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Harden DSML and JSON parsing in the server #104

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160 changes: 145 additions & 15 deletions ds4_server.c
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Original file line number Diff line number Diff line change
Expand Up @@ -16,6 +16,7 @@
#include <errno.h>
#include <fcntl.h>
#include <limits.h>
#include <math.h>
#include <netinet/in.h>
#include <poll.h>
#include <pthread.h>
Expand Down Expand Up @@ -214,9 +215,11 @@ static bool json_string(const char **p, char **out) {
while (**p && **p != '"') {
unsigned char c = (unsigned char)*(*p)++;
if (c != '\\') {
if (c < 0x20) goto fail;
buf_putc(&b, (char)c);
continue;
}
if (!**p) goto fail;
c = (unsigned char)*(*p)++;
switch (c) {
case '"': buf_putc(&b, '"'); break;
Expand All @@ -231,8 +234,11 @@ static bool json_string(const char **p, char **out) {
*p -= 2;
uint32_t cp = 0, lo = 0;
if (!json_u16(p, &cp)) goto fail;
if (cp >= 0xd800 && cp <= 0xdbff && json_u16(p, &lo) && lo >= 0xdc00 && lo <= 0xdfff) {
if (cp >= 0xd800 && cp <= 0xdbff) {
if (!json_u16(p, &lo) || lo < 0xdc00 || lo > 0xdfff) goto fail;
cp = 0x10000u + ((cp - 0xd800u) << 10) + (lo - 0xdc00u);
} else if (cp >= 0xdc00 && cp <= 0xdfff) {
goto fail;
}
utf8_put(&b, cp);
break;
Expand All @@ -250,11 +256,47 @@ static bool json_string(const char **p, char **out) {
return false;
}

static const char *json_number_end(const char *p) {
const char *start = p;
if (*p == '-') p++;

if (*p == '0') {
p++;
if (isdigit((unsigned char)*p)) return NULL;
} else {
if (!isdigit((unsigned char)*p)) return NULL;
while (isdigit((unsigned char)*p)) p++;
}

if (*p == '.') {
p++;
if (!isdigit((unsigned char)*p)) return NULL;
while (isdigit((unsigned char)*p)) p++;
}

if (*p == 'e' || *p == 'E') {
p++;
if (*p == '+' || *p == '-') p++;
if (!isdigit((unsigned char)*p)) return NULL;
while (isdigit((unsigned char)*p)) p++;
}

return p > start ? p : NULL;
}

static bool json_number(const char **p, double *out) {
json_ws(p);
char *end = NULL;
double v = strtod(*p, &end);
if (end == *p) return false;
const char *end = json_number_end(*p);
if (!end) return false;

char *num = xstrndup(*p, (size_t)(end - *p));
char *parsed_end = NULL;
errno = 0;
double v = strtod(num, &parsed_end);
bool ok = parsed_end && *parsed_end == '\0' && errno != ERANGE && isfinite(v);
free(num);
if (!ok) return false;

*p = end;
*out = v;
return true;
Expand Down Expand Up @@ -2702,17 +2744,39 @@ static char *dsml_unescape_text(const char *s) {
}

static char *dsml_attr(const char *tag, const char *name) {
char pat[64];
snprintf(pat, sizeof(pat), "%s=\"", name);
const char *p = strstr(tag, pat);
if (!p) return NULL;
p += strlen(pat);
const char *q = strchr(p, '"');
if (!q) return NULL;
char *raw = xstrndup(p, (size_t)(q - p));
char *decoded = dsml_unescape_text(raw);
free(raw);
return decoded;
size_t name_len = strlen(name);
const char *p = tag;

if (*p == '<') p++;
while (*p && !isspace((unsigned char)*p) && *p != '>' && *p != '/') p++;

while (*p) {
while (*p && isspace((unsigned char)*p)) p++;
if (!*p || *p == '>' || (*p == '/' && p[1] == '>')) return NULL;

const char *attr = p;
while (*p && !isspace((unsigned char)*p) && *p != '=' && *p != '>' && *p != '/') p++;
const char *attr_end = p;
while (*p && isspace((unsigned char)*p)) p++;
if (*p != '=') return NULL;
p++;
while (*p && isspace((unsigned char)*p)) p++;
if (*p != '"') return NULL;
p++;

const char *value = p;
while (*p && *p != '"') p++;
if (*p != '"') return NULL;

if ((size_t)(attr_end - attr) == name_len && !memcmp(attr, name, name_len)) {
char *raw = xstrndup(value, (size_t)(p - value));
char *decoded = dsml_unescape_text(raw);
free(raw);
return decoded;
}
p++;
}
return NULL;
}

static void tool_call_json_args_add(buf *args, const char *name, const char *value, const char *is_string) {
Expand Down Expand Up @@ -9548,6 +9612,69 @@ static void test_stop_list_streaming_holds_and_trims_stop_text(void) {
free(stops.v);
}

static void test_json_number_rejects_non_json_forms(void) {
const char *p = "0";
double v = 0.0;
TEST_ASSERT(json_number(&p, &v));
TEST_ASSERT(v == 0.0);
TEST_ASSERT(*p == '\0');

p = "-12.5e+2";
TEST_ASSERT(json_number(&p, &v));
TEST_ASSERT(v == -1250.0);
TEST_ASSERT(*p == '\0');

p = "NaN";
TEST_ASSERT(!json_number(&p, &v));

p = "Infinity";
TEST_ASSERT(!json_number(&p, &v));

p = "+1";
TEST_ASSERT(!json_number(&p, &v));

p = "01";
TEST_ASSERT(!json_number(&p, &v));
}

static void test_json_string_rejects_raw_control_chars(void) {
const char *p = "\"line1\\nline2\"";
char *s = NULL;
static const char raw_newline[] = {'"', 'l', 'i', 'n', 'e', '1', '\n', 'l', 'i', 'n', 'e', '2', '"', '\0'};
static const char raw_tab[] = {'"', 't', 'a', 'b', '\t', 'i', 'n', 's', 'i', 'd', 'e', '"', '\0'};
TEST_ASSERT(json_string(&p, &s));
TEST_ASSERT(!strcmp(s, "line1\nline2"));
TEST_ASSERT(*p == '\0');
free(s);

p = raw_newline;
s = NULL;
TEST_ASSERT(!json_string(&p, &s));
free(s);

p = raw_tab;
s = NULL;
TEST_ASSERT(!json_string(&p, &s));
free(s);
}

static void test_dsml_parser_rejects_prefixed_attribute_names(void) {
const char *generated =
DS4_TOOL_CALLS_START "\n"
DS4_INVOKE_START " xname=\"bash\">\n"
DS4_PARAM_START " xname=\"command\" string=\"true\">pwd" DS4_PARAM_END "\n"
DS4_INVOKE_END "\n"
DS4_TOOL_CALLS_END;

char *content = NULL;
char *reasoning = NULL;
tool_calls calls = {0};
TEST_ASSERT(!parse_generated_message(generated, &content, &reasoning, &calls));
free(content);
free(reasoning);
tool_calls_free(&calls);
}

static char *test_nested_json_array(int depth) {
buf b = {0};
for (int i = 0; i < depth; i++) buf_putc(&b, '[');
Expand Down Expand Up @@ -10319,6 +10446,9 @@ static void ds4_server_unit_tests_run(void) {
test_dsml_prompt_escapes_tool_supplied_text();
test_stop_list_parses_all_sequences();
test_stop_list_streaming_holds_and_trims_stop_text();
test_json_number_rejects_non_json_forms();
test_json_string_rejects_raw_control_chars();
test_dsml_parser_rejects_prefixed_attribute_names();
test_json_skip_has_nesting_limit();
test_model_metadata_clamps_completion_to_context();
test_client_socket_nonblocking_flag();
Expand Down