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Fix New World NVRAM limits calculations.

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It was possible to corrupt New World nvram using dingusppc setenv command.

- setenv must call get_config_vars to set data_length so that it can calculate free space.
- data_length represents the number of bytes taken by nvram variables including the terminating null for the value (name, '=', value, '\0'). Previously, it did not include the terminating null.
- The list of variables and values ends at a '\0' or at pos == 4096 bytes. Previously, data_length wouldn't get set if pos >= 4096.
- Allow setenv to create new nvram variables.
- Since data_length now represents the total number of used bytes, free_space now represents the actual free space, so use > free_space (instead of >= free_space) to determine insufficient space.
- While parsing nvram variable name, do not read beyond 4096 bytes.
- Use a different error message for each problem that can occur while parsing nvram variable name.
This commit is contained in:
joevt 2023-06-04 08:25:32 -07:00
parent 07f57a1e9b
commit 439509b408
1 changed files with 55 additions and 28 deletions
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83
devices/common/ofnvram.cpp
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@ -391,27 +391,47 @@ const OfConfigImpl::config_dict& OfConfigChrp::get_config_vars() {
this->_config_vars.clear();
this->data_length = 0;
if (!this->validate())
return _config_vars;
for (int pos = 0; pos < 4096;) {
char *pname = (char *)&this->buf[pos];
bool got_name = false;
// scan property name until '=' is encountered
// or max length is reached
for (len = 0; len < 32; pos++, len++) {
if (pname[len] == '=' || pname[len] == '\0')
for (len = 0; ; pos++, len++) {
if (len >= 32) {
cout << "name > 31 chars" << endl;
break;
}
if (pos >= 4096) {
cout << "no = sign before end of partition" << endl;
break;
}
if (pname[len] == '=') {
if (len) {
got_name = true;
}
else {
cout << "got = sign but no name" << endl;
}
break;
}
if (pname[len] == '\0') {
if (len) {
cout << "no = sign before termminating null" << endl;
}
else {
// empty property name -> free space reached
}
break;
}
}
// empty property name -> free space reached
if (!len) {
this->data_length = pos;
break;
}
if (pname[len] != '=') {
cout << "no = sign found or name > 31 chars" << endl;
if (!got_name) {
break;
}
@ -436,8 +456,11 @@ const OfConfigImpl::config_dict& OfConfigChrp::get_config_vars() {
this->_config_vars.push_back(std::make_pair(prop_name, pval));
pos++; // skip past null terminator
this->data_length = pos; // point to after null
}
//cout << "Read " << this->data_length << " bytes from nvram." << endl;
return this->_config_vars;
}
@ -447,7 +470,7 @@ bool OfConfigChrp::update_partition() {
memset(this->buf, 0, 4096);
for (auto& var : this->_config_vars) {
if ((var.first.length() + var.second.length() + 2) >= 4096) {
if ((pos + var.first.length() + var.second.length() + 2) > 4096) {
cout << "No room in the partition!" << endl;
return false;
}
@ -464,6 +487,7 @@ bool OfConfigChrp::update_partition() {
this->nvram_obj->write_byte(this->data_offset + i, this->buf[i]);
}
//cout << "Wrote " << pos << " bytes to nvram." << endl;
return true;
}
@ -471,25 +495,25 @@ bool OfConfigChrp::set_var(std::string& var_name, std::string& value) {
if (!this->validate())
return false;
bool found = false;
// see if we're about to change a flag
if (var_name.back() == '?') {
if (value != "true" && value != "false") {
cout << "Flag value can be 'true' or 'false'" << endl;
return false;
}
}
unsigned free_space = 4096 - this->data_length;
bool found = false;
// see if the user tries to change an existing property
for (auto& var : this->_config_vars) {
if (var.first == var_name) {
found = true;
// see if we're about to change a flag
if (var_name.back() == '?') {
if (value != "true" && value != "false") {
cout << "Flag value can be 'true' or 'false'" << endl;
return false;
}
}
if (value.length() > var.second.length()) {
unsigned free_space = 4096 - this->data_length;
if ((value.length() - var.second.length()) >= free_space) {
cout << "No room for new data!" << endl;
if ((value.length() - var.second.length()) > free_space) {
cout << "No room for updated nvram variable!" << endl;
return false;
}
}
@ -500,8 +524,11 @@ bool OfConfigChrp::set_var(std::string& var_name, std::string& value) {
}
if (!found) {
cout << "Attempt to change unknown variable " << var_name << endl;
return false;
if ((var_name.length() + value.length() + 2) > free_space) {
cout << "No room for new nvram variable!" << endl;
return false;
}
this->_config_vars.push_back(std::make_pair(var_name, value));
}
return this->update_partition();
@ -551,12 +578,10 @@ static std::string ReplaceAll(std::string& str, const std::string& from, const s
}
void OfConfigUtils::printenv() {
OfConfigImpl::config_dict vars;
if (!this->open_container())
return;
vars = this->cfg_impl->get_config_vars();
OfConfigImpl::config_dict vars = this->cfg_impl->get_config_vars();
for (auto& var : vars) {
std::string val = var.second;
@ -572,6 +597,8 @@ void OfConfigUtils::setenv(string var_name, string value)
if (!this->open_container())
return;
OfConfigImpl::config_dict vars = this->cfg_impl->get_config_vars();
if (!this->cfg_impl->set_var(var_name, value)) {
cout << " Please try again" << endl;
} else {