imap: replace atoi() with strtol_i() for UIDVALIDITY and UIDNEXT parsing

Replace unsafe uses of atoi() with strtol_i() to improve error handling
when parsing UIDVALIDITY, UIDNEXT, and APPENDUID in IMAP commands.
Invalid values, such as those with letters, now trigger error messages and
prevent malformed status responses.
I did not add any test for this commit as we do not have any test
for git-imap-send(1) at this point.

Signed-off-by: Usman Akinyemi <[email protected]>
Signed-off-by: Taylor Blau <[email protected]>

Author: Unique-Usman

imap-send.c

@@ -668,12 +668,12 @@ static int parse_response_code(struct imap_store *ctx, struct imap_cmd_cb *cb,
 		return RESP_BAD;
 	}
 	if (!strcmp("UIDVALIDITY", arg)) {
-		if (!(arg = next_arg(&s)) || !(ctx->uidvalidity = atoi(arg))) {
+		if (!(arg = next_arg(&s)) || strtol_i(arg, 10, &ctx->uidvalidity) || !ctx->uidvalidity) {
 			fprintf(stderr, "IMAP error: malformed UIDVALIDITY status\n");
 			return RESP_BAD;
 		}
 	} else if (!strcmp("UIDNEXT", arg)) {
-		if (!(arg = next_arg(&s)) || !(imap->uidnext = atoi(arg))) {
+		if (!(arg = next_arg(&s)) || strtol_i(arg, 10, &imap->uidnext) || !imap->uidnext) {
 			fprintf(stderr, "IMAP error: malformed NEXTUID status\n");
 			return RESP_BAD;
 		}
@@ -686,8 +686,8 @@ static int parse_response_code(struct imap_store *ctx, struct imap_cmd_cb *cb,
 		for (; isspace((unsigned char)*p); p++);
 		fprintf(stderr, "*** IMAP ALERT *** %s\n", p);
 	} else if (cb && cb->ctx && !strcmp("APPENDUID", arg)) {
-		if (!(arg = next_arg(&s)) || !(ctx->uidvalidity = atoi(arg)) ||
-		    !(arg = next_arg(&s)) || !(*(int *)cb->ctx = atoi(arg))) {
+		if (!(arg = next_arg(&s)) || strtol_i(arg, 10, &ctx->uidvalidity) || !ctx->uidvalidity ||
+		    !(arg = next_arg(&s)) || strtol_i(arg, 10, (int *)cb->ctx) || !cb->ctx) {
 			fprintf(stderr, "IMAP error: malformed APPENDUID status\n");
 			return RESP_BAD;
 		}
@@ -773,7 +773,10 @@ static int get_cmd_result(struct imap_store *ctx, struct imap_cmd *tcmd)
 			if (!tcmd)
 				return DRV_OK;
 		} else {
-			tag = atoi(arg);
+			if (strtol_i(arg, 10, &tag)) {
+				fprintf(stderr, "IMAP error: malformed tag %s\n", arg);
+				return RESP_BAD;
+			}
 			for (pcmdp = &imap->in_progress; (cmdp = *pcmdp); pcmdp = &cmdp->next)
 				if (cmdp->tag == tag)
 					goto gottag;