"It happened a few nights ago," a friend of the Good Charlotte rocker said of the proposal. "All of Benji's friends are aware and happy for him."
Confirmed: Cameron Diaz and Benji Madden are engaged
Rumours have been flying around for weeks now that Benji had popped the question, fuelled further when Cameron was spotted wearing what looked like an engagement ring as the couple made their way through JFK airport on Wednesday.
Although the 42-year-old actress is yet to confirm her engagement, she did share some advice about love in the latest issue of Cosmopolitan magazine.
"If you get into a relationship where you want something the guy doesn't want, it's never gonna work," Cameron said. "Timing is everything.
"You're never going to get him to be in that place. No matter how old you are, finding the guy who's in the same place as you are and wants to show up is the only way a relationship works, period."
Cameron Diaz and Benji Madden will reportedly marry in early 2015
According to reports, Cameron was totally "swept off her feet" by "chivalrous" Benji after the pair were introduced by Nicole Richie – who is married to Benji's twin brother Joel Madden.
Just six weeks after they started dating, Cameron took 35-year-old Benji to meet her family in Florida, where he got the blessing of her mother Billie.
"Billie absolutely loved Benji," a source said at the time. "She has been gushing about the relationship, saying she hopes Cameron settles down with him."
The pair are said to have chosen a date in early 2015 for their wedding. Back in September, a source said Benji was keen to go down the traditional route of getting married first and then start thinking about a family.
"She doesn't really care about getting married but wants babies," the insider said. "He wants to get engaged and married first."
Another friend told US Weekly: "Everyone thinks it's wild but are so happy for them. Benji always tends to fall in love easily, but this time it's for real and he landed a great girl. They obviously both make each other incredibly happy and there's nothing better than that."