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[analyzer] Fix taint sink rules for exec-like functions (#66358)
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Variadic arguments were not considered as taint sink arguments. I also
decided to extend the list of exec-like functions.

(Juliet CWE78_OS_Command_Injection__char_connect_socket_execl)
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@steakhal
steakhal committed Sep 22, 2023
1 parent 1d0b7b6 commit f90e063
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Showing 2 changed files with 167 additions and 8 deletions.
14 changes: 8 additions & 6 deletions clang/lib/StaticAnalyzer/Checkers/GenericTaintChecker.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -744,12 +744,14 @@ void GenericTaintChecker::initTaintRules(CheckerContext &C) const {
// Sinks
{{{"system"}}, TR::Sink({{0}}, MsgSanitizeSystemArgs)},
{{{"popen"}}, TR::Sink({{0}}, MsgSanitizeSystemArgs)},
{{{"execl"}}, TR::Sink({{0}}, MsgSanitizeSystemArgs)},
{{{"execle"}}, TR::Sink({{0}}, MsgSanitizeSystemArgs)},
{{{"execlp"}}, TR::Sink({{0}}, MsgSanitizeSystemArgs)},
{{{"execvp"}}, TR::Sink({{0}}, MsgSanitizeSystemArgs)},
{{{"execvP"}}, TR::Sink({{0}}, MsgSanitizeSystemArgs)},
{{{"execve"}}, TR::Sink({{0}}, MsgSanitizeSystemArgs)},
{{{"execl"}}, TR::Sink({{}, {0}}, MsgSanitizeSystemArgs)},
{{{"execle"}}, TR::Sink({{}, {0}}, MsgSanitizeSystemArgs)},
{{{"execlp"}}, TR::Sink({{}, {0}}, MsgSanitizeSystemArgs)},
{{{"execv"}}, TR::Sink({{0, 1}}, MsgSanitizeSystemArgs)},
{{{"execve"}}, TR::Sink({{0, 1, 2}}, MsgSanitizeSystemArgs)},
{{{"fexecve"}}, TR::Sink({{0, 1, 2}}, MsgSanitizeSystemArgs)},
{{{"execvp"}}, TR::Sink({{0, 1}}, MsgSanitizeSystemArgs)},
{{{"execvpe"}}, TR::Sink({{0, 1, 2}}, MsgSanitizeSystemArgs)},
{{{"dlopen"}}, TR::Sink({{0}}, MsgSanitizeSystemArgs)},
{{CDF_MaybeBuiltin, {{"malloc"}}}, TR::Sink({{0}}, MsgTaintedBufferSize)},
{{CDF_MaybeBuiltin, {{"calloc"}}}, TR::Sink({{0}}, MsgTaintedBufferSize)},
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161 changes: 159 additions & 2 deletions clang/test/Analysis/taint-generic.c
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Original file line number Diff line number Diff line change
Expand Up @@ -64,6 +64,8 @@ void clang_analyzer_isTainted_wchar(wchar_t);
void clang_analyzer_isTainted_charp(char*);
void clang_analyzer_isTainted_int(int);

int coin();

int scanf(const char *restrict format, ...);
char *gets(char *str);
char *gets_s(char *str, rsize_t n);
Expand Down Expand Up @@ -118,6 +120,41 @@ void *malloc(size_t);
void *calloc(size_t nmemb, size_t size);
void bcopy(void *s1, void *s2, size_t n);


// function | pathname | filename | fd | arglist | argv[] | envp[]
// ===============================================================
// 1 execl | X | | | X | |
// 2 execle | X | | | X | | X
// 3 execlp | | X | | X | |
// 4 execv | X | | | | X |
// 5 execve | X | | | | X | X
// 6 execvp | | X | | | X |
// 7 execvpe | | X | | | X | X
// 8 fexecve | | | X | | X | X
// ===============================================================
// letter | | p | f | l | v | e
//
// legend:
// - pathname: rel/abs path to the binary
// - filename: file name searched in PATH to execute the binary
// - fd: accepts a file descriptor
// - arglist: accepts variadic arguments
// - argv: accepts a pointer to array, denoting the new argv
// - envp: accepts a pointer to array, denoting the new envp

int execl(const char *path, const char *arg, ...);
int execle(const char *path, const char *arg, ...);
int execlp(const char *file, const char *arg, ...);
int execv(const char *path, char *const argv[]);
int execve(const char *path, char *const argv[], char *const envp[]);
int execvp(const char *file, char *const argv[]);
int execvpe(const char *file, char *const argv[], char *const envp[]);
int fexecve(int fd, char *const argv[], char *const envp[]);
FILE *popen(const char *command, const char *type);
int pclose(FILE *stream);
int system(const char *command);


typedef size_t socklen_t;

struct sockaddr {
Expand Down Expand Up @@ -224,7 +261,6 @@ void testUncontrolledFormatString(char **p) {

}

int system(const char *command);
void testTaintSystemCall(void) {
char buffer[156];
char addr[128];
Expand Down Expand Up @@ -287,7 +323,6 @@ void testTaintedBufferSize(void) {
#define SOCK_STREAM 1
int socket(int, int, int);
size_t read(int, void *, size_t);
int execl(const char *, const char *, ...);

void testSocket(void) {
int sock;
Expand Down Expand Up @@ -1129,6 +1164,128 @@ void testConfigurationSinks(void) {
// expected-warning@-1 {{Untrusted data is passed to a user-defined sink}}
}

int test_exec_like_functions() {
char buf[100] = {0};
scanf("%99s", buf);
clang_analyzer_isTainted_char(buf[0]); // expected-warning {{YES}}

char *cleanArray[] = {"ENV1=V1", "ENV2=V2", NULL};
char *taintedArray[] = {buf, "ENV2=V2", NULL};
clang_analyzer_isTainted_char(taintedArray[0][0]); // expected-warning {{YES}}
clang_analyzer_isTainted_char(*(char*)taintedArray[0]); // expected-warning {{YES}}
clang_analyzer_isTainted_char(*(char*)taintedArray); // expected-warning {{NO}} We should have YES here.
// FIXME: Above the triple pointer indirection will confuse the checker,
// as we only check two levels. The results would be worse, if the tainted
// subobject ("buf") would not be at the beginning of the enclosing object,
// for the same reason.

switch (coin()) {
default: break;
// Execute `path` with all arguments after `path` until a NULL pointer
// and environment from `environ'.
case 0: return execl("path", "arg0", "arg1", "arg2", NULL); // no-warning
case 1: return execl(buf, "arg0", "arg1", "arg2", NULL); // expected-warning {{Untrusted data is passed to a system call}}
case 2: return execl("path", buf, "arg1", "arg2", NULL); // expected-warning {{Untrusted data is passed to a system call}}
case 3: return execl("path", "arg0", buf, "arg2", NULL); // expected-warning {{Untrusted data is passed to a system call}}
case 4: return execl("path", "arg0", "arg1", buf, NULL); // expected-warning {{Untrusted data is passed to a system call}}
}

switch (coin()) {
default: break;
// Execute `path` with all arguments after `PATH` until a NULL pointer,
// and the argument after that for environment.
case 0: return execle("path", "arg0", "arg1", NULL, cleanArray); // no-warning
case 1: return execle( buf, "arg0", "arg1", NULL, cleanArray); // expected-warning {{Untrusted data is passed to a system call}}
case 2: return execle("path", buf, "arg1", NULL, cleanArray); // expected-warning {{Untrusted data is passed to a system call}}
case 3: return execle("path", "arg0", buf, NULL, cleanArray); // expected-warning {{Untrusted data is passed to a system call}}
case 4: return execle("path", "arg0", "arg1", NULL, buf); // expected-warning {{Untrusted data is passed to a system call}}
case 5: return execle("path", "arg0", "arg1", NULL, taintedArray); // FIXME: We might wanna have a report here.
}

switch (coin()) {
default: break;
// Execute `file`, searching in the `PATH' environment variable if it
// contains no slashes, with all arguments after `file` until a NULL
// pointer and environment from `environ'.
case 0: return execlp("file", "arg0", "arg1", "arg2", NULL); // no-warning
case 1: return execlp( buf, "arg0", "arg1", "arg2", NULL); // expected-warning {{Untrusted data is passed to a system call}}
case 2: return execlp("file", buf, "arg1", "arg2", NULL); // expected-warning {{Untrusted data is passed to a system call}}
case 3: return execlp("file", "arg0", buf, "arg2", NULL); // expected-warning {{Untrusted data is passed to a system call}}
case 4: return execlp("file", "arg0", "arg1", buf, NULL); // expected-warning {{Untrusted data is passed to a system call}}
}

switch (coin()) {
default: break;
// Execute `path` with arguments `ARGV` and environment from `environ'.
case 0: return execv("path", /*argv=*/ cleanArray); // no-warning
case 1: return execv( buf, /*argv=*/ cleanArray); // expected-warning {{Untrusted data is passed to a system call}}
case 2: return execv("path", /*argv=*/taintedArray); // FIXME: We might wanna have a report here.
}

switch (coin()) {
default: break;
// Replace the current process, executing `path` with arguments `ARGV`
// and environment `ENVP`. `ARGV` and `ENVP` are terminated by NULL pointers.
case 0: return execve("path", /*argv=*/ cleanArray, /*envp=*/cleanArray); // no-warning
case 1: return execve( buf, /*argv=*/ cleanArray, /*envp=*/cleanArray); // expected-warning {{Untrusted data is passed to a system call}}
case 2: return execve("path", /*argv=*/taintedArray, /*envp=*/cleanArray); // FIXME: We might wanna have a report here.
case 3: return execve("path", /*argv=*/cleanArray, /*envp=*/taintedArray); // FIXME: We might wanna have a report here.
}

switch (coin()) {
default: break;
// Execute `file`, searching in the `PATH' environment variable if it
// contains no slashes, with arguments `ARGV` and environment from `environ'.
case 0: return execvp("file", /*argv=*/ cleanArray); // no-warning
case 1: return execvp( buf, /*argv=*/ cleanArray); // expected-warning {{Untrusted data is passed to a system call}}
case 2: return execvp("file", /*argv=*/taintedArray); // FIXME: We might wanna have a report here.
}

// execvpe
switch (coin()) {
default: break;
// Execute `file`, searching in the `PATH' environment variable if it
// contains no slashes, with arguments `ARGV` and environment `ENVP`.
// `ARGV` and `ENVP` are terminated by NULL pointers.
case 0: return execvpe("file", /*argv=*/ cleanArray, /*envp=*/ cleanArray); // no-warning
case 1: return execvpe( buf, /*argv=*/ cleanArray, /*envp=*/ cleanArray); // expected-warning {{Untrusted data is passed to a system call}}
case 2: return execvpe("file", /*argv=*/taintedArray, /*envp=*/ cleanArray); // FIXME: We might wanna have a report here.
case 3: return execvpe("file", /*argv=*/ cleanArray, /*envp=*/taintedArray); // FIXME: We might wanna have a report here.
}

int cleanFD = coin();
int taintedFD;
scanf("%d", &taintedFD);
clang_analyzer_isTainted_int(taintedFD); // expected-warning {{YES}}

switch (coin()) {
default: break;
// Execute the file `FD` refers to, overlaying the running program image.
// `ARGV` and `ENVP` are passed to the new program, as for `execve'.
case 0: return fexecve( cleanFD, /*argv=*/ cleanArray, /*envp=*/ cleanArray); // no-warning
case 1: return fexecve(taintedFD, /*argv=*/ cleanArray, /*envp=*/ cleanArray); // expected-warning {{Untrusted data is passed to a system call}}
case 2: return fexecve( cleanFD, /*argv=*/taintedArray, /*envp=*/ cleanArray); // FIXME: We might wanna have a report here.
case 3: return fexecve( cleanFD, /*argv=*/ cleanArray, /*envp=*/taintedArray); // FIXME: We might wanna have a report here.
}

switch (coin()) {
default: break;
// Create a new stream connected to a pipe running the given `command`.
case 0: return pclose(popen("command", /*mode=*/"r")); // no-warning
case 1: return pclose(popen( buf, /*mode=*/"r")); // expected-warning {{Untrusted data is passed to a system call}}
case 2: return pclose(popen("command", /*mode=*/buf)); // 'mode' is not a taint sink.
}

switch (coin()) {
default: break;
// Execute the given line as a shell command.
case 0: return system("command"); // no-warning
case 1: return system( buf); // expected-warning {{Untrusted data is passed to a system call}}
}

return 0;
}

void testUnknownFunction(void (*foo)(void)) {
foo(); // no-crash
}
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