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ad88be9e7

Denys Vlasenko

2026-02-25

SUCCESS Duration: 146s

Subject

*: don't use getservbyname, it links in a static buffer

Binary

No binary (build failed)

Architecture & Compiler Flags

Architecture: x86_64-linux-gnu Compiler: gcc (Ubuntu 11.4.0-1ubuntu1~22.04.3) 11.4.0

gcc -Wp,-MD,applets/.usage.d -Wall -Wstrict-prototypes -O2 -fomit-frame-pointer      -Iinclude -Iinclude -o applets/usage applets/usage.c

Build Log

(log yok)

Commit Diff GitHub →

include/libbb.h +3 -1 libbb/bb_get_servname_by_port.c +2 -4 libbb/bb_get_servport_by_name.c +129 -0 libbb/xconnect.c +0 -21 networking/inetd.c +11 -11

include/libbb.h+3 -1

@@ -911,9 +911,11 @@ char* xmalloc_sockaddr2hostonly_noport(const struct sockaddr *sa) FAST_FUNC RETU
	/* inet_[ap]ton on steroids */
	char* xmalloc_sockaddr2dotted(const struct sockaddr *sa) FAST_FUNC RETURNS_MALLOC;
	char* xmalloc_sockaddr2dotted_noport(const struct sockaddr *sa) FAST_FUNC RETURNS_MALLOC;
-	// NB: unlike getservbyport, port parameter is NOT in network order
+	// NB: unlike getservbyport, port parameter/retval are in host, NOT network order!
	#define getservbyport dont_use_getservbyport_uses_global_buffer
	char* bb_get_servname_by_port(char *p_etc_services, int port, const char type) FAST_FUNC RETURNS_MALLOC;
+	#define getservbyname dont_use_getservbyname_uses_global_buffer
+	int bb_get_servport_by_name(char *p_etc_services, const char name, const char *type) FAST_FUNC;
	// "old" (ipv4 only) API
	// users: traceroute.c hostname.c - use _list_ of all IPs
	struct hostent xgethostbyname(const char name) FAST_FUNC;

libbb/bb_get_servname_by_port.c+2 -4

@@ -9,11 +9,9 @@
	//kbuild:lib-$(CONFIG_PSCAN) += bb_get_servname_by_port.o
	#include "libbb.h"

-	//Rationale for exising:
+	//Rationale for existing:
	//#define getservbyport dont_use_getservbyport_uses_global_buffer
	//(for example: -280 bytes on musl, x86-32)
-	//TODO:
-	//avoid getservbyname() as well

	char* FAST_FUNC bb_get_servname_by_port(char *p_etc_services, int port, const char type)
	{
@@ -45,7 +43,7 @@ char* FAST_FUNC bb_get_servname_by_port(char **p_etc_services, int port, const c
	end = is_prefixed_with(end, type);
	if (!end
	\|\| !(isspace(end) \|\| end == '\0'
-	\|\| *end == '#') // glibc treats "http 80/tcp#COMMENT" as valid
+	\|\| *end == '#') // glibc treats "http 80/tcp#COMMENT" (no space!) as valid
	) {
	goto next;
	}

libbb/bb_get_servport_by_name.c+129 -0

@@ -0,0 +1,129 @@
+	/*
+	* Utility routines.
+	*
+	* Copyright (C) 2026 Denys Vlasenko
+	*
+	* Licensed under GPLv2, see file LICENSE in this source tree.
+	*/
+	//kbuild:lib-y += bb_get_servport_by_name.o
+	//kbuild:lib-y += bb_get_servport_by_name.o
+	#include "libbb.h"
+
+	//Rationale for existing:
+	//#define getservbyname dont_use_getservbyname_uses_global_buffer
+	//(for example: -32 BSS bytes on musl, x86-32)
+
+	int FAST_FUNC bb_get_servport_by_name(char *p_etc_services, const char name, const char *proto)
+	{
+	unsigned namelen;
+	char *sp;
+
+	if (!name[0]) // This can hang the search (strstr advances by 0 bytes)
+	return -1; // bad service name form: ""
+	// Any other bogosity to reject?
+	// Or just enforce isalnum_or_dash_or_slash(name[i])?
+	// Yes, service name like "cl/1" is allowed and _exists_.
+	//
+	// Protect against finding service "www#c" in "http 10/tcp www#c" line
+	//if (strchr(name, '#'))
+	// return -1; // bad service name form
+	//^^^^ the main code already catches this possibility.
+	//
+	// Current code allows e.g. service names like "http 80/tcp"
+	// to map to port 80. Probably harmless?
+	//if (skip_non_whitespace(name)[0])
+	// return -1; // bad service name form (has whitespace)
+
+	sp = *p_etc_services;
+	if (!sp) {
+	//TODO: we need mmap_entire_file() for this use case!
+	sp = xmalloc_open_read_close("/etc/services", NULL);
+	if (!sp)
+	return -1;
+	*p_etc_services = sp;
+	}
+	namelen = strlen(name);
+	while (*sp) {
+	const char *pnstr;
+	char start, end;
+	unsigned n;
+
+	// First, find a possible service name without regard for line separators (!)
+	start = strstr(sp, name);
+	if (!start)
+	return -1;
+	sp = start + namelen;
+	if (start != *p_etc_services && !isspace(start[-1])) {
+	// There is a char before it, and it's not whitespace
+	continue;
+	}
+	if (!(isspace(sp) \|\| sp == '\0' \|\| *sp == '#'))
+	// After it: not whitespace/EOF/comment
+	continue;
+	// The found substring _is_ correctly delimited before and after
+
+	// Find beginning of the line we are on
+	while (start != *p_etc_services && start[-1] != '\n')
+	start--;
+	start = skip_whitespace(start);
+	// Is there a comment char between start of line and "service name"?
+	if (memchr(start, '#', sp - start)) {
+	// The "service name" we found is actually in comment / has comment in it.
+	// Also rejects names with #:
+	// service "www#c" won't be found even on "http 80/tcp www#c" line
+	continue;
+	}
+	// Is the [start...sp) of the form "SERVNAME NUM/PROTO[ ALIAS[ ALIAS...][ ]]"?
+	pnstr = skip_whitespace(skip_non_whitespace(start)); // go to NUM...
+
+	// I've seen this line in /etc/services of a real-world machine:
+	//914c/g 211/tcp 914c-g
+	// Now consider just a bit more pathological example:
+	//914c/tcp 914/tcp 914/tcp
+	// If we search for service name "914/tcp",
+	// we'll find it at second word first, yet we must not reject this line
+	// because the THIRD word also matches, and it's a valid match (tested on glibc!).
+	// But in this case we must not match:
+	//914c/tcp 914/tcp something-else
+	if (sp - namelen == pnstr)
+	continue; // the match is at NUM..., try matching further
+
+	n = bb_strtou(pnstr, &end, 10);
+	if (n > 0xffff \|\| *end != '/')
+	continue; // NUM... part is not a valid port#, or has no slash
+
+	if (proto) {
+	end++; // points to PROTO
+	end = is_prefixed_with(end, proto);
+	if (!end
+	\|\| !(isspace(end) \|\| end == '\0'
+	\|\| *end == '#') // glibc treats "http 80/tcp#COMMENT" (no space!) as valid
+	) {
+	continue; // PROTO does not match
+	}
+	}
+	// By now, either WORD or one of the ALIASes has to be the part
+	// which was found by strstr()!
+	return n;
+	}
+	return -1;
+	}
+
+	// Return port number for a service.
+	// If "port" is a number use it as the port.
+	// If "port" is a name it is looked up in /etc/services.
+	// if NULL, return default_port
+	unsigned FAST_FUNC bb_lookup_port(const char port, const char protocol, unsigned port_nr)
+	{
+	if (port) {
+	port_nr = bb_strtou(port, NULL, 10);
+	if (errno \|\| port_nr > 65535) {
+	char *p_etc_services = NULL;
+	port_nr = bb_get_servport_by_name(&p_etc_services, port, protocol);
+	if (port_nr > 0xffff) // -1?
+	bb_error_msg_and_die("bad port '%s'", port);
+	free(p_etc_services);
+	}
+	}
+	return (uint16_t)port_nr;
+	}

libbb/xconnect.c+0 -21

@@ -113,29 +113,8 @@ void FAST_FUNC xconnect(int s, const struct sockaddr *s_addr, socklen_t addrlen)
	}
	}

-	/* Return port number for a service.
-	* If "port" is a number use it as the port.
-	* If "port" is a name it is looked up in /etc/services.
-	* if NULL, return default_port
-	*/
-	unsigned FAST_FUNC bb_lookup_port(const char port, const char protocol, unsigned port_nr)
-	{
-	if (port) {
-	port_nr = bb_strtou(port, NULL, 10);
-	if (errno \|\| port_nr > 65535) {
-	struct servent *tserv = getservbyname(port, protocol);
-	if (!tserv)
-	bb_error_msg_and_die("bad port '%s'", port);
-	port_nr = ntohs(tserv->s_port);
-	}
-	}
-	return (uint16_t)port_nr;
-	}
-
-
	/* "New" networking API */

-
	int FAST_FUNC get_nport(const struct sockaddr *sa)
	{
	#if ENABLE_FEATURE_IPV6

networking/inetd.c+11 -11

@@ -969,9 +969,8 @@ static void reread_config_file(int sig UNUSED_PARAM)
	servtab_t sep, cp, **sepp;
	len_and_sockaddr *lsa;
	sigset_t omask;
-	unsigned n;
-	uint16_t port;
	int save_errno = errno;
+	char *p_etc_services = NULL;

	if (!reopen_config_file())
	goto ret;
@@ -1039,7 +1038,9 @@ static void reread_config_file(int sig UNUSED_PARAM)
	break;

	default: /* case AF_INET, case AF_INET6 */
-	n = bb_strtou(sep->se_service, NULL, 10);
+	{
+	unsigned portno;
+	portno = bb_strtou(sep->se_service, NULL, 10);
	#if ENABLE_FEATURE_INETD_RPC
	if (is_rpc_service(sep)) {
	sep->se_rpcprog = n;
@@ -1059,26 +1060,23 @@ static void reread_config_file(int sig UNUSED_PARAM)
	}
	#endif
	/* what port to listen on? */
-	port = htons(n);
-	if (errno \|\| n > 0xffff) { /* se_service is not numeric */
+	if (errno \|\| portno > 0xffff) { /* se_service is not numeric */
	char protoname[4];
-	struct servent *sp;
	/* can result only in "tcp" or "udp": */
	safe_strncpy(protoname, sep->se_proto, 4);
-	sp = getservbyname(sep->se_service, protoname);
-	if (sp == NULL) {
+	portno = bb_get_servport_by_name(&p_etc_services, sep->se_service, protoname);
+	if (portno > 0xffff) {
	bb_error_msg("%s/%s: unknown service",
	sep->se_service, sep->se_proto);
	goto next_cp;
	}
-	port = sp->s_port;
	}
	if (LONE_CHAR(sep->se_local_hostname, '*')) {
	lsa = xzalloc_lsa(sep->se_family);
-	set_nport(&lsa->u.sa, port);
+	set_nport(&lsa->u.sa, htons(portno));
	} else {
	lsa = host_and_af2sockaddr(sep->se_local_hostname,
-	ntohs(port), sep->se_family);
+	portno, sep->se_family);
	if (!lsa) {
	bb_error_msg("%s/%s: unknown host '%s'",
	sep->se_service, sep->se_proto,
@@ -1087,6 +1085,7 @@ static void reread_config_file(int sig UNUSED_PARAM)
	}
	}
	break;
+	}//default:
	} /* end of "switch (sep->se_family)" */

	/* did lsa change? Then close/open */
@@ -1134,6 +1133,7 @@ static void reread_config_file(int sig UNUSED_PARAM)
	}
	restore_sigmask(&omask);
	ret:
+	free(p_etc_services);
	errno = save_errno;
	}