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[PATCHv2 10/15] drop length limitations on gecos-derived names and emails

From
Jeff King <peff@peff.net>
Date
May 21, 2012, 23:10 UTC
Message-ID
<20120521231017.GJ10981@sigill.intra.peff.net>
In-Reply-To
<20120521230917.GA474@sigill.intra.peff.net>

When we pull the user's name from the GECOS field of the passwd file (or generate an email address based on their username and hostname), we put the result into a static buffer. While it's extremely unlikely that anybody ever hit these limits (after all, in such a case their parents must have hated them), we still had to deal with the error cases in our code.

Converting these static buffers to strbufs lets us simplify the code and drop some error messages from the documentation that have confused some users.

The conversion is mostly mechanical: replace string copies with strbuf equivalents, and access the strbuf.buf directly. There are a few exceptions:

  - copy_gecos and copy_email are the big winners in code
    reduction (since they no longer have to manage the
    string length manually)
  - git_ident_config wants to replace old versions of
    the default name (e.g., if we read the config multiple
    times), so it must reset+add to the strbuf instead of
    just adding

Note that there is still one length limitation: the gethostname interface requires us to provide a static buffer, so we arbitrarily choose 1024 bytes for the hostname.

Signed-off-by: Jeff King <peff@peff.net>
---
 Documentation/git-commit-tree.txt |   4 --
 Documentation/git-var.txt         |   4 --
 ident.c                           | 104 ++++++++++++++------------------------
 3 files changed, 39 insertions(+), 73 deletions(-)
diff --git a/Documentation/git-commit-tree.txt b/Documentation/git-commit-tree.txt
index cfb9906..eb12b2d 100644
--- a/Documentation/git-commit-tree.txt
+++ b/Documentation/git-commit-tree.txt
@@ -92,10 +92,6 @@ Diagnostics
 -----------
 You don't exist. Go away!::
     The passwd(5) gecos field couldn't be read
-Your parents must have hated you!::
-    The passwd(5) gecos field is longer than a giant static buffer.
-Your sysadmin must hate you!::
-    The passwd(5) name field is longer than a giant static buffer.
 
 Discussion
 ----------
diff --git a/Documentation/git-var.txt b/Documentation/git-var.txt
index 988a323..3f703e3 100644
--- a/Documentation/git-var.txt
+++ b/Documentation/git-var.txt
@@ -63,10 +63,6 @@ Diagnostics
 -----------
 You don't exist. Go away!::
     The passwd(5) gecos field couldn't be read
-Your parents must have hated you!::
-    The passwd(5) gecos field is longer than a giant static buffer.
-Your sysadmin must hate you!::
-    The passwd(5) name field is longer than a giant static buffer.
 
 SEE ALSO
 --------
diff --git a/ident.c b/ident.c
index 87e3cbe..73a06a1 100644
--- a/ident.c
+++ b/ident.c
@@ -7,9 +7,8 @@
  */
 #include "cache.h"
 
-#define MAX_GITNAME (1000)
-static char git_default_name[MAX_GITNAME];
-static char git_default_email[MAX_GITNAME];
+static struct strbuf git_default_name = STRBUF_INIT;
+static struct strbuf git_default_email = STRBUF_INIT;
 static char git_default_date[50];
 int user_ident_explicitly_given;
 
@@ -19,42 +18,27 @@ int user_ident_explicitly_given;
 #define get_gecos(struct_passwd) ((struct_passwd)->pw_gecos)
 #endif
 
-static void copy_gecos(const struct passwd *w, char *name, size_t sz)
+static void copy_gecos(const struct passwd *w, struct strbuf *name)
 {
-	char *src, *dst;
-	size_t len, nlen;
-
-	nlen = strlen(w->pw_name);
+	char *src;
 
 	/* Traditionally GECOS field had office phone numbers etc, separated
 	 * with commas.  Also & stands for capitalized form of the login name.
 	 */
 
-	for (len = 0, dst = name, src = get_gecos(w); len < sz; src++) {
+	for (src = get_gecos(w); *src && *src != ','; src++) {
 		int ch = *src;
-		if (ch != '&') {
-			*dst++ = ch;
-			if (ch == 0 || ch == ',')
-				break;
-			len++;
-			continue;
-		}
-		if (len + nlen < sz) {
+		if (ch != '&')
+			strbuf_addch(name, ch);
+		else {
 			/* Sorry, Mr. McDonald... */
-			*dst++ = toupper(*w->pw_name);
-			memcpy(dst, w->pw_name + 1, nlen - 1);
-			dst += nlen - 1;
-			len += nlen;
+			strbuf_addch(name, toupper(*w->pw_name));
+			strbuf_addstr(name, w->pw_name + 1);
 		}
 	}
-	if (len < sz)
-		name[len] = 0;
-	else
-		die("Your parents must have hated you!");
-
 }
 
-static int add_mailname_host(char *buf, size_t len)
+static int add_mailname_host(struct strbuf *buf)
 {
 	FILE *mailname;
 
@@ -65,7 +49,7 @@ static int add_mailname_host(char *buf, size_t len)
 				strerror(errno));
 		return -1;
 	}
-	if (!fgets(buf, len, mailname)) {
+	if (strbuf_getline(buf, mailname, '\n') == EOF) {
 		if (ferror(mailname))
 			warning("cannot read /etc/mailname: %s",
 				strerror(errno));
@@ -74,85 +58,73 @@ static int add_mailname_host(char *buf, size_t len)
 	}
 	/* success! */
 	fclose(mailname);
-
-	len = strlen(buf);
-	if (len && buf[len-1] == '\n')
-		buf[len-1] = '\0';
 	return 0;
 }
 
-static void add_domainname(char *buf, size_t len)
+static void add_domainname(struct strbuf *out)
 {
+	char buf[1024];
 	struct hostent *he;
-	size_t namelen;
 	const char *domainname;
 
-	if (gethostname(buf, len)) {
+	if (gethostname(buf, sizeof(buf))) {
 		warning("cannot get host name: %s", strerror(errno));
-		strlcpy(buf, "(none)", len);
+		strbuf_addstr(out, "(none)");
 		return;
 	}
-	namelen = strlen(buf);
-	if (memchr(buf, '.', namelen))
+	strbuf_addstr(out, buf);
+	if (strchr(buf, '.'))
 		return;
 
 	he = gethostbyname(buf);
-	buf[namelen++] = '.';
-	buf += namelen;
-	len -= namelen;
+	strbuf_addch(out, '.');
 	if (he && (domainname = strchr(he->h_name, '.')))
-		strlcpy(buf, domainname + 1, len);
+		strbuf_addstr(out, domainname + 1);
 	else
-		strlcpy(buf, "(none)", len);
+		strbuf_addstr(out, "(none)");
 }
 
-static void copy_email(const struct passwd *pw)
+static void copy_email(const struct passwd *pw, struct strbuf *email)
 {
 	/*
 	 * Make up a fake email address
 	 * (name + '@' + hostname [+ '.' + domainname])
 	 */
-	size_t len = strlen(pw->pw_name);
-	if (len > sizeof(git_default_email)/2)
-		die("Your sysadmin must hate you!");
-	memcpy(git_default_email, pw->pw_name, len);
-	git_default_email[len++] = '@';
-
-	if (!add_mailname_host(git_default_email + len,
-				sizeof(git_default_email) - len))
+	strbuf_addstr(email, pw->pw_name);
+	strbuf_addch(email, '@');
+
+	if (!add_mailname_host(email))
 		return;	/* read from "/etc/mailname" (Debian) */
-	add_domainname(git_default_email + len,
-			sizeof(git_default_email) - len);
+	add_domainname(email);
 }
 
 const char *ident_default_name(void)
 {
-	if (!git_default_name[0]) {
+	if (!git_default_name.len) {
 		struct passwd *pw = getpwuid(getuid());
 		if (!pw)
 			die("You don't exist. Go away!");
-		copy_gecos(pw, git_default_name, sizeof(git_default_name));
+		copy_gecos(pw, &git_default_name);
 	}
-	return git_default_name;
+	return git_default_name.buf;
 }
 
 const char *ident_default_email(void)
 {
-	if (!git_default_email[0]) {
+	if (!git_default_email.len) {
 		const char *email = getenv("EMAIL");
 
 		if (email && email[0]) {
-			strlcpy(git_default_email, email,
-				sizeof(git_default_email));
+			strbuf_addstr(&git_default_email, email);
 			user_ident_explicitly_given |= IDENT_MAIL_GIVEN;
 		} else {
 			struct passwd *pw = getpwuid(getuid());
 			if (!pw)
 				die("You don't exist. Go away!");
-			copy_email(pw);
+			copy_email(pw, &git_default_email);
 		}
 	}
-	return git_default_email;
+	return git_default_email.buf;
 }
 
 const char *ident_default_date(void)
@@ -327,7 +299,7 @@ const char *fmt_ident(const char *name, const char *email,
 		struct passwd *pw;
 
 		if (error_on_no_name) {
-			if (name == git_default_name)
+			if (name == git_default_name.buf)
 				fputs(env_hint, stderr);
 			die("empty ident %s <%s> not allowed", name, email);
 		}
@@ -397,7 +369,8 @@ int git_ident_config(const char *var, const char *value, void *data)
 	if (!strcmp(var, "user.name")) {
 		if (!value)
 			return config_error_nonbool(var);
-		strlcpy(git_default_name, value, sizeof(git_default_name));
+		strbuf_reset(&git_default_name);
+		strbuf_addstr(&git_default_name, value);
 		user_ident_explicitly_given |= IDENT_NAME_GIVEN;
 		return 0;
 	}
@@ -405,7 +378,8 @@ int git_ident_config(const char *var, const char *value, void *data)
 	if (!strcmp(var, "user.email")) {
 		if (!value)
 			return config_error_nonbool(var);
-		strlcpy(git_default_email, value, sizeof(git_default_email));
+		strbuf_reset(&git_default_email);
+		strbuf_addstr(&git_default_email, value);
 		user_ident_explicitly_given |= IDENT_MAIL_GIVEN;
 		return 0;
 	}

-- 
1.7.10.1.19.g711d603
Previous: Jeff KingNext: Jonathan Nieder
Message 28 of 45 in “ident cleanups and bugfixes”
  1. 0/13 ident cleanups and bugfixesJeff King, May 18, 2012
  2. 01/13 ident: split setup_ident into separate functionsJeff King, May 18, 2012
  3. 02/13 http-push: do not access git_default_email directlyJeff King, May 18, 2012
  4. 03/13 fmt-merge-msg: don't use static buffer in record_personJeff King, May 18, 2012
  5. 04/13 move identity config parsing to ident.cJeff King, May 18, 2012
  6. 05/13 move git_default_* variables to ident.cJeff King, May 18, 2012
  7. Junio C HamanoMay 21, 2012
  8. Jeff KingMay 21, 2012
  9. Jeff KingMay 21, 2012
  10. 06/13 format-patch: use default email for generating message idsJeff King, May 18, 2012
  11. Junio C HamanoMay 21, 2012
  12. Jeff KingMay 21, 2012
  13. 07/13 fmt_ident: drop IDENT_WARN_ON_NO_NAME codeJeff King, May 18, 2012
  14. 08/13 ident: don't write fallback username into git_default_nameJeff King, May 18, 2012
  15. Junio C HamanoMay 21, 2012
  16. Jeff KingMay 21, 2012
  17. Junio C HamanoMay 21, 2012
  18. 0/15 ident cleanups git_default_nameJeff King, May 21, 2012
  19. 01/15 ident: split setup_ident into separate functionsJeff King, May 21, 2012
  20. 02/15 http-push: do not access git_default_email directlyJeff King, May 21, 2012
  21. 03/15 fmt-merge-msg: don't use static buffer in record_personJeff King, May 21, 2012
  22. 04/15 move identity config parsing to ident.cJeff King, May 21, 2012
  23. 05/15 move git_default_* variables to ident.cJeff King, May 21, 2012
  24. 06/15 ident: trim trailing newline from /etc/mailnameJeff King, May 21, 2012
  25. 07/15 format-patch: use default email for generating message idsJeff King, May 21, 2012
  26. 08/15 fmt_ident: drop IDENT_WARN_ON_NO_NAME codeJeff King, May 21, 2012
  27. 09/15 ident: don't write fallback username into git_default_nameJeff King, May 21, 2012
  28. 10/15 drop length limitations on gecos-derived names and emailsJeff King, May 21, 2012
  29. [regression] Re: [PATCHv2 10/15] drop length limitations on gecos-derived names and emailsJonathan Nieder, Jan 24, 2013
  30. Jeff KingJan 25, 2013
  31. Junio C HamanoJan 25, 2013
  32. Jeff KingJan 25, 2013
  33. 11/15 ident: report passwd errors with a more friendly messageJeff King, May 21, 2012
  34. 12/15 ident: use full dns names to generate email addressesJeff King, May 21, 2012
  35. 13/15 ident: use a dynamic strbuf in fmt_identJeff King, May 21, 2012
  36. 14/15 ident: trim whitespace from default name/emailJeff King, May 21, 2012
  37. Junio C HamanoMay 22, 2012
  38. Jeff KingMay 22, 2012
  39. Junio C HamanoMay 22, 2012
  40. 15/15 format-patch: refactor get_patch_filenameJeff King, May 21, 2012
  41. 09/13 drop length limitations on gecos-derived names and emailsJeff King, May 18, 2012
  42. 10/13 ident: report passwd errors with a more friendly messageJeff King, May 18, 2012
  43. 11/13 ident: use full dns names to generate email addressesJeff King, May 18, 2012
  44. 12/13 ident: use a dynamic strbuf in fmt_identJeff King, May 18, 2012
  45. 13/13 format-patch: refactor get_patch_filenameJeff King, May 18, 2012

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