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options.c: Rewrite the ifchd_cmd_* options command generation functions.

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The old functions were harder to audit.  The new ones factor out most
of the work into a common ifcmd_raw() helper, and make sure to perform
the updates atomically wrt the output buffer.

snprintf is used heavily, as the C99 semantics should be on any targetted
system.

The atomicity will be improved in the next patch, allowing the number
of command buffers to be reduced.
This commit is contained in:
Nicholas J. Kain 2014-03-19 06:07:01 -04:00
parent 89d4649439
commit a2e8136bc9
1 changed files with 85 additions and 37 deletions
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122
ndhc/ifchange.c
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@ -33,6 +33,7 @@
#include <arpa/inet.h>
#include <sys/types.h>
#include <errno.h>
#include <limits.h>
#include "options.h"
#include "ndhc.h"
@ -46,12 +47,40 @@
static struct dhcpmsg cfg_packet; // Copy of the current configuration packet.
static int ifcmd_raw(char *buf, size_t buflen, char *optname,
char *optdata, ssize_t optlen)
{
if (!optdata)
return -1;
if (buflen < strlen(optname) + optlen + 3)
return -1;
if (optlen > INT_MAX || optlen < 0)
return -1;
int ioptlen = (int)optlen;
ssize_t olen = snprintf(buf, buflen, "%s:%.*s;",
optname, ioptlen, optdata);
if (olen < 0 || (size_t)olen >= buflen)
return -2;
return olen;
}
static int ifchd_cmd_bytes(char *buf, size_t buflen, char *optname,
uint8_t *optdata, ssize_t optlen)
{
return ifcmd_raw(buf, buflen, optname, (char *)optdata, optlen);
}
static int ifchd_cmd_u8(char *buf, size_t buflen, char *optname,
uint8_t *optdata, ssize_t optlen)
{
if (!optdata || optlen < 1)
return -1;
return snprintf(buf, buflen, "%s:%c;", optname, *optdata);
char numbuf[16];
uint8_t c = optdata[0];
ssize_t olen = snprintf(numbuf, sizeof numbuf, "%c", c);
if (olen < 0 || (size_t)olen >= sizeof numbuf)
return -1;
return ifcmd_raw(buf, buflen, optname, numbuf, strlen(numbuf));
}
static int ifchd_cmd_u16(char *buf, size_t buflen, char *optname,
@ -59,10 +88,14 @@ static int ifchd_cmd_u16(char *buf, size_t buflen, char *optname,
{
if (!optdata || optlen < 2)
return -1;
char numbuf[16];
uint16_t v;
memcpy(&v, optdata, 2);
v = ntohs(v);
return snprintf(buf, buflen, "%s:%hu;", optname, v);
ssize_t olen = snprintf(numbuf, sizeof numbuf, "%hu", v);
if (olen < 0 || (size_t)olen >= sizeof numbuf)
return -1;
return ifcmd_raw(buf, buflen, optname, numbuf, strlen(numbuf));
}
static int ifchd_cmd_s32(char *buf, size_t buflen, char *optname,
@ -70,59 +103,69 @@ static int ifchd_cmd_s32(char *buf, size_t buflen, char *optname,
{
if (!optdata || optlen < 4)
return -1;
char numbuf[16];
int32_t v;
memcpy(&v, optdata, 4);
v = ntohl(v);
return snprintf(buf, buflen, "%s:%d;", optname, v);
ssize_t olen = snprintf(numbuf, sizeof numbuf, "%d", v);
if (olen < 0 || (size_t)olen >= sizeof numbuf)
return -1;
return ifcmd_raw(buf, buflen, optname, numbuf, strlen(numbuf));
}
static int ifchd_cmd_ip(char *buf, size_t buflen, char *optname,
uint8_t *optdata, ssize_t optlen)
{
char ipbuf[INET_ADDRSTRLEN];
if (!optdata || optlen < 4)
return -1;
inet_ntop(AF_INET, optdata, ipbuf, sizeof ipbuf);
return snprintf(buf, buflen, "%s:%s;", optname, ipbuf);
char ipbuf[INET_ADDRSTRLEN];
if (!inet_ntop(AF_INET, optdata, ipbuf, sizeof ipbuf)) {
log_warning("%s: (%s) inet_ntop failed: %s",
client_config.interface, __func__, strerror(errno));
return -1;
}
return ifcmd_raw(buf, buflen, optname, ipbuf, strlen(ipbuf));
}
static int ifchd_cmd_iplist(char *buf, size_t buflen, char *optname,
static int ifchd_cmd_iplist(char *out, size_t outlen, char *optname,
uint8_t *optdata, ssize_t optlen)
{
char buf[2048];
char ipbuf[INET_ADDRSTRLEN];
char *obuf = buf;
size_t bufoff = 0;
size_t optoff = 0;
if (!optdata || optlen < 4)
return -1;
inet_ntop(AF_INET, optdata, ipbuf, sizeof ipbuf);
ssize_t wc = snprintf(buf, buflen, "%s:%s", optname, ipbuf);
if (wc <= 0)
return wc;
optlen -= 4;
optdata += 4;
buf += wc;
while (optlen >= 4) {
inet_ntop(AF_INET, optdata, ipbuf, sizeof ipbuf);
if (buflen < strlen(ipbuf) + (buf - obuf) + 2)
break;
buf += snprintf(buf, buflen - (buf - obuf), ",%s", ipbuf);
optlen -= 4;
optdata += 4;
}
buf += snprintf(buf, buflen - (buf - obuf), ";");
return buf - obuf;
}
static int ifchd_cmd_bytes(char *buf, size_t buflen, char *optname,
uint8_t *optdata, ssize_t optlen)
{
char *obuf = buf;
if (buflen < strlen(optname) + optlen + 3)
if (!inet_ntop(AF_INET, optdata + optoff, ipbuf, sizeof ipbuf)) {
log_warning("%s: (%s) inet_ntop failed: %s",
client_config.interface, __func__, strerror(errno));
return -1;
buf += snprintf(buf, buflen, "%s:", optname);
memcpy(buf, optdata, optlen);
buf[optlen] = ';';
buf[optlen+1] = '\0';
return (buf - obuf) + optlen + 1;
}
ssize_t wc = snprintf(buf + bufoff, sizeof buf, "%s:%s", optname, ipbuf);
if (wc < 0 || (size_t)wc >= sizeof buf)
return -1;
optoff += 4;
bufoff += wc;
while (optlen - optoff >= 4) {
if (!inet_ntop(AF_INET, optdata + optoff, ipbuf, sizeof ipbuf)) {
log_warning("%s: (%s) inet_ntop failed: %s",
client_config.interface, __func__, strerror(errno));
return -1;
}
wc = snprintf(buf + bufoff, sizeof buf, ",%s", ipbuf);
if (wc < 0 || (size_t)wc >= sizeof buf)
return -1;
optoff += 4;
bufoff += wc;
}
wc = snprintf(buf + bufoff, sizeof buf, ";");
if (wc < 0 || (size_t)wc >= sizeof buf)
return -1;
return ifcmd_raw(out, outlen, optname, buf, strlen(buf));
}
#define CMD_ROUTER "routr"
@ -263,8 +306,13 @@ static size_t send_cmd(char *out, size_t olen, struct dhcpmsg *packet,
oldlen = get_dhcp_opt(&cfg_packet, code, olddata, sizeof olddata);
if (oldlen == optlen && !memcmp(optdata, olddata, optlen))
return 0;
if (ifchd_cmd(buf, sizeof buf, optdata, optlen, code) == -1)
int r = ifchd_cmd(buf, sizeof buf, optdata, optlen, code);
if (r == -1)
return 0;
else if (r < -1) {
log_warning("Error happened generating ifch cmd string.");
return 0;
}
strnkcat(out, buf, olen);
return strlen(buf);
}