From f833c847b8fa4782efab45c8371d3cee64292d9b Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Sat, 1 Apr 2017 21:44:54 -0400 Subject: [PATCH] Allow psql variable substitution to occur in backtick command strings. Previously, text between backquotes in a psql metacommand's arguments was always passed to the shell literally. That considerably hobbles the usefulness of the feature for scripting, so we'd foreseen for a long time that we'd someday want to allow substitution of psql variables into the shell command. IMO the addition of \if metacommands has brought us to that point, since \if can greatly benefit from some sort of client-side expression evaluation capability, and psql itself is not going to grow any such thing in time for v10. Hence, this patch. It allows :VARIABLE to be replaced by the exact contents of the named variable, while :'VARIABLE' is replaced by the variable's contents suitably quoted to become a single shell-command argument. (The quoting rules for that are different from those for SQL literals, so this is a bit of an abuse of the :'VARIABLE' notation, but I doubt anyone will be confused.) As with other situations in psql, no substitution occurs if the word following a colon is not a known variable name. That limits the risk of compatibility problems for existing psql scripts; but the risk isn't zero, so this needs to be called out in the v10 release notes. Discussion: https://postgr.es/m/9561.1490895211@sss.pgh.pa.us --- doc/src/sgml/ref/psql-ref.sgml | 29 ++++++--- src/bin/psql/common.c | 98 +++++++++++++++++++---------- src/bin/psql/common.h | 3 +- src/bin/psql/psqlscanslash.l | 52 ++++++++++++--- src/fe_utils/psqlscan.l | 13 ++-- src/fe_utils/string_utils.c | 33 +++++++--- src/include/fe_utils/psqlscan.h | 15 ++++- src/include/fe_utils/psqlscan_int.h | 2 +- src/include/fe_utils/string_utils.h | 1 + 9 files changed, 180 insertions(+), 66 deletions(-) diff --git a/doc/src/sgml/ref/psql-ref.sgml b/doc/src/sgml/ref/psql-ref.sgml index b51b11baa3..ad463e71c1 100644 --- a/doc/src/sgml/ref/psql-ref.sgml +++ b/doc/src/sgml/ref/psql-ref.sgml @@ -769,18 +769,33 @@ testdb=> quotes that single character, whatever it is. - - Within an argument, text that is enclosed in backquotes - (`) is taken as a command line that is passed to the - shell. The output of the command (with any trailing newline removed) - replaces the backquoted text. - - If an unquoted colon (:) followed by a psql variable name appears within an argument, it is replaced by the variable's value, as described in . + The forms :'variable_name' and + :"variable_name" described there + work as well. + + + + Within an argument, text that is enclosed in backquotes + (`) is taken as a command line that is passed to the + shell. The output of the command (with any trailing newline removed) + replaces the backquoted text. Within the text enclosed in backquotes, + no special quoting or other processing occurs, except that appearances + of :variable_name where + variable_name is a psql variable name + are replaced by the variable's value. Also, appearances of + :'variable_name' are replaced by the + variable's value suitably quoted to become a single shell command + argument. (The latter form is almost always preferable, unless you are + very sure of what is in the variable.) Because carriage return and line + feed characters cannot be safely quoted on all platforms, the + :'variable_name' form prints an + error message and does not substitute the variable value when such + characters appear in the value. diff --git a/src/bin/psql/common.c b/src/bin/psql/common.c index b06ae9779d..a2f1259c1e 100644 --- a/src/bin/psql/common.c +++ b/src/bin/psql/common.c @@ -116,19 +116,19 @@ setQFout(const char *fname) * If the specified variable exists, return its value as a string (malloc'd * and expected to be freed by the caller); else return NULL. * - * If "escape" is true, return the value suitably quoted and escaped, - * as an identifier or string literal depending on "as_ident". - * (Failure in escaping should lead to returning NULL.) + * If "quote" isn't PQUOTE_PLAIN, then return the value suitably quoted and + * escaped for the specified quoting requirement. (Failure in escaping + * should lead to printing an error and returning NULL.) * * "passthrough" is the pointer previously given to psql_scan_set_passthrough. * In psql, passthrough points to a ConditionalStack, which we check to * determine whether variable expansion is allowed. */ char * -psql_get_variable(const char *varname, bool escape, bool as_ident, +psql_get_variable(const char *varname, PsqlScanQuoteType quote, void *passthrough) { - char *result; + char *result = NULL; const char *value; /* In an inactive \if branch, suppress all variable substitutions */ @@ -139,40 +139,74 @@ psql_get_variable(const char *varname, bool escape, bool as_ident, if (!value) return NULL; - if (escape) + switch (quote) { - char *escaped_value; + case PQUOTE_PLAIN: + result = pg_strdup(value); + break; + case PQUOTE_SQL_LITERAL: + case PQUOTE_SQL_IDENT: + { + /* + * For these cases, we use libpq's quoting functions, which + * assume the string is in the connection's client encoding. + */ + char *escaped_value; - if (!pset.db) - { - psql_error("cannot escape without active connection\n"); - return NULL; - } + if (!pset.db) + { + psql_error("cannot escape without active connection\n"); + return NULL; + } - if (as_ident) - escaped_value = - PQescapeIdentifier(pset.db, value, strlen(value)); - else - escaped_value = - PQescapeLiteral(pset.db, value, strlen(value)); + if (quote == PQUOTE_SQL_LITERAL) + escaped_value = + PQescapeLiteral(pset.db, value, strlen(value)); + else + escaped_value = + PQescapeIdentifier(pset.db, value, strlen(value)); - if (escaped_value == NULL) - { - const char *error = PQerrorMessage(pset.db); + if (escaped_value == NULL) + { + const char *error = PQerrorMessage(pset.db); - psql_error("%s", error); - return NULL; - } + psql_error("%s", error); + return NULL; + } - /* - * Rather than complicate the lexer's API with a notion of which - * free() routine to use, just pay the price of an extra strdup(). - */ - result = pg_strdup(escaped_value); - PQfreemem(escaped_value); + /* + * Rather than complicate the lexer's API with a notion of + * which free() routine to use, just pay the price of an extra + * strdup(). + */ + result = pg_strdup(escaped_value); + PQfreemem(escaped_value); + break; + } + case PQUOTE_SHELL_ARG: + { + /* + * For this we use appendShellStringNoError, which is + * encoding-agnostic, which is fine since the shell probably + * is too. In any case, the only special character is "'", + * which is not known to appear in valid multibyte characters. + */ + PQExpBufferData buf; + + initPQExpBuffer(&buf); + if (!appendShellStringNoError(&buf, value)) + { + psql_error("shell command argument contains a newline or carriage return: \"%s\"\n", + value); + free(buf.data); + return NULL; + } + result = buf.data; + break; + } + + /* No default: we want a compiler warning for missing cases */ } - else - result = pg_strdup(value); return result; } diff --git a/src/bin/psql/common.h b/src/bin/psql/common.h index 3d8b8da7fe..1ceb8ae386 100644 --- a/src/bin/psql/common.h +++ b/src/bin/psql/common.h @@ -12,11 +12,12 @@ #include "libpq-fe.h" #include "fe_utils/print.h" +#include "fe_utils/psqlscan.h" extern bool openQueryOutputFile(const char *fname, FILE **fout, bool *is_pipe); extern bool setQFout(const char *fname); -extern char *psql_get_variable(const char *varname, bool escape, bool as_ident, +extern char *psql_get_variable(const char *varname, PsqlScanQuoteType quote, void *passthrough); extern void psql_error(const char *fmt,...) pg_attribute_printf(1, 2); diff --git a/src/bin/psql/psqlscanslash.l b/src/bin/psql/psqlscanslash.l index 319afdc744..db7a1b9eea 100644 --- a/src/bin/psql/psqlscanslash.l +++ b/src/bin/psql/psqlscanslash.l @@ -242,8 +242,7 @@ other . yytext + 1, yyleng - 1); value = cur_state->callbacks->get_variable(varname, - false, - false, + PQUOTE_PLAIN, cur_state->cb_passthrough); free(varname); @@ -268,14 +267,16 @@ other . } :'{variable_char}+' { - psqlscan_escape_variable(cur_state, yytext, yyleng, false); + psqlscan_escape_variable(cur_state, yytext, yyleng, + PQUOTE_SQL_LITERAL); *option_quote = ':'; unquoted_option_chars = 0; } :\"{variable_char}+\" { - psqlscan_escape_variable(cur_state, yytext, yyleng, true); + psqlscan_escape_variable(cur_state, yytext, yyleng, + PQUOTE_SQL_IDENT); *option_quote = ':'; unquoted_option_chars = 0; } @@ -337,9 +338,8 @@ other . { /* - * backticked text: copy everything until next backquote, then evaluate. - * - * XXX Possible future behavioral change: substitute for :VARIABLE? + * backticked text: copy everything until next backquote (expanding + * variable references, but doing nought else), then evaluate. */ "`" { @@ -350,6 +350,44 @@ other . BEGIN(xslasharg); } +:{variable_char}+ { + /* Possible psql variable substitution */ + if (cur_state->callbacks->get_variable == NULL) + ECHO; + else + { + char *varname; + char *value; + + varname = psqlscan_extract_substring(cur_state, + yytext + 1, + yyleng - 1); + value = cur_state->callbacks->get_variable(varname, + PQUOTE_PLAIN, + cur_state->cb_passthrough); + free(varname); + + if (value) + { + appendPQExpBufferStr(output_buf, value); + free(value); + } + else + ECHO; + } + } + +:'{variable_char}+' { + psqlscan_escape_variable(cur_state, yytext, yyleng, + PQUOTE_SHELL_ARG); + } + +:'{variable_char}* { + /* Throw back everything but the colon */ + yyless(1); + ECHO; + } + {other}|\n { ECHO; } } diff --git a/src/fe_utils/psqlscan.l b/src/fe_utils/psqlscan.l index 19b3e57aa4..27689d72da 100644 --- a/src/fe_utils/psqlscan.l +++ b/src/fe_utils/psqlscan.l @@ -699,8 +699,7 @@ other . yyleng - 1); if (cur_state->callbacks->get_variable) value = cur_state->callbacks->get_variable(varname, - false, - false, + PQUOTE_PLAIN, cur_state->cb_passthrough); else value = NULL; @@ -737,11 +736,13 @@ other . } :'{variable_char}+' { - psqlscan_escape_variable(cur_state, yytext, yyleng, false); + psqlscan_escape_variable(cur_state, yytext, yyleng, + PQUOTE_SQL_LITERAL); } :\"{variable_char}+\" { - psqlscan_escape_variable(cur_state, yytext, yyleng, true); + psqlscan_escape_variable(cur_state, yytext, yyleng, + PQUOTE_SQL_IDENT); } /* @@ -1415,7 +1416,7 @@ psqlscan_extract_substring(PsqlScanState state, const char *txt, int len) */ void psqlscan_escape_variable(PsqlScanState state, const char *txt, int len, - bool as_ident) + PsqlScanQuoteType quote) { char *varname; char *value; @@ -1423,7 +1424,7 @@ psqlscan_escape_variable(PsqlScanState state, const char *txt, int len, /* Variable lookup. */ varname = psqlscan_extract_substring(state, txt + 2, len - 3); if (state->callbacks->get_variable) - value = state->callbacks->get_variable(varname, true, as_ident, + value = state->callbacks->get_variable(varname, quote, state->cb_passthrough); else value = NULL; diff --git a/src/fe_utils/string_utils.c b/src/fe_utils/string_utils.c index d1a9ddc4c6..dc84d32a09 100644 --- a/src/fe_utils/string_utils.c +++ b/src/fe_utils/string_utils.c @@ -425,13 +425,30 @@ appendByteaLiteral(PQExpBuffer buf, const unsigned char *str, size_t length, * arguments containing LF or CR characters. A future major release should * reject those characters in CREATE ROLE and CREATE DATABASE, because use * there eventually leads to errors here. + * + * appendShellString() simply prints an error and dies if LF or CR appears. + * appendShellStringNoError() omits those characters from the result, and + * returns false if there were any. */ void appendShellString(PQExpBuffer buf, const char *str) +{ + if (!appendShellStringNoError(buf, str)) + { + fprintf(stderr, + _("shell command argument contains a newline or carriage return: \"%s\"\n"), + str); + exit(EXIT_FAILURE); + } +} + +bool +appendShellStringNoError(PQExpBuffer buf, const char *str) { #ifdef WIN32 int backslash_run_length = 0; #endif + bool ok = true; const char *p; /* @@ -442,7 +459,7 @@ appendShellString(PQExpBuffer buf, const char *str) strspn(str, "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789-_./:") == strlen(str)) { appendPQExpBufferStr(buf, str); - return; + return ok; } #ifndef WIN32 @@ -451,10 +468,8 @@ appendShellString(PQExpBuffer buf, const char *str) { if (*p == '\n' || *p == '\r') { - fprintf(stderr, - _("shell command argument contains a newline or carriage return: \"%s\"\n"), - str); - exit(EXIT_FAILURE); + ok = false; + continue; } if (*p == '\'') @@ -481,10 +496,8 @@ appendShellString(PQExpBuffer buf, const char *str) { if (*p == '\n' || *p == '\r') { - fprintf(stderr, - _("shell command argument contains a newline or carriage return: \"%s\"\n"), - str); - exit(EXIT_FAILURE); + ok = false; + continue; } /* Change N backslashes before a double quote to 2N+1 backslashes. */ @@ -524,6 +537,8 @@ appendShellString(PQExpBuffer buf, const char *str) } appendPQExpBufferStr(buf, "^\""); #endif /* WIN32 */ + + return ok; } diff --git a/src/include/fe_utils/psqlscan.h b/src/include/fe_utils/psqlscan.h index 0cc632b821..e9c8143925 100644 --- a/src/include/fe_utils/psqlscan.h +++ b/src/include/fe_utils/psqlscan.h @@ -48,13 +48,22 @@ typedef enum _promptStatus PROMPT_COPY } promptStatus_t; +/* Quoting request types for get_variable() callback */ +typedef enum +{ + PQUOTE_PLAIN, /* just return the actual value */ + PQUOTE_SQL_LITERAL, /* add quotes to make a valid SQL literal */ + PQUOTE_SQL_IDENT, /* quote if needed to make a SQL identifier */ + PQUOTE_SHELL_ARG /* quote if needed to be safe in a shell cmd */ +} PsqlScanQuoteType; + /* Callback functions to be used by the lexer */ typedef struct PsqlScanCallbacks { - /* Fetch value of a variable, as a pfree'able string; NULL if unknown */ + /* Fetch value of a variable, as a free'able string; NULL if unknown */ /* This pointer can be NULL if no variable substitution is wanted */ - char *(*get_variable) (const char *varname, bool escape, - bool as_ident, void *passthrough); + char *(*get_variable) (const char *varname, PsqlScanQuoteType quote, + void *passthrough); /* Print an error message someplace appropriate */ /* (very old gcc versions don't support attributes on function pointers) */ #if defined(__GNUC__) && __GNUC__ < 4 diff --git a/src/include/fe_utils/psqlscan_int.h b/src/include/fe_utils/psqlscan_int.h index b4044e806a..af62f5ebdf 100644 --- a/src/include/fe_utils/psqlscan_int.h +++ b/src/include/fe_utils/psqlscan_int.h @@ -141,6 +141,6 @@ extern char *psqlscan_extract_substring(PsqlScanState state, const char *txt, int len); extern void psqlscan_escape_variable(PsqlScanState state, const char *txt, int len, - bool as_ident); + PsqlScanQuoteType quote); #endif /* PSQLSCAN_INT_H */ diff --git a/src/include/fe_utils/string_utils.h b/src/include/fe_utils/string_utils.h index 6fb7f5e30e..c68234335e 100644 --- a/src/include/fe_utils/string_utils.h +++ b/src/include/fe_utils/string_utils.h @@ -42,6 +42,7 @@ extern void appendByteaLiteral(PQExpBuffer buf, bool std_strings); extern void appendShellString(PQExpBuffer buf, const char *str); +extern bool appendShellStringNoError(PQExpBuffer buf, const char *str); extern void appendConnStrVal(PQExpBuffer buf, const char *str); extern void appendPsqlMetaConnect(PQExpBuffer buf, const char *dbname); -- 2.40.0