Replace a bunch more uses of strncpy() with safer coding.

strncpy() has a well-deserved reputation for being unsafe, so make an
effort to get rid of nearly all occurrences in HEAD.

A large fraction of the remaining uses were passing length less than or
equal to the known strlen() of the source, in which case no null-padding
can occur and the behavior is equivalent to memcpy(), though doubtless
slower and certainly harder to reason about.  So just use memcpy() in
these cases.

In other cases, use either StrNCpy() or strlcpy() as appropriate (depending
on whether padding to the full length of the destination buffer seems
useful).

I left a few strncpy() calls alone in the src/timezone/ code, to keep it
in sync with upstream (the IANA tzcode distribution).  There are also a
few such calls in ecpg that could possibly do with more analysis.

AFAICT, none of these changes are more than cosmetic, except for the four
occurrences in fe-secure-openssl.c, which are in fact buggy: an overlength
source leads to a non-null-terminated destination buffer and ensuing
misbehavior.  These don't seem like security issues, first because no stack
clobber is possible and second because if your values of sslcert etc are
coming from untrusted sources then you've got problems way worse than this.
Still, it's undesirable to have unpredictable behavior for overlength
inputs, so back-patch those four changes to all active branches.

contrib/fuzzystrmatch/dmetaphone.c

@@ -247,7 +247,7 @@ NewMetaString(char *init_str)
 	META_MALLOC(s->str, s->bufsize, char);
 	assert(s->str != NULL);
 
-	strncpy(s->str, init_str, s->length + 1);
+	memcpy(s->str, init_str, s->length + 1);
 	s->free_string_on_destroy = 1;
 
 	return s;

contrib/isn/isn.c

@@ -825,18 +825,18 @@ string2ean(const char *str, bool errorOK, ean13 *result,
 				goto eanwrongtype;
 			break;
 		case ISMN:
-			strncpy(buf, "9790", 4);	/* this isn't for sure yet, for now
+			memcpy(buf, "9790", 4);		/* this isn't for sure yet, for now
 										 * ISMN it's only 9790 */
 			valid = (valid && ((rcheck = checkdig(buf, 13)) == check || magic));
 			break;
 		case ISBN:
-			strncpy(buf, "978", 3);
+			memcpy(buf, "978", 3);
 			valid = (valid && ((rcheck = weight_checkdig(buf + 3, 10)) == check || magic));
 			break;
 		case ISSN:
-			strncpy(buf + 10, "00", 2); /* append 00 as the normal issue
+			memcpy(buf + 10, "00", 2);	/* append 00 as the normal issue
 										 * publication code */
-			strncpy(buf, "977", 3);
+			memcpy(buf, "977", 3);
 			valid = (valid && ((rcheck = weight_checkdig(buf + 3, 8)) == check || magic));
 			break;
 		case UPC:

contrib/pg_trgm/trgm_regexp.c

@@ -877,7 +877,7 @@ convertPgWchar(pg_wchar c, trgm_mb_char *result)
 #endif
 
 	/* Fill result with exactly MAX_MULTIBYTE_CHAR_LEN bytes */
-	strncpy(result->bytes, s, MAX_MULTIBYTE_CHAR_LEN);
+	memcpy(result->bytes, s, MAX_MULTIBYTE_CHAR_LEN);
 	return true;
 }
 

contrib/pgbench/pgbench.c

@@ -829,7 +829,7 @@ replaceVariable(char **sql, char *param, int len, char *value)
 
 	if (valueln != len)
 		memmove(param + valueln, param + len, strlen(param + len) + 1);
-	strncpy(param, value, valueln);
+	memcpy(param, value, valueln);
 
 	return param + valueln;
 }

contrib/pgcrypto/crypt-des.c

@@ -708,7 +708,7 @@ px_crypt_des(const char *key, const char *setting)
 			if (des_setkey((char *) keybuf))
 				return (NULL);
 		}
-		strncpy(output, setting, 9);
+		StrNCpy(output, setting, 10);
 
 		/*
 		 * Double check that we weren't given a short setting. If we were, the
@@ -716,7 +716,6 @@ px_crypt_des(const char *key, const char *setting)
 		 * salt, but we don't really care. Just make sure the output string
 		 * doesn't have an extra NUL in it.
 		 */
-		output[9] = '\0';
 		p = output + strlen(output);
 	}
 	else

contrib/xml2/xpath.c

@@ -327,7 +327,7 @@ xpath_string(PG_FUNCTION_ARGS)
 	/* We could try casting to string using the libxml function? */
 
 	xpath = (xmlChar *) palloc(pathsize + 9);
-	strncpy((char *) xpath, "string(", 7);
+	memcpy((char *) xpath, "string(", 7);
 	memcpy((char *) (xpath + 7), VARDATA(xpathsupp), pathsize);
 	xpath[pathsize + 7] = ')';
 	xpath[pathsize + 8] = '\0';

src/backend/libpq/hba.c

@@ -1996,6 +1996,8 @@ check_ident_usermap(IdentLine *identLine, const char *usermap_name,
 
 		if ((ofs = strstr(identLine->pg_role, "\\1")) != NULL)
 		{
+			int			offset;
+
 			/* substitution of the first argument requested */
 			if (matches[1].rm_so < 0)
 			{
@@ -2012,8 +2014,9 @@ check_ident_usermap(IdentLine *identLine, const char *usermap_name,
 			 * plus null terminator
 			 */
 			regexp_pgrole = palloc0(strlen(identLine->pg_role) - 2 + (matches[1].rm_eo - matches[1].rm_so) + 1);
-			strncpy(regexp_pgrole, identLine->pg_role, (ofs - identLine->pg_role));
-			memcpy(regexp_pgrole + strlen(regexp_pgrole),
+			offset = ofs - identLine->pg_role;
+			memcpy(regexp_pgrole, identLine->pg_role, offset);
+			memcpy(regexp_pgrole + offset,
 				   ident_user + matches[1].rm_so,
 				   matches[1].rm_eo - matches[1].rm_so);
 			strcat(regexp_pgrole, ofs + 2);

src/backend/postmaster/pgstat.c

@@ -3095,7 +3095,7 @@ pgstat_send_archiver(const char *xlog, bool failed)
 	 */
 	pgstat_setheader(&msg.m_hdr, PGSTAT_MTYPE_ARCHIVER);
 	msg.m_failed = failed;
-	strncpy(msg.m_xlog, xlog, sizeof(msg.m_xlog));
+	StrNCpy(msg.m_xlog, xlog, sizeof(msg.m_xlog));
 	msg.m_timestamp = GetCurrentTimestamp();
 	pgstat_send(&msg, sizeof(msg));
 }

src/backend/regex/regerror.c

@@ -111,7 +111,7 @@ pg_regerror(int errcode,		/* error code, or REG_ATOI or REG_ITOA */
 			strcpy(errbuf, msg);
 		else
 		{						/* truncate to fit */
-			strncpy(errbuf, msg, errbuf_size - 1);
+			memcpy(errbuf, msg, errbuf_size - 1);
 			errbuf[errbuf_size - 1] = '\0';
 		}
 	}

src/backend/replication/logical/logical.c

@@ -244,9 +244,7 @@ CreateInitDecodingContext(char *plugin,
 
 	/* register output plugin name with slot */
 	SpinLockAcquire(&slot->mutex);
-	strncpy(NameStr(slot->data.plugin), plugin,
-			NAMEDATALEN);
-	NameStr(slot->data.plugin)[NAMEDATALEN - 1] = '\0';
+	StrNCpy(NameStr(slot->data.plugin), plugin, NAMEDATALEN);
 	SpinLockRelease(&slot->mutex);
 
 	/*

src/backend/replication/slot.c

@@ -266,8 +266,7 @@ ReplicationSlotCreate(const char *name, bool db_specific,
 	slot->data.persistency = persistency;
 	slot->data.xmin = InvalidTransactionId;
 	slot->effective_xmin = InvalidTransactionId;
-	strncpy(NameStr(slot->data.name), name, NAMEDATALEN);
-	NameStr(slot->data.name)[NAMEDATALEN - 1] = '\0';
+	StrNCpy(NameStr(slot->data.name), name, NAMEDATALEN);
 	slot->data.database = db_specific ? MyDatabaseId : InvalidOid;
 	slot->data.restart_lsn = InvalidXLogRecPtr;
 

src/backend/utils/adt/datetime.c

@@ -4052,7 +4052,7 @@ EncodeDateTime(struct pg_tm * tm, fsec_t fsec, bool print_tz, int tz, const char
 			day = date2j(tm->tm_year, tm->tm_mon, tm->tm_mday);
 			tm->tm_wday = j2day(day);
 
-			strncpy(str, days[tm->tm_wday], 3);
+			memcpy(str, days[tm->tm_wday], 3);
 			strcpy(str + 3, " ");
 
 			if (DateOrder == DATEORDER_DMY)

src/backend/utils/adt/name.c

@@ -192,7 +192,7 @@ namecpy(Name n1, Name n2)
 {
 	if (!n1 || !n2)
 		return -1;
-	strncpy(NameStr(*n1), NameStr(*n2), NAMEDATALEN);
+	StrNCpy(NameStr(*n1), NameStr(*n2), NAMEDATALEN);
 	return 0;
 }
 

src/backend/utils/adt/varlena.c

@@ -2936,7 +2936,7 @@ SplitIdentifierString(char *rawstring, char separator,
 			len = endp - curname;
 			downname = downcase_truncate_identifier(curname, len, false);
 			Assert(strlen(downname) <= len);
-			strncpy(curname, downname, len);
+			strncpy(curname, downname, len);	/* strncpy is required here */
 			pfree(downname);
 		}
 

src/backend/utils/error/elog.c

@@ -2240,7 +2240,7 @@ setup_formatted_log_time(void)
 
 	/* 'paste' milliseconds into place... */
 	sprintf(msbuf, ".%03d", (int) (tv.tv_usec / 1000));
-	strncpy(formatted_log_time + 19, msbuf, 4);
+	memcpy(formatted_log_time + 19, msbuf, 4);
 }
 
 /*

src/bin/initdb/initdb.c

@@ -386,9 +386,9 @@ replace_token(char **lines, const char *token, const char *replacement)
 
 		pre = where - lines[i];
 
-		strncpy(newline, lines[i], pre);
+		memcpy(newline, lines[i], pre);
 
-		strcpy(newline + pre, replacement);
+		memcpy(newline + pre, replacement, replen);
 
 		strcpy(newline + pre + replen, lines[i] + pre + toklen);
 

src/bin/pg_dump/pg_backup_archiver.c

@@ -2064,7 +2064,7 @@ _discoverArchiveFormat(ArchiveHandle *AH)
 	}
 
 	/* Save it, just in case we need it later */
-	strncpy(&AH->lookahead[0], sig, 5);
+	memcpy(&AH->lookahead[0], sig, 5);
 	AH->lookaheadLen = 5;
 
 	if (strncmp(sig, "PGDMP", 5) == 0)

src/bin/pg_dump/pg_backup_db.c

@@ -399,7 +399,7 @@ ExecuteSqlCommand(ArchiveHandle *AH, const char *qry, const char *desc)
 			break;
 		default:
 			/* trouble */
-			strncpy(errStmt, qry, DB_MAX_ERR_STMT);
+			strncpy(errStmt, qry, DB_MAX_ERR_STMT);		/* strncpy required here */
 			if (errStmt[DB_MAX_ERR_STMT - 1] != '\0')
 			{
 				errStmt[DB_MAX_ERR_STMT - 4] = '.';

src/interfaces/ecpg/ecpglib/execute.c

@@ -882,7 +882,7 @@ ecpg_store_input(const int lineno, const bool force_indicator, const struct vari
 								return false;
 							}
 
-							strncpy(mallocedval + strlen(mallocedval), str, slen + 1);
+							memcpy(mallocedval + strlen(mallocedval), str, slen + 1);
 							strcpy(mallocedval + strlen(mallocedval), ",");
 							ecpg_free(str);
 						}
@@ -949,7 +949,7 @@ ecpg_store_input(const int lineno, const bool force_indicator, const struct vari
 								return false;
 							}
 
-							strncpy(mallocedval + strlen(mallocedval), str, slen + 1);
+							memcpy(mallocedval + strlen(mallocedval), str, slen + 1);
 							strcpy(mallocedval + strlen(mallocedval), ",");
 							ecpg_free(str);
 						}
@@ -969,7 +969,7 @@ ecpg_store_input(const int lineno, const bool force_indicator, const struct vari
 						}
 
 						/* also copy trailing '\0' */
-						strncpy(mallocedval + strlen(mallocedval), str, slen + 1);
+						memcpy(mallocedval + strlen(mallocedval), str, slen + 1);
 						ecpg_free(str);
 					}
 
@@ -1000,7 +1000,7 @@ ecpg_store_input(const int lineno, const bool force_indicator, const struct vari
 								return false;
 							}
 
-							strncpy(mallocedval + strlen(mallocedval), str, slen + 1);
+							memcpy(mallocedval + strlen(mallocedval), str, slen + 1);
 							strcpy(mallocedval + strlen(mallocedval), ",");
 							ecpg_free(str);
 						}
@@ -1020,7 +1020,7 @@ ecpg_store_input(const int lineno, const bool force_indicator, const struct vari
 						}
 
 						/* also copy trailing '\0' */
-						strncpy(mallocedval + strlen(mallocedval), str, slen + 1);
+						memcpy(mallocedval + strlen(mallocedval), str, slen + 1);
 						ecpg_free(str);
 					}
 
@@ -1055,7 +1055,7 @@ ecpg_store_input(const int lineno, const bool force_indicator, const struct vari
 								return false;
 							}
 
-							strncpy(mallocedval + strlen(mallocedval), str, slen + 1);
+							memcpy(mallocedval + strlen(mallocedval), str, slen + 1);
 							strcpy(mallocedval + strlen(mallocedval), ",");
 							ecpg_free(str);
 						}
@@ -1075,7 +1075,7 @@ ecpg_store_input(const int lineno, const bool force_indicator, const struct vari
 						}
 
 						/* also copy trailing '\0' */
-						strncpy(mallocedval + strlen(mallocedval), str, slen + 1);
+						memcpy(mallocedval + strlen(mallocedval), str, slen + 1);
 						ecpg_free(str);
 					}
 

src/interfaces/ecpg/ecpglib/prepare.c

@@ -82,7 +82,7 @@ replace_variables(char **text, int lineno)
 				return false;
 			}
 
-			strncpy(newcopy, *text, ptr);
+			memcpy(newcopy, *text, ptr);
 			strcpy(newcopy + ptr, buffer);
 			strcat(newcopy, (*text) +ptr + len);
 

src/interfaces/ecpg/pgtypeslib/datetime.c

@@ -264,8 +264,8 @@ PGTYPESdate_fmt_asc(date dDate, const char *fmtstring, char *outbuf)
 			{
 				case PGTYPES_TYPE_STRING_MALLOCED:
 				case PGTYPES_TYPE_STRING_CONSTANT:
-					strncpy(start_pattern, replace_val.str_val,
-							strlen(replace_val.str_val));
+					memcpy(start_pattern, replace_val.str_val,
+						   strlen(replace_val.str_val));
 					if (replace_type == PGTYPES_TYPE_STRING_MALLOCED)
 						free(replace_val.str_val);
 					break;
@@ -277,7 +277,7 @@ PGTYPESdate_fmt_asc(date dDate, const char *fmtstring, char *outbuf)
 							return -1;
 						snprintf(t, PGTYPES_DATE_NUM_MAX_DIGITS,
 								 "%u", replace_val.uint_val);
-						strncpy(start_pattern, t, strlen(t));
+						memcpy(start_pattern, t, strlen(t));
 						free(t);
 					}
 					break;
@@ -289,7 +289,7 @@ PGTYPESdate_fmt_asc(date dDate, const char *fmtstring, char *outbuf)
 							return -1;
 						snprintf(t, PGTYPES_DATE_NUM_MAX_DIGITS,
 								 "%02u", replace_val.uint_val);
-						strncpy(start_pattern, t, strlen(t));
+						memcpy(start_pattern, t, strlen(t));
 						free(t);
 					}
 					break;
@@ -301,7 +301,7 @@ PGTYPESdate_fmt_asc(date dDate, const char *fmtstring, char *outbuf)
 							return -1;
 						snprintf(t, PGTYPES_DATE_NUM_MAX_DIGITS,
 								 "%04u", replace_val.uint_val);
-						strncpy(start_pattern, t, strlen(t));
+						memcpy(start_pattern, t, strlen(t));
 						free(t);
 					}
 					break;

src/interfaces/ecpg/pgtypeslib/dt_common.c

@@ -929,7 +929,7 @@ EncodeDateTime(struct tm * tm, fsec_t fsec, bool print_tz, int tz, const char *t
 			day = date2j(tm->tm_year, tm->tm_mon, tm->tm_mday);
 			tm->tm_wday = (int) ((day + date2j(2000, 1, 1) + 1) % 7);
 
-			strncpy(str, days[tm->tm_wday], 3);
+			memcpy(str, days[tm->tm_wday], 3);
 			strcpy(str + 3, " ");
 
 			if (EuroDates)

src/interfaces/ecpg/test/pg_regress_ecpg.c

@@ -60,8 +60,7 @@ ecpg_filter(const char *sourcefile, const char *outfile)
 			if (plen > 1)
 			{
 				n = (char *) malloc(plen);
-				strncpy(n, p + 1, plen - 1);
-				n[plen - 1] = '\0';
+				StrNCpy(n, p + 1, plen);
 				replace_string(linebuf, n, "");
 			}
 		}

src/interfaces/libpq/fe-exec.c

@@ -2910,9 +2910,9 @@ PQoidStatus(const PGresult *res)
 		return "";
 
 	len = strspn(res->cmdStatus + 7, "0123456789");
-	if (len > 23)
-		len = 23;
-	strncpy(buf, res->cmdStatus + 7, len);
+	if (len > sizeof(buf) - 1)
+		len = sizeof(buf) - 1;
+	memcpy(buf, res->cmdStatus + 7, len);
 	buf[len] = '\0';
 
 	return buf;

src/interfaces/libpq/fe-protocol2.c

@@ -1586,6 +1586,7 @@ pqBuildStartupPacket2(PGconn *conn, int *packetlen,
 
 	startpacket->protoVersion = htonl(conn->pversion);
 
+	/* strncpy is safe here: postmaster will handle full fields correctly */
 	strncpy(startpacket->user, conn->pguser, SM_USER);
 	strncpy(startpacket->database, conn->dbName, SM_DATABASE);
 	strncpy(startpacket->tty, conn->pgtty, SM_TTY);

src/interfaces/libpq/fe-secure-openssl.c

@@ -941,7 +941,7 @@ initialize_SSL(PGconn *conn)
 
 	/* Read the client certificate file */
 	if (conn->sslcert && strlen(conn->sslcert) > 0)
-		strncpy(fnbuf, conn->sslcert, sizeof(fnbuf));
+		strlcpy(fnbuf, conn->sslcert, sizeof(fnbuf));
 	else if (have_homedir)
 		snprintf(fnbuf, sizeof(fnbuf), "%s/%s", homedir, USER_CERT_FILE);
 	else
@@ -1132,7 +1132,7 @@ initialize_SSL(PGconn *conn)
 #endif   /* USE_SSL_ENGINE */
 		{
 			/* PGSSLKEY is not an engine, treat it as a filename */
-			strncpy(fnbuf, conn->sslkey, sizeof(fnbuf));
+			strlcpy(fnbuf, conn->sslkey, sizeof(fnbuf));
 		}
 	}
 	else if (have_homedir)
@@ -1195,7 +1195,7 @@ initialize_SSL(PGconn *conn)
 	 * verification after the connection has been completed.
 	 */
 	if (conn->sslrootcert && strlen(conn->sslrootcert) > 0)
-		strncpy(fnbuf, conn->sslrootcert, sizeof(fnbuf));
+		strlcpy(fnbuf, conn->sslrootcert, sizeof(fnbuf));
 	else if (have_homedir)
 		snprintf(fnbuf, sizeof(fnbuf), "%s/%s", homedir, ROOT_CERT_FILE);
 	else
@@ -1233,7 +1233,7 @@ initialize_SSL(PGconn *conn)
 		if ((cvstore = SSL_CTX_get_cert_store(SSL_context)) != NULL)
 		{
 			if (conn->sslcrl && strlen(conn->sslcrl) > 0)
-				strncpy(fnbuf, conn->sslcrl, sizeof(fnbuf));
+				strlcpy(fnbuf, conn->sslcrl, sizeof(fnbuf));
 			else if (have_homedir)
 				snprintf(fnbuf, sizeof(fnbuf), "%s/%s", homedir, ROOT_CRL_FILE);
 			else