在firefox浏览器的认证过程是在netwerk/protocol/http目录下的nsHttpBasicAuth.cpp文件中实现的：
NS_IMETHODIMP
nsHttpBasicAuth::GenerateCredentials(nsIHttpAuthenticableChannel *authChannel,
const char *challenge,
bool isProxyAuth,
const PRUnichar *domain,
const PRUnichar *user,
const PRUnichar *password,
nsISupports **sessionState,
nsISupports **continuationState,
uint32_t *aFlags,
char **creds)
{
LOG(("nsHttpBasicAuth::GenerateCredentials [challenge=%s]\n", challenge));
NS_ENSURE_ARG_POINTER(creds);
*aFlags = 0;
// we only know how to deal with Basic auth for http.
bool isBasicAuth = !PL_strncasecmp(challenge, "basic", 5);
NS_ENSURE_TRUE(isBasicAuth, NS_ERROR_UNEXPECTED);
// we work with ASCII around here
nsAutoCString userpass;
LossyCopyUTF16toASCII(user, userpass);
userpass.Append(':'); // always send a ':' (see bug 129565)
if (password)
LossyAppendUTF16toASCII(password, userpass);
// plbase64.h provides this worst-case output buffer size calculation.
// use calloc, since PL_Base64Encode does not null terminate.
*creds = (char *) calloc(6 + ((userpass.Length() + 2)/3)*4 + 1, 1);
if (!*creds)
return NS_ERROR_OUT_OF_MEMORY;
memcpy(*creds, "Basic ", 6);
PL_Base64Encode(userpass.get(), userpass.Length(), *creds + 6);
return NS_OK;
}
通过PL_Base64Encode(userpass.get(), userpass.Length(), *creds + 6)函数去获取浏览器中设置的用户名和密码信息，userpass.get()表示用户名和密码信息，中间用：号隔开，而userpass.Length()表示userpass.get()的字符长度。因此，要想给firefox浏览器添加默认的认证信息，只要对这个函数进行修改则可，例如：
PL_Base64Encode(“abc:123”, 7, *creds + 6)则将用户名默认为abc，密码默认为123。