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tom_modem: gate Turkish GSM-7 shift table behind UDH language IE #259

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tom_modem: gate Turkish GSM-7 shift table behind UDH language IE #259

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82fff5d
tom_modem: add Turkish character support for SMS
ozgunokan Aug 29, 2026
49e2f81
tom_modem: gate Turkish GSM-7 shift table behind UDH language IE
ozgunokan Aug 30, 2026
0a5b566
tom_modem: fix Turkish UDH parsing and PDU validation
FUjr Sep 8, 2026
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159 changes: 133 additions & 26 deletions application/tom_modem/src/extlib/pdu.c
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Original file line number Diff line number Diff line change
Expand Up @@ -142,19 +142,128 @@ static const unsigned char gsm7bits_extend_to_latin1[128] = {
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
};

/* 3GPP TS 23.038 Turkish National Language Single Shift table.
* Only used when the PDU's UDH explicitly selects it (IEI 0x24/0x25,
* language identifier 0x01 = Turkish) -- see udh_has_turkish_shift().
* Non-Turkish messages must never be decoded through this table. */
static const unsigned char turkish_extend_to_latin1[128] = {
0, 0, 0, 0, 0, 0, 0, 0, 0, 0,'\f', 0, 0, 0, 0, 0,
0, 0, 0, 0, '^', 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, '{', '}', 0, 0, 0, 0, 0,'\\',
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, '[', '~', ']', 0,
'|', 0, 0, 0xC7, 0, 0, 0, 0xD0, 0, 0xDD, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0xDE, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0xE7, 0, 0, 0, 0xF0, 0, 0xFD, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0xFE, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
};

/* Walks the PDU's User Data Header looking for a National Language
* Locking Shift (IEI 0x24) or Single Shift (IEI 0x25) IE whose data
* byte selects Turkish (0x01, per 3GPP TS 23.038 table 6.2.1.2.5).
* Returns 1 only if such an IE is present; every other message keeps
* using the standard extension table. */
struct udh_info {
int present;
int bytes;
int turkish_locking;
int turkish_single;
int concat_ref;
int concat_total;
int concat_part;
};

/* Parse every IE in the UDH. Concatenation is not required to be the last
* IE; language shift IEs and application IEs may follow it. */
static int
parse_udh(const unsigned char *buffer, int buffer_length, int sms_start,
struct udh_info *info)
{
memset(info, 0, sizeof(*info));
if (sms_start < 0 || sms_start + 1 >= buffer_length ||
!(buffer[sms_start] & 0x40))
return 0;
const int udhl = buffer[sms_start + 1];
const int first = sms_start + 2;
const int end = first + udhl;
if (end > buffer_length)
return -1;
info->present = 1;
info->bytes = udhl + 1;
for (int pos = first; pos < end;) {
if (pos + 2 > end)
return -1;
const unsigned char iei = buffer[pos];
const unsigned char iedl = buffer[pos + 1];
if (pos + 2 + iedl > end)
return -1;
if (iei == 0x24 && iedl >= 1 && buffer[pos + 2] == 0x01)
info->turkish_locking = 1;
if (iei == 0x25 && iedl >= 1 && buffer[pos + 2] == 0x01)
info->turkish_single = 1;
if (iei == 0x00 && iedl == 3) {
info->concat_ref = buffer[pos + 2];
info->concat_total = buffer[pos + 3];
info->concat_part = buffer[pos + 4];
} else if (iei == 0x08 && iedl == 4) {
info->concat_ref = (buffer[pos + 2] << 8) | buffer[pos + 3];
info->concat_total = buffer[pos + 4];
info->concat_part = buffer[pos + 5];
}
pos += 2 + iedl;
}
if (info->concat_total <= 1) {
info->concat_ref = info->concat_total = info->concat_part = 0;
}
return 0;
}

static unsigned char
gsm7_locking_to_latin1(unsigned char value)
{
switch (value) {
case 0x07: return 0xFD; /* dotless i */
case 0x0B: return 0xD0; /* G */
case 0x0C: return 0xF0; /* g */
case 0x1C: return 0xDE; /* S */
case 0x1D: return 0xFE; /* s */
case 0x40: return 0xDD; /* I with dot */
case 0x5B: return 0xC4;
case 0x5C: return 0xD6;
case 0x5D: return 0xD1;
case 0x5E: return 0xDC;
case 0x60: return 0xE7;
case 0x7B: return 0xE4;
case 0x7C: return 0xF6;
case 0x7D: return 0xF1;
case 0x7E: return 0xFC;
case 0x7F: return 0xE0;
default: return gsm7bits_to_latin1[value];
}
}

static int
G7bitToAscii(char* buffer, int buffer_length)
G7bitToAscii(char* buffer, int buffer_length, int use_turkish_locking,
int use_turkish_single)
{
int i;
const unsigned char *ext_table = use_turkish_single ? turkish_extend_to_latin1 : gsm7bits_extend_to_latin1;

for (i = 0; i<buffer_length; i++) {
if (buffer[i] < 128) {
for (i = 0; i < buffer_length; i++) {
if ((unsigned char)buffer[i] < 128) {
if (buffer[i] == GSM_7BITS_ESCAPE) {
buffer[i] = gsm7bits_extend_to_latin1[buffer[i + 1]];
memmove(&buffer[i + 1], &buffer[i + 2], buffer_length - i - 1);
if (i + 1 >= buffer_length) {
// Bozuk veri: ESCAPE tamponun son baytı, genişletilecek
// karakter yok. Bu baytı at ve döngüyü sonlandır.
buffer_length--;
break;
}
buffer[i] = ext_table[(unsigned char)buffer[i + 1]];
if (i + 2 < buffer_length)
memmove(&buffer[i + 1], &buffer[i + 2], buffer_length - i - 2);
buffer_length--;
} else {
buffer[i] = gsm7bits_to_latin1[buffer[i]];
buffer[i] = use_turkish_locking ? gsm7_locking_to_latin1((unsigned char)buffer[i]) :
gsm7bits_to_latin1[(unsigned char)buffer[i]];
}
}
}
Expand Down Expand Up @@ -339,16 +448,14 @@ int pdu_decode(const unsigned char* buffer, int buffer_length,
if (sms_deliver_start + 1 > buffer_length)
return -2;

const int user_data_header_length = (buffer[sms_deliver_start]>>4);

const int sender_number_length = buffer[sms_deliver_start + 1];
if (sender_number_length + 1 > sender_phone_number_size)
return -3; // Buffer too small to hold decoded phone number.

const int sender_type_of_address = buffer[sms_deliver_start + 2];
if (sender_type_of_address == TYPE_OF_ADDRESS_ALPHANUMERIC) {
int sender_len1 = DecodePDUMessage_GSM_7bit(buffer + sms_deliver_start + 3, (sender_number_length + 1) / 2, output_sender_phone_number, sender_number_length);
int sender_len2 = G7bitToAscii(output_sender_phone_number, sender_len1 - 1);
int sender_len2 = G7bitToAscii(output_sender_phone_number, sender_len1 - 1, 0, 0);
output_sender_phone_number[sender_len2] = 0;
} else {
DecodePhoneNumber(buffer + sms_deliver_start + 3, sender_number_length, output_sender_phone_number);
Expand All @@ -367,22 +474,15 @@ int pdu_decode(const unsigned char* buffer, int buffer_length,
(*output_sms_time) = timegm(&sms_broken_time);

const int sms_start = sms_pid_start + 2 + 7;
if (sms_start + 1 > buffer_length) return -1; // Invalid input buffer.

int tmp;
if((user_data_header_length&0x04)==0x04) {
tmp = buffer[sms_start + 1] + 1;
*skip_bytes = tmp;
*ref_number = 0x000000FF&buffer[sms_start + tmp - 2];
*total_parts = 0x000000FF&buffer[sms_start + tmp - 1];
*part_number = 0x000000FF&buffer[sms_start + tmp];
} else {
tmp = 0;
*skip_bytes = tmp;
*ref_number = tmp;
*total_parts = tmp;
*part_number = tmp;
}
if (sms_start + 1 >= buffer_length) return -1; // Invalid input buffer.

struct udh_info udh;
if (parse_udh(buffer, buffer_length, sms_start, &udh) < 0)
return -1;
*skip_bytes = udh.present ? udh.bytes : 0;
*ref_number = udh.concat_ref;
*total_parts = udh.concat_total;
*part_number = udh.concat_part;

int output_sms_text_length = buffer[sms_start];
if (sms_text_size < output_sms_text_length) return -1; // Cannot hold decoded buffer.
Expand All @@ -398,7 +498,14 @@ int pdu_decode(const unsigned char* buffer, int buffer_length,
int decoded_sms_text_size = DecodePDUMessage_GSM_7bit(buffer + sms_start + 1, buffer_length - (sms_start + 1),
output_sms_text, output_sms_text_length);
if (decoded_sms_text_size != output_sms_text_length) return -1; // Decoder length is not as expected.
output_sms_text_length = G7bitToAscii(output_sms_text, output_sms_text_length);
int skip_septets = 0;
if (*skip_bytes > 0)
skip_septets = (*skip_bytes * 8 + 6) / 7;
if (skip_septets > output_sms_text_length)
return -1;
output_sms_text_length = skip_septets + G7bitToAscii(output_sms_text + skip_septets,
output_sms_text_length - skip_septets, udh.turkish_locking,
udh.turkish_single);
break;
}
case 2:
Expand Down
24 changes: 20 additions & 4 deletions application/tom_modem/src/operations.c
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Original file line number Diff line number Diff line change
Expand Up @@ -114,12 +114,18 @@ int sms_read(PROFILE_T *profile, void *transport_ptr)
dbg_msg("No PDU found for line: %s", line);
pdu = strtok(NULL, "\n");
}
sms->sms_pdu = (char *)malloc(strlen(pdu));
if (pdu == NULL) {
dbg_msg("PDU still NULL after fallback, skipping entry for line: %s", line);
free(sms);
line = strtok(NULL, "\n");
continue;
}
sms->sms_pdu = (char *)malloc(strlen(pdu) + 1);
sms->sender = (char *)malloc(PHONE_NUMBER_SIZE);
sms->sms_text = (char *)malloc(SMS_TEXT_SIZE);
memset(sms->sms_text, 0, SMS_TEXT_SIZE);
sms->sms_index = get_sms_index(line);
memcpy(sms->sms_pdu, pdu, strlen(pdu));
memcpy(sms->sms_pdu, pdu, strlen(pdu) + 1);
int sms_len = decode_pdu(sms);
if (sms_len > 0)
{
Expand Down Expand Up @@ -154,6 +160,10 @@ int sms_send(PROFILE_T *profile, void *transport_ptr)
}

int pdu_len = strlen(profile->sms_pdu);
if (pdu_len <= 0 || pdu_len > 255) {
dbg_msg("SMS PDU length invalid or too large for buffer (len=%d)", pdu_len);
return INVALID_PARAM;
}
int pdu_expected_len = (pdu_len) / 2 - 1;
char send_sms_cmd[32];
char pdu_hex[512];
Expand Down Expand Up @@ -243,12 +253,18 @@ int sms_read_unread(PROFILE_T *profile, void *transport_ptr)
dbg_msg("No PDU found for line: %s", line);
pdu = strtok(NULL, "\n");
}
sms->sms_pdu = (char *)malloc(strlen(pdu));
if (pdu == NULL) {
dbg_msg("PDU still NULL after fallback, skipping entry for line: %s", line);
free(sms);
line = strtok(NULL, "\n");
continue;
}
sms->sms_pdu = (char *)malloc(strlen(pdu) + 1);
sms->sender = (char *)malloc(PHONE_NUMBER_SIZE);
sms->sms_text = (char *)malloc(SMS_TEXT_SIZE);
memset(sms->sms_text, 0, SMS_TEXT_SIZE);
sms->sms_index = get_sms_index(line);
memcpy(sms->sms_pdu, pdu, strlen(pdu));
memcpy(sms->sms_pdu, pdu, strlen(pdu) + 1);
int sms_len = decode_pdu(sms);
if (sms_len > 0)
{
Expand Down
115 changes: 109 additions & 6 deletions application/tom_modem/src/utils.c
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Original file line number Diff line number Diff line change
Expand Up @@ -73,10 +73,22 @@ int decode_pdu(SMS_T *sms)
int pdu_str_len;
unsigned char hex_pdu[SMS_PDU_HEX_SIZE] = {0};
pdu_str_len = strlen(sms->sms_pdu);
if (pdu_str_len == 0 || (pdu_str_len & 1) != 0 ||
pdu_str_len / 2 > (int)sizeof(hex_pdu))
{
err_msg("Invalid PDU length");
return -1;
}
for (int i = 0; i < pdu_str_len; i += 2)
{
hex_pdu[i / 2] = char_to_hex(sms->sms_pdu[i]) << 4;
hex_pdu[i / 2] |= char_to_hex(sms->sms_pdu[i + 1]);
int high = char_to_hex(sms->sms_pdu[i]);
int low = char_to_hex(sms->sms_pdu[i + 1]);
if (high < 0 || low < 0)
{
err_msg("Invalid hexadecimal digit in PDU");
return -1;
}
hex_pdu[i / 2] = (unsigned char)((high << 4) | low);
}
int sms_len = pdu_decode(hex_pdu, pdu_str_len/2,
&sms->timestamp,
Expand All @@ -94,22 +106,113 @@ int decode_pdu(SMS_T *sms)
}
sms->sms_lenght = sms_len;

// Convert sender to UTF-8 in place
{
char temp_sender[64];
int s_offset = 0;
for (int i = 0; sms->sender[i] != '\0'; i++)
{
unsigned char c = (unsigned char)sms->sender[i];
if (c < 128)
{
temp_sender[s_offset++] = c;
}
else if (c == 0xD0) { // Ğ
temp_sender[s_offset++] = 0xC4;
temp_sender[s_offset++] = 0x9E;
}
else if (c == 0xF0) { // ğ
temp_sender[s_offset++] = 0xC4;
temp_sender[s_offset++] = 0x9F;
}
else if (c == 0xDD) { // İ
temp_sender[s_offset++] = 0xC4;
temp_sender[s_offset++] = 0xB0;
}
else if (c == 0xFD) { // ı
temp_sender[s_offset++] = 0xC4;
temp_sender[s_offset++] = 0xB1;
}
else if (c == 0xDE) { // Ş
temp_sender[s_offset++] = 0xC5;
temp_sender[s_offset++] = 0x9E;
}
else if (c == 0xFE) { // ş
temp_sender[s_offset++] = 0xC5;
temp_sender[s_offset++] = 0x9F;
}
else
{
temp_sender[s_offset++] = 0xC0 | (c >> 6);
temp_sender[s_offset++] = 0x80 | (c & 0x3F);
}
if (s_offset >= 62) break; // prevent temp_sender overflow
}
temp_sender[s_offset] = '\0';

// sms->sender, operations.c'de PHONE_NUMBER_SIZE ile ayrilmistir.
// strcpy YERINE strncpy + garantili null-terminate kullaniliyor ki
// temp_sender (64 byte'a kadar) hedef tamponu tasirmasin.
strncpy(sms->sender, temp_sender, PHONE_NUMBER_SIZE - 1);
sms->sender[PHONE_NUMBER_SIZE - 1] = '\0';
}

switch ((tp_dcs / 4) % 4)
{
case 0:
{
// GSM 7 bit
sms->type = SMS_CHARSET_7BIT;
int i;
int offset = 0;
i = skip_bytes;
if (skip_bytes > 0)
i = (skip_bytes * 8 + 6) / 7;
for (; i < strlen(sms_text); i++)
for (; i < sms_len; i++)
{
sprintf(sms->sms_text + i, "%c", sms_text[i]);
if (offset >= SMS_TEXT_SIZE - 2)
{
dbg_msg("SMS text truncated to fit buffer (SMS_TEXT_SIZE=%d)", SMS_TEXT_SIZE);
break;
}
unsigned char c = (unsigned char)sms_text[i];
if (c < 128)
{
sms->sms_text[offset++] = c;
}
else if (c == 0xD0) { // Ğ
sms->sms_text[offset++] = 0xC4;
sms->sms_text[offset++] = 0x9E;
}
else if (c == 0xF0) { // ğ
sms->sms_text[offset++] = 0xC4;
sms->sms_text[offset++] = 0x9F;
}
else if (c == 0xDD) { // İ
sms->sms_text[offset++] = 0xC4;
sms->sms_text[offset++] = 0xB0;
}
else if (c == 0xFD) { // ı
sms->sms_text[offset++] = 0xC4;
sms->sms_text[offset++] = 0xB1;
}
else if (c == 0xDE) { // Ş
sms->sms_text[offset++] = 0xC5;
sms->sms_text[offset++] = 0x9E;
}
else if (c == 0xFE) { // ş
sms->sms_text[offset++] = 0xC5;
sms->sms_text[offset++] = 0x9F;
}
else
{
// Latin-1'den UTF-8'e Donusum
sms->sms_text[offset++] = 0xC0 | (c >> 6);
sms->sms_text[offset++] = 0x80 | (c & 0x3F);
}
}
i++;
sprintf(sms->sms_text + i, "%c", '\0');
if (offset >= SMS_TEXT_SIZE) offset = SMS_TEXT_SIZE - 1;
sms->sms_text[offset] = '\0';
break;
}
case 2:
Expand Down
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