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Don't overwrite a possibly valid leasefile if we have no valid lease.

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Nicholas J. Kain 2023-01-18 08:08:33 -05:00
parent 1b8dc7f05e
commit 44511e6789
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1 changed files with 5 additions and 2 deletions
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7
leasefile.c
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@ -33,7 +33,7 @@ void open_leasefile(void)
{ {
char leasefile[PATH_MAX]; char leasefile[PATH_MAX];
get_leasefile_path(leasefile, sizeof leasefile, client_config.interface); get_leasefile_path(leasefile, sizeof leasefile, client_config.interface);
leasefilefd = open(leasefile, O_WRONLY|O_TRUNC|O_CREAT|O_CLOEXEC, 0644); leasefilefd = open(leasefile, O_WRONLY|O_CREAT|O_CLOEXEC, 0644);
if (leasefilefd < 0) if (leasefilefd < 0)
suicide("%s: (%s) Failed to create lease file '%s': %s", suicide("%s: (%s) Failed to create lease file '%s': %s",
client_config.interface, __func__, leasefile, strerror(errno)); client_config.interface, __func__, leasefile, strerror(errno));
@ -59,6 +59,10 @@ static void do_write_leasefile(struct in_addr ipnum)
log_line("%s: (%s) memccpy failed", client_config.interface, __func__); log_line("%s: (%s) memccpy failed", client_config.interface, __func__);
return; return;
} }
size_t outlen = strlen(out);
// Make sure that we're not overwriting the leasefile with an invalid
// IP address. This is a very minimal check.
if (outlen < 7) return;
if (safe_ftruncate(leasefilefd, 0)) { if (safe_ftruncate(leasefilefd, 0)) {
log_line("%s: (%s) Failed to truncate lease file: %s", log_line("%s: (%s) Failed to truncate lease file: %s",
client_config.interface, __func__, strerror(errno)); client_config.interface, __func__, strerror(errno));
@ -69,7 +73,6 @@ static void do_write_leasefile(struct in_addr ipnum)
client_config.interface, __func__, strerror(errno)); client_config.interface, __func__, strerror(errno));
return; return;
} }
size_t outlen = strlen(out);
ssize_t ret = safe_write(leasefilefd, out, outlen); ssize_t ret = safe_write(leasefilefd, out, outlen);
if (ret < 0 || (size_t)ret != outlen) if (ret < 0 || (size_t)ret != outlen)
log_line("%s: (%s) Failed to write ip to lease file.", log_line("%s: (%s) Failed to write ip to lease file.",