +XPath evaluation returned no result. diff --git a/contrib/xml2/sql/xml2.sql b/contrib/xml2/sql/xml2.sql index ef99d16..9d42ac8 100644 --- a/contrib/xml2/sql/xml2.sql +++ b/contrib/xml2/sql/xml2.sql @@ -153,3 +153,11 @@ $$<xsl:stylesheet version="1.0" </sax:output> </xsl:template> </xsl:stylesheet>$$); + +-- detecting missing stylesheet parameter +SELECT xslt_process('<xml/>', +$$<stylesheet version="1.0" xmlns="http://www.w3.org/1999/XSL/Transform";> + <template match="/"> + <value-of select="$n1"/> + </template> +</stylesheet>$$)::xml; diff --git a/contrib/xml2/xslt_proc.c b/contrib/xml2/xslt_proc.c index b720d89..f17cf9f 100644 --- a/contrib/xml2/xslt_proc.c +++ b/contrib/xml2/xslt_proc.c @@ -61,6 +61,10 @@ xslt_process(PG_FUNCTION_ARGS) xmlChar *resstr = NULL; int reslen = 0; + /* the previous libxslt error context */ + xmlGenericErrorFunc saved_errfunc; + void *saved_errcxt; + if (fcinfo->nargs == 3) { paramstr = PG_GETARG_TEXT_PP(2); @@ -74,35 +78,46 @@ xslt_process(PG_FUNCTION_ARGS) } /* Setup parser */ - xmlerrcxt = pgxml_parser_init(PG_XML_STRICTNESS_LEGACY); + xmlerrcxt = pgxml_parser_init(PG_XML_STRICTNESS_ALL); + + /* + * Save the previous libxslt error context. + */ + saved_errfunc = xsltGenericError; + saved_errcxt = xsltGenericErrorContext; + xsltSetGenericErrorFunc(xmlerrcxt, xml_generic_error_handler); PG_TRY(); { xmlDocPtr ssdoc; bool xslt_sec_prefs_error; - /* Parse document */ + /* + * Parse document. + * It's important to set an "URL", so libxslt includes + * line numbers in error messages (cf. xsltPrintErrorContext()). + */ doctree = xmlReadMemory((char *) VARDATA_ANY(doct), - VARSIZE_ANY_EXHDR(doct), NULL, NULL, + VARSIZE_ANY_EXHDR(doct), "SQL", NULL, XML_PARSE_NOENT); - if (doctree == NULL) + if (doctree == NULL || pg_xml_error_occurred(xmlerrcxt)) xml_ereport(xmlerrcxt, ERROR, ERRCODE_INVALID_XML_DOCUMENT, "error parsing XML document"); /* Same for stylesheet */ ssdoc = xmlReadMemory((char *) VARDATA_ANY(ssheet), - VARSIZE_ANY_EXHDR(ssheet), NULL, NULL, + VARSIZE_ANY_EXHDR(ssheet), "SQL", NULL, XML_PARSE_NOENT); - if (ssdoc == NULL) + if (ssdoc == NULL || pg_xml_error_occurred(xmlerrcxt)) xml_ereport(xmlerrcxt, ERROR, ERRCODE_INVALID_XML_DOCUMENT, "error parsing stylesheet as XML document"); /* After this call we need not free ssdoc separately */ stylesheet = xsltParseStylesheetDoc(ssdoc); - if (stylesheet == NULL) + if (stylesheet == NULL || pg_xml_error_occurred(xmlerrcxt)) xml_ereport(xmlerrcxt, ERROR, ERRCODE_INVALID_ARGUMENT_FOR_XQUERY, "failed to parse stylesheet"); @@ -137,11 +152,14 @@ xslt_process(PG_FUNCTION_ARGS) restree = xsltApplyStylesheetUser(stylesheet, doctree, params, NULL, NULL, xslt_ctxt); - if (restree == NULL) + if (restree == NULL || pg_xml_error_occurred(xmlerrcxt)) xml_ereport(xmlerrcxt, ERROR, ERRCODE_INVALID_ARGUMENT_FOR_XQUERY, "failed to apply stylesheet"); resstat = xsltSaveResultToString(&resstr, &reslen, restree, stylesheet); + if (resstat < 0 || pg_xml_error_occurred(xmlerrcxt)) + xml_ereport(xmlerrcxt, ERROR, ERRCODE_INVALID_ARGUMENT_FOR_XQUERY, + "failed to save result to string"); } PG_CATCH(); { @@ -157,6 +175,7 @@ xslt_process(PG_FUNCTION_ARGS) xmlFreeDoc(doctree); xsltCleanupGlobals(); + xsltSetGenericErrorFunc(saved_errcxt, saved_errfunc); pg_xml_done(xmlerrcxt, true); PG_RE_THROW(); @@ -170,12 +189,9 @@ xslt_process(PG_FUNCTION_ARGS) xmlFreeDoc(doctree); xsltCleanupGlobals(); + xsltSetGenericErrorFunc(saved_errcxt, saved_errfunc); pg_xml_done(xmlerrcxt, false); - /* XXX this is pretty dubious, really ought to throw error instead */ - if (resstat < 0) - PG_RETURN_NULL(); - result = cstring_to_text_with_len((char *) resstr, reslen); if (resstr) diff --git a/src/backend/utils/adt/xml.c b/src/backend/utils/adt/xml.c index db8d0d6..74f78c5 100644 --- a/src/backend/utils/adt/xml.c +++ b/src/backend/utils/adt/xml.c @@ -2078,6 +2078,43 @@ xml_errsave(Node *escontext, PgXmlErrorContext *errcxt, detail ? errdetail_internal("%s", detail) : 0)); } +/* + * Generic error handler for libxml errors and warnings. + * This is not used by this module, but may be useful for + * libxml-based libraries like libxslt, which do not support + * structured error handlers. + */ +void +xml_generic_error_handler(void *data, const char * msg, ...) +{ + PgXmlErrorContext *xmlerrcxt = (PgXmlErrorContext *) data; + StringInfo errorBuf; + va_list ap; + + /* + * Defend against someone passing us a bogus context struct. + * + * We force a backend exit if this check fails because longjmp'ing out of + * libxslt would likely render it unsafe to use further. + */ + if (xmlerrcxt->magic != ERRCXT_MAGIC) + elog(FATAL, "xml_generic_error_handler called with invalid PgXmlErrorContext"); + + /* Prepare error message in errorBuf */ + errorBuf = makeStringInfo(); + va_start(ap, msg); + appendStringInfoVA(errorBuf, msg, ap); + va_end(ap); + + /* Get rid of any trailing newlines in errorBuf */ + chopStringInfoNewlines(errorBuf); + + appendStringInfoLineSeparator(&xmlerrcxt->err_buf); + appendBinaryStringInfo(&xmlerrcxt->err_buf, errorBuf->data, + errorBuf->len); + + destroyStringInfo(errorBuf); +} /* * Error handler for libxml errors and warnings diff --git a/src/include/utils/xml.h b/src/include/utils/xml.h index 0d7a816..a754d8f 100644 --- a/src/include/utils/xml.h +++ b/src/include/utils/xml.h @@ -66,6 +66,8 @@ extern void pg_xml_init_library(void); extern PgXmlErrorContext *pg_xml_init(PgXmlStrictness strictness); extern void pg_xml_done(PgXmlErrorContext *errcxt, bool isError); extern bool pg_xml_error_occurred(PgXmlErrorContext *errcxt); +extern void xml_generic_error_handler(void *data, const char * msg, ...) + pg_attribute_printf(2, 3); extern void xml_ereport(PgXmlErrorContext *errcxt, int level, int sqlcode, const char *msg); -- 2.48.1
