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tool_homedir: Change GetEnv() to use libcurl's curl_getenv()

- Deduplicate GetEnv() code.

- On Windows change ultimate call to use Windows API
  GetEnvironmentVariable() instead of C runtime getenv().

Prior to this change both libcurl and the tool had their own GetEnv
which over time diverged. Now the tool's GetEnv is a wrapper around
curl_getenv (libcurl API function which is itself a wrapper around
libcurl's GetEnv).

Furthermore this change fixes a bug in that Windows API
GetEnvironmentVariable() is called instead of C runtime getenv() to get
the environment variable since some changes aren't always visible to the
latter.

Reported-by: Christoph M. Becker

Fixes #4774
Closes #4863
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jay committed Jan 29, 2020
1 parent 39d5621 commit 9dc350b60c1345aea548847de414c55468a4d123
Showing with 58 additions and 42 deletions.
  1. +34 −11 lib/getenv.c
  2. +24 −31 src/tool_homedir.c
@@ -27,25 +27,48 @@

#include "memdebug.h"

static
char *GetEnv(const char *variable)
static char *GetEnv(const char *variable)
{
#if defined(_WIN32_WCE) || defined(CURL_WINDOWS_APP)
(void)variable;
return NULL;
#else
#ifdef WIN32
char env[4096];
char *temp = getenv(variable);
env[0] = '\0';
if(temp != NULL)
ExpandEnvironmentStringsA(temp, env, sizeof(env));
return (env[0] != '\0')?strdup(env):NULL;
#elif defined(WIN32)
/* This uses Windows API instead of C runtime getenv() to get the environment
variable since some changes aren't always visible to the latter. #4774 */
char *buf = NULL;
char *tmp;
DWORD bufsize;
DWORD rc = 1;
const DWORD max = 32768; /* max env var size from MSCRT source */

for(;;) {
tmp = realloc(buf, rc);
if(!tmp) {
free(buf);
return NULL;
}

buf = tmp;
bufsize = rc;

/* It's possible for rc to be 0 if the variable was found but empty.
Since getenv doesn't make that distinction we ignore it as well. */
rc = GetEnvironmentVariableA(variable, buf, bufsize);
if(!rc || rc == bufsize || rc > max) {
free(buf);
return NULL;
}

/* if rc < bufsize then rc is bytes written not including null */
if(rc < bufsize)
return buf;

/* else rc is bytes needed, try again */
}
#else
char *env = getenv(variable);
return (env && env[0])?strdup(env):NULL;
#endif
#endif
}

char *curl_getenv(const char *v)
@@ -25,50 +25,35 @@
# include <pwd.h>
#endif

#include <curl/mprintf.h>

#include "tool_homedir.h"

#include "memdebug.h" /* keep this as LAST include */

static char *GetEnv(const char *variable, char do_expand)
static char *GetEnv(const char *variable)
{
char *env = NULL;
#ifdef WIN32
char buf1[1024], buf2[1024];
DWORD rc;
char *dupe, *env;

/* Don't use getenv(); it doesn't find variable added after program was
* started. Don't accept truncated results (i.e. rc >= sizeof(buf1)). */
env = curl_getenv(variable);
if(!env)
return NULL;

rc = GetEnvironmentVariableA(variable, buf1, sizeof(buf1));
if(rc > 0 && rc < sizeof(buf1)) {
env = buf1;
variable = buf1;
}
if(do_expand && strchr(variable, '%')) {
/* buf2 == variable if not expanded */
rc = ExpandEnvironmentStringsA(variable, buf2, sizeof(buf2));
if(rc > 0 && rc < sizeof(buf2) &&
!strchr(buf2, '%')) /* no vars still unexpanded */
env = buf2;
}
#else
(void)do_expand;
/* no length control */
env = getenv(variable);
#endif
return (env && env[0]) ? strdup(env) : NULL;
dupe = strdup(env);
curl_free(env);
return dupe;
}

/* return the home directory of the current user as an allocated string */
char *homedir(void)
{
char *home;

home = GetEnv("CURL_HOME", FALSE);
home = GetEnv("CURL_HOME");
if(home)
return home;

home = GetEnv("HOME", FALSE);
home = GetEnv("HOME");
if(home)
return home;

@@ -86,10 +71,18 @@ char *homedir(void)
}
#endif /* PWD-stuff */
#ifdef WIN32
home = GetEnv("APPDATA", TRUE);
if(!home)
home = GetEnv("%USERPROFILE%\\Application Data", TRUE); /* Normally only
on Win-2K/XP */
home = GetEnv("APPDATA");
if(!home) {
char *env = GetEnv("USERPROFILE");
if(env) {
char *path = curl_maprintf("%s\\Application Data", env);
if(path) {
home = strdup(path);
curl_free(path);
}
free(env);
}
}
#endif /* WIN32 */
return home;
}

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