From c919bbbdd370f86af37e18ca991c936d3bf36cfa Mon Sep 17 00:00:00 2001 From: David Gibson Date: Thu, 6 Jun 2024 20:09:47 +1000 Subject: [PATCH] conf: Safer parsing of MAC addresses In conf() we parse a MAC address in two places, for the --ns-mac-addr and the -M options. As well as duplicating code, the logic for this parsing has several bugs: * The most serious is that if the given string is shorter than a MAC address should be, we'll access past the end of it. * We don't check the endptr supplied by strtol() which means we could ignore certain erroneous contents * We never check the separator characters between each octet * We ignore certain sorts of garbage that follow the MAC address Correct all these bugs in a new parse_mac() helper. Signed-off-by: David Gibson Signed-off-by: Stefano Brivio --- conf.c | 53 ++++++++++++++++++++++++++++++++++++----------------- 1 file changed, 36 insertions(+), 17 deletions(-) diff --git a/conf.c b/conf.c index 72ca1fc..fdeb9db 100644 --- a/conf.c +++ b/conf.c @@ -1124,6 +1124,39 @@ static void conf_open_files(struct ctx *c) c->pidfile_fd = pidfile_open(c->pidfile); } +/** + * parse_mac - Parse a MAC address from a string + * @mac: Binary MAC address, initialised on success + * @str: String to parse + * + * Parses @str as an Ethernet MAC address stored in @mac on success. Exits on + * failure. + */ +static void parse_mac(unsigned char mac[ETH_ALEN], const char *str) +{ + size_t i; + + if (strlen(str) != (ETH_ALEN * 3 - 1)) + goto fail; + + for (i = 0; i < ETH_ALEN; i++) { + const char *octet = str + 3 * i; + unsigned long b; + char *end; + + errno = 0; + b = strtoul(octet, &end, 16); + if (b > UCHAR_MAX || errno || end != octet + 2 || + *end != ((i == ETH_ALEN - 1) ? '\0' : ':')) + goto fail; + mac[i] = b; + } + return; + +fail: + die("Invalid MAC address: %s", str); +} + /** * conf() - Process command-line arguments and set configuration * @c: Execution context @@ -1200,9 +1233,9 @@ void conf(struct ctx *c, int argc, char **argv) unsigned int ifi4 = 0, ifi6 = 0; const char *logfile = NULL; const char *optstring; - int name, ret, b, i; size_t logsize = 0; char *runas = NULL; + int name, ret; uid_t uid; gid_t gid; @@ -1243,14 +1276,7 @@ void conf(struct ctx *c, int argc, char **argv) if (c->mode != MODE_PASTA) die("--ns-mac-addr is for pasta mode only"); - for (i = 0; i < ETH_ALEN; i++) { - errno = 0; - b = strtol(optarg + (intptr_t)i * 3, NULL, 16); - if (b < 0 || b > UCHAR_MAX || errno) - die("Invalid MAC address: %s", optarg); - - c->mac_guest[i] = b; - } + parse_mac(c->mac_guest, optarg); break; case 5: if (c->mode != MODE_PASTA) @@ -1510,14 +1536,7 @@ void conf(struct ctx *c, int argc, char **argv) break; case 'M': - for (i = 0; i < ETH_ALEN; i++) { - errno = 0; - b = strtol(optarg + (intptr_t)i * 3, NULL, 16); - if (b < 0 || b > UCHAR_MAX || errno) - die("Invalid MAC address: %s", optarg); - - c->mac[i] = b; - } + parse_mac(c->mac, optarg); break; case 'g': if (c->mode == MODE_PASTA)